steel building construction and technology 5
TRANSCRIPT
BUILDING CONSTRUCTION AND TECHNOLOGY 5
ASSIGNMENT 1: RESEARCH REPORT
PREPARED FOR:
AR. CHIA LIN LIN
PREPARED BY:
DANIEL NG SHI JUN (1000819417)
SAIDU ALHASSAN UMAR (1000819783)
JONATHAN LEONG CHENG CHIEN (1000820475)
KEYMAN ASSAFI (1000)
NG SHING YIE (1000820122)
TARANEH BAHMANROKH (1000)
YEAR 3 SEM 1
JAN – MAY 2012
EXECUTIVE SUMMARY
The purpose of this report was to analyze steel framing systems to create
consciousness of architecture students to the interrelationship between engineering
and architecture design.
Structural components of advanced and general construction techniques are
identified and illustrated. This is backed up by necessary documentations to the
standards acceptable to the profession.
To organize the research, steel framing systems findings been categorized into its
general information such as characteristics and typology and its architecture
elements such as foundation systems, wall systems, roof systems, etc.
Various case studies are then done to prove steel framing systems effectiveness and
design capabilities.
In conclusion, steel framing systems prove to not only be design flexible, it is more
cost saving, faster, effective, and stronger than other building materials or systems.
1.0 INTRODUCTION
1.1 Purpose
The purpose of this report was to analyze steel framing systems and
identify its structural components of advanced construction techniques
and illustrate the implementation of advance construction techniques
which will demonstrate the interrelationship between engineering and
architecture design.
1.2 Scope
While researching, it is important to consider the difference in steel
construction. Not all steel construction uses the steel framing system.
1.3 Methodology
The research group consists of 6 individuals for which are paired into
sub-groups to deal with given tasks. Research components and case
studies are derived from book/magazine sources and from in the
internet from architecture websites and e-books. The task distribution is
categorized like so:
Tasks Members
1.0 Introduction
Task Distribution and Planning
Conclusion
Compilation
Daniel
Saidu
2.0 Steel Framing Systems General Information
Characteristics
Cold-Formed Steel Framing
Benefits of Steel Framing Systems
Prefabrication and IBS
Design Process Procedures
Plan Check and Building Inspection
Differences with other Materials
Daniel
Saidu
Consultants and Specialization
Fasteners and Tools
Training and Licenses
Types of Steel Framing Systems
Steel Specifications and Standards
Steel Suppliers and Ordering
Local and International Differences
3.0 Foundation Systems
Deep foundation
Right Foundation for Steel Frame Structure
Pile Foundation
Pile Caps
Citeria and Requirements
Steel Panel Foundations
Pole Foundations
Taraneh
4.0 Floor Systems
Structural Steel Framing
One-Way Beam System
Two-Way Beam System
Triple Beam System
Types of Steel Beams
Types of Steel Connections
Types of Decking
Light-Gauge Steel
Light-Gauge Stud Framing
Shing Yie
5.0 Wall Systems
Exterior Wall Studs
Curtain Wall
Interior Wall
Light-Gauge Metal Framing
Types of Furring and Studs
Material Specification
Staggered Truss Steel Framing System
Taraneh
6.0 Roof Systems Jonathan
Structural Steel Roof Framing
Assembly Methods
Steel Rigid Frame (Portal Frame)
Space Frames
Open-web steel Joists
Open-Web Steel Joists Framing
Metal Roof Decking
Light-gauge roof framing
Keyman
7.0 Moisture and Thermal Protection
Sheet Metal Roofing
Corrugate Metal Roofing
Metal Cladding
Joint Sealant
Expansion Joists
Jonathan
Keyman
8.0 Doors and Windows
Doors and Doorways
Door Operation
Window Elements
Window Operation
Jonathan
Keyman
9.0 Complete System Case Study:
OS House – NOLASTER
All
10.0 Individual Case Study
Case Study 1:
11 Boxes – Keiji Ashizawa Design
Case Study 2:
Big Dig House - Single Speed Design
Case Study 3:
Case Study 4:
Case Study 5:
Daniel
Saidu
Jonathan
Keyman
Shing Yie
Taraneh
Case Study 6:
1.4 Limitations
1.4.1 Case study or research is not in Malaysia. No on-site research is
done and research is highly based on information documented
by authors or reviewers and publishers.
1.4.2 Most books and online information did not possess full drawings
for referencing.
1.5 Assumptions
1.5.1 Due to the lack of some illustrations of detailed joinery
information of particular case studies, precise assumptions are
made based on written text information.
1.5.2 Converting written text information into illustrations are not as
detailed because for example; if connections between a joinery
is written as ‘welded’ or ‘bolted’ then illustrations drawn would be
based on general building construction methods. E.g.: Solution
for written text ‘bolted corner joints’ would be a L-shaped bolt
connection (unless specified in detail).
2.0 STEEL FRAMING SYSTEMS GENERAL INFORMATION
2.1 History of Steel
Steel has been used for more than 150 years in shaping the built
environment. Although the idea of steel conjures up images of a heavy or
cumbersome material, the steel used in residential construction is quite the
opposite. Cold-formed steel (CFS) is lightweight, easy to handle, cost
effective, and a high quality alternative to traditional residential framing
materials. CFS offers the builder a strong, dimensionally stable, easy-to-work
framing system whose use can be traced back to 1850.
In the late 1920s and early 1930s cold-formed steel entered the building
construction arena with products manufactured by a handful of fabricators.
Although these products were successful in performance, they faced
difficulties with acceptance for two reasons: (1) there was no standard design
methodology available, and (2) cold-formed steel was not included in the
building codes at that time. Many of the CFS applications were unable to be
used due to the lack of design methodology and product recognition.
Steel framing is a practical, code approved solution to many of the limitations
that builders face today when using traditional building materials.
The strength and ductility of structural cold-formed steel (CFS) framing, along
with the holding power of CFS connections, make it the ideal material for
construction in high wind speed and seismic zones such as the U. S. eastern
seaboard, the Gulf Coast states, California and Hawaii. Characteristics such
as non-combustibility, termite resistance, and dimensional stability can lower
construction and home ownership costs. CFS can provide the framework for a
solid sustainable building program. Each piece of CFS shipped to the jobsite
contains a minimum of 25% recycled content and is 100% recyclable at the
end of its lifespan. And a recent study, conducted by the NAHB Research
Center, showed that the zinc coating on steel framing materials can protect
against corrosion for hundreds of years.
For these reasons, and many others, the use of steel framing continues to
grow every year with more than 40% of commercial structures now using steel
framing and with nearly 500,000 homes built with steel framing over the past
decade.
2.2 Growth in Popularity
Between 1979 and 1992 the number of steel-framed homes saw a substantial
increase. Cold-formed steel framing was used in 5% of housing starts in the
U.S. in 1993. This percentage increased to 8% in 2000 and had reached 12%
in 2005. The emphasis has been on single-family homes in the Sunbelt and
on multi-family homes in the north. The popularity of steel framing in the
Sunbelt is expected to continue to increase rapidly because of the concern
over termites, decay, and high winds. Urban areas and fire hazard districts
are also expected to show a growing interest in steel framing.
According to the Washington DC-based Steel Framing Alliance there is no
national system http://www.steelframingalliance.com) in place to track the use
of steel framing in homes accurately. However, the Alliance estimates that
steel was being used in 3 to 6 percent of the housing starts in the S in 1999.
In Florida, however, every building built must have an Energy Code
Compliance Form prepared and submitted when applying for a permit.
Included in this form is a description of the exterior all configurations including
the type of building system. Presented below is a summary of the mix of
building systems used in Florida in 2000 and 2001. Based on a random
sample of over 1,600 single-family detached homes, less than 1% of the
homes built in the Central climatic zone employed steel framing.
2.3 Environmentally Friendly
The Steel Framing Alliance claims that cold-formed steel framing is an
environmentally friendly building system because:
• Steel is recyclable, using old cars, buildings, bridges, steel cans, etc.
• Steel is the world’s most versatile material to recycle.
• Yearly, steelmakers recycle about 500 million tons of steel world-
wide.
• It takes at least 60% less energy to produce steel from scrap than it
does from iron ore.
• It takes about 6 old cars to produce enough steel to frame a basic
residential dwelling.
2.4 Easy on Land Fills
In addition to being environmentally friendly, steel framing results in a
reduction in construction waste that would normally end up in a land fill:
• The average landfill consists of approximately 60% construction
debris – mostly concrete, wood, and plastic.
• Every ton of steel recycled conserves 2,500 pounds of iron ore, 1,400
pounds of coal, and 120 pounds of limestone.
• Less than 6% of landfill is steel - such as staples, nails in wood and
steel rebar inside chunks of concrete.
• Debris from a typical wood-framed home accounts for 50 ft3 of landfill
waste, compared to only 2 ft3 from a steel-framed house
2.5 Advantages of Steel Framing
• Consistent Material Quality
• Non-Combustible Material
• Dimensionally Stable in any Climate
• Insect Resistance and steel will not rot
• Engineering not required for common home designs
2.6 Manufacturing Process
Cold-formed steel products begin as a very large coil of steel. These
coils may weight up to 13 tons.
After the hot coil has been rolled to the desired thickness and after it
has cooled, the ribbon of steel passes through a series of rollers to
form the desired products:
However, the basic cold-formed C-shape is by far the most common
component.
2.7 Steel Studs and Joists
Structural cold-formed steel studs are produced with a 1-5/8” flange and ½”
return lips using a 33-97 mil thickness steel covered with a G60 galvanized
coating.
Non-structural cold-formed steel studs are not intended to carry loads. They
typically are produced with 1.25” flanges and ¼” return lips using steel with a
33 mil thickness-or-less and a G40 galvanized coating.
Floor joists are produced the same as the structural studs but their webs
range from 6”, 8”, 10”, or 12”.
2.8 Specification
A universal designator system, similar to a grade stamp used for lumber
products, is typically used to identify each steel component produced. The
designator for at 5-1/2”, 16-gauge, C-shape stud with 1-5/8” flanges and 54-
mil galvanized coating would appear as: 550S162-54. The elements of the
designator are described in the diagram below.
The product specification is imprinted on members produced at intervals of
48” much like the grade stamp applied to lumber products. The label typically
includes:
• Manufacturer’s identification or logo
• Minimum uncoated steel thickness
• Minimum yield strength
• Coating designation if other than minimum
2.9 Steel and Fire
Steel is non-combustible, will not support flame, and does not generate
smoke. However, steel looses strength at high temperatures and should be
protected from excessive temperatures in accordance with code requirements
(e.g., gypsum wallboard or other approved material).
2.10 Price Stability
Price and stability of supply have driven many builders to adopt residential
steel framing.While the price of steel has remained relatively stable since the
1980s and continuing through 2003, teel mill product prices jumped about
50% in 2004. In 2005, steel prices declined about 12% and then climbed
nearly 30%. (See figure below) Such volatility in pricing makes it very difficult
for estimators to predict prices more than a couple weeks ahead, let alone
months ahead. As a result, the market penetration of cold-formed steel has
slowed significantly. In addition to steel fluctuating, concrete prices have risen
15%; asphalt has increased 14%; and lumber has increased 7% during the
same period. (Source: Department of Labor, Bureau of Labor Statistics,
www.bls.gov).
According to the NAHB Research Center’s Toolbase Services (See:
www.toolbase.org), at current steel prices, the steel framing materials
required to frame a typical house (average 2,150 sq. ft.) will be less expensive
than the wood framing materials required to frame the same house when the
“Random Lengths Composite Index” is ~$350 or higher for lumber. However,
if the builder, framing contractor or other subcontractor is new to steel, then
labor costs could account for a $1.00 – $2.50 per square foot premium for
steel framing. Historically speaking, steel material prices have remained flat,
while wood material prices have fluctuated greatly. The steel industry
continues to improve the processes by which steel homes are built, bringing
hard construction costs down to a minimum, so that builders will be able to
enjoy a competitive and stable framing package price.
2.11 Cold-formed steel framing
Cold-formed steel framing is sheet steel that is formed into shapes and sizes
that are similar to what builders are accustomed to seeing in dimensional
lumber (2x4, 2x6, 2x8, 2x10, 2x12, and so forth). Steel framing members are
formed in a process called roll forming by passing sheet steel through a series
of rollers to form the bends that make the shape, e.g. the web, flanges, and
lips of a stud or C-shape. Because this process is done without heat (also
called “cold forming”) the studs and joists are made stronger than the original
sheet steel.
2.12 Considerations when Building with Cold-formed Steel Framing
Steel framing can lower construction costs.
• Warranty call-backs are minimized because steel does not shrink, split, or
warp. As a result, there are no nail pops or drywall cracks to fix after the
structure is completed.
• Consistent quality means that scrap is drastically reduced (2% for steel
versus 20% for wood). These savings also translate into lower costs for
jobsite culling of wood materials and haul off and disposal of discarded
material.
• Discounts on builders risk insurance for steel framed structures can result in
significant cost savings for builders.
Steel framing is easier to handle because steel studs weigh 1/3less than
wood studs, and can be installed at 24” on center.
Steel framing offers marketing advantages because consumers recognize
steel as a superior framing product for its fundamental characteristics:
• Long term maintenance costs are reduced because steel is resistant to rot,
mold, termite and insect infestation.
• Good indoor air quality (IAQ) is promoted because steel does not emit
volatile organic compounds (VOCs).
• Steel is “Green” because it contains a minimum of 25% recycled steel and is
100% recyclable.
• Steel framing has proven performance in high wind and seismic zones.
The non-combustibility of steel allows a significant density increase in
commercial and multi-family structures, offering building owners with the
potential for higher revenue.
2.13 Cold-formed Steel Framing Cost and Type
The method of construction, stick framing or panelization, and type of project
will have a direct bearing on the cost of the steel frame system.
2.13.1 Stick Framing
“Stick framing” is the method most commonly used to build wood
framed homes today, and involves assembling the floors and walls
using individual studs and joists on the construction site. This method
often requires extensive cutting of individual framing members, and
requires a fairly high level of skill of framers who must know how to
assemble the elements within the house.
Framing and trusses represent approximately 20% of the total cost of
the house construction. If the conventional “stick framing” method of
construction is used, steel framing can add 3% to the total cost of a
house. When only the framing system is considered, studies have
shown that a stick-framed steel system can cost 15% more than wood
framing. However there are a number of savings that builders realize
when they use steel framing1, including;
• Warranty callbacks associated with the seasonal movement of
framing members are virtually eliminated
• Save on waste haul off
• Insurance savings
• Site culling of wood framing
2.13.2 Panelization
Panelization, or assembling the components of the house (walls, floors,
roofs) in a controlled manufacturing environment, is increasingly being
used in home building today.
Steel framing is particularly suited for panelization because it is
precision manufactured to meet exacting tolerances, and its light
weight allows for easier handling of assembled components. Panels
are typically shipped unsheathed which, when combined with the light
weight of cold-formed steel, allows CFS fabricators to service a large
distribution area. The capability of delivering product to a large market
allows fabricators to recognize economies of scale that keep CFS
panel costs in check.
The component (panels) approach will speed construction and reduce
the number of skilled framers that are required on site. As a result,
steel framing can cost the same or less than wood framing in many
parts of the country.
2.14 Benefits of Steel
There are benefits for both the builder and the homeowner associated with
steel. From the builder’s perspective it is important that steel will not rot, twist,
warp, swell, or split and it is non-combustible. Steel framing is a proven
technology that is considered to be user friendly and offers an easy transition
from other materials. Competitive pricing and consistent quality are clearly
important benefits to builders. The strength of steel usually translates into
fewer members and many of those members are as much as 60% lighter than
the corresponding wood members. Nationally, cold-formed steel members
have come to be produced in a variety of standard pre-cut shapes and sizes.
Standardized patterns for pre-punched holes for running electrical wiring and
plumbing lines help to minimize preparation work for tradesmen. This
standardization serves to minimize construction waste. The finished steel
framing accommodates all types of commonly used finish materials.
Homeowners reap many of the same benefits. In addition, homes can be
designed to meet the highest seismic and wind load specifications in any part
of the country. Because steel framed homes can be so resistant to natural
forces, some homeowners save as much as 30% on their homeowner’s
insurance. Steel framing does not need to be treated to resist termites and is
free of resin adhesives and other chemicals used to treat wood. Because of
its strength, steel can span greater distances offering the homeowner larger
open spaces and greater design flexibility. Remodeling is also easily
accomplished by removing, altering, and relocating non-load-bearing walls.
2.15 Environmentally Sensitive
All steel products are recyclable! The overall recycling rate for steel products
in the US is 60%. In steel building products, the minimum recycled content is
25%. This recycling is accomplished with no degradation in product quality or
loss of properties. A contributing factor in the steel industry’s ability to achieve
significant recycling is that magnetic separation is the easiest and most
economical method of removing steel from the solid waste stream. The
amount of energy needed to produce a ton of steel has been reduced by 34%
since 1972.
2.15 Steel Framing Components
The steel component known as the structural “C” is the predominant shape for
framing floors, walls, and roofs. The primary difference from one use to
another is the thickness of the steel and the depth of the member.
Floors – Builders commonly opt for steel floor joists ranging in depth from 6-
to 12-inches and steel thickness from 0.034- to 0.101-inches. Instead of using
overlapped joists at a center support, a single length of steel joist is commonly
used to span continuously.
Walls – There are two basic types of studs:
• Structural “C” studs for interior and exterior load-bearing walls that
range in depth from 2½” to 8” to accommodate the necessary
insulation thickness and ranging in thickness from 0.034- to 0.071-
inches depending on the anticipated load.
• Drywall studs for non-load-bearing partitions that range in depth from
1⅝- to 6-inches and metal thickness ranging from 0.01- to 0.034-
inches.
The thermal efficiency of the steel-framed exterior walls may be
increased by installing insulation board on the exterior of the wall.
Roofs – The broad range of available sizes and thicknesses allow steel
framing to be used in virtually any roof system. Steel trusses can be built on-
site or off-site in truss fabrication plants.
2.16 Framing Methods
There are three basic residential steel framing methods: stick-built, panelized,
and pre-engineered.
• Stick-built - Replace wood members with steel members (one-for-one
replacement). As shown below, the steel-framed non-load-bearing wall
appears very similar to that of a comparable wood-framed wall.
• Panelized - Factory-assembled panels delivered to site and connected
together. The panelized approach represents an efficient approach for
repetitive building designs and, as a result, is a popular approach in
hotel/motel construction and other multi-unit applications.
• Engineered - Location and placement of framing members is engineered to
take advantage of steel’s properties. Spacing of framing members may
increase to as much as 8-feet with orizontal stabilizers.
2.17 Barriers to Steel Framing
Five key barriers to the expansion of residential steel framing have been
identified.
• Cost of Construction - To have wide spread markets, the steel industry has
to make cold-formed steel framing economically competitive. It is not now
competitive because it costs more in labor to frame a house out of steel. All of
the workers have tools and accessories that were optimized for wood
construction, not steel. The steel industry is committed to taking away this
barrier by doing their own product development, causing product development
to happen, or funding product development as necessary to bring these things
for steel framing
at the same price.
• Distribution Infrastructure - Buying 800 wooden studs from a lumberyard
is routine. Steel framing has achieved that status in most markets. One of the
reasons is that the industry did not have the material distribution system in
place to provide the necessary supply quantities.
• Standardized Product - Another barrier was that there were no
standardized products. There were 73 steel manufactures in the nation, and
all of them previously made basically identical shapes, called them all different
names, published different section properties, and published different load
tables. The industry has now standardized these products. • Consumer
Preference - The last barrier is consumer preference. What the industry did
was turn the standard profiles into standard section properties with standard
load tables and then into prescriptive methods. Houses in about 80% of the
country are designed by purely prescriptive methods, no engineering is
required. The other 20% are a combination of prescriptive and engineering.
Steel framed structures originally had to be completely engineered and that
costs three to six weeks and $0.70 to $2.00 a square foot. The prescriptive
tables have solved the problem and may be found in the International
Residential Code (IRC).
Even though the steel products were standardized, the whole world doesn’t
know what they are. Nearly everyone knows what a 2x4 is; not everyone
knows what a C-section steel stud is designated with the designation:
“550S162-54”. As a result software has been developed and is available for
building designers. If you can do a takeoff with wood, then this software will
turn it into a steel takeoff and produce the order sheets and the sheets for the
job site.
• Thermal Performance - Steel studs are excellent conductors of heat. They
conduct heat better than wood. Because of this characteristic, the steel
industry has had to take remedial action such as adding foam board on the
outside of the exterior wall framing. As long as builders have to take this step,
it may solve the thermal problem, but it costs something. It costs $0.65 a
square foot or more to make steel houses as energy efficient as wood framed
houses. This added insulation is a major cost barrier that will have to be
resolved for steel to become a serious competitor for wood. Framer training is
a major issue that the steel industry is attacking on two fronts. It is very simple
to frame a house out of steel. The problem is you have to use different tools;
you have to cut it a little differently; you have to know what you are looking at;
and you have to screw it together. Using screws is a giant pain for carpenters
compared to nailing it together. All of the differences conspire to cause a
framer not to have a big incentive to try steel framing. Even if they like the
idea, they don’t have the time or can’t afford to take the time. Therefore the
steel industry developed a national training curriculum. It’s a huge impressive
document that has been widely acclaimed everywhere that it was introduced.
The training arterials are getting into junior colleges and vo-tech schools by
the thousands. The goal is to grow a generation of framers that will be ready
to use this product as the other elements come together. The industry is
working with the NAHB and NAHB Research Center to come up with a way to
rain existing framers that makes it worthwhile for them.
2.18 The Design Process Work
Comprehensive provisions for steel framing are found in the International
Code Council’s (ICC) International Building Code (IBC) and International
Residential Code (IRC), which are recognized as the governing building
codes by most building departments in the United States. (See Resources for
the ICC website that provides an overview of code adoption across the United
States.) The building codes also reference a series of Standards that have
been developed by the American Iron & Steel Institute (AISI) to provide
additional information for the design of steel structures. (See Standards for
Cold-Formed Steel Framing table.)
2.19 Residential Conventional Construction
Builders can design one- and two-story structures without the support of an
engineer by using the American Iron and Steel Institute’s Prescriptive Method,
one of the AISI standards referenced by the building codes. The Prescriptive
Method provides load and span tables, fastener requirements, etc. in a
“cookbook” format similar to what is available for wood framing design. The
Prescriptive Method and other design standards can be purchased from the
Online Store on the Steel Framing Alliance’s website (www.steelframing.org).
Should the structure go beyond simple design or the applicability limits of the
Prescriptive Method, a qualified engineer will be needed to develop or
complete the structural design. This is also true for certain states, like
California, as well as other jurisdictions, where prescriptive design is not
allowed. Fortunately, the number of professional engineers who have
experience with steel framing has grown exponentially over the last decade
and the Cold-Formed Steel Engineers Institute (CFSEI) has an on-line
member database (www.cfsei.org).
2.20 Pre-fabricated Systems
Walls, floor panels and roof trusses of CFS that are built in a factory will
require engineered drawings and layouts for building code approval, just like
any other pre-manufactured structural component. Panel and truss
manufacturers are staffed to provide engineered designs, based on the
builder’s architectural drawings, along with the components and jobsite
delivery. Some manufacturers can offer a “turn-key” solution to builders with
the inclusion of product installation by trained crews.
Non-residential Construction
Commercial designs will require
an engineer’s review and seal
regardless of material of
construction.
2.21 The Plan Check and Building Inspection Process Work
One of the first steps in implementing any project should be a conversation
with the local building department. This is the best way to uncover the
particulars that relate to your project and building code jurisdiction.
The plan check process is similar to what is encountered for other structural
systems:
1. The reviewer will verify that all specifications are accurate and that they
match local code requirements.
2. Architectural drawings are checked to ensure that wall types are correctly
marked, fire-rated assemblies, if required are shown, details are provided
for key connections, and mechanical, electrical and plumbing drawings are
coordinated with the structural drawings.
3. Structural drawings will be reviewed for consistency with the architectural
drawings, and to ensure that specific system detailing for items like
components and trusses, are provided.
Progress inspections by the building department are required at the same
stages of completion as structures built with any other building materials.
The Steel Framing Alliance (SFA) has provided training to thousands of
building plan reviewers and inspectors across the United States. Training
seminars for state and municipal building departments, builders, and trades
persons, as well as, vocational/technical school curriculum development are
some of the on-going activities sponsored by the SFA.
2.22 Order Steel Framing
The process for ordering steel framing materials will differ greatly according to
the type of construction method that will be used.
2.22.1 Conventional Framing
Although some large builders order steel directly from the stud
manufacturers, cold-formed steel is typically supplied by a regional
distributor. Steel distributors include traditional lumber yards and
gypsum board supply warehouses. The SFA’s membership includes
some of the major manufacturers of cold-formed steel in North America
which can be identified through the Member Directory found on the
SFA website (www.steelframing.org). Many manufacturers will provide
a link to distributors and a technical service contact on their website.
Please visit the Steel Stud Manufacturer’s Association website for
further information (www.ssma.com).
In addition, manufacturers of proprietary products (which often consist
of non-generic steel shapes) will work directly with the builder to
develop a framing package. Specifying:
When ordering steel framing materials, it’s important to be aware of the
variety and applications of the various shapes, encapsulated by the
acronym STUFL.
These letters stand for Stud, Track, U channel, Furring, and L-
header, pictured at the bottom of the page.
1. A stud includes wall studs, joists and rafters because they are
all of the same shape.
2. Track is the top and bottom “plates” of a steel wall or the rim of
floors and rafters.
3. U-channel can be used for bridging, blocking and customized
for cabinet backing.
4. Furring channel is used as purlins, bridging, backing, and for
subassembly sound separation.
5. L-headers are brake-metal shaped members that can be
doubled and used as headers.
Cold-formed steel is specified by a universal designator system called
out by web dimension, shape, flange dimension and thickness. Web
and flange sizes are expressed in 1/100ths of an inch and thickness is
expressed in 1/1000ths of an inch, or “mils”.
2.22.2 Material Cut Lists:
Distributors may not be staffed to develop cut lists or provide quantity
take offs for steel framed jobs. Details on how to raise material cut lists
can be found in the SFA’s National Training Curriculum and in Steel
Framed House Construction, a publication of the Craftsman Book
Company.
2.22.3 Pre-fabricated System Suppliers
Some builders have found that ordering factory fabricated steel wall
panels and trusses is an ideal way to move into steel framing because
it minimizes the need for highly skilled framers on site and provides
access to experienced design and layout professionals. Typically, the
builder simply provides the panel or system manufacturer with
architectural drawings and they do the rest. There are numerous CFS
panel manufacturers across the country that can be located by using
SFA’s online Member Directory (www.steelframing.org).
2.23 Differences in construction details between CFS and wood?
• Steel framing is usually spaced at
24” O.C. and wood framing is
typically spaced at 16” O.C.
• C section studs replace wood
studs and single tracks replace
top and bottom wood plates.
• Studs are connected to track
flanges with screws, or pins,
installed through the face of the
track flange into the stud flange.
Three threads or 3/8” of the
screw should be visible on the
back side of the connection.
• Headers are built up from multiple steel members just like with wood,
or by using time saving L-headers.
• Layouts proceed just as they
do with wood frame
construction. Installation is
typically handled by building a
wall section on the deck and
later raising it.
• With panelized construction
many of these steps are
eliminated, reducing the
framing responsibility to
positioning and fastening the
pre-assembled components.
• In most residential applications, plywood or OSB is used for floor, wall and
roof sheathing, just as in a wood framed house. Sheathing is attached to steel
framing using pins shot from a pneumatic gun at a cost and rate of speed
similar to the tools used for wood construction.
• Backing the frame for cabinet
installation requires some
customization with C-shaped
stud, steel strap, track, or there are a handful of proprietary products that can
be used.
• The only major differences in
building with steel framing are
in-line framing techniques, the
tools, fasteners and
accessories used, and the
need for foam insulation on
the exterior side of the wall
studs in some geographic
regions.
• In addition, MEP trades will see minor differences in how they install wiring
and plumbing (see MEP Trades section 8 for more detail).
2.24 Affected Trades
Framers
Experienced framers will find it
relatively easy to transition to
steel framing. They understand
floor plans and elevations and
can covert these to floor and wall
layouts. With assistance and
training, experienced carpenters
adapt to CFS very quickly. However, there is a learning curve associated with
new tools and fasteners.
Basic steel framing tools are a screw gun (adjustable torque, 0-2500 rpm),
bits and bit holders for structural steel to steel connections, chop saw,
pneumatic pin nailer for steel to steel connections and sheathing to steel
connections, clamps, aviation snips, swivel head electric shear, and a
magnetic level.
New, faster and more efficient tools are coming onto the market all the time.
Please follow the manufacturer’s specifications for products and applications.
The Steel Framing Alliance website is a good source of contact information for
tool and fastener manufacturers.
Mechanical / Electrical / Plumbing
MEP (mechanical, electrical and plumbing) trades can be retrained rather
quickly for cold-formed steel installations.
For the plumber and
electrician, routing
wire and pipes
through steel walls
may prove simpler
than what they’re
used to with wood
frames, as the studs
come pre-punched
with holes along the
stud and joist length.
Plastic grommets, installed by the trades, snap in place through the punch-out
openings. The grommets protect wire and PEX from the sharp steel edges or
provide corrosion protection for copper. Duct, pipe, and wire supports will be
fastened to the framing with screws and accessories that are widely available.
The allowable electrical wiring methods referenced in Table 3701.2of the
International Residential Code include non-metallic sheathed cable, also
known as “Romex”, which can be used in steel framing. The code also covers
grounding.
Fasteners
The key to fastener selection with steel framing is to keep it simple. Basically
there are three head and two point styles.
Hex, pan and bugle head screws will easily address almost all applications.
• Hex heads are used where they won’t be covered by another material like
drywall or sheathing.
• Pan heads are typically used in areas where drywall or sheathing will be
applied.
• Bugle heads are designed to countersink into the material they are driven
into, so are ideal for installing drywall.
There are two types of screw points to choose from, self
piercing when working with thinner material (like interior
drywall studs), and self-drilling when penetrating into the
thicker structural steel studs.
Other Types of Fasteners
Other cold-formed steel connection techniques exist and many are code
approved.
Pneumatically-driven fasteners, powder-actuated fasteners, crimping and
riveting have all been developed for steel-to-steel and sheathing-to-steel
connections. Review the application with a manufacturer’s representative and
local code officials before implementing usage of alternative fasteners.
Sheathing and drywall may be attached to steel frames with pneumatically-
driven nails. These nails are specifically designed with spiral grooves or knurls
on the nail shaft to penetrate the steel and, like automatic nail delivery in
wood framing, are applied with air guns.
2.3 References
Books
Steel-Frame House Construction - Timothy J. Waite Commercial Metal Stud Framing - Ray Clark Residential Steel Framing Handbook - Robert Scharff Advanced Analysis and Design of Steel Frames - Gou-Qiang Li, Jin-Jin Li Metal Building Systems: Design and Specifications - Alexander Newman Graphic Guide to Frame Construction (For Pros By Pros) - Rob Thallon
Internet
http://www.steelconstruction.org/resources/commercial/forecasts-and- statistics.html
http://www.constructionweblinks.com/Industry_Topics/Statistics/statistics.html http://www.steel.org/ http://www.worldsteel.org/ http://www.steelframingsystems.com.au http://www.ibscentre.com.my http://en.wikipedia.org/wiki/Steel_frame http://www.primaryframes.com/ http://www.scottsdalesteelframes.com/ http://www.steelframe.co.za/
2.0 FOUNDATION SYSTEMS
2.1 Introduction
The first step in the building erection process is constructing a suitable
foundation that will bear the weight of metal building. There are a couple of
different foundation layouts you can choose from, depending on whether or
not you are going to have a complete concrete slab floor in your metal
building.
The type of foundation system
selected depends on:
soils
loads
structural system
2.1 Definition
2.1.1 Deep foundation:
Deep foundations are structural assemblies that transfer load down
through weak soil strata and into deeper and stronger strata to
minimize the settlement of a structure. Caltrans deep foundations
consist of a single pile or a group of piles with a pile cap.
These deep foundation piles can be driven, drilled, cast-in-place, or
alternatively grouted-in-place.
.
Pile driving operations in, Florida, US
Deep foundation installation for a bridge in US
A deep foundation distinguished from shallow foundations by the depth
they are embedded into the ground.
The common reasons to choose a deep foundation over a shallow
foundation, are very large design loads, a poor soil at shallow depth, or
site constraints (like property lines).
Deep foundations can be made out of timber, steel, reinforced concrete
and prestressed concrete
There are different terms used to describe different types of deep
foundations including:
the pile (which is analogous to a pole)
the pier (which is analogous to a column
drilled shafts
caissons
2.2 What is the right foundation for steel frame structure?
On clay soil Pile foundation or Pier foundation depending on the SBC (Safe
Bearing Capacity) of the clay soil. when the building gets heavy, you start to
use steel. For heavy building, you would use piles. And all piles must go all
the way to bedrock, no matter what type of soil.
.
2.3 Type of Foundation used for steel frame structure
2.3.1 Pile
2.3.1.1 Steel HP Piles
Steel HP sections are usually specified when hard driving is anticipated
such as where displacement piles cannot penetrate difficult soil layers
containing rock, cobbles, gravel, and dense sand. Steel sections are
also preferable for longer piles because they are more easily spliced
than precast prestressed options. Steel HP piles may not be feasible
where highly corrosive soils and/or waters are encountered or where
large lateral load resistance is required.
If steel HP piles are allowed as an alternative to a Class pile, the
Structure Designer shall provide allowable HP sizes to the
Specification Engineer. The HP 360x132 steel pile is usually specified
for 900 kN, HP 250x85 for 625 kN and HP 250x62 for 400 kN. The
design engineer should note in the Memo to Specification Engineer
when other steel sections are acceptable for substitution, and verify
with Estimating that a nonstandard HP section is available. Larger pile
sections may be required if increased lateral load resistance is needed
or hard driving is anticipated. Refer to BDS 4.5.6.5.1 for the assumed
lateral pile resistance values under Service Loading. Pile anchors must
be designed for the pile’s design load in tension. In the case of
compressiononly piles, a nominal anchor is required. Anchor bars
should be epoxy-coated.
2.3.1.2 Cast-in-Steel-Shell (CISS) Concrete Piles and Steel Pipe
Piles
Cast-in-steel-shell concrete piles are driven pipe piles that are filled
with cast-in-place reinforced concrete no deeper than the shell tip
elevation. CISS piles provide excellent lateral resistance and are a
good option under the following conditions: 1) where poor soil
conditions exist, such as soft bay mud deposits or loose sands; 2) if
liquefaction or scour potential exists that will cause long unsupported
pile lengths; or 3) if large lateral soil movements or flows are
anticipated from a seismic event.
If composite action is required for flexural capacity, the design engineer
must assure that a reliable shear transfer mechanism exists. Welded
studs or shear rings may be required, especially for large diameter
piles. CISS piles and steel pipe piles can be driven open ended or
closed ended. Caution should be exercised when requiring closed end
pipe piles to penetrate very dense granular soils, very hard cohesive
soils or soft rock. Generally, pipe piles up to 400 mm in diameter tend
to plug during driving while diameters 600 mm and greater tend not to
plug. Once plugged, an open-ended pipe behaves like a displacement
pile and driving becomes more difficult. When faced with excessive
blow counts or high driving stresses, DSF may recommend center
relief drilling to achieve the specified tip elevation. When appropriate,
DSF will perform a driveability analysis and recommend a pile wall
thickness suitable for the expected driving stresses. The soil plug is left
intact at the tip of open-ended CISS piles so that the pile is not
undermined during cleaning out. A plug two diameters in length can
usually maintain water control, but a seal course may be required for
some combinations of high water level and permeable soils.
2.3.1.3 Micropiles
Micropiles, also called mini piles, are often used for underpinning. They
are also used to create foundations for a variety of project types,
including highway, bridge and transmission tower projects. They are
especially useful at sites with difficult or restricted access, or with
environmental sensitivity. Micropiles are normally made of steel with
diameters of 60 to 200 mm. Installation of micropiles can be achieved
using drilling, impact driving, jacking, vibrating or screwing machinery.
2.3.1.4 Sheet piles
Sheet piling is a form of driven piling using thin interlocking sheets of
steel to obtain a continuous barrier in the ground. The main application
of sheet piles is in retaining walls and cofferdams erected to enable
permanent works to proceed. Normally, vibrating hammer, t-crane and
crawle drilling are used to establish sheet piles.
2.3.1.5 Soldier piles
A soldier pile wall using reclaimed railway sleepers as lagging.
Soldier piles, also known as king piles or Berlin walls, are constructed
of wide flange steel H sections spaced about 2 to 3 m apart and are
driven prior to excavation. As the excavation proceeds, horizontal
timber sheeting (lagging) is inserted behind the H pile flanges.
The horizontal earth pressures are concentrated on the soldier piles
because of their relative rigidity compared to the lagging. Soil
movement and subsidence is minimized by maintaining the lagging in
firm contact with the soil.
Soldier piles are most suitable in conditions where well constructed
walls will not result in subsidence such as over-consolidated clays,
soils above the water table if they have some cohesion, and free
draining soils which can be effectively dewatered, like sands.
Unsuitable soils include soft clays and weak running soils that allow
large movements such as loose sands. It is also not possible to extend
the wall beyond the bottom of the excavation and dewatering is often
required.
2.3.1.6 Steel Suction Piles
Suction piles are used underwater to secure floating platforms. Tubular
piles are driven into the seabed (or more commonly dropped a few
metres into a soft seabed) and then a pump sucks water out at the top
of the tubular, pulling the pile further down.
The proportions of the pile (diameter to height) are dependent upon the
soil type: Sand is difficult to penetrate but provides good holding
capacity, so the height may be as short as half the diameter; Clays and
muds are easy to penetrate but provide poor holding capacity, so the
height may be as much as eight times the diameter. The open nature
of gravel means that water would flow through the ground during
installation, causing 'piping' flow (where water boils up through weaker
paths through the soil). Therefore suction piles cannot be used in
gravel seabeds.
2.3.1.7 Caltran
Caltrans typically includes a corrosion allowance (sacrificial metal loss)
for steel pile foundations. Other corrosion mitigation measures may
include coatings and/or cathodic protection. Caltrans currently uses the
following corrosion rates for steel piling exposed to corrosive soil and
water:
Soil Embedded Zone: 0.025 mm per year
Immersed Zone (salt water): 0.100 mm per year
Scour Zone (salt water): 0.125 mm per year
Splash Zone (salt water): 0.150 mm per year
For steel piling driven into undisturbed soil, the region of greatest
concern for corrosion is the portion of the pile from the bottom of the
pile cap or footing down to 1 meter below the water table. This region
of the soil typically has a replenishible source of oxygen needed to
sustain corrosion.
The corrosion loss should be doubled for steel H-piling since there are
two surfaces on either side of the web and flanges that are exposed to
the corrosive soil and/or water. For pipe piles, shells, and casings, the
corrosion allowance is only needed for the exterior surface of the pile.
The interior surface of the pile (soil plug side) will not be exposed to
sufficient oxygen to support significant corrosion.
2.3.1.8 Alternative Piles
The Alternative Pile option is an attempt to take advantage of new pile
types that can be used, where appropriate, as alternatives to a State-
designed pile. A number of proprietary systems have been approved,
including variations on micropiles and grout injection piles. To be
approved, each vendor’s pile system must go through an extensive
review process, including both analysis and full-scale load testing to
geotechnical failure.
The design engineer should consult with DSF when a site appears
favorable for an Alternative Pile. Alternative Pile designs have been
developed in response to site constraints such as low overhead
clearance (2 meters minimum), vibration restrictions, and hard-driving
soils containing large cobbles. High-capacity micropiles can be
successfully installed through an existing pile cap to seismically retrofit
a foundation without increasing its size.
When an Alternative Pile is listed in the specifications, the contractor
has the option to select an Alternative Pile vendor. The contractor is
responsible to prepare pile working drawings and to design the pile to
satisfy the demands shown in the Pile Data Table. The pile vendor is
required to verify the pile’s geotechnical design with a performance test
prior to production installation. Proof testing of the production piles is
also required.
2.3.2 Design of pile cap
2.3.2.1 Pile layout pattern:
Pile under pile cap should be layout symmetrically in both directions.
The column or wall on pile cap should be centered at the geometric
center of the pile cap in order to transferred load evenly to each pile.
Example of pile layout pattern is shown below:
2.3.2.2 Pile spacing, edge distance, and pile cap thickness:
In general, piles should be spacing at 3 times of pile diameter in order
to transfer load effectively to soil. If the spacing is less than 3 times of
diameter, pile group settlement and bearing capacity should be
checked.
Pile cap thickness is normal determined by shear strength. For smaller
pile cap, the thickness is normally governed by deep beam shear. For
large pile cap, the thickness is governed by direct shear. When
Pile
diameter
12” 14” 16” 18” 20” 22” 24”
Pile spacing 3’-0” 3’-6” 4’-0” 4’-6” 5’-0” 5’-6” 6’-0”
necessary, shear reinforcement may be used to reduced thickness pile
cap.
The edge distance is normally governed by punching shear capacity of
corner piles.
2.3.3 Pile Cap Analysis & Design (TGPiles)
Analyzing pile groups is tedious, error prone work, especially for large
numbers of piles. Digital Canal’s Pile Cap Analysis and Design can turn this
task into a simple matter of entering the loads and the pile locations and
pressing “Perform Analysis”. However, Digital Canal’s Pile Cap Analysis &
Design can do more than just analyze the pile group—it can design the cap’s
thickness and reinforcement as well! Check out these specs:
Analyze design pile caps for a column with up to 200 piles.
The column’s loads can include axial loads and biaxial bending moments
for dead, live and wind loads.
The weight of the pile cap is automatically included in the analysis.
Pile group analysis is made using a linear strain model. In the case of wind
loads, moment directionality (positive or negative sign) is accounted for
automatically.
The centroid of the pile group is computed and displayed in the report.
Design the pile cap for shear, flexure and temperature & shrink using ACI
318-95. Shear design includes one way, two way and deep beam shear.
Reinforcement design includes suggested bar size & spacing and material
quantities.
A minimum thickness is input and incremented to satisfy shear
requirements.
Output includes a list of minimum and maximum loads on each pile. If the
user inputted allowable working load for a pile is exceeded, the user is
flagged.
The user is warned if the inputted cap does not have sufficient edge
distance.
The column can be either circular or rectangular.
Units include US Customary and metric.
2.4 Pier Columns
Pier columns are utilized when the presence of rock precludes the use of
conventional drilling equipment. Excavation by hand, blasting, and
mechanical/chemical splitting are some methods used in hard rock. Pier column
excavation is considerably more expensive than conventional auger drilling and
the pay limits must be clearly defined.
.
The main disadvantage of pile and beam foundations is cost. The technique
requires specialist plant and labour; however, the extra expense can be offset
against the rising cost of spoil removal and time savings.
2.5 Pile cages
2.6 Pile cage ready to receive pile cap
2.7 Pile Driving Criteria
The specifications required that a Wave Equation Analysis of Piles (WEAP)
be used to select the pile driving equipment. The WEAP model estimates
hammer performance, driving stresses, and driving resistance for an assumed
hammer configuration, pile type, and soil profile. The acceptability of the
hammer system was based on the successful demonstration that the pile
could be driven to the required capacity or tip elevation without damage to the
pile, within a penetration resistance of 3 to 15 blows per 2.5 cm.
The pile driving resistance criteria estimated from the WEAP analysis was
also used as the initial driving criteria for the installation of the test piles.
Additional WEAP analyses were required for changes in the hammer type,
pile type or size, or for significant variations in the soil profile. It was also
specified that the WEAP analyses be rerun with modifications to the input
parameters to match the results obtained from the dynamic or static load test
results. Modifications to the driving criteria could be made as appropriate,
based on the results of the pile load tests.
Notes:
a. Unit costs include the costs of materials and labor for pile driving only.
Preaugering is not included unless otherwise noted. See table 14 for
preaugering unit costs. Mobilization and/or demobilization costs are not
included.
b. Unit costs include the costs of preaugering.
2.8 Pier Columns
Pier columns are utilized when the presence of rock precludes the use of
conventional drilling equipment. Excavation by hand, blasting, and
mechanical/chemical splitting are some methods used in hard rock.
Pier column excavation is considerably more expensive than conventional
auger drilling and the pay limits must be clearly defined.
2-2- Steel Panel Foundations
Steel Panel Foundations has introduced a steel panel basement foundation
design that enables builders and developers to construct a watertight, finished
basement.
The galvanized steel foundation materials are made from 18-ga. studs for
load-bearing walls. The 16-in. on-center construction is ramset into concrete
footing. It is asphalt-coated for moisture resistance and is adaptable to various
wall configurations, including daylight walls, frost walls, brick ledge walls,
interior walls, and multiple above-ground configurations. The galvanized and
painted steel decking features 26-ga. ribbed construction for increased earth-
bearing load strength.
A membrane prevents hydrostatic wicking and forms a complete seal from the
bottom sill to the outer surface of the exterior decking, the manufacturer
states. A moisture-resistant spray foam adheres to every framing member,
and substrate offers a watertight seal.
innovative steel-panel basement foundation technology that enables builders
and developers to construct watertight foundations – which are ready for
finishing – at a competitive price and in less time than conventional cement
foundations. The Steel Panel Foundations’ system is composed of galvanized
steel studs and tracks fastened to corrugated steel decking that is galvanized,
painted, spray-foam insulated and sealed with a continuous, waterproof
membrane. The result is a superior basement for residential and light
commercial use, which can be customized for any building site and house
plan.
After months of research and development, material improvements and
laboratory testing, Steel Panel Foundations (SPF) announced today that it will
debut a newly enhanced composite panel foundation technology that enables
builders and developers to construct watertight foundations that are ready for
finishing, at a competitive price and in less time than conventional concrete
foundations. This unprecedented system will be on display next week at
METALCON, Oct. 3-5, at the Las Vegas Convention Center in Las Vegas
(Booth #360).
The only foundation technology of its kind, SPF is a professionally
engineered, composite panel foundation system that employs modular
construction, allowing builders and developers to construct watertight
foundations that don't promote mold growth, can protect occupants from
radon exposure and are insulated to keep cold and heat outside the
foundation.
The system's lightweight construction promotes more economical
transportation costs and enables long wall lengths, thus reducing both seams
and on-site labor costs. Further, installing a Steel Panel Foundations system
allows builders to begin construction the same day the foundation walls are
set. There is no waiting for the material to cure to begin framing, and the
below-grade living area is ready for drywall. The SPF system eliminates the
scheduling hassles associated with concrete curing times and coordinating
concrete and foundation contractors.
"Since our initial debut last year at METALCON, we have further enhanced
the technology to give the builder and homeowner even more benefit," said
Sal Scuderi, president of Steel Panel Foundations. "The system is more
environmentally friendly, requires less time to install and is still a competitively
priced alternative to conventional concrete foundations. For the homeowner it
creates a safe, warm and dry environment. And for the builder, it's still an
easy-to-install system that can be set in one day and eliminates costly
callbacks due to wet basements. Since there is no waiting for concrete to
cure, framing can begin immediately, and the below-grade living area is ready
to finish."
Highlights of the new technology include:
-- The panels are made of magnesium oxide (MgO) with a foam core, along
with an exterior panel of MgO, giving the foundation extra protection when
backfilled as well as from insects.
-- Panels are now factory-made, thus eliminating the need for assembly at
the job site, providing precise control of the assembly process improving
product quality and reducing installation time and associated costs.
-- Materials are waterproof and resistant to both impact and ultraviolet
light.
-- While the standard height of the panels is eight, nine or 10 feet,
panels can be made to any size.
-- Because the SPF materials are considered "green" and contain recycled
content, the system is environmentally friendly and can support green
building initiatives.
-- Unlike concrete foundations that can crack, SPF can flex without
cracking, thus keeping out moisture, insects and radon.
The panels are made from 16-gauge, galvanized steel studs for load-bearing
walls and meet all foundation-bearing pressures. The 16-inch on-center
construction is fastened into the concrete footing. It is easily adaptable to
meet various wall configurations, including full load-bearing walls, daylight
walls, frost walls, brick-ledge walls, interior walls and multiple above-ground
configurations. The composite panel deck is 9/16-Inch MgO for increased
diaphragm and transverse load-bearing strength.
About Steel Panel Foundations, LLC
Steel Panel Foundations, LLC was founded to develop innovative building
products and related building material and services that are economical,
strong, dependable, energy-efficient and environmentally friendly. Utilizing
proven technology and a patented design, Steel Panel Foundations' break-
through foundation system is a complete, end-to-end structural foundation
system for superior value, durability and strength.
Sixteen-Gauge Steel Studs and MgO Decking: an Impenetrable Union of
Strength and Flexibility: The heart of a SPF composite foundation system is
its framework of galvanized-steel studs and tracks. It's the ideal structural
support for our innovative magnesium-oxide (MgO) composite wall: two
panels fused to each side of an insulating, waterproof extruded-polystyrene
core. With a higher compressive strength than concrete, this International
Code Council-approved MgO panel is waterproof, nonconductive, and impact-
resistant and also resists insects and backfill damage. The end result is a dry,
living-room-quality area that is suitable for multiple uses-a ready-for-drywall
structure that can be customized for any building site and house plan.
2-3- Pole Foundation System
Light poles are structures designed to support single or multiple luminaire
configurations. First and foremost a light pole is an engineered structure—
sufficiently strong to withstand the physical forces of the application, capable
of providing a long, relatively maintenance-free service life and pleasing in
appearance. Their primary function is to resist the combinations of luminaire
weight, ice and wind forces which poles may encounter over their expected
life. Along with the foundation system, the primary force a pole must withstand
is from wind. The variety of pole shapes, heights, sizes and quantity of
luminaires to be supported necessitate the completion of an engineering
analysis to ensure suitable strength to safely accommodate various loads.
Due to unforeseen loadings and wind events which may occur, it is advisable
to select a pole with ample capacity.
Reference:
http://www.fhwa.dot.gov/publications/research/infrastructure/geotechnical/
05159/05159.pdf
http://www.metal-steel-buildings.com/building-assembly.html
http://www.cooperindustries.com/content/dam/public/lighting/resources/
library/literature/Pole-WhitePaper_Invue.pdf
http://en.wikipedia.org/wiki/Deep_foundation
http://www.metalbuilding.com/article_lookup.html?articleid=128
3.0 FLOOR SYSTEMS
3.1 Structural Steel Framing
Structural Steel girders, beams, and columns are used to construct a skeleton
frame for structures ranging in size from one-story buildings to skyscrapers.
Because structural steel is difficult to work on site, it is normally cut, shaped,
and drilled in a fabrication shop according to design specifications; this can
result in relatively fast, precise construction of a structural frame. Structural
steel may be left exposed in unprotected noncombustible construction, but
because steel can lose strength rapidly in a fire, fire-rated assemblies or
coatings are required to qualify as fire-resistive construction. In exposed
conditions, corrosion resistance is also required.
Connections usually use transitional elements, such as steel angles, tees, or
plates. The actual connections may be riveted but are more often bolted or
welded.
3.1.1 One-Way Beam System
Each pair of external columns supports a long-spanning beam or girder. This
system is suitable for long, narrow buildings, especially when a column-free
space is desired.
Lateral-load carrying mechanisms are required in both directions, but lateral
forces tend to be more critical in the short direction.
3.1.2 Two-Way Beam System
Steel framing should utilize rectangular bay units, with comparatively lightly
loaded beams spanning farther than more heavily loaded girders.
3.1.3 Triple Beam System
When a large, column free space is required, long spanning plate girders or
trusses can be used to carry the primary beam, which in turn support a layer
of secondary beams.
3.2 Steel Beams
More structurally efficient wide-flange(W) shapes have largely superseded the
classic I-beam (S) shapes. Beams may also be in the form of channel ©
sections, structural tubing, or composite sections.
Rules of thumb for estimating depth:
Beams: span/20
Girders: span/15
Width – 1/3 – ½ of depth
The general objective is to use the lightest steel section that will resist
bending and shear forces within allowable limits of stress and without
excessive deflection for intended use.
In addition to material costs, also consider the labor costs required for
erection.
3.2.1 Plate Girders
Plate girders are built up from plates or shapes that are welded or riveted
together. A web plate forms the web of a plate girder, while flange angles form
the top and bottom flanges. Shear plates may be fastened to the web of the
girder to increase its resistance to shearing stresses.
3.2.2 Box Girder
Box girders are built up from shapes and have a hollow, rectangular cross
section.
3.2.3 Castellated Beams
It is fabricated by dividing the web of a wide-flange section with a lengthwise
zigzag cut, then welding both halves together at the peaks, thus increasing its
depth without increasing its weight.
3.3 Steel Beam Connections
There are many ways in which steel connections can be made, using different
types of connectors and various combinations of bolts and welds. Refer to the
American Institute of Steel Construction’s (AISC’s) Manual of Steel
Construction for steel section properties and dimensions, allowable load
tables for beams and columns, and requirements for bolted and welded
connections. In addition to strength and degree of rigidity, connections should
be evaluated for economy of fabrication and erection and for visual
appearance if the structure is exposed to view.
The strength of a connection depends on the sizes of the members and the
connecting tees, or plates, as well as the configuration of bolts or welds used.
There are defines to three types of steel framing that govern the sizes of
members and the methods for their connections: moment resisting
connections, shear connections, and semi-rigid connections.
3.3.1 Moment Connections
AISC Type 1 – Rigid Frame- connections are able to hold their original angle
under loading by developing a specified resisting moment, usually by means
of plates welded or bolted to the beam flanges and the supporting column.
3.3.2 Shear Connections
AISC Type 2- Simple Frame- connections are made to resist only shear and
are free to rotate under gravity loads. Shear walls or diagonal bracing is
required for lateral stability of the structure.
A framed connection is a shear-resisting steel connection made by welding or
bolting the web of a beam to the supporting column or girder with two angles
or a single tab plate.
A seated connection is a shear-resisting steel connection made by welding or
bolting the flanges of a beam to the supporting column with a seat angle
below and a stabilizing angle above. It may be stiffened to resist large beam
reactions, usually by means of a vertical plate or pair of angles directly below
the horizontal component of the seat angle.
3.3.3 Semi-Rigid Connections
AISC Type 3- Semi-Rigid Frame- connections assume beam and girder
connections possess a limited but known moment-resisting capacity.
All-welded connections are aesthetically pleasing, especially when ground
smooth, but they can be very expensive to fabricate.
3.4 Open-Web Steel Joists
Open-web joists are lightweight, shop-fabricated steel members having a
trussed web. AK series joists has a web consisting of a single bent bar,
running in a zigzag pattern between the upper and lower chords. LH and DLH
series joists have heavier web and chord members for increased loads and
spans.
3.4.1 Span Ranges for Open-web Joists
-K series standard joists; 8”to 30” (205-760) depths
8K1
12' to
16' (4 to 5m)
10K1
12' to
20' (4 to 6m)
12K3
12' to
24' (4 to 7m)
14K4
16' to
28' (5 to 8m)
16K5
16' to
32'
(5 to
10m)
18K6
20' to
36'
(6 to
11m)
22K9
24' to
42'
(7 to
12m)
24K9
24' to
48'
(7 to
14m)
28K10
28' to
54'
(8 to
16m)
30K12
32' to
60'
(10 to
18m)
-LH series longspan joists; 18” to 48” (455 -1220) depths
18LH5
28' to
36'
(8 to
11m)
24LH7
36' to
48'
(11to
14m)
28LH9
42' to
54'
(12 to
16m)
32LH1
0
54' to
60'
(16 to
18m)
-DLH series deep longspan joists are available in 52” to 72” ( 1320-1830)
depths and can span up to 144’(44m)
3.5 Open-web Joist Framing
Open-web steel joists may be supported by a bearing wall of masonry or
reinforced concrete, or by steel beams or joist girders, which are heavier
versions of open-web joists. Fire-resistance rating depends on the fire rating
of the floor and ceiling assemblies.
3.5.1 Floor Deck
Floor deck may consist of Metal decking w/concrete fill; precast concrete
planks; plywood panel.
3.6 Metal Decking
Metal decking is corrugated to increase its stiffness and spanning capability.
The floor deck serves as a working platform during construction and as
formwork for a sitecast concrete slab.
- The decking panels are secured with puddle-welds or shear studs welded
through the decking to the supporting stel joists or beams.
- The panels are fastened to each other along their sides with screws, welds,
or button punching standing seams.
- If the deck is to serve as a structural diaphragm and transfer lateral loads to
shear walls, its entire perimeter must be welded to steel supports. In addition,
more stringent requirements for support and side lap fastening may apply.
There are three major types of metal decking:
3.6.1 Form Decking
Form decking serves as permanent formwork for a reinforced concrete
slab until the slab can support itself and its live load.
3.6.2 Composite Decking
Composite decking serves as tensile reinforcement for the concrete
slab to which it is bonded with embossed rib patterns.
Composite action between the concrete slab and the floor beams or
joists can be achieved by welding shear studs through the decking to
the supporting beam below.
3.6.3 Cellular Decking
Cellular decking is manufactured by welding a corrugated sheet to a
flat steel sheet, forming a series of spaces or raceways for electrical
and communications wiring; special cutouts are available for floor
outlets. The decking may serve as an acoustic ceiling when the
perforated cells are filled with glass fiber.
Rule of thumb for overall depth: span/24
Consult the manufacturer for patterns, widths, lengths, gauges, finishes, and
allowable spans.
3.7 Light-Gauge Steel Joists
Light-gauge steel joists are manufactured by cold-forming sheet or strip steel.
The resulting steel joists are lighter, more dimensionally stable, and can span
longer distances than their wood counterparts but conduct more heat and
require more energy to process and manufacture. The cold-formed steel joists
can be easily cut and assembled with simple tools into a floor structure that is
lightweight, noncombustible, and damp proof. As in wood light frame
construction, the framing contains cavities for utilities and thermal insulation
and accepts a wide range of finishes.
3.7.1 Types of Light-Gauge Steel Joists
3.7.2 Span Ranges for Light-Gauge Steel Joists
-6” (150) joists 10’ to 14’ (3050 to 4265)
-8” (205) joists 12’ to 18’ (3660 to 5485)
-10” (255) joists 14’ to 22’ (4265 to 6705)
-12” (305) joists 18’ to 26’ (5485 to 7925)
-Rule of thumb for estimating joist depth : span/20
-Consult manufacturer for exact joist dimensions, framing details, and
allowable spans and loads.
3.8 Light-Gauge Joist Framing
Light-gauge steel joists are laid out in and assembled in a manner similar to
wood joist framing.
Connections are made with self-drilling, self-tapping screws inserted with an
electric or pneumatic tool, or with pneumatically driven pins; welded
connections are also possible.
3.8.1 Interior and Exterior Bearing
Interior Bearing Exterior Bearing
Interior Bearing Exterior Bearing
Floor Projections and Openings Exterior Bearing
Exterior wall section of Light-gauge Stud Framing
4.0 WALL SYSTEMS
4.1 Steel Wall Structural System
Steel frame usually refers to a building technique with a "skeleton frame" of
vertical steel columns and horizontal I-beams, constructed in a rectangular
grid to support the floors, roof and walls of a building which are all attached to
the frame.
Structural steel formed with a specific shape or cross section and certain
standards of chemical composition and mechanical properties.
I-beams, have high second moments of area, which allow them to be very
stiff in respect to their cross-sectional area.
4.1 Common Structural Shapes
I-beam: I-beam (I-shaped cross-section - in Britain these include Universal
Beams (UB) and Universal Columns (UC); in Europe it includes the IPE, HE,
HL, HD and other sections; in the US it includes Wide Flange (WF) and H
sections). Z-Shape (half a flange in opposite directions)
a. HSS-Shape: Hollow structural section also known as SHS (structural
hollow section) and including square, rectangular, circular (pipe) and
elliptical cross sections)
b. Angle : (L-shaped cross-section)
c. Channel: ( [-shaped cross-section)
d. Tee : (T-shaped cross-section)
e. Rail profile : (asymmetrical I-beam)
i. Railway rail
ii. Vignoles rail
iii. Flanged T rail
iv. Grooved rail
f. Bar: A piece of metal, rectangular cross sectioned (flat) and long, but
not so wide so as to be called a sheet.
g. Rod: Around or square and long piece of metal or wood.
h. Plate: Metal sheets thicker than 6 mm or 1⁄4 in.
i. Open web steel joist
While many sections are made by hot or cold rolling, others are made by
welding together flat or bent plates (for example, the largest circular hollow
sections are made from flat plate bent into a circle and seam-welded).
4.2 Types of wall steel structural system:
o Exterior Wall
Exterior wall Studs / (Load bearing)
Curtain wall / (Non-Load bearing )
o Interior Wall
Interior wall / (Non-Load bearing or partitions)
4.2.1 Exterior wall studs / (Load bearing):
Wall framing in house construction includes the vertical and horizontal
members of exterior walls and interior partitions. These members,
referred to as studs, wall plates and lintels, serve as a nailing base for
all covering material and support the upper floors, ceiling and roof.
Exterior wall studs are the vertical members to which the wall
sheathing and cladding are attached. They are supported on a bottom
plate or foundation sill and in turn support the top plate. Studs usually
consist of 2 × 4 in (51 × 100 mm) or 2 × 6 in (51 × 150 mm) lumber and
are commonly spaced at 16 in (410 mm) on centre. This spacing may
be changed to 12 in (300 mm) or 24 in (610 mm) on centre depending
on the load and the limitations imposed by the type and thickness of
the wall covering used. Wider 2 × 6 in (51 × 150 mm) studs may be
used to provide space for more insulation. Insulation beyond that which
can be accommodated within a 3.5 in (89 mm) stud space can also be
provided by other means, such as rigid or semi-rigid insulation or batts
between 2 × 2 in (51 × 51 mm) horizontal furring strips, or rigid or semi-
rigid insulation sheathing to the outside of the studs. The studs are
attached to horizontal top and bottom wall plates of 2 in (nominal)
(38 mm) lumber that are the same width as the studs.
4.2.2 Curtain wall / (Non-Load bearing )
A curtain wall is an outer covering of a
building in which the outer walls are
non-structural, but merely keep out the
weather. As the curtain wall is non-
structural it can be made of a
lightweight material reducing
construction costs. When glass is used
as the curtain wall, a great advantage
is that natural light can penetrate
deeper within the building. The curtain
wall façade does not carry any dead
load weight from the building other than
its own dead load weight. The wall
transfers horizontal wind loads that are incident upon it to the main
building structure through connections at floors or columns of the
building. A curtain wall is designed to resist air and water infiltration,
sway induced by wind and seismic forces acting on the building, and its
own dead load weight forces.
Curtain walls are typically designed with extruded aluminum members,
although the first curtain walls were made of steel. The aluminium
frame is typically infilled with glass, which provides an architecturally
pleasing building, as well as benefits such as daylighting. However,
parameters related to solar gain control such as thermal comfort and
visual comfort are more difficult to control when using highly-glazed
curtain walls. Other common infills include: stone veneer, metal panels,
louvers, and operable windows or vents.
Curtain walls differ from store-front systems in that they are designed
to span multiple floors, and take into consideration design requirements
such as: thermal expansion and contraction; building sway and
movement; water diversion; and thermal efficiency for cost-effective
heating, cooling, and lighting in the building.
4.3Systems and Principles
4.3.1 Stick systems
The vast majority of curtain walls are installed long pieces (referred to
as sticks) between floors vertically and between vertical members
horizontally. Framing members may be fabricated in a shop, but all
installation and glazing is typically performed at the jobsite.
4.3.2 Unitized systems
Unitized curtain walls entail factory fabrication and assembly of panels and
may include factory glazing. These completed units are hung on the
building structure to form the building enclosure. Unitized curtain wall has
the advantages of: speed; lower field installation costs; and quality control
within an interior climate controlled environment. The economic benefits
are typically realized on large projects or in areas of high field labor rates.
4.3.3 Rainscreen principle
A common feature in curtain wall technology, the rainscreen principle
theorizes that equilibrium of air pressure between the outside and
inside of the "rainscreen" prevents water penetration into the building
itself. For example the glass is captured between an inner and an outer
gasket in a space called the glazing rebate. The glazing rebate is
ventilated to the exterior so that the pressure on the inner and outer
sides of the exterior gasket is the same. When the pressure is equal
across this gasket water cannot be drawn through joints or defects in
the gasket.
4.3.4 Interior wall / (Non-Load bearing or partitions)
Interior partitions supporting floor, ceiling or roof loads are called
loadbearing walls; others are called non-loadbearing or simply
partitions. Interior loadbearing walls are framed in the same way as
exterior walls. Studs are usually 2 × 4 in (51 × 100 mm) lumber spaced
at 16 in (410 mm) on centre. This spacing may be changed to 12 in
(300 mm) or 24 in (610 mm) depending on the loads supported and the
type and thickness of the wall finish used.
Partitions can be built with 2 × 3 in (51 × 76 mm) or 2 × 4 in
(51 × 100 mm) studs spaced at 16 or 24 in (400 or 600 mm) on center
depending on the type and thickness of the wall finish used. Where a
partition does not contain a swinging door, 2 × 4 in (51 × 100 mm)
studs at 16 in (410 mm) on centre are sometimes used with the wide
face of the stud parallel to the wall. This is usually done only for
partitions enclosing clothes closets or cupboards to save space. Since
there is no vertical load to be supported by partitions, single studs may
be used at door openings. The top of the opening may be bridged with
a single piece of 2 in (nominal) (38 mm) lumber the same width as the
studs. These members provide a nailing support for wall finish, door
frames and trim.
4.4 Light Gauge Metal Framing:
Non-load bearing or non-structural metal studs and framing are not designed
or intended to carry any axial loads. Axial loads would include such elements
as floor joists, ceiling joists, roof rafters, or roof trusses. They are, however,
designed to carry the dead load of many typical wall finishes such as gypsum
board, plaster work, or similar finishes, and to provide resistance to normal
transverse loads. Lateral loads cannot exceed 10 lb/sq. ft on a steel framed
wall system as defined by ASTM C645.
Light gauge metal framing used for interior wall partitions comes in various
shapes, thicknesses, sizes, and finishes. Each of these components has a
specific function in the wall assembly. Selecting the correct size and thickness
will depend primarily on the spacing of the framing members and the height of
the wall. Center to center stud spacing for typical interior applications will
either be 12", 16", or 24". Other considerations in the selection process
include the makeup of the wall finishes, whether the wall finishes will be
applied to one or both sides, and impact resistance requirements, if
applicable. As a general rule of thumb, interior walls of a public space may
require more resistance to impact than do those of a private office.
Metal studs are typically manufactured in lengths ranging from 8'-0" to 24'-0"
and tracks which come in 10'-0" lengths. These are referenced by
manufacturers with the acronym S T U F L. In addition to this acronym, other
series of numbers are used to identify specific framing members, as shown in
the gallery below. The smaller the gauge number the thicker and heavier the
metal stud will be. See the Minimum Steel Sheet Thickness chart in the
gallery below for a comparison of gauge numbers to actual metal thickness.
Advantages
Large clear span open areas for ballrooms, or other wide concourse are possible
at the first floor level, because columns are located only on the exterior faces of
the building. This allows for spaces as much as 60 feet in each direction with
columns often only appearing on the perimeter of a structure. This also increases
design flexibility especially for atrium placement and open space floor plans.
Floor spans may be short bay lengths, while providing two column bay spacing
for room arrangements.[1] This results in low floor-to-floor heights. Typically, an 8'-
8" floor-to-floor height is achieved.[4]
Columns have minimum bending moments due to gravity and wind loads,
because of the cantilever action of the double-planar system of framing.[1]
Columns are oriented with their strong axis resisting lateral forces in the
longitudinal direction of the building.[1]
Maximum live load reductions may be realized because tributary areas may be
adjusted to suit code requirements.[1]
Foundations are on column lines only and may consist of two strip footings. [1]
Because the vertical loads are concentrated at a few column points, less
foundation formwork is required.[4]
Drift is small, because the total frame is acting as a stiff truss with direct axial
loads only acting in most structural members. Secondary bending occurs only in
the chords of the trusses.[1]
High strength steels may be used to advantage, because all truss members and
columns are subjected, for all practical purposes, to axial loads only.[1]
A lightweight steel structure is achieved by the use of high strength steels and an
efficient framing system.[1] Since this reduces the weight of the superstructure,
there is a substantial cost savings in foundation work.[4]
Faster to erect than comparable concrete structures. Once two floors are
erected, window installation can start and stay right behind the steel and floor
erection. No time is lost in waiting for other trades, such as bricklayers, to start
work. Except for foundations, topping slab, and grouting, all "wet" trades are
eliminated.[4]
Fire resistance; steel is localized to the trusses, which only occur at every 58-to-
70-feet on a floor, so the fireproofing operation can be completed efficiently.
Furthermore, the trusses are typically placed within demising walls and it is
possible that the necessary fire rating can be entirely by enclosing the trusses
with gypsum wallboard. Finally, if spray-on protection is desired, the applied
thickness can be kept to a minimum due to the compact nature of the truss
elements.[
Reference:
http://buildipedia.com/on-site/construction-materials-methods/light-gauge-
metal-stud-framing
http://en.wikipedia.org/wiki/Structural_steel
http://www.alibaba.com/products/u-channel_sizes/--92502.html
http://en.wikipedia.org/wiki/Staggered_truss_system
Books:
Building construction illustrated, Francis D.K Ching
Construction Technology, Roy Chudley
Fundamental of Building Construction
Imitechell’s Structure and Fabric, Jack Stroud Foster
5.0 ROOF SYSTEMS
5.1 Structural Steel Roof Framing
Where the whole weight of the walls, floors & roof is carried by the steel
frame. Structural steel is accurate in size and positioning and can be erected
very quickly. Usually use standard hot rolled universal beam & column
sections together with a range of tees, channels and angles while keeping the
weight to a minimum. UB’s and UC’s are produced in a range of standard
sizes and weights designated by serial number.
A flat roof sturucture may be framed with structural steel members similar to
the way steel floors are framed. See the diagram below:
5.1.1 Benefits of Steel Frames
Value for money
Flexibility
Speed
Safety
Quality & Reliability
Professional Approach
Sustainability
Prestige
5.1.2 There are three basic residential steel framing assembly methods:
Stick built construction
Panelized systems
Pre–engineered systems
5.1.2.1 Stick Built Construction
Stick built construction is virtually the same in wood and steel. This
framing method has actually gone through a transformation incorporating
many of the techniques used in panelized construction. The steel
materials are delivered to the job site in stock lengths or in some cases cut
to length. The layout and assembly of steel framing is the same as for
lumber, except components are screwed together rather than nailed.
Steel joists can be ordered in long lengths to span the full width of the
home. This expedites the framing process and eliminates lap joints.
Sheathing and finish materials are fastened with screws or pneumatic
pins.
5.1.2.2 Panelized Systems
Panelization consists of a system for prefabricating walls, floors and/or
roof components into sections. This method of construction is most
efficient where there is a repetition of panel types and dimensions. Panels
can be made in the shop or in the field. Steel studs and joists are ordered
cut to length for most panel work, placed into a jig and fastened by either
screws or welding. The exterior sheathing, or in some cases the complete
exterior finish, is applied to the panel prior to erection. Shop panelization
can offer several significant advantages to the builder. The panel shop
provides a controlled environment where work can proceed regardless of
the weather conditions. Application of sheathing and finish systems is
easier and faster with the panels in a horizontal position. The panels are
then transported from the panel shop to the job site. A major benefit of
panelization is the speed of erection. A job can usually be framed in about
one quarter of the time required to stick–build. When you consider that the
exterior finish system may also be part of the panel, the overall time
savings may be even greater.
5.1.2.3 Pre–engineered Systems
With steel's high strength and design flexibility, innovative systems are
possible which are not possible using other materials. Engineered
systems may space the primary load carrying members more the 24
inches on centre, sometimes up to 8 feet. These systems use either
secondary horizontal members to distribute wind loads to the columns or
lighter weight steel in–fill studs between the columns. Furring channels
used to support sheathing materials also provide a break in the heat flow
path to the exterior, which increases thermal efficiency. Many of the pre–
engineered systems provide framing members which are pre–cut to length
with pre–drilled holes for bolts or screws. Most of the fabrication labour is
done by the supplier, allowing a home to be framed in as little as one day.
5.2 Steel Rigid Frame (Portal Frame)
A continuous frame which has restrained jointed between vertical supporting
members and the spanning members Used in Warehouses, factories and
Sports Halls Basic Layout – columns at regular centres along two sides of
building with roof structure spanning between Frame then clad in light weight
cladding sheets Usually constructed using off shelf pre fab sections Most
common uses standard rolled steel sections Also common to use lattice
girders Lattice – open grid of slender members fixed across or between each
other usually in rectangular pattern or cross diagonals or as a rec. grid. Joints
introduced at base connections, centre or apex of spanning members giving
three forms of portal frames.
Rigid frames consist of two columns and a beam or girder that are rigidly
connected at their joints. Applied loads produce axial, bending, and shear
forces in all members of the frame since the rigid joints restrain the ends of
the members from rotating freely. In addition, vertical loads cause a rigid
frame to develop horizontal thrusts at its base. A rigid frame is statically
indeterminate and rigid only in its plane.
Steel frames may be left exposed in unprotected non-combustible
construction.
Some building codes reduce the fire-protection requirements for steel roof
structure
5.2.1 Benefits of Portal Frame
Can economically enclose a large area, has a small CSA producing a
saving in floor space. Floor areas unrestricted by long runs of walls,
more flexible in use. Good floor to ceiling heights. Frame quicker to
build than walls saving time and money.
5.2.2 Advantages of Steel Portal Frames
Prefab off site, reducing on site times. Factory accurate. No curing time
needed, capable of taking loadings immediately once constructed.
Capable of being adapted, extended and added to easily. Low
maintenance although corrosion can be problem. Steel is versatile,
strong and relatively cheap.
5.2.3 Disadvantages:
Corrosion. Not fireproof. Purlins & Sheeting Rails. Purlins fixed across
rafters. Sheeting rails fixed across columns to provide support and fixing
for roof, wall cladding & insulation
Spacings & sizes will depend on type and spec of roof and cladding
panels being used
5.3 Space Frames
A space frame is a long-spanning three-dimensional plate structure based on
the rigidity of the triangle and composed of linear elements subject only to
axial tension or compression. The simplest spatial unit of a space frame is a
tetrahedron having four joints and six structural members
.
5.3 Open Web Joist Framing
Roof systems utilizing open-web steel joists are similar in layout and
construction to steel joist floor systems.
5.4 Metal roof decking
Metal roof decking is corrugated to increase its stiffness and ability to span
across open-web steel joists or more widely spaced steel beams and to serve
as a base for thermal insulation and membrane roofing. The decking panels
are puddle-welded or mechanically fastened to the supporting steel joists or
beam. The panels are fastened to each other along their sides with screws,
welds, or button punching standing seams. If the deck is to serve as a
structural diaphragm and transfer lateral loads to shear walls, its entire
perimeter must be welded to steel supports. In addition, more stringent
requirements for support and side lap fastening may apply.
Metal roof decking is commonly used without a concrete topping, requiring
structural wood or cementations panels or rigid foam insulation panels to
bridge the gaps in the corrugation and provide a smooth, firm surface for the
thermal insulation and membrane roofing.
Metal decking has low-vapor permeance but because of the many
discontinuities between the panels, it’s not airtight .if an air barrier is required
to prevent the migration of moisture vapour into the roofing assembly, a
concrete topping can be used. When a lightweight insulating concrete fill is
used, the decking may have perforated vents for the release of latent moisture
and vapour pressure.
5.06 Light-gauge roof framing
Roofs and ceilings may be constructed with light-gauge steel members in a
manner similar to wood light frame construction; the light-gauge steel
members may also be screwed or welded together to form roof trusses similar
to those described on figure.
6.0 THERMAL AND MOISTURE PROTECTION
6.1 Sheet Metal Roofing
A sheet metal roof is characterized by a strong visual pattern of interlocking
seams and articulated ridges and roof edge. The metal sheets may be of
copper, zinc alloy, galvanized steel, or terne metal. A stainless steel plated
with an alloy of tin and lead. To avoid possible galvanic action in the presence
of rain water, flashing, fastenings, and metal accessories should be of the
same metal as the roofing material. Other factors to consider in the use of
metal roofing are the weathering characteristics and coefficient of expansion
of the metal.
6.2 Corrugate metal roofing
Corrugated or ribbed roofing panels span between roof beams or purlins
running across the slope. The roofing panels may be of:
Aluminium with a natural mill or enamelled finish
Galvanized steel
Fiberglass or reinforced plastic
Corrugated structural glass
Many corrugation and ribbed patterns are available. Translucent fiberglass or
plastic panels with matching profiles are available for use as skylights.
6.3 Metal cladding
Insulated and bonded metal panels are used primarily to clad industrial-type
buildings. They may have facings of anodized aluminium or steel with
porcelain, vinyl, acrylic, or enmel finishes. The panels are typically3’(915)
wide and span vertically between horizontal steel girts spaced8’to24’ apart,
depending on the type and profile of panel used. Consult manufacturer for
profiles, sizes, allowable spans, thermal and acoustical ratings, and
installation details.
6.4 Joint sealant
To provide an effective seal against the passage of water and air, a joint
sealant must be durable, resilient, and have both cohesive and adhesive
strength. Sealants can be classified according to the amount of extension and
compression they can withstand before failure.
Low Range sealant
Movement capability of +/- 5%
Oil-based or acrylic compounds
Often referred to as caulking and used for small joints where little
movement is expected
Medium Range sealant
Movement capacity of +/- 5% to 10%
Butyl rubber, acrylic, or neoprene compounds
Used for nonworking, mechanically fastened joints
High Range sealant
Movement capacity of +/- 12% to 25%
Polymercaptans, polysulfides, polyurethanes, and silicones
Used for workingjoints subject to a significant amount of movement, such
as those in curtain.
6.5 Expansion Joints
All building materials expand and contract in response to normal changes in
temperature. Some also swell and shrink with changes in moisture content,
while others deflect under loading. Joints must be constructed to allow this
movement to occur in order to prevent distortion, cracking or breaks in the
building materials. Movement joints should provide a complete separation of
materials. Movement joints should provide a complete separation of materials
and allow free movement while, at the same time, maintaining the weather
tightness of the construction.
Expansion joints are continuous, unobstructed slots constructed between two
part of a building.
Control joints are continuous grooves or separations formed in concrete
ground slabs and concrete masonry wall.
7.0
DOORS AND WINDOWS
7.1
Doors & windows
Doors and doorways provide access form the outside into the interior of a
building as well as passage between interior spaces. Doorways should
therefore be large enough to move through easily and accommodate the
moving of furnishings and equipment. They should be located so that the
patterns of movement they create between and within spaces are appropriate
to the uses and activities housed by the spaces.
Exterior doors should provide weathertight seals when closed and maintain
the approximate thermal insulation value of the exterior walls they penetrate.
Interior doors should offer the desired degree of visual and acoustical privacy.
All doors should be evaluated for their ease of operation, durability under the
anticipated frequency of use, security provisions, and the light, ventilation, and
view they may offer. Further, there may be building code requirements for fire
resistance, emergency egress, and safety glazing must be satisfied.
There are many types and sizes of windows, the choice of which affects not
only the physical appearance of a building, but also the natural lighting,
ventilation, view potential, and spatial quality of the building’s interior spaces.
As with exterior doors, windows should provide a weathertight seal when
closed. Window frames should have low thermal conductivity or be
constructed to interrupt the flow of heat. Window glazing should retard the
transmission of heat and control solar radiation and glare.
Because door and window units are normally factory-built, their manufacturers
may have standard sizes and corresponding rough-opening requirements for
the various door and window types. The size and location of doors and
windows should be carefully planned so that adequate rough openings with
properly sized lintels can be built into the wall systems that will receive them.
From an exterior point of view, doors and windows are important
compositional elements in the design of building facades. The manner in
which they punctuate or divide exterior wall surfaces affects the massing,
visual weight, scale, and articulation of the building form.
7.2 Doors and doorways
The detailing of a doorframe establishes the appearance of a doorway.
Depending on the thickness of the wall construction, a doorframe may be set
within the rough opening or overlap its edges.
7.3 Door Operation
7.4 Window Elements
In selecting a window unit, review the building code requirements for:
Natural light and ventilation of habitable spaces.
Thermal insulation value of the window assembly.
Structural resistance to wind loads.
Clear opening of any operable window that serves as an emergency exit
for a residential sleeping space: such windows are typically required to be
at least 5.7 sf (0.35 sm) in area and have a minimum clear width of
20”(510), a minimum clear height of 24”(610), and a sill no higher than
44”(1120) above the floor.
Safety glazing for a window that could be mistaken for an open doorway;
any window that is more than 9sf (0.84sm) and within 24 of a doorway or
less than 60 above the floor be safety glazed with tempered glass,
laminated glass, or plastic.
Type and size of glazing allowable in fire-rated walls and corridors.
7.5 Window Operation
10.0 INDIVIDUAL CASE STUDY
10.1 11 Boxes
Architect: Keiji Ashizawa Design
Location: Saitama, Japan
Project Architect: Keiji Ashizama
Structural Engineer: Ejiri Engneer
Project Year: 2007
10.1.1 Features
The most interesting thing about this particular building is the
fact that it is made out of 11 prefabricated steel frame boxes.
Diagram 10.1.1a: Architect’s conceptual sketches
Due to site constraints and the need to maximize space of the
site, this simple construction method was chosen so as not to
affect its existing neighboring context (Japanese housing areas
are normally tight and compact). External panels are attached to
the frames without the need of any additional structure.
Diagram 10.1.1b: An individual prefabricated steel frame box on a truck
However, the size of steel boxes needed to be considered
carefully since each had to fit on a truck to be transported to
site.
Diagram 10.1.1c: High tensile bolts
It is then joined together with high tension bolts. The steel frame
boxes are basically tailored made to be designed as a slot-in
and bolted-in (a more realistic version of Lego).
Diagram 10.1.1d: Central stairway
Though the central span holds the main structural strength of
the building, the circulation staircase is intentionally positioned
there to operate as an earthquake-proof element as well as to
rationalize the plan of the house.
10.1.2 Drawings
Diagram 10.1.2a: Plan Drawings of the 11 boxes
In the plans, one can see that the boxes stack on top of each
other, which the middle box slightly smaller. Each floor is
categorized into specific functions with the bottom floor being
the office, and the top floor being its most private area, the
bathing and sleeping zones. The roof top acts like a viewing
balcony.
Diagram 10.1.2b: Section and Detail of Steel Frame Box System
The section clearly shows how the boxes are cleverly stacked
on top of each other. The only formwork on site is the base
foundation. The central smaller boxes act as the core stabilizer
that holds both sides of the building together. The front façade is
generally more opened, if full height windows. Interesting
enough, the floors are slotted onto the L-shape steel frame box.
The 1st floor, 3rd floor and roof floor uses precast concrete
flooring but only the second floor uses timber panels. This is
because there exist a large void, double volume in fact, to give a
sense or larger space in the zone.
L-shaped boxes are bolted together creating a combined T-
shape bracket which allows floors to be installed on both side.
10.1.3 Advantages
Diagram 10.1.3a: Skeletal framework of the building and construction
The greatest advantage of the building it’s the construction
speed and accuracy. The prefabricated frames can be
transported to site easily, installed via a crane and a few
workers, and once the framework is up, it will be easy for the
workers to install the walls and floors since those too are
prefabricated.
Since everything is made in the factory and sent to site, cost is
lower. Normally, construction is expensive due to the on-site
welding, time consuming elements to site adjustments and also,
inaccuracy might occur.
Diagram 10.1.3b: Building’s front elevation and façade
This steel frame box system also eliminates the need of
installing columns on site. The angles on each box acts like a
truss that channels forces safely down the ground. Interesting
construction and design, sadly no books or e-books have
published anything about this work of wonder.
Diagram 10.4a: Skeletal framework of the building and construction
Diagram 10.4b: Skeletal framework of the building and construction
References:
http://www.homedsgn.com/2012/01/12/11-boxes-by-keiji-ashizawa-design/
http://www.archdaily.com/172087/11-boxes-keiji-ashizawa-design/
http://www.keijidesign.com/
Building Construction Illustrated – Francis D.K. Ching
10.2 Big Dig House
Building Name : Big Dig House
Architects : Single Speed Design
Location ： Lexington, MA, USA
Programme ： Private House
Completion year ： 2008
Site Area ： 1,784 sqm
Constructed Area ： 353 sqm
The Big Dig is the most expensive highway project in the history
of the US. The project included rerouting the Central Artery into
a tunnel under the heart of Boston, requiring a tremendous
engineering work due to underlaying metro lines and pipes and
utility lines that would have to be replaced or moved. Tunnel
workers encountered many unexpected geological and
archaeological barriers, ranging from glacial debris to
foundations of buried houses and a number of sunken ships
lying within the reclaimed land.
The Big Dig House
by Single Speed
Design reutilizes materials
from the Big Dig. In that
aspect, it´s a remarkable
example of recycling in
architecture. Project
description by the
architects after the break.
Salvaged Columns Salvaged Inversets
As a prototype building that
demonstrates how infrastructural refuse
can be salvaged and reused, the
structural system for this 3,400sf house
is comprised of steel and concrete
discarded from Boston’s Big Dig
utilizing over 600,000 lbs of salvaged
materials from elevated portions of the
now dismantled I-93 highway. Planning
the reassembly of the materials in a
similar way one would systematically
compose with a pre-fab system, subtle
spatial arrangements are created from
the large-scale highway components.
SEQUENCE OF INSTALLATION
vv
10.3 Jonathan’s House
10.4 COX House
Introduction:
Exterior view
Determined to create a new architectural language for the property, the owner hired a progressive architecture firm from Kansas City to design the warehouse. As a response to the budget constraints, the architects immediately suggested to work with a pre-engineered metal building system. After careful research of the system’s constraints and capabilities, a design direction was proposed to meet the project’s program, consisting of an 8,500 square foot open floor plate warehouse. The program also required an inventory check-out desk as well as a loading dock for incoming supplies. The project solution, composed of striking, yet elegant structural bays, implements sustainable strategies which aide in holding energy demands to a minimum. A soaring cantilever completely shades the long, south metal wall system from the hot, summer sun. The generous overhang also provides a sheltered loading and unloading area for service vans. A linear clerestory window allows indirect south light to flood the warehouse – the south shelving aisle does not require electric light during the day. Linear louvered vents along the base of the north and south facades activate a convection cooling system, allowing outside air to enter the warehouse at floor level, replacing the hot air exiting the building through large roof vents. Fully
integrated fluorescent building lighting creates efficient expanses of indirect site illumination, eliminating the need for additional lighting parking lot pole-lights. though small in area, the new distribution centre for Cox Communications commands a large site presence through elegant proportions, crisp detailing, and smart energy conservation.
Image :
Building Specification:
Architects: el dorado inc.
Location: Topeka, Kansas, USA
Principal in Charge: Josh Shelton
Project Architect: Sean Slattery, AIA, LEEP AP
Custom Steel Fabrication: Doug Hurt
Structural Engineers: Genesis Structures
Metal Building Engineering: Steelmaster USA
MEP: Lankford and Associates
Landscaping: el dorado inc
Lighting: el dorado inc
General Contractor: Kelley Construction Company
Owner: Henderson Development, Inc.
Project Area: 9,200 sqf
Project Year: 2007
Rendererings: el dorado
Photographs: Mike Sinclair
Design concept and solution:
The architects designed a distribution center that fit within the parameters of the owner’s renewed lease terms. An additional constraint was the budget: the architects were given the challenge to work with $80 per square foot. To work within the limited budget, the architects chose a pre-engineered metal building system. Energy efficient design was also important. A soaring cantilever shades the south metal wall system and provides shelter for the loading dock. A clerestory window allows indirect south light into the warehouse. The louvered vents of the north and south facades activate a convection cooling system, allowing outside air to enter the warehouse at floor level.
Foundation System
The monolithic slab foundation was made up of a large block of reinforced
concrete, whilst footings were used to hold up the section of the house. The steel
frame structure is then secured to the foundation using steel beam to concrete
connections.
Structural Framing
prefabricated offsite and was transported to the site as a single frame. The
structural frame was constructed using the one-way beam system on all
longitudinal sides. The connections between beams used steel angles that were
bolted onto each other to create a rigid frame. Due to exposure, fire resistant and
corrosion resistant coatings were also added to the frame.
Flooring System
Ground floor is made up of steel floor structure beams which cantilever out along
the bottom of the steel frame. SIPS floor panels are then placed along the length of
the floor and jointed to the structural beams.
Wall System
The wall system of the house, used SIP panels that were hung along the steel
frame, creating a wall. The method of jointing used bolting to create a secure wall
system. These panels also include window panels, all with similar dimensions . This
enclosure system is designed to allow a range of window or curtain wall systems
by various manufacturers thus creating a customizable interior.
Roof Structure/Material
For the roof structure, SIPS roof panels were placed along the entire stretch of the
roof on top of roof structure beams that rest upon the steel frame. A waterproof
roof membrane which is a one-piece, prefabricated sheet was attached to the roof
section to block water leakage due to heavy rain. The roof is also airtight as SIP
roof panels meet requirements in the new Building Regulations code.
light diagram
airflow diagram
structure diagram
Conclusion
Based on the research and observations, there are disadvantages and
advantages of such steel frame construction to be used in small residential projects.
Among them include:
Advantages of structural steel framing
1) The architect has carefully constructed the interior spaces to allow for this
house to be interchangeable and linkable with other prefabricated
pieces, which allows for further expansion using the same eco techniques
used to build the main structure.
2) The major structural and enclosure elements are all panelized systems,
pre-fabricated off-site. This approach minimizes unpredictable site labor
costs, speeds construction, and minimizes disturbance to the existing
site context. The minimal foundation requirements also speed
construction, reduce labour costs and reduce site disturbance.
3) No interior elements are essential to the structural integrity of the building,
thus the interior can be constructed by less skilled labourers in a faster
time frame.
Disadvantages of structural steel framing
1) There is a difficulty in transporting and erecting the steel frame as it is
prefabricated to be used as one piece and also weighs a large amount.
This may cause delays if construction is to be carried out in rural areas or
terrain.
10.5 Cantilever House
