FRAME STRUCTURE

Post & Lintel Structure,

Frame Structure & its types

The Simple Frame &

Multiple Frame

LECTURE # 3

TERMINOLOGIES

TENSION: Tension is a state of Stress in

which particles of material are tend to pull

apart. For example a steel cable pulling

or lowering an elevator tends to pull a

part by the weight of elevator.

Lengthening is typical of tension. And the

elongation of a unit length of cable is

called its tensile strain.

COMPRESSION: Compression is a state of

stress in which particles of the material are

pushed one against the other. For

example a column supports a load is

under compression, its height shortens

under load. The shortening of a unit

length or compressive strain is

proportional to the load applied unit area

of the column or compressive stress

SIMPLE BENDING: The state in which a stress

varies as a straight line from a maximum tension

to maximum compression is called simple

bending

SHEAR: The sliding action of particles relative to

each other in state of stress.

One of the essential characteristic of

Shear is that it produces sliding action between

two planes that are always at right

Angle to each other. Punch hole machine is an

Example of shear force.

FRAME STRUCTURE

Initially there was no distinction between the

supporting structure and the protecting skin. However

separation of supporting and protecting function

leads to the framed system.

A framed system may be defined as

“A framed structure in any material is one that is made

stable by a skeleton that is able to stand by itself as a

rigid structure without depending on floors or walls to

resist deformation. ”

Materials such as wood, steel, and reinforced

concrete, which are strong in both tension and

compression, make the best members for framing.

POST & LINTEL SYSTEM Post-and-lintel system, in building construction

is a system in which two upright members, the

posts, hold up a third member, the lintel, laid

horizontally across their top surfaces.

The lintel is a beam that is simply supported on

a posts and it carries the roof load. The

material used for lintel should have strong

tensile and compressive strength

While the posts are vertical struts compressed

by the lintels. The materials for post should

have strong compressive strength.

The post must also resist some horizontal loads,

such as the wind pressure; this resistance

comes from a bending capacity in case of

wooden and steel posts and from their own

weight in stone and masonry piers.

The foundation of the post carry roofs and the post loads to the ground by means

of footings in any case the posts and the foundation are under compression;

characteristic of post and lintel system.

Post and Lintel System may be built one over another to frame multistory buildings;

In this case the lintels are supported by vertical columns or wall of masonry as high

as entire building.

Construction of this type for multistory building can not resist horizontal loads and

easily damaged by hurricane and earthquakes due to low bending resistance of

stone and masonry.

Strong connection between horizontal and vertical member is not easily built.

All the members of post and lintel system act independently although connected

together.

EXAMPLES OF POST AND LINTEL SYSTEM

From prehistoric times to the Roman Empire, the post-and-lintel system was

the root of architectural design. The interiors of Egyptian temples and the

exteriors of Greek temples are delineated by columns covered by stone

lintels. The Greeks opened their interior spaces by substituting wooden

beams for stone, since the wood required fewer supports.

StonehengePARTHENON

SIMPLE FRAME STRUCTURE The action of the post and lintel system changes substantially, if a rigid connection is

developed between the lintel and bending resistant posts.

This structure behaves monolithically and is more stronger to horizontal loads and

vertical loads.

This structure system is called single bay rigid frame or simple frame.

Three consequences arises when we rigidly connect the horizontal member with the

vertical ones

1. The beam will restrained its end and will become more rigid and would be capable of

supporting heavier loads.

2. The columns are not only subjected to compressive loads and their own loads but also to

the bending stresses due to continuity with the beam.

3. A new horizontal force would be required to maintain the frame in equilibrium under vertical

loads. ( The thrust that bring back the columns to their vertical position).

A thrust may be provided by a tie rod that does not allow the frame to open up.

SIMPLE FRAME STRUCTURE

Frames are stronger against vertical loads

than post and lintel system and are more

advantageous in resisting lateral loads.

A post loaded by horizontal load acts as a

single cantilevered beam while in frame

structure horizontal member transfer the

lateral load from wind ward column to lee

word column.

By this way deflection and bending stresses

are reduced.

MULTIPLE FRAMES

The advantage of continuity can be compounded by the use of multiple frames in which a horizontal beam is rigidly supported by 3 or more columns. It is also called multiple bay frame.

Theoretically the two outer columns need to be tied but practically some mean should also be provided to take care of un even loading.

Multiple frames are efficient in absorbing lateral loads. The rigidity of beams against compressive loads makes the lateral deflection of all columns identical; Hence the lateral loads are beard by all columns of the frame.

The multiple frames are used to span large areas as they areas and are often used at he outer side of building to resist lateral loads

Types of Frames (Simple/ Multiple)

RIGID STRUCTURAL FRAME: the word rigid

means ability to resist the deformation. Rigid

frame structures can be defined as the

structures in which beams & columns are

made monolithically and act collectively to

resist the moments which are generating due

to applied load. Rigid frame structures

provide more stability. This type of frame

structures resists the shear, moment and

torsion more effectively than any other type

of frame structures. That's why this frame

system is used in world's most astonishing

building Burj Al-Arab.

BRACED FRAME STRUCTURE: In this

frame system, bracing are usually

provided between beams and

columns to increase their resistance

against the lateral forces and side

ways forces due to applied load.

Bracing is usually done by placing

the diagonal members between the

beams and columns. This frame

system provides more efficient

resistance against the earthquake

and wind forces. This frame system is

more effective than rigid frame

system

CONCRETE FRAME STRUCTURES Concrete frame structures are a very common

- or perhaps the most common- type of modern building.

this type of building consists of a frame or skeleton of concrete. Horizontal members of this frame are called beams, and vertical members are called columns. Humans walk on flat planes of concrete called slabs.

the column is the most important, as it is the primary load-carrying element of the building.

If you damage a beam in a building, it will usually affect only one floor, but damage to a column could bring down the entire building.

When we say concrete in the building trade, we actually mean reinforced concrete. Its full name is reinforced cement concrete, or RCC. RCC is concrete that contains steel bars, called reinforcement bars, or rebar. This combination works very well, as concrete is very strong in compression, easy to produce at site, and inexpensive, and steel is very strong in tension

STEEL FRAME STRUCTURE

Most steel construction is done with a type

of steel called mild steel. Mild steel is a

material that is immensely strong.

The other important feature of steel framing

is its flexibility. It can bend without cracking,

which is another great advantage, as a

steel building can flex when it is pushed to

one side by say, wind, or an earthquake.

when subjected to great force, it will not

suddenly crack like glass, but slowly bend

out of shape.

one important property of steel is that it

quickly loses its strength in a fire. At 500

degrees Celsius (930 degrees F), mild steel

can lose almost half its strength. This is what

happened at the collapse of WTC in 2001.

Steel construction is most often used in

High rise buildings because of its strength, low weight, and speed of construction

Industrial buildings because of its ability to create large span spaces at low cost

Warehouse buildings for the same reason

Residential buildings in a technique called light gauge steel construction

Temporary Structures as these are quick to set up and remove

ADVANTAGES OF STEEL STRUCTURES

Steel structures have the following advantages:

They are super-quick to build at site, as a lot of work can be pre-fab at the factory.

They are flexible, which makes them very good at resisting dynamic (changing) forces such as wind or earthquake forces.

A wide range of ready-made structural sections are available, such as I, C, and

angle sections

They can be made to take any kind of shape, and clad with any type of material

A wide range of joining methods is available, such as bolting, welding, and riveting

WOODEN FRAME

Light wooden framed construction is one of the most popular types of building methods for homes in the United States and parts of Europe.

It has the following characteristics:

It is light, and allows quick construction with no heavy tools or equipment. Every component can easily be carried by hand - a house essentially becomes a large carpentry job. The main tool is a handheld nail gun.

It is able to adapt itself to any geometric shape, and can be clad with a variety of materials.

There are a huge variety of products and systems tailored to this type of construction.

It has these negative characteristics:

It is not highly fireproof, as it is made of wood.

It is not strong enough to resist major wind events such as tornadoes and hurricanes.