steel is widely used in many shapes to act as reinforcing material

8/21/2019 Steel is Widely Used in Many Shapes to Act as Reinforcing Material

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Steel is widely used in many shapes to act as reinforcing material (Mild steel, High

tension steel etc.) in R.C.C. structures I-sections, -sections, !-sections and

channel sections are commonly used in the construction of Industrial "uildings,

Railways "ridges, o#er head tan$s, towers. %tc.

Steel is an alloy of iron and car"on. &ure iron is #ery soft.

'd#atages of steel as structural material-

. Steel mem"er ha#e strength per unit weight. ' steel mem"er of small section

which has little weight can withstand hea#y loads.

*. +eing light steel mem"er can "e con#eniently handled.

. he properties of steel mostly donot change with time, which ma$es steel

most suita"le material for structure.

. &roperly maintained steel structure has long life.

. Steel "eing ductile material, doesnot fail suddenly.

/isad#antages-

. Steel structure needs fire proof treatment which increases cost.

*. 0hen in e1posed condition it can "e su"2ected to corrosion. &ainting fromtime to time is #ery necessary.

Mechanical properties of steel-

he important mechanical properties of steel are-

i. %lasticity

ii. &lasticity

iii. /uctilityi#. Mallea"ility

#. 3atigue

#i. +rittleness

#ii. Hardness

#iii. %lastic toughness

i1. Creep


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. %lasticity he steel is said to "e perfectly elastic if the deformation

produced in it disappears completely on the remo#al of applied load such a

property possessed "y a metal is $nown as elasticity.

*. &lasticity 0hen a metal shows that it has gained permanent deformation

without rupture with comparati#ely less load is called state of plasticity.

. /uctility 0hen a metal can "e drawn out to a similar section under the

action of tensile force is called a ductile metal. his property of metal is

$nown as ductility.

. +rittleness It is lac$ness of ductility. he metal "rea$s into pieces without

#isi"le deformation under the action of impact or tensile load.

. Mallea"ility 0hen a metal can "e rolled or hammered into thin sheets,the

property of the metal is called it is mallea"le and the related significant term

mallea"ility.

4. Hardness he property of material "y #irtue of which it can resist a"rasion

scratching wear "y harder "odies as $nown as hardness.

5. Creep- he continuous deformation of material under a constant load at

high temperature is $nown as creep.

ypes of Steel In general there one two types of steel-

i. Mild steel ii. High steel

In case of mild steel the percentage of car"on ranges from 6.7 to 6.67 where

in high tensile steel the percentage of car"on #aries from 6.87 to .7

3ollowing are some common rolled steel sections which ha#e "een standardi9ed "y

+ureau of Indian Standards.

i. I-section

ii. Channel section

iii. 'ngle section

i#. ee- Section

#. &lates


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#i. 3lats

#ii. S:uare "ars

#iii. Round "ars

. I-section, generally $nown as "eam section or rolled steel 2oints, ha#e "een

classified into fi#e categories.

a. IS;+ Indian Standard ;unior "eams

". IS!+ Indian Standard !ight +eams

c. ISM+ Indian Standard Medium 0eight +eams.

d. IS0+ Indian Standard 0ide 3lange +eams.

e. ISH+ Indian Standard hea#y weight "eams.

*. Channels sections Channel section ha#e "een classified into the followingthree categories

a. IS;C Indian Standard ;unior Channels.

". IS!C Indian Standard !ight Channels.

c. ISMC Indian Standard Medium Channels.

. 'ngle Section here are three categories of angle section as per ISI

a. IS' Indian Standard e:ual angles

". IS' Indian standard une:ual angles.

c. IS+' Indian Standard +ul" 'ngles.

Structural steel connection

Introduction

he following one the connection of 2oint

i. +eam and column

ii. +eam with "eam

iii. Column with columni#. Column with "ase

#. +rac$et with column

#i. Steel truss mem"er through gusset plate.

#ii. +attening and lacing in columns

#iii. 3lange and we" connections in plate griddles

i1. Splicing for continuity of mem"er.


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Important ri#eted connection for different structural mem"ers

. Sla" "ase ' steel column ha#ing concrete sla" as "ase. he element are

i. +ase plate

ii. Steel I-sectioniii. Cleat angles we" of I-section and cleat.

*.


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Ri#ets are also classified according to the shape of their heads.

i. Snap head

ii. &an head

iii. &an head with tapered headi#. 3lat counter sun heat

#. Round counter sun$ head

#i. 3lat head

Ri#eting process he process of 2oining two or more than two parts "y means of

ri#et "y gi#ing the final shape of ri#et head on "oth sides to act as a prominent

fastener is $nown as ri#eting.

Important term used in ri#eting-

&itch (&)- he pitch of ri#et is the center to center distance "etween consecuti#e

ri#ets.


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%dge distance- It is the distance of the edge of the mem"er or the co"er plates

from the center of the e1treme ri#et hole.

!ap- It is the distance normal to the 2oint "etween the edges of the o#erlapping

plates in a lap 2oint or "etween the 2oint and the end of the co#er plates in a "uilt

2oint.

Specification for ri#eted connection

. 'ssumption It is assume that

a. he distri"ution of shear stress across the ri#et cross section in uniform.

". /irect force is uniformly distri"uted among a group of ri#ets.

c. Ri#et fills the hole completely.

ypes of ri#eted 2oints-

Ri#eted 2ointed are classified as

. !ap 2oints

*. +utt 2oints

i. !ap 2oints ' lap 2oints is connection in which the mem"er 2oined lap or

o#erlap each other. he 2oint may ha#e one or more row of ri#ets. In the

case of lap 2oint the lines forces are eccentric which de#elop "ending

stresses and therefore ha#e the tendency to deform the "ending of the

plates and the ri#et tends to wea$en the 2oint.

!ap 2oints are further classified as to the num"er of ri#ets used.

i. Single ri#eted lap 2oint

ii. /ou"le ri#eted lap 2oint

Single ri#eted lap 2oint ' lap 2oint ha#ing only one row of ri#ets are called single

ri#et.


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/ou"le ri#eted lap 2oint ' lap 2oint ha#ing the rows of ri#ets is called as dou"le

ri#eted lap 2oint.

+utt 2oint ' "utt 2oint is one in which the end of th mem"er that 2oin come

together or "utt against each other.

+utt 2oints are two types

Single co#er "utt 2oint.

/ou"le co#er "utt 2oint.

Single co#er "utt 2oint In this case co#er plate is pro#ided on one side of main plates. It has pull p as eccentric with respect to co#er plate and hence tend to

deform to "ending.

/ou"le co#er "utt 2oint In this case co#er plates are pro#ided on either sides of the

main plates. here is no possi"ility of the de#elopment of "ending stress and

deformation of this 2oint.

a. /ou"le co#er single ri#eted 2oint.

". /ou"le co#er dou"le ri#eted "ut 2oint.

c. /ou"le co#er 9ig 9ag ri#eted "ut 2oint.

d. /iamond ri#eted "ut 2oint.

3ailure of ri#eted 2oint

he 2oint may fail in any of the following ways

i. Shear failure of ri#etsii. Shear failure of plates

iii. earing failure of plates

i#. +earing failure of plates.

#. +earing failure of ri#ets.

#i. Splitting failure of plates at the edges


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. Shear failure of ri#ets 0hen a ri#et connecting two plates in tension is

su"2ected to shear stress. If the ri#et is wea$, the shear failure of ri#et will

occur.

*. Shear failure of plates ' plate may fail in shear this will happen when the

edge distance pro#ided is inade:uate edge distance is pecified.

. earing failure of plates 3ailure may "e due to the tearing of a plate or a

num"er of plates "etween the ri#et holes. /ue to drilling of ri#et holes the

strength of plate in tension is reduced and conse:uently the plates may tear

off.

. +earing failure of plates ri#ets 3ailure of the 2oint the 2oint may "e there due

to the crushing of the plate or of the ri#et due to the mutual pressure on the

cylindrical surface of the ri#et and the plate around the ri#et this type of

failure is called failure "earing.

. Splitting failure of plate Splitting failure of plate may occur "ecause of in

sufficient edge distance in the ri#eted 2oint crac$ing of plate.

%fficiency of 2oint It is defined as the percentage ratio of strength of ri#eted 2oint

to the strength of solid plate

%fficiency of ri#eted 2oint (n) > !east strength of ri#eted 2oint?strength of soild

plate166

=um"er of ri#ets =um"er of ri#et can "e determine after calculating ri#et #alue

Hence no. of ri#ets > !oad?ri#et #alue

> ne1t whole num"er

+olted and welded connection


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he structural mem"er generally consist of structural section which are 2oined

together the most common types of structural steel connection are ri#eted

connection "olted connection and welded connection. In "olted connection nuts

and "olts are used.

'd#antages of "olted connection

i. +olting is cold process

ii. +olting operation is :uic$er

iii. here is no noise in "olting operation

i#. 3or ma$ing the connection less man power is re:uired.

/isad#antages

i. Strength of 2oint is reduced if they get loosened due to #i"ration.

ii. he dia of the hole is $ept more than diameter of "olt. he e1tra

clearance does not get filed up.

+olt ' "olt is a metal pin with a head formed at one end and shan$ threaded at the

other end to recei#e a nut

ypes of "olt-

Structural "olt are classified as gi#en "elow-

i. 'ccording to shape of head.

S:uare "olt ii. He1agonal +olt

ii. 'ccording to pitchStandard pitch "olt

Coarse pitch "olt

3i#e pitch "olt

iii. 'ccording to material

@rdinary structure "olt

High strength steel "olt


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i#. 'ccording to tyoe of shan$

Anfinished or "lac$ "olt

urned "olt

Specification for "olted 2oints-

. Clearance for holes for fasteners "olts may "e located in standard si9e, o#er

si9e, short or long slotted hole.

a. Standard clearance hole- %1cept where fitted "olt, "olt in low clearance

or o#ersi9e holes are specified the diameter of standard clearance holes

for fasteners ". @#er si9e hole- Holes of si9e larger than the standard clearance holes

may "e used in slip resistant connection and hole down "olted connection

only where specified pro#ide the o#er si9e holes in the outter is co#ered

"y a co#er plate.

Minimum spacing- the distance "etween center of fasteners shall not "e less than

*. times the nominal diameter of the fastener.

Ma1imum Spacing- he distance "etween the centres of any two ad2acent fastener

shall not e1ceed * or 66mm which e#ery class.

%dge distance- he edge distance is the distance at right angles to the direction of

stress from the center of a hole to the ad2acent edge.

%nd distance- he end distance is the distance in the direction of stress from the

centre of a hole to the end of the element.

0elded 2oints- 0elding 2oin two parts together permanently and they canBt "e

separated without "rea$ing ri#eted 2oints, welding pro#ide good mechanical

strength to the 2oined part.


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0elded connections- 0hen two mem"er are 2oined together permanently "y

welding the connection is called a welded connection.

0elding- he process of ma$ing a permanent connection "etween two metal parts

"y heating them to molten state along with additional metal $nown as filler is

called welding.

'd#antages-

i. 0elded 2oints affect a sa#ing on the total weight of gusset plates are

rarely re:uired this reduces the cost after structure.

ii. he welding process doesnot in#ol#e dri#ing holes as in the case of

ri#eted tension mem"er deduction ha#e to mode for the one lost due to

punching of holes.

iii. 0elded structure are stiffer, lighter, cheaper and none efficient as

compare to ri#eted structures.

i#. he process of welding is :uic$er than ri#eting.

/isad#antage

. 0elding re:uire s$illed la"our and suppression.

*. 's there is une#en heating and colling the welded mem"er are li$ely to get

wrapped at the welded surface.

. he process of welding may set up se#eral internal stress in the #icinity of

the welds.

. esting a welding 2oint is difficult.

ypes of weld-

here are two types of weld-

. +utt welds

*. 3illet welds


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. +utt weld his type of weld is used when the mem"er to "e connected "utt

against each other. arious types of "utt 2oints are named depending upon

shape of groo#e made for welding.

i. &lane or re:uire weld

ii. Single -"utt weld.

iii. /ou"le -"utt weld.

i#. Single u-"utt weld.

#. /ou"le -"utt weld.

#i. Single ;-"utt weld.

#ii. /ou"le ;-"utt weld.

#iii. Single "e#el "utt weld.

i1. /ou"le "e#el "utt weld.

ypes of "olted 2oints here are two types of "olted 2oint.

i. !a" 2oint

ii. +utt 2oint

. !ap 2oint- he mem"ers to "e connected are o#erlapped and connected

together lap 2oint can "e single "olted or dou"le "olted. In a lap 2oint

eccentricity is de#eloped as the center of gra#ity of load in one mem"er is

away from the center of gra#ity of load in other mem"er create couple and

the 2oint can fail in "ending. his failure can "e a#oided "y pro#iding two

"olts per 2oint

*. +utt 2oint- he "utt 2oint is used to connect the structural mem"er placed in

line i.e. there is no lap which eliminates the eccentricity as de#eloped in lap

2oint.

Co#er plate is pro#ided on "oth sides of 2oint co#er plate pro#ided on one

side is called single co#er "utt 2oint and if pro#ided on "oth sides is called

dou"le co#er "utt 2oint.


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3ailure of "olted 2oint-

he failure of "olted 2oint Is due to failure of the "olt and the failure of connected

mem"ers.

. Shear failure of "olts- 0hen the connected mem"er slip due to the forces

applied shear stress de#elop the nominal shear capacity of the "olt "eing

e1ceeded than the ma1imum shear capacity of "olt.

*. +earing failure of the "olts- 0hen slip ta$es palce and the material of the

connected mem"er is wea$er then it gets crushed to the near "y "olt or the

edge distance towards load gets effected.

. earing failure of plates- he failure occurs when the strength of the "olt ismore than the plate. he plate gets tear.

Strength of "olt 2oint-

he strength of "olting 2oint "earing type connections should "e ta$en as least of

strength #alue in shearing, "earing of 2oint.

3illet weld- 0hen two mem"ers o#erlap and are 2oin "y welding is called a filletweld. It is also $nown as lap weld. ' fillet weld is a weld of appro1imately

triangular cross section 2oining two surfaces appro1imately at right angles to each

other in lap 2oint.

ypes of fillet weld

i. Side fillet weld

ii. %nd fillet weld.iii. /iagonal fillet weld.

echnical term used in the design of fillet weld-


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a. Si9e of fillet weld- he si9e of normal fillet weld specified as minimum leg

length or a con#e1 or minor fitted weld.

". %ffecti#e throat thic$ness- It is the perpendicular distance from the root of

fillet weld to the line of 2oining it toes.

ension mem"er

Introduction- ension mem"er is defined as a structural mem"er su"2ected to

tensile force tension mem"er is also called as tie mem"er or simply a tie.

ypes of tension mem"er -

Single rolled steel structural mem"ers and plates- he angle section structural

shapes li$e angle and tee section are normally used as tension mem"er and the

angle section are considera"le more rigid than the roads and "ars. Single angle

section are widely used as tension mem"ers in plate girder etc.

/ou"le angle section- Ased e1tensi#ely in roof trusses may "e connected to gusset

plate on the same or opposite faces. In placing the gusset plate in "etween the two

angles.

-section tee section as a su"stitute for dou"le angles on "oth sides of gusset plate.

Compression mem"er

' mem"er ina structure which is su"2ected to compression is $nown as

compression mem"er.

Classification of compression mem"er

Struts ' strut is defined as structural mem"er su"2ected to compression in a

direction parallel to its longitudinal a1is.


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Columns a column is defined as a structural mem"er su"2ected to compressi#e

force in direction parallel to its longitudinal a1is.

+ooms Compression mem"er of a crane are called "oom.

Single angle section

. his is the most common and simple type of compression mem"ers used in

roof trusses. It is also used as "racing in plate girder.

*. +oth e:ual and une:ual angles can "e used.

. he angle section are considered to "e uneconomical "ecause they pro#ide

#ery small #alue of radius of gyration a"out minor principle a1is.

. Single angle sections pro#ide more eccentricity than dou"le angle sections

"ecause only one leg is attached to the gusset plate.

. he single angle section are commonly used in the single plane trusses.

4. Single angle section one not suita"le for compression mem"er of long

lengths.

/ou"le angle section

. /ou"le angle section can"e used as struts "y placing them either on thesame side or on "oth sides of the gusset plate.

*. +oth une:ual and e:ual angle section can "e used as a strut.

. /ou"les angle should "e so arranged that they gi#e ma1imum moment of

inertia.

Some common terms used in design of struts

. Radius of gyration (r)- he radius of gyration of a section is a geometrical

property of the section and is denoted "y r.

*. Slenderness ratio- he slenderness ratio of a compression mem"er is

defined as ratio of effecti#e length of compression mem"er to its least radius

of gyration


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'ngle struts- he compression mem"ers consisting of angle section are of two

types

Case I Continuous mem"er- he compression mem"ers which are continuous

o#er a num"er of 2oints are $nown as continuous mem"er. he top chord mem"ers

of truss girder and principal after of a roof trusses are e1amples of continuous

mem"ers.

Continuous mem"er may "e single angle or dou"le angle struts and may "e

connected "y one or more ri#ets, "olts or welding.

i. %ffecti#e length- he effecti#e length of continuous compression

mem"er is adopted as depending upon degree of end restraining

conditions.

ii. &ermissi"le a1ial compressi#e stress

Common section of compression mem"ers-

. Single angle section hey are the simplest type of compression mem"er

used in roof trusses and as "racing in plate girder. 'ngle section can "e e:ual

or une:ual. he angle are uneconomical section as these gi#e #ery small

radii of gyration a"out minor principal a1is moreo#er "ending is caused due

to eccentricity as only one leg is attached to gusset plate.

*. /ou"le angle section- he angle section can "e used as struts "y placing

these either on the same side of a gusset plate or on "oth sides of a gusset

plate angle section may "e e:ual or une:ual. +ut these should "e arranged to

get the ma1imum #alue of least moment of inertia.

ypes of section

he following are different forms of section used as compressi#e mem"ers-


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. Single angle section- hese can "e used as light load struts in roof trusses

une:ual angle section ha#e only one leg is attached to gusset plate.

*. /ou"le angle secton- he angle section can "e used as struts "y fi1ing them

either on the same sides of gusset plate or on "oth sides of gusset plate.

/ou"le angle section may "e e:ual or une:ual.

. I-section I-section can "e used as a column and H-"eams are more suita"le

as these pro#ide minimum difference in two radii of gyrations. o get

stronger section additional plates can "e attached on "oth flang of H-"eams.

. Channel section- Single ISMC and IS!C are suita"le as columns for light

loads. /ou"le IS;C, IS!C and ISMC can ser#e as good columns when laced

or "attened and these can supports moderate loads.

Roof trusses

he roof truses may "e defined as the framed structures in which separate straight

mem"er are so arranged and connected at their ends that the mem"ers from tringles

which lie in the same plane.

'd#antages of roof truss- 3ollowing are the ad#antages of roof truss.

. he roof trusses are pro#ided at places which re:uires sloping roofs. he

sloping roofs are necessary where rainfall and snowfall is more.

*. he roof trusses are suita"le for relati#ely light loads and large spans.

. he roof trusses ha#e the ad#antage of permitting #ariety of roof shapes.

. It is economical for spans more than 4 meters.

. /ead load of structure reduces.

Components of a roof trusses

he mem"er of a trusses are "roadly classified as main mem"ers and secondary

mem"ers. he main mem"ers are the structural mem"er which are responsi"le for


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carrying and distri"uting the applied load and pro#ide sta"ility to truss. he

secondary mem"er are the structural mem"er which are pro#ided for sta"ility and

restraining the main mem"ers from "uc$ling or similar modes of failure.

arious parts of steel roof truss are

. op chord mem"ers op chord is defined as the uppermost line of mem"ers

e1tending from one support to the other and passing through the pea$ point

of truss are called top chord of a roof truss. his is the main mem"er of a

truss and is helpful in carrying loads and distri"uting it further to other

mem"ers.

*. +ottom chord mem"ers he "ottom chord is defined as the lower most line

of mem"ers of truss e1tending from one support to other. he "ottom chord

is also $nown as the lower chord of the roof truss. In simply supported

trusses mem"er in the "ottom chord are su"2ected to tension "ut in case of

cantile#er trusses the lower chord mem"ers will "e in compression.

. 0e" mem"ers- Mem"ers connecting the top and "ottom chord mem"ers are

called we" mem"ers. 0e" mem"ers can "e #ertically or diagonal. hese

mem"ers are considered as secondary mem"ers which are helpful in

pro#iding sta"ility and restraining the main mem"er from "uc$ling.

arious terms used in steel roofs trusses

. Span he span of a roof truss is defined as the distance "etween center to

center of supports. he span of a roof truss is decided "y the dimesnions of

area to "e $ept free of columns.*. Rise he rise of roof truss is defined as the distance from the highest point

to the line 2oining supports. It is #ertical distance "etween "ottom chord to

the pea$ of the truss.

. &itch- he ratio of the rise to the fall span is called the pitch.


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. Slope he slope of a symmetrical truss is defined as ratio of rise to half the

span. It is the tangent of the angle "etween top and "ottom chord of the roof

truss. he slope pro#ided must "e sufficient to drain of the rain water must

"e sufficient to drain of the rain water without lea$age at the 2oint of

co#ering material.

. &urlins he purlins are the structural mem"ers su"2ected to trans#erse loads

and rest on the top chord of roof trusses. he purlins support the sheathing

co#ering or roofing material

4. Rafter he rafters are "eams and rest on purnils. Rafter support the

gal#ani9ed iron and as"estos cement sheets. hese are called common rafters

so as to distinguish them from principal rafter.5. Sheathing he sheathing are co#ering of "oards or reinforced concrete. he

sheathing one supported on purlins or rafters. he sheathing pro#ide support

for the roof co#ering.

8. &anel- he panel is defined as a distance "etween two ad2acent 2oints in a

principle rafter of a roof truss. It may also "e defined as the distance "etween

two ad2acent purlins.

ypes of roof trusses-

he #arious types of roof trusses are

. Ding post truss- Ding post truss is a wooden truss. It can also "e "uilt of a

com"ination of wood and steel. It is suita"le for spans upto 8m.

*. Eueen post truss It is also a wooden truss and it is suita"le for spans upto

6m.

. Howe truss- this truss is made up of com"ination of wood and steel. he

#ertical mem"ers one tension mem"ers made of com"ination of wood and

steel.

. 3in$ for 3rench roof truss hese type of truss are suita"le for spans upto

6m. these are made up of steel. hey are #ery economical from of roof


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truss. he length of compression mem"er one small in these type of trusses.

3in$ trusses one also $nown as 3rench roof trusses.

Spacing of roof trusses-

3or a roof structure the most economical spacing of trusses depend upon num"er of

factors. he economical spacing of the trusses are defined as the spacing that

ma$es the o#erall cost of trusses, purlins roof co#ering column etc.

&itch of roof truss he ratio of the rise to the full span is called as pitch. It is also

sometimes e1pressed as the angle "etween upper and lower chords. he #alue of

pitch depends upon

a. Climatic conditions

". !ight and #entilation re:uired

c. =ature of the load on the trusses

d. Roofing material selected.

Columns

' column is defined as #ertical structural mem"er su"2ected to compressi#e forcein a direction parallel to its longitudinal a1is.

Classification of columns

' column may "e classified as long medium or a short column depending upon the

mode of its failure.

. !ong column It is that column which fails mostly due to "uc$ling or side "ending. Its failure is "ecause the length of the column is so proportioned to

the lateral dimensions that slenderness ratio of mem"er increases and hence

chances of "uc$ling also increases.


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*. Medium column ' column in which failure occurs "oth due to direct stress

and "uc$ling.

. Short column In short columns, the length of the column is so proportional

to the lateral dimension that the failure of the lateral dimesion that the failure

of the column purely due to crushing.

+uc$ling of columns

he outward "ending of column is called "uc$ling commences is called "uc$ling

load.

%ffecti#e length of column the length of column which participates in "uc$ling is

called effecti#e length of the column.

ypes of column "ases

he column are supported on the column "ases. he column "ases are used to

transfer the load from the column to "ase and further distri"ute it uniformly on the

concrete foundation "loc$s. Column "ases are the important and integral part of the

structure and should "e designed with utmost core and s$ill.

he column "ases can "e of two types-

. Sla" "ase- he sla" "ase consist of cleat angles and "ase plate. he ends of

the column one machined for "earing o#er the whole one. his type of "ase

suita"le for carrying load of less intensity. he column end is connected to

"ase plate "y welding or "y means of ri#et cleat angles. In sla" "ase no

gusset plates are re:uired in order to secure the hori9ontal mo#ement of

plate, four rag "olts are pro#ided in the four corners of the plate and are

em"edded in the concrete "ase.


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*.


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*. !intel - +eam spaning o#er the door openings and windows are called

lintels.

. &urlins his is a roof "eam supported "y the purlins.

. Spandrel "eam- It is a "eam at the outermost wall of the "uilding supporting

the floor and the wall upto the floor.

. &late


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+ending stresses due to e1ternal loading on "eams, the shear force and "ending

moments are de#eloped at all the sections of the "eam. /ue to the shear force and

"ending moment, the "eam undergo certain deformation.

Section modulus- It is defined as the ratio of moment of inertia of a section to

distance of theremost edge of the section from the neutral a1is, therefore we can

represent section modulus.

!aterally supported "eam

he laterally supported "eam are also called laterally restrained "eams when lateral

deflection of the compression flang of a "eam is pre#ented "y pro#iding effecti#e

lateral support then the "eam is $nown as laterally supported. In the laterally

restrained "eams, the #alue of allowa"le "ending empressi#e stress remains

unchanged and no reduction is made in its #alue. herefore "ending stress in

compression is consideration e:ual to "ending stress in tension.

3a"rication and erection of steel structure

It is the process of preparing components ready for assem"ly at site. Steel wor$ is

fa"rication in afactory into components of #arious shape and si9es.

3ollowing steps are followed in fa"rication of steel structure

. +ased on design drawings, shop drawing are prepared after ta$ing into

account the codal pro#isions and permissi"le clearances.

*. Euantities are calculated from drawings and accordingly the materials are

arranged sometimes templates are prepared for repetition wor$.

. +est fit to $eep minimum wastage in generated manually or through

computer aided programs.

. Cutting and welding facilities should "e pro#ided for use.

. Material is cut to re:uired si9es and dimensions chec$s are applied.


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4. he prepared mem"ers frames are sent for sand "lasting, priming coat, paint

applications.

5. he material are stored or transported depending upon re:uirements.

%rection %recrtion is the process of assem"ling the fa"ricated components on site

with careful planning. he errection wor$ can "e completed relati#ely faster. @nce

the pieces ha#e "een fa"ricated they are transported to site and connected together

to ma$e the framewor$ which forms the s$eleton of the "uilding. o ta$e full

ad#antage of "enefit of speed of construction which steel wor$ offers. It is

necessary to order material sufficiently in ad#ance and prepare the site to recei#e

the steel frames well in time.

he following precautions are e1ercised while erection of steel frames

. he proper layout and se:uence of erection is planned and drawn along with

handling lifting e:uipments, machinery and proper manpower as per the

re:uirement of end product.

*. 'fter e#ery fi1ing chec$s are applied. he elements in general ha#e not to "e

forced fit and corrections ha#e to "e made if found misfit.. he erection se:uence must match the sta"ility of structure and "alance has

to "e made at e#ery step.

ypical erection steps of multistory "uilding including following wor$ se:uence

a. &ile?Raft footing with pro#ision of foundation "olts.

". 3i1ing of "ase mem"ers on foundation "olts with le#eling nuts.

c. %rection of tower cranes.

d. %rection of #ertical mem"ers with columns supports.e. ;oining of hori9ontal and diagonal mem"ers at floor le#els.

f. %rection may "e done for all the storeys as re:uired.

g. Simultaneously gla9ing, fi1ing of


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3ollowing points "e $ept in mind for the erection of columns at site-

. %ach column has to "e correctly positioned in plan or cline "ut side "y side

it is also necessary to chec$ the correct le#el and orientation.

*.

steel is widely used in many shapes to act as reinforcing material

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