assignment 2 anchal

8/17/2019 Assignment 2 Anchal

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STRUCTURES ASSIGNMENT

ANCHAL TIBREWAL

3-A

Roll No.8

Q.1)What is the method of cement manufacturin! I""ustrate it #ith the

he"$ of %o#chart.

Ans. MANU&ACTURING '& CEMENT(

To make cement, four essential elements are reuire! in a "ro"er ratio an! t#ese

elements are silicon, calcium, iron an! aluminum. Calcium for cement makin$

#as %een o%taine! from limestone, ic# is a natural source of calcium. 'n t#e

ot#er #an!, silicon #as %een e(tracte! from san! or cla) an! *nall) iron as &ell

as aluminum #as %een !eri+e! from iron ore an! %au(ite res"ecti+el).

A t#oste$ $rocess(

Basicall), cement is "ro!uce! in t&o ste"s

irst, clinker is "ro!uce! from ra& materials.

In t#e secon! ste" cement is "ro!uce! from cement clinker.

T#e *rst ste" can %e a !r), &et, semi-!r) or semi-&et "rocess accor!in$ to t#e

state of t#e ra& material.

Ste$ 1( Ma*in c"in*er

T#e ra& materials are !eli+ere! in %ulk, crus#e! an! #omo$enie! into a mi(ture

ic# is fe! into a rotar) kiln. T#is is an enormous rotatin$ "i"e of /0 to 10 mlon$ an! u" to / m in !iameter. T#is #u$e kiln is #eate! %) a 2000C 4ame insi!e

of it. T#e kiln is sli$#tl) incline! to allo& for t#e materials to slo&l) reac# t#e

ot#er en!, ere it is uickl) coole! to 500-200C.

our %asic o(i!es in t#e correct "ro"ortions make cement clinker

Calcium o(i!e 6/79

:ilicon o(i!e 6209

Alumina o(i!e 6509

Iron o(i!e 679.

T#ese elements mi(e! #omo$eneousl) 6calle! ;ra& meal< or slurr)9 &ill com%ine

en #eate! %) t#e 4ame at a tem"erature of a""ro(imatel) 5=70C.Ne& com"oun!s are forme! silicates, aluminates an! ferrites of calcium.

H)!raulic #ar!enin$ of cement is !ue to t#e #)!ration of t#ese com"oun!s.

T#e *nal "ro!uct of t#is "#ase is calle! ;clinkererent "lace to t#e clinker "lant. ?)"sum 6Calcium :ul"#ates9 an! "ossi%l)

a!!itional cementitious 6suc# as %last furnace sla$, coal 4) as#, natural"oolanas, etc.9 or inert materials 6limestone9 are a!!e! to t#e clinker. All


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constituents are $roun! lea!in$ to a *ne an! #omo$enous "o&!er. T#e cement

is t#en store! in silos %efore %ein$ !is"atc#e! eit#er in %ulk or %a$$e!.

Q.+) What are the di,erent t-$es of Concrete!

Ans. T)"es of concrete &it# a""lications for !i>erent structural com"onents like%eams, columns, sla%s, foun!ations are e("laine! #ere. :"ecial concrete &it#

uses.

iht #eiht concrete

• 'ne of t#e main a!+anta$es of con+entional concrete is t#e self &ei$#t of

concrete. @ensit) of normal concrete is of t#e or!er of 2200 to 2/00. T#is

self &ei$#t &ill make it to some e(ten! an uneconomical structural

material.

• :elf &ei$#t of li$#t &ei$#t concrete +aries from 300 to 5870 k$m3.

• It #el"s re!uce t#e !ea! loa!, increase t#e "ro$ress of %uil!in$ an! lo&ers

t#e #aulin$ an! #an!lin$ cost.

• T#e &ei$#t of %uil!in$ on foun!ation is an im"ortant factor in t#e !esi$n ,

"articularl) in case of &eak soil an! tall structures. In frame! structure ,

t#e %eam an! column #a+e to carr) loa! of &all an! 4oor. If t#ese &all an!

4oor are ma!e of li$#t &ei$#t concrete it &ill result in consi!era%le

econom).

• Li$#t &ei$#t concrete #a+e lo& t#ermal con!ucti+it).6 In e(treme climatic

con!ition ere air con!ition is to installe! t#e use of li$#t &ei$#t

concrete &it# lo& t#ermal con!ucti+it) is a!+anta$eous from t#e "oint of

t#ermal comfort an! lo& "o&er consum"tion.

•

'nl) met#o! for makin$ concrete li$#t %) inclusion of air. T#is is ac#ie+e!%) a9 re"lacin$ ori$inal mineral a$$re$ate %) li$#t &ei$#t a$$re$ate, %9 B)


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intro!ucin$ $as or air %u%%le in mortar c9 B) omittin$ san! fraction from

concrete. T#is is calle! no *ne concrete.

• Li$#t &ei$#t a$$re$ate inclu!e "umice, sa& !ust rice #usk, t#ermocole

%ea!s, forme! sla$. Etc

• Li$#t &ei$#t concrete a$$re$ate e(#i%it #i$# *re resistance.

• :tructural li$#t&ei$#t a$$re$ates cellular structure "ro+i!es internalcurin$ t#rou$# &ater entrainment ic# is es"eciall) %ene*cial for #i$#-

"erformance concrete

• li$#t&ei$#t a$$re$ate #as %etter t#ermal "ro"erties, %etter *re ratin$s,

re!uce! s#rinka$e, e(cellent freein$ an! t#a&in$ !ura%ilit), im"ro+e!

contact %et&een a$$re$ate an! cement matri(, less micro-crackin$ as a

result of %etter elastic com"ati%ilit), more %last resistant, an! #as %etter

s#ock an! soun! a%sor"tion, Hi$#-Derformance li$#t&ei$#t a$$re$ate

concrete also #as less crackin$, im"ro+e! ski! resistance an! is rea!il)

"lace! %) t#e concrete "um"in$ met#o!.

• Aerate! concrete is ma!e %) intro!ucin$ air or $as into a slurr) com"ose!

of Dortlan! cement.

• No *ne concrete is ma!e u" of onl) coarse a$$re$ate , cement an! &ater.

T#ese t)"e of concrete is use! for loa! %earin$ cast in situ e(ternal &alls

for %uil!in$. T#e) are also use! for tem"orar) structures %ecause of lo&

initial cost an! can %e reuse! as a$$re$ate.

/ih densit- concrete

• T#e !ensit) of #i$# !ensit) concrete +aries from 33/0 k$m3 to 38=0

k$m3.T#e) can #o&e+er %e "ro!uce! &it# !ensit) u"to 7820 k$m3 usin$

iron as %ot# *ne an! coarse a$$re$ate.

• Hea+)&ei$#t concrete uses #ea+) natural a$$re$ates suc# as %arites orma$netite or manufacture! a$$re$ates suc# as iron or lea! s#ot. T#e

!ensit) ac#ie+e! &ill !e"en! on t#e t)"e of a$$re$ate use!. T)"icall)

usin$ %arites t#e !ensit) &ill %e in t#e re$ion of 3,700k$m3, ic# is =7

$reater t#an t#at of normal concrete, ile &it# ma$netite t#e !ensit) &ill

%e 3,100k$m3, or /0 $reater t#an normal concrete. er) #ea+)

concretes can %e ac#ie+e! &it# iron or lea! s#ot as a$$re$ate, is

7,100k$m3 an! 8,100k$m3res"ecti+el).

• T#e) are mainl) use! in t#e construction of ra!iation s#iel!s 6me!ical or

nuclear9. '>s#ore, #ea+)&ei$#t concrete is use! for %allastin$ for

"i"elines an! similar structures

• T#e i!eal "ro"ert) of normal an! #i$# !ensit) concrete are #i$# mo!ulusof elasticit) , lo& t#ermal e("ansion , an! cree" !eformation

• Because of #i$# !ensit) of concrete t#ere &ill %e ten!enc) for se$re$ation.

To a+oi! t#is "re "lace! a$$re$ate met#o! of concretin$ is a!o"te!.

• Hi$# Fo!ulus of Elasticit), Lo& t#ermal E("ansion ,Lo& elasticit) an!

cree" !eformation are i!eal "ro"erties.

• T#e #i$# !ensit). Concrete is use! in construction of ra!iation s#iel!s.

T#e) are e>ecti+e an! economic construction material for "ermanent

s#iel!in$ "ur"ose.

• Fost of t#e a$$re$ate s"eci*c $ra+it) is more t#an 3.7

Mass concrete


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Fass concrete is !e*ne! in ACI as ;an) +olume of concrete &it# !imensions lar$e

enou$# to reuire t#at measures %e taken to co"e &it# $eneration of #eat from

#)!ration of t#e cement an! atten!ant +olume c#an$e to minimie crackin$.<

T#e !esi$n of mass concrete structures is $enerall) %ase! on !ura%ilit),

econom), an! t#ermal action, &it# stren$t# often %ein$ a secon!ar), rat#er t#an

a "rimar), concern. T#e one c#aracteristic t#at !istin$uis#es mass concrete fromot#er concrete &ork is t#ermal %e#a+ior. Because t#e cement-&ater reaction is

e(ot#ermic %) nature, t#e tem"erature rise &it#in a lar$e concrete mass, ere

t#e #eat is not uickl) !issi"ate!, can %e uite #i$#. :i$ni*cant tensile stresses

an! strains ma) result from t#e restraine! +olume c#an$e associate! &it# a

!ecline in tem"erature as #eat of #)!ration is !issi"ate!. Feasures s#oul! %e

taken ere crackin$ !ue to t#ermal %e#a+ior ma) cause a loss of structural

inte$rit) an! monolit#ic action, e(cessi+e see"a$e an! s#ortenin$ of t#e ser+ice

life of t#e structure, or %e aest#eticall) o%Gectiona%le. Fan) of t#e "rinci"les in

mass concrete "ractice can also %e a""lie! to $eneral concrete &ork, ere%)

economic an! ot#er %ene*ts ma) %e realie!. Fass concretin$ "ractices &ere

!e+elo"e! lar$el) from concrete !am construction, ere tem"erature-relate!crackin$ &as *rst i!enti*e!. Tem"erature-relate! crackin$ #as also %een

e("erience! in ot#er t#ick-section concrete structures, inclu!in$ mat

foun!ations, "ile ca"s, %ri!$e "iers, t#ick &alls, an! tunnel linin$s

Read-mi0 Concrete

Rea!)-mi( concrete #as cement, a$$re$ates, &ater an! ot#er in$re!ients,

ic# are &ei$#-%atc#e! at a centrall) locate! "lant. T#is is t#en

!eli+ere! to t#e construction site in truck mounte! transit mi(ers an! can %e

use! strai$#t a&a) &it#out an) furt#er treatment. T#is results in a "recise

mi(ture, allo&in$ s"ecialt) concrete mi(tures to %e !e+elo"e! an! im"lemente!

on construction sites. Rea!)-mi( concrete is sometimes "referre! o+er on-site

concrete mi(in$ %ecause of t#e "recision of t#e mi(ture an! re!uce! &orksite

confusion. Ho&e+er, usin$ a "re-!etermine! concrete mi(ture re!uces 4e(i%ilit),

%ot# in t#e su""l) c#ain an! in t#e actual com"onents of t#e concrete. Rea!)

Fi(e! Concrete, or RFC as it is "o"ularl) calle!, refers to concrete t#at is

s"eci*call) manufacture! for !eli+er) to t#e customers construction site in a

fres#l) mi(e! an! "lastic or un#ar!ene! state. Concrete itself is a mi(ture of

Dortlan! cement, &ater an! a$$re$ates com"risin$ san! an! $ra+el or crus#e!

stone. In tra!itional &ork sites, eac# of t#ese materials is "rocure! se"aratel)

an! mi(e! in s"eci*e! "ro"ortions at site to make concrete. Rea!) Fi(e!

Concrete is %ou$#t an! sol! %) +olume usuall) e("resse! in cu%ic meters.Rea!) Fi(e! Concrete is manufacture! un!er com"uter-controlle! o"erations

an! trans"orte! an! "lace! at site usin$ so"#isticate! eui"ment an! met#o!s.

RFC assures its customers numerous %ene*ts.

o"-mer concrete

Concrete is "orous. T#e "orosit) is !ue to air +oi!s , &ater +oi!s or !ue to

in#erent "ro"ert) of $el structures. 'n account of "orosit) stren$t# of concrete is

re!uce! , re!uction of "orosit) result in increase in stren$t# of concrete. T#e

im"re$nation of monomer an! su%seuent "ol)meriation is t#e latest tec#niue

a!o"te! to re!uce in#erent "orosit) of concrete an! increase stren$t# an! ot#er

"ro"erties of concrete. T#ere are mainl) = t)"es of "ol)mer concrete


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5. Dol)mer im"re$nate! concrete

2. Dol)mer cement concrete

3. Dol)mer concrete

=. Dartiall) im"re$nate! an! surface coate! "ol)mer concrete.

o"-mer im$renated concrete

It is a "recast con+entional concrete cure! an! !rie! in o+en or %) !ielectric

#eatin$ from ic# t#e air in t#e o"en cell is remo+e! %) +acuum. T#en a lo&

+iscosit) monomer is !i>use! t#rou$# t#e o"en cell an! "ol)merie! %) usin$

ra!iation, a""lication of #eat or %) c#emical initiation.

o"-mer cement concrete

Dol)mer cement concrete is ma!e %) mi(in$ cement, a$$re$ate, &ater an!

monomer. :uc# "lastic mi(ture is cast in moul!s , cure! !rie! an! "ol)merie!.

T#e monomer t#at are use! in DCC are

5. Dol)ster- st)rene

2. E"o()-st)rene

3. urans

=. in)l!ene c#lori!e

DCC "ro!uce! in t#is &a) #a+e %een !isa""ointin$. In man) cases material

"oorer t#an or!inar) concrete is o%taine!. T#is is %ecause or$anic material are

incom"ata%le &it# aueous s)stems an! some times interfere &it# t#e alkaline

cement #)!ration "rocess. Russians !e+elo"e! a su"erior "ol)mer %)

incor"oration of furfur)l alco#ol an! aniline #)!roc#lori!e in t#e &et mi(. T#is

material is !ense an! non s#rinkin$ an! to #a+e #i$# corrosion resistance, lo&

"ermea%ilit) an! #i$# resistance to +i%ration an! a(ial e(tension .DCC can %e

cast in situ for *el! a""lication.o"-mer concrete

Dol)mer concrete is an a$$re$ate %oun! &it# a "ol)mer %in!er instea! of

Dortlan! cement as in con+entional concrete. T#e main tec#niue in "ro!ucin$

DC is to minimie +oi! +olume in t#e a$$re$ate mass so as to re!uce t#e

uantit) of "ol)mer nee!e! for %in!in$ t#e a$$re$ate. T#is is ac#ie+e! %)

"ro"erl) $ra!in$ an! mi(in$ t#e a$$re$ate to attain ma(imum !ensit) an!

minimum +oi!s

Shotcrete

It is !e*ne! as a mortar con+e)e! t#rou$# a #ose an! "neumaticall) "roGecte! at#i$# +elocit) on to a surface. T#ere are mainl) t&o !i>erent met#o!s namel) &et

mi( an! !r) mi( "rocess. In &et mi( "rocess t#e material is con+e)e! after

mi(in$ &it# &ater.

re $ac*ed concrete

In constructions ere t#e reinforcement is +er) com"licate! or ere certain

arran$ements like "i"e, o"enin$ or ot#er arran$ements are incor"orate! t#is

t)"e of concretin$ is a!o"te!. 'ne of t#e met#o!s is concrete "rocess in ic#

mortar is ma!e in a #i$# s"ee! !ou%le !rum an! $routin$ is !one %) "ourin$ on

"re"acke! a$$re$ate. T#is is mainl) a!o"te! for "a+ement sla%s2acuum concrete


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Concrete "oure! into a frame&ork t#at is *tte! &it# a +acuum mat to remo+e

&ater not reuire! for settin$ of t#e cement in t#is frame&ork, concrete attains

its 28-!a) stren$t# in 50 !a)s an! #as a 27 #i$#er crus#in$ stren$t#. T#e

elastic an! s#rinka$e !eformations are consi!era%l) $reater t#an for normal-

&ei$#t concrete.

um$ed concrete

Dum"e! concrete must %e !esi$ne! to t#at it can %e easil) con+e)e! %) "ressure

t#rou$# a ri$i! "i"e of 4e(i%le #ose for !isc#ar$e !irectl) into t#e !esire! area.

Doocrete use can $reatl) im"ro+e concrete 4o& c#aracteristics makin$ it muc#

easier to "um", ile en#ancin$ t#e ualit) of t#e concrete an! controllin$

costs.

o33ocrete E,ecti4e

nfortunatel), a!!in$ e(tra &ater an! *ne a$$re$ate lea!s to a &eaker

concrete. T#e usual reme!ies for t#is are eit#er to increase t#e cement content,

ic# is costl), or to use c#emical a!mi(tures, ic# can also %e costl) an! ma)

lea! to se$re$ation in mar$inal mi(es. T#ere is anot#er an! far more e>ecti+e

alternati+e

'55'CRETE

T#ere are man) a!+anta$es to inclu!in$ D'JJ'CRETE in concrete mi(es to %e

"um"e!.

5. Darticle :ie. Doocrete meets I: 3852 :"eci*cation &it# // "assin$ t#e 327

6=7-micron9 sie+e an! t#ese *ne "articles are i!eal for +oi! *llin$. Kust a small

!e*cienc) in t#e mi( *nes can often "re+ent successful "um"in$.

2. Darticle :#a"e. Ficrosco"ic e(amination s#o&s most Doocrete "articles are

s"#erical an! act like miniature %all %earin$s ai!in$ t#e mo+ement of t#e

concrete %) re!ucin$ frictional losses in t#e "um" an! "inin$. :tu!ies #a+e

s#o&n t#at Doocrete can %e t&ice as e>ecti+e as cement in im"ro+in$

&orka%ilit) an!, t#erefore, im"ro+e "um"in$ c#aracteristics.

.39 W#at are t#e !i>erent t)"es of concrete structuresM Illustrate &it# !ia$rams.

Ans. TDE: ' C'NCRETE :TRCTRE: ARE-

• Drecast sla%s

•

Drecast %eam an! $ir!ers• Drecast columns

• Drecast &alls

• Drecast stairs

Q.6) What are minera" admi0tures! What are the di,erent t-$es of

minera" admi0tures added to concrete!

Ans. Minera" admi0tures are t#e *ne $roun! soli! materials I.e. l) as#, sla$

an! silica fume. It is a!!e! to t#e concrete $enerall) in lar$er amount t#an an)

ot#er t)"e. Because mineral a!mi(tures #a+e an a%ilit) to en#ance &orka%ilit)

as &ell as *nis#-a%ilit) of fres#l) lai! concrete. Fineral a!mi(tures are also

utilie! as a re"lacement of cement. As cement is t#e most e("ensi+e material in


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concrete. Hence, &it# t#e use of mineral a!mi(tures re!ucin$ concrete cost is

+er) likel) "ossi%le.

Fineral a!mi(tures are t#e &aste "ro!ucts of in!ustries. Hence %) usin$ in

concrete, ma(imum sustaina%ilit) can %e ac#ie+e!. It also su""orts in re!ucin$

t#ermal crackin$ in concrete %) re!ucin$ #eat of #)!ration. At t#e en! &e can

sa) t#at t#is t)"e of a!mi(tures en#ances t#e !ura%ilit) an! ser+icea%ilit) of

concrete.

Minera" Admi0tures in Concrete

T-$es of Minera" Admi0tures

1. Cementitious T#ese #a+e cementin$ "ro"erties t#emsel+es. or

e(am"le ?roun! $ranulate! %last furnace sla$ 6??B:9

+. o33o"anic A "oolan is a material ic#, en com%ine! &it# calcium

#)!ro(i!e 6lime9, e(#i%its cementitious "ro"erties. Doolans are

commonl) use! as an a!!ition 6t#e tec#nical term is Ocement e(ten!erO9

to Dortlan! cement concrete mi(tures to increase t#e lon$-term stren$t#

an! ot#er material "ro"erties of Dortlan! cement concrete an! in some

cases re!uce t#e material cost of concrete. E(am"les are l) as#, :ilica

ume7 Rice Husk As#7 Fetakaolin

8. Ground Granu"ated 9"ast &urnace S"a :GG9&S)

?roun! $ranulate! %last-furnace sla$ is t#e ranu"ar materia" forme! en

molten iron %last furnace sla$ 6a %)-"ro!uct of iron an! steel makin$9 is ra"i!l)

c#ille! 6uenc#e!9 %) immersion in &ater. It is a $ranular "ro!uct, hih"-

cementitious in nature an!, $roun! to cement *neness, #)!rates like Dortlan!

cement. ??B: is use! to make !ura%le concrete structures in com%ination &it#

or!inar) Dortlan! cement an!or ot#er "oolanic materials. ??B: #as %een

&i!el) use! in Euro"e, an! increasin$l) in t#e nite! :tates an! in Asia6"articularl) in Ka"an an! :in$a"ore9 for its su"eriorit) in concrete !ura%ilit),

e(ten!in$ t#e lifes"an of %uil!in$s from *ft) )ears to a #un!re! )ears.

Concrete ma!e &it# ??B: cement sets more s"o#"- t#an concrete ma!e &it#

or!inar) Dortlan! cement, !e"en!in$ on t#e amount of ??B: in t#e

cementitious material, %ut also continues to $ain stren$t# o+er a lon$er "erio! in

"ro!uction con!itions. T#is results in "o#er heat of h-dration an! "o#er

tem$erature rises, an! makes a+oi!in$ co"d ;oints easier, %ut ma) also a>ect

construction sc#e!ules ere uick settin$ is reuire!.

se of ??B: si$ni*cantl) re!uces t#e risk of !ama$es cause! %) alkali-silica

reaction 6A:R9, "ro+i!es #i$#er resistance to c#lori!e in$ress, re!ucin$ t#e risk of

reinforcement corrosion, an! "ro+i!es #i$#er resistance to attacks %) sulfate an!

ot#er c#emicals.

9enei"it-

5. ??B: cement is routinel) s"eci*e! in concrete to "ro+i!e

"rotection a$ainst %ot# sul"#ate attack an! c#lori!e attack

2. ??B: is also routinel) use! to limit t#e tem"erature rise in lar$e

concrete "ours. T#e more $ra!ual #)!ration of ??B: cement

$enerates %ot# lo&er "eak an! less total o+erall #eat t#an Dortlan!

cement.

2. A$$earance


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5. In contrast to t#e ston) $re) of concrete ma!e &it# Dortlan!

cement, t#e near-ite color of ??B: cement "ermits arc#itects to

ac#ie+e a li$#ter colour for e("ose! fair-face! concrete *nis#es, at

no e(tra cost.

3. Strenth

5. Concrete containin$ ??B: cement #as a #i$#er ultimate stren$t#t#an concrete ma!e &it# Dortlan! cement. It #as a #i$#er

"ro"ortion of t#e stren$t#-en#ancin$ calcium silicate #)!rates

6C:H9 t#an concrete ma!e &it# Dortlan! cement onl), an! a

re!uce! content of free lime, ic# !oes not contri%ute to concrete

stren$t#. Concrete ma!e &it# ??B: continues to $ain stren$t#

o+er time, an! #as %een s#o&n to !ou%le its 28 !a) stren$t# o+er

"erio!s of 50 to 52 )ears.

6. &"- Ash( T#e *nel) !i+i!e! resi!ue resultin$ from t#e com%ustion of $roun!

or "o&!ere! coal. l) as# is $enerall) ca"ture! from t#e c#imne)s of coal-*re!"o&er "lants it #as D'JJ'LANIC "ro"erties, an! is sometimes %len!e! &it#

cement for t#is reason.

C"ass & &"- Ash(

T#e %urnin$ of #ar!er, ol!er ant#racite an! %ituminous coal t)"icall) "ro!uces

Class 4) as#. T#is 4) as# is "oolanic in nature, an! contains less t#an 50

lime 6Ca'9. T#e $lass) silica an! alumina of Class 4) as# reuires a cementin$

a$ent, suc# as Dortlan! cement, uicklime, or #)!rate! lime, &it# t#e "resence

of &ater in or!er to react an! "ro!uce cementitious com"oun!s.

C"ass C &"- Ash(l) as# "ro!uce! from t#e %urnin$ of )oun$er li$nite or su%%ituminous coal, in

a!!ition to #a+in$ "oolanic "ro"erties, also #as some self-cementin$

"ro"erties. In t#e "resence of &ater, Class C 4) as# &ill #ar!en an! $ain stren$t#

o+er time. Class C 4) as# $enerall) contains more t#an 20 lime 6Ca'9. nlike

Class , self-cementin$ Class C 4) as# !oes not reuire an acti+ator. Alkali an!

sulfate 6:'=9 contents are $enerall) #i$#er in Class C 4) as#es.

In a!!ition to economic an! ecolo$ical %ene*ts, t#e use of 4) as# in concrete

im"ro+es its &orka%ilit), re!uces se$re$ation, %lee!in$, #eat e+olution an!

"ermea%ilit), in#i%its alkali-a$$re$ate reaction, an! en#ances sulfate resistance.

'ne of t#e most im"ortant *el!s of a""lication for 4) as# is DCC "a+ement,

ere a lar$e uantit) of concrete is use! an! econom) is an im"ortant factor in

concrete "a+ement construction.

?. Si"ica &ume 6B)-"ro!uct of semicon!uctor in!ustr)9

T#e terms con!ense! silica fume, microsilica, silica fume an! +olatilie! silica are

often use! to !escri%e t#e %)-"ro!ucts e(tracte! from t#e e(#aust $ases of

silicon, ferrosilicon an! ot#er metal allo) furnaces. Ho&e+er, t#e terms

microsilica an! silica fume are use! to !escri%e t#ose con!ense! silica fumes

t#at are of #i$# ualit), for use in t#e cement an! concrete in!ustr).


9/25

Because of its e(treme *neness an! #i$# silica content, :ilica ume is a #i$#l)

e>ecti+e "oolanic material. :ilica ume is use! in concrete to im"ro+e its

"ro"erties. It #as %een foun! t#at :ilica ume im"ro+es com"ressi+e stren$t#,

%on! stren$t#, an! a%rasion resistance re!uces "ermea%ilit) of concrete to

c#lori!e ions an! t#erefore #el"s in "rotectin$ reinforcin$ steel from corrosion,

es"eciall) in c#lori!e-ric# en+ironments suc# as coastal re$ions.

@. Rice /us* Ash( T#is is a %io &aste from t#e #usk left from t#e $rains of rice.

It is use! as a "oolanic material in cement to increase !ura%ilit) an! stren$t#.

T#e silica is a%sor%e! from t#e $roun! an! $at#ere! in t#e #usk ere it makes

a structure an! is *lle! &it# cellulose. W#en cellulose is %urne!, onl) silica is left

ic# is $rin!e! to *ne "o&!er ic# is use! as "oolana.

Q.?) What are the di,erent t-$es of Chemica" admi0tures added to

concrete!

Ans. Chemica" admi0tures are materials in t#e form of "o&!er or 4ui!s t#at

are a!!e! to t#e concrete to $i+e it certain c#aracteristics not o%taina%le &it#

"lain concrete mi(es. In normal use, a!mi(ture !osa$es are less t#an 7 %)

mass of cement an! are a!!e! to t#e concrete at t#e time of %atc#in$mi(in$.

• Acce"erators s"ee! u" t#e #)!ration 6#ar!enin$9 of t#e concrete. T)"ical

materials use! are CaCl2, Ca6N'392 an! NaN'3. Acceleratin$ a!mi(tures

are es"eciall) useful for mo!if)in$ t#e "ro"erties of concrete in col!

&eat#er.

• Retarders slo& t#e #)!ration of concrete an! are use! in lar$e or !iPcult

"ours ere "artial settin$ %efore t#e "our is com"lete is un!esira%le.

T)"ical retar!ers are su$ar, sucrose, so!ium $luconate, $lucose, citric aci!,

an! tartaric aci!.

• Air entrainments a!! an! entrain tin) air %u%%les in t#e concrete, ic#

re!uces !ama$e !urin$ freee-t#a& c)cles, increasin$ !ura%ilit). Ho&e+er,

entraine! air entails a tra!e o> &it# stren$t#, as eac# 5 of air ma)

!ecrease com"ressi+e stren$t# %) 7

• "astici3ers increase t#e &orka%ilit) of "lastic or Ofres#O concrete,

allo&in$ it %e "lace! more easil), &it# less consoli!atin$ e>ort. A t)"ical

"lasticier is li$nosulfonate. Dlasticiers can %e use! to re!uce t#e &ater

content of a concrete ile maintainin$ &orka%ilit) an! are sometimes

calle! &ater-re!ucers !ue to t#is use. :uc# treatment im"ro+es its

stren$t# an! !ura%ilit) c#aracteristics.• iments can %e use! to c#an$e t#e color of concrete, for aest#etics.

• Corrosion inhi>itors are use! to minimie t#e corrosion of steel an!

steel %ars in concrete.

• 9ondin aents are use! to create a %on! %et&een ol! an! ne&

concrete 6t)"icall) a t)"e of "ol)mer9 &it# &i!e tem"erature tolerance

an! corrosion resistance.

Q.@)What is the ro"e of #ater in concrete! Wh- is curin of concrete

im$ortant!


10/25

Ans. T#e #ater is use! in concrete "la)s an im"ortant "art in t#e mi(in$, la)in$

com"action settin$ an! #ar!enin$ of concrete. T#e stren$t# of concrete !irectl)

!e"en!s on t#e uantit) an! ualit) of &ater is use! in t#e mi(.

unctions

5. Water is onl) t#e in$re!ient t#at reacts c#emicall) &it# cement an! t#us

settin$ an! #ar!enin$ takes "lace.

2. Water acts as a lu%ricant for t#e a$$re$ate an! makes t#e concrete &orka%le.

3. It facilitates t#e s"rea!in$ of cement o+er t#e *ne a$$re$ate.

Curin is t#e "rocess of controllin$ t#e rate an! e(tent of moisture loss from

concrete to ensure an uninterru"te! #)!ration of Dortlan! cement after concrete

#as %een "lace! an! *nis#e! in its *nal "osition. Curin$ also ensures to maintain

an a!euate tem"erature of concrete in its earl) a$es, as t#is !irectl) a>ects t#e

rate of #)!ration of cement an! e+entuall) t#e stren$t# $ain of concrete or

mortars.

Curin$ of concrete must %e$in as soon as "ossi%le after "lacement Q *nis#in$

an! must continue for a reasona%le "erio! of time as "er t#e rele+ant stan!ar!s,

for t#e concrete to ac#ie+e its !esire! stren$t# an! !ura%ilit). niform

tem"erature s#oul! also %e maintaine! t#rou$#out t#e concrete !e"t# to a+oi!

t#ermal s#rinka$e cracks. Also "rotecti+e measures to control moisture loss from

t#e concrete surface are essential to "re+ent "lastic s#rinka$e cracks.

In a nut s#ell, curin$ "rocess is !esi$ne! "rimaril) to kee" t#e concrete moist %)

controllin$ t#e loss of moisture from t#e %o!) of concrete, !urin$ t#e $i+en

"erio! in ic# it $ains stren$t#.

Reasons to Cure Concrete

i$ure 5 E>ect of !uration of &ater curin$ on

stren$t# of concrete6CCAA, !ata s#eet, A"ril

200/, *$ure-5, "a$e29

Concrete strenth ain - Concrete stren$t# increase &it# a$e as moisture an!

a fa+ora%le tem"erature is "resent for #)!ration of cement.

Im$ro4ed dura>i"it- of concrete T#e !ura%ilit) of concrete is a>ecte! %) a

num%er of factors inclu!in$ its "ermea%ilit), "orosit) an! a%sor"ti+it). Well cure!

concrete can minimie t#ermal, "lastic Q !r)in$ s#rinka$e cracks, makin$

concrete more &ater ti$#t, t#us "re+entin$ moisture an! &ater %orne c#emicals

from enterin$ into t#e concrete an! t#ere%) increasin$ its !ura%ilit).


11/25

Enhanced ser4icea>i"it- - Concrete t#at is allo&e! to !r) out uickl)

un!er$oes consi!era%le earl) a$e s#rinka$e. Ina!euate curin$ contri%utes to

&eak an! !ust) surfaces #a+in$ a "oor a%rasion resistance.

Im$ro4ed microstructure Faterial "ro"erties are !irectl) relate! to t#eir

microstructure. Curin$ assists t#e cement #)!ration reaction to "ro$ress stea!il)

an! !e+elo"s calcium silicate #)!rate $el, ic# %in!s t#e a$$re$ates lea!in$ to

a rock soli! mass, makes t#e concrete !enser, !ecreases t#e "orosit) an!

en#ances t#e "#)sical an! mec#anical "ro"erties of concrete.

Q.) What are the di,erent t-$es of ort"and Cement!

Ans. T#e cement use! s#all #e an) of t#e follo&in$ an! t#e t)"e selecte! s#oul!

%e a""ro"riate for t#e inten!e! use

a9 33 ?ra!e or!inar) Dortlan! cement conformin$ to I: 2/1

%9 =3 ?ra!e or!inar) Dortlan! cement conformin$ to I: 8552

c9 :3 ?ra!e or!inar) Dortlan! cement conformin$ to I: 522/1

!9 Ra"i! #ar!enin$ Dortlan! cement conformin$ to I: 80=5

e9 Dortlan! sla$ cement conformin$ to I: =77

f9 Dortlan! "oolana cement 64) as# %ase!9 conformin$ to I: 5=81 6Dart 59

$9 Dortlan! "oolana cement 6calcine! cla) %ase!9 conformin$ to I: 5=81 6Dart

29

#9 H)!ro"#o%ic cement conformin$ to I: 80=3

G9 Lo& #eat Dortlan! cement conformin$ to I: 52/00

k9 :ul"#ate resistin$ Dortlan! cement conformin$ to I: 52330

Q.B) What is the >asic conce$t of #or*in stress method :WSM) and

U"timate oad Method :UM)!Ans.or #or*in stress a""roac#, ser+ice loa!s are use! in t#e ole !esi$n

an! t#e stren$t# of material is not utilie! in t#e full e(tent.

In t#is met#o! of !esi$n, stresses actin$ on structural mem%ers are calculate!

%ase! on elastic met#o! an! t#e) are !esi$ne! not to e(cee! certain allo&a%le

+alues. In fact, t#e ole structure !urin$ t#e lifes"an ma) onl) e("erience

loa!in$ stresses far %elo& t#e ultimate state an! t#at is t#e reason ) t#is

met#o! is calle! &orkin$ stress a""roac#. n!er suc# scenario, t#e most

economical !esi$n can #ar!l) %e o%taine! %) usin$ &orkin$ stress a""roac#

ic# is no& commonl) use! in t#e !esi$n of tem"orar) &orks.

Assum$tions in #or*in stress method(

• Dlane section %efore %en!in$ &ill remain "lane after %en!in$.

• :tress-strain relations o%e) Hooks la& 6linear9

• Tensile stresses are taken %) steel onl).

• T#e Fo!ular ratio m 280 3S c%c

o T#e :tresses in an element is o%taine! from t#e &orkin$ loa!s an!

com"are! &it# "ermissi%le stresses.o T#e met#o! follo&s linear stress-strain %e#a+iour of %ot# t#e materials.

o Fo!ular ratio can %e use! to !etermine allo&a%le stresses.

o Faterial ca"a%ilities are un!er estimate! to lar$e e(tent. actor of safet)

are use! in &orkin$ stress met#o!.o T#e mem%er is consi!ere! as &orkin$ stress.


12/25

o ltimate loa! carr)in$ ca"acit) cannot %e "re!icte! accuratel).

o T#e main !ra&%ack of t#is met#o! is t#at it results in an uneconomical

section.

UTIMATE 'A= &ACT'R MET/'=- A maGor !efect of t#e mo!ular ratio or

&orkin$ stress met#o! of !esi$n is t#at it !oes not $i+e a true factor of safet)

a$ainst failure. To o+ercome t#is, t#e ultimate loa! met#o! of !esi$n &as

intro!uce! in reinforce! concrete !esi$n. T#is met#o! later &as mo!i*e! as Loa!

actor Fet#o!. T#is met#o! takes into account t#e non-linear stress-strain

%e#a+ior of concrete. T#e term safet) factor #as %een use! in t#e &orkin$ stress

met#o! to !enote t#e ratio %et&een t#e )iel! stress an! t#e "ermissi%le stress.

Q.) =escri>e The "imit state method of concrete desin! Wh- is the

"imit state method $referred o4er WSM and UM! What are the imit

state of Co""a$se and imit state of ser4icea>i"it-!

Ans. or "imit state a$$roach, for eac# material an! loa!, a "artial safet)factor is assi$ne! in!i+i!uall) !e"en!in$ on t#e material "ro"erties an! loa!

"ro"erties.

o T#erefore, eac# element of loa! an! material "ro"erties is accuratel)

assesse! resultin$ in a more re*ne! an! accurate anal)sis of t#e

structure.o T#e material stren$t# can %e utilie! to its ma(imum +alue !urin$ its

lifes"an an! loa!s can %e assesse! &it# reasona%le "ro%a%ilit) of

occurrence.o Limit state a""roac# is commonl) use! for t#e maGorit) of reinforce!

concrete !esi$n %ecause it ensures t#e utiliation of material stren$t# &it#t#e lo&est construction cost in"ut.

o Limit states are t#e acce"ta%le limits for t#e safet) an! ser+icea%ilit)

reuirements of t#e structure %efore failure occurs.o T#e !esi$n of structures %) t#is met#o! &ill t#us ensure t#at t#e) &ill not

reac# limit states an! &ill not %ecome un*t for t#e use for ic# t#e) are

inten!e!.o It is &ort# mentionin$ t#at structures &ill not Gust fail or colla"se %)

+iolatin$ 6e(cee!in$9 t#e limit states. ailure, t#erefore, im"lies t#at

clearl) !e*ne! limit states of structural usefulness #as %een e(cee!e!.

Ad4antaes o4er WSM and UM

o T#e stresses are o%taine! from !esi$n loa!s an! com"are! &it# !esi$n

stren$t#.o In t#is met#o!, it follo&s linear strain relations#i" %ut not linear stress

relations#i" 6one of t#e maGor !i>erence %et&een t#e t&o met#o!s of

!esi$n9.o T#e ultimate stresses of materials itself are use! as allo&a%le stresses.

o T#e material ca"a%ilities are not un!er estimate! as muc# as t#e) are in

&orkin$ stress met#o!. Dartial safet) factors are use! in limit state

met#o!.o Limit :tate of colla"se Wit# res"ect to stren$t# in s#ear, 4e(ure, torsion,

%on! or com%ine! e>ects. It !eals &it# t#e stren$t# an! sta%ilit) ofstructures su%Gecte! to t#e ma(imum !esi$n loa!s out of t#e "ossi%le


13/25

com%inations of se+eral t)"es of loa!s. T#erefore, t#is limit state ensures

t#at neit#er an) "art nor t#e ole structure s#oul! colla"se or %ecome

unsta%le un!er an) com%ination of e("ecte! o+erloa!s.o :er+icea%ilit) Limit :tate Wit# res"ect to !e4ection Q crackin$. T#e

a""earance, !ura%ilit) an! "erformance of t#e structure must not %e

a>ecte! %) !e4ection Q crackin$.

Q.1D) =escri>e di,erent t-$es of connections in stee"! What are the

merits of #e"ded connections o4er ri4eted connections!

Ans. T#e !i>erent kin!s of Goints are

o Ri+ete! Goints

o Bolte! Koints

o Wel!e! Koints

Ri4eted oints- A Ri+et is a s#ort c)lin!rical ro! #a+in$ a #ea! an! a ta"ere!

tail. T#e main %o!) of t#e ri+et is calle! s#ank 6see *$ure9. Accor!in$ to In!ian

stan!ar! s"eci*cations ri+et #ea!s are of +arious t)"es.

Ri+etin$ is an o"eration ere%) t&o "lates are Goine! &it# t#e #el" of a ri+et.

A!euate mec#anical force is a""lie! to make t#e Goint stron$ an! leak "roof.

:moot# #oles are !rille! 6or "unc#e! an! reame!9 in t&o "lates to %e Goine! an!

t#e ri+et is inserte!. Hol!in$, t#en, t#e #ea! %) means of a %ackin$ u" %ar,

necessar) force is a""lie! at t#e tail en! &it# a !ie until t#e tail !eforms

"lasticall) to t#e reuire! s#a"e. @e"en!in$ u"on et#er t#e ri+et is initiall)

#eate! or not, t#e ri+etin$ o"eration can %e of t&o t)"es 6a9 col! ri+etin$ is

!one at am%ient tem"erature an! 6%9 #ot ri+etin$

TFES '& RI2ETING


14/25

T-$es of ri4eted ;oints and ;oint ecienc-(

Ri+ete! Goints are mainl) of t&o t)"es

o La" Goints

o Butt Goints

a$ oints( T#e "lates t#at are to %e Goine! are %rou$#t face to face suc# t#at

an o+erla" e(ists.

9utt oint( T&o mem%ers or t#e elements are linke! e!$e to e!$e in one

strai$#t line. T#e clam"in$ is "ro!uce! usin$ an e(ternal co+er "late ic# is

t#en ri+ete! t#rou$# t#e !rille! #oles.

WE=E= 'INTS

A &el!e! Goint is a "ermanent Goint ic# is o%taine! %) t#e fusion of t#e e!$es

of t#e t&o "arts to %e Goine! to$et#er, &it# or &it#out t#e a""lication of "ressure

an! a *ller material.

5. Butt Koint

2. Corner Koint

3. T Koint

=. La" Koint

7. E!$e Koint

A 'INT(


15/25

9UTT 'INT

C'RNER 'INT Corner Goint - a Goint %et&een t&o mem%ers locate! at ri$#t

an$les to eac# ot#er


16/25

T'INT T- Goint - a Goint %et&een t&o mem%ers locate! a""ro(imatel) at ri$#t

an$les to eac# ot#er in t#e form of a T.

E=GE 'INT- E!$e &el!in$ Goints, a $roo+e t)"e of &el!, are "lace! si!e %) si!ean! &el!e! on t#e same e!$e. T#e) are t#e most commonl) re"lace! t)"e of

Goints !ue to %uil! u" accumulatin$ on t#e e!$es. T#e) are often a""lie! to "arts

of s#eet metal t#at #a+e e!$es 4an$in$ u" or forme! at a "lace ere a &el!

must %e ma!e to Goin t&o a!Gacent "ieces to$et#er.

Ad4antaes of We"ded oints o4er Ri4eted oints

59 T#e &el!e! structures are usuall) li$#ter t#an ri+ete! structures.

29 T#e &el!e! Goints "ro+i!e ma(imum ePcienc) 6ma) %e 5009 ic# is not

"ossi%le in case of ri+ete! Goints.

39 Alterations an! a!!itions can %e easil) ma!e in t#e e(istin$ structures.

=9 As t#e &el!e! structure is smoot# in a""earance, t#erefore it looks "leasin$.

79 In &el!e! connections, t#e tension mem%ers are not &eakene! as in t#e case

of ri+ete! Goints.

/9 A &el!e! Goint #as a $reat stren$t#.

9 :ometimes, t#e mem%ers are of suc# a s#a"e 6i.e. circular steel "i"es9 t#at

t#e) a>or! !iPcult) for ri+etin$. But t#e) can %e easil) &el!e!.89 It is "ossi%le to &el! an) "art of a structure at an) "oint. But ri+etin$ reuires

enou$# clearance.

19 T#e "rocess of &el!in$ takes less time t#an t#e ri+etin$.

Q.11)What are the di,erent t-$es of stee" structures! /o# is "oad

ca"cu"ated for desin of stee" structures!

Ans. T#e !i>erent t)"es of :teel structures are


17/25

Classi*cation of :teel :tructures

5. Tension Fem%ers2. Com"ression Fem%ers3. Truss :)stems an! rame :)stems=. Built-u" Fem%ers an! :tructures7. :#ell :tructures/. :us"ension :tructures. Tension Fem%ers8. Drimaril) occur as1. C#or! Fem%ers in trusses

50.In !ia$onal %racin$ in %racin$ s)stems55.Ca%le elements in sus"ension roofs, main ca%les of sus"ension %ri!$es

an! sus"en!ers.

Com$ression Mem>ers

Drimaril) 'ccur as

o Columns in %uil!in$s

o C#or! Fem%ers in trusses an! !ia$onal mem%ers in en! "anels of trusses

o :ta%ilit) is an im"ortant consi!eration in !esi$n an! %e#a+iour of

com"ression mem%erso Area is $enerall) s"rea! out to ma(imie Ra!ius of ?)ration

9eam Mem>ers(o Drimaril) loa!e! trans+erse to t#e lon$itu!inal a(is an! resist loa!in$ %)

4e(ureo U-sectional area is locate! as far from t#e neutral a(is as is "ractical

o Commonl) W s#a"es are use! in most cases

o or !ee"er %eams I-s#a"e! sections ma!e %) &el!in$ "lates are

commonl) use!o or smaller loa!s an! s"ans o"en-&e% Goists are commonl) use!

o Insta%ilit) !ue to lateral Torsional Bucklin$ is an im"ortant consi!eration

'$enWe> Stee" oist

Economical Q "o"ular for Roof Q 4oor framin$.

Bar Goist are su""orte! %) %earin$ &alls or steel $ir!ers.

loor of t#in concrete reinforce! in %ot# !irections &it# re%ars or &el!e! &ire

fa%ric.


18/25

Q.1+) What are the di,erent t-$es of stee" roof trusses! =iscuss #ith

diarams and e0am$"es.

Ans. @i>erent t)"es of :teel Roof Trusses

o Vin$ Dost Truss

o ueen Dost Trusso Ho&e Truss

o Dratt Truss

o an Truss

o Nort# Li$#t Roof Truss

o ua!ran$ular Roof Truss

Trusses for lar$e s"an constructions

o Tu%ular :teel Roof Truss

o Tu%ular Fonitor :teel Roof Truss

Hin ost Truss

o Vin$ Dost roof truss 6s"ans u"to8F9

o Vin$ Dost Truss is a &oo!en truss.

o It can also %e %uilt of com%ination of &oo! an! steel.

o It can %e use! for s"ans u"to 8m.

Queen ost Truss

o ueen Dost Truss 6s"ans u"to 50F9

o ueen Dost Truss is also a &oo!en truss.

o It can %e use! for s"ans u"to 50m.

/o#e Truss

o Ho&e Truss 6s"ans u"to /F to 30F9

o It is ma!e of com%ination of &oo! an! steel.

o T#e +ertical mem%ers or tension mem%ers are ma!e of steel.

o It can %e use! for s"ans from /-30m.

ratt Truss


19/25

o

Dratt truss 6s"ans u"to /F to 50F9o Dratt Truss is ma!e of steel.

o T#ese are less economical t#an t#e ink Trusses.

o ertical mem%ers are tension an! !ia$onal mem%ers are com"ression.

o ink Trusses are +er) economical form of roof trusses.

o It can %e use! for s"ans from /-50m.

&an Truss

o an Truss 6s"ans u"to 50F to 57F9

o It is ma!e of steel.

o an trusses are form of ink roof truss.

o In an Trusses, to" c#or!s are !i+i!e! into small len$t#s in or!er to "ro+i!e

su""orts for "urlins ic# &oul! not come at Goints in ink trusses.o It can %e use! for s"ans from 50-57m.

North iht Roof Truss

o Nort# li$#t roof truss 6s"ans u"to 20F to 30F9

o W#en t#e 4oor s"an e(cee!s 57m, it is $enerall) more economical to

c#an$e from a sim"le truss arran$ement to one em"lo)in$ &i!e s"anlattice $ir!ers ic# su""ort trusses at ri$#t an$les.

o In or!er to li$#t u" t#e s"ace satisfactoril), roof li$#tin$ #as to re"lace or

su""lement, si!e li$#tin$ "ro+ision must also %e ma!e for +entilation form

t#e roof.o 'ne of t#e ol!est an! economical met#o!s of co+erin$ lar$e areas is t#e

Nort# Li$#t an! Lattice $ir!er.o T#is roof consists of a series of trusses *(e! to $ir!ers. T#e s#ort +ertical

si!e of t#e truss is $lae! so t#at en t#e roof is use! in t#e Nort#ern

Hemis"#ere, t#e $lae! "ortion faces Nort# for t#e %est li$#t.o It can %e use! for s"ans from 20-30m.

o se! for in!ustrial %uil!in$s, !ra&in$ rooms etc.


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Quadranu"ar roof Trusses

o ua!ran$ular Roof Truss 6for lar$e s"ans9

o T#ese trusses are use! for lar$e s"ans suc# as rail&a) s#e!s an!

Au!itoriums.

are S$an Trusses

Q.18) =escri>e the =esin of stee" com$ression mem>ersJ! /o# is it

di,erent from concrete com$ression mem>ersJ! =escri>e the

conce$ts of >ui"t u$ stee" co"umn sections and "acin #ithout desin

ca"cu"ations!

Ans. A structural mem%er loa!e! a(iall) in com"ression is $enerall) calle! a

com"ression mem%er. ertical com"ression mem%ers in %uil!in$s are calle!

columns, "osts or stanc#ions. A com"ression mem%er in roof trusses is calle!

struts an! in a crane is calle! a %oom.

Columns ic# are s#ort are su%Gecte! to crus#in$ an! %e#a+e like mem%ers

un!er "ure com"ression. Columns ic# are lon$ ten! to %uckle out of t#e "laneof t#e loa! a(is.

T/E'RF '& C'UMNS

Eulers formula for critical loa! for a "in-en!e! column su%Gecte! to

a(ial loa! is

W#ere, L len$t# of column %et&een t#e #in$e! en!s,

E mo!ulus of elasticit), an!

I moment of inertia of t#e column section.

T#e column &ill %ecome unser+icea%le if t#e loa!s are lar$er t#an . In t#e

Euler euation, it is assume! t#at stress is "ro"ortional to strain, t#erefore,

Critical :tress


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W#ere, A area of cross-section, an!

r ra!ius of $)ration a%out t#e %en!in$ a(is

slen!erness ratio

A com"ression mem%er com"ose! of t&o an$les, c#annels or tees, %ack to %ack,

in contact or se"arate! %) a small !istance s#oul! %e connecte! to$et#er %)

ri+etin$, %oltin$ or &el!in$ so t#at t#e slen!erness ratio of eac# mem%er

%et&een t#e connections is not $reater t#an =0 nor $reater t#an 0./0 times t#e

most unfa+oura%le slen!erness ratio of t#e strut as a ole. In no case, t#e

s"acin$ of tackin$ ri+ets in a line e(cee! /00mm for suc# mem%ers.

or ot#er t)"es of %uilt-u" com"ression mem%ers, ere co+er "lates are use!,

t#e "itc# of tackin$ ri+ets s#oul! not e(cee! 32t or 300mm, ic#e+er is less,

ere t is t#e t#ickness of t#e t#inner outsi!e "late. W#ere "lates are e("ose! to

%a! &eat#er con!itions, t#e "itc# s#oul! not e(cee! 5/ t or 200mm ic#e+er is

less.

T#e ri+ets, &el!s an! %olts in t#ese connections s#oul! %e suPcient to carr) t#e

s#ear force an! %en!in$ moments, if an), s"eci*e! for %attene! struts. T#e

!iameter of t#e connectin$ ri+ets s#oul! not %e less t#an t#e minimum !iameter

$i+en in t#e ta%le %elo&

Thic*ness of mem>er Minimum diameter of

ri4ets

"to 50mm 5/mm

'+er 50mm u"to 5/mm 20mm

'+er 5/mm 22 mm

:oli! "ackin$ or &as#ers s#oul! %e use! for ri+etin$, %oltin$, ere t#e

mem%ers are se"arate! %ack to %ack.

T#e en! struts s#oul! %e connecte! to$et#er &it# not less t#an t&o ri+ets or

%olts or t#eir eui+alent in &el!in$ an! t#ere s#oul! %e not less t#an t&o

a!!itional connections s"ace! eui!istant in t#e len$t# of t#e strut.

A minimum of t&o ri+et or %olts s#oul! %e use! in eac# connection, one on line

of eac# $au$e mark, ere t#e le$s of t#e connecte! an$les or ta%les of t#e


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connecte! tees are 527mm &i!e or o+er, or ere t#e &e%s of c#annel are

570mm &i!e or o+er.

ACINGS AN= 9ATTENS &'R 9UITU C'MRESSI'N MEM9ERS

As "er In!ian :tan!ar!, I: 800-518=, t#e follo&in$ s"eci*cations are use! for t#e

!esi$n of lacin$ an! %atten "lates.

In a %uilt-u" section, t#e !i>erent com"onents are connecte! to$et#er so t#at

t#e) act as a sin$le column. Lacin$ is $enerall) "referre! in case of eccentric

loa!s. Battenin$ is normall) use! for a(iall) loa!e! columns an! in sections

ere t#e com"onents are not far a"art. lat %ars are $enerall) use! for lacin$.

An$les, c#annels an! tu%ular sections are also use! for lacin$ of +er) #ea+il)

columns. Dlates are use! for %attens.

acins

A "acin s-stem shou"d enera""- conform to the fo""o#in

reKuirements(

i. T#e com"ression mem%er com"risin$ t&o main com"onents lace! an!

tie! s#oul!, ere "ractica%le, #a+e a ra!ius of $)ration a%out t#e a(is

"er"en!icular to t#e "lane of lacin$ not less t#an t#e ra!ius of $)ration atri$#t an$les to t#at a(is.


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ii. T#e lacin$ s)stem s#oul! not %e +arie! t#rou$#out t#e len$t# of t#e strut

as far as "ractica%le.

iii. Cross 6e(ce"t tie "lates9 s#oul! not %e "ro+i!e! alon$ t#e len$t# of t#e

column &it# lacin$ s)stem, unless all forces resultin$ from !eformation of

column mem%ers are calculate! an! "ro+i!e! for in t#e lacin$ an! its

fastenin$.i+. T#e sin$le-lace! s)stems on o""osite si!es of t#e main com"onents

s#oul! "refera%l) %e in t#e same !irection so t#at one s)stem is t#e

s#a!o& of t#e ot#er.

+. Lace! com"ression mem%ers s#oul! %e "ro+i!e! &it# tie "lates at t#e

en!s of t#e lacin$ s)stem an! at "oints ere t#e lacin$ s)stem are

interru"te!. T#e tie "lates s#oul! %e !esi$ne! %) t#e same met#o! as

follo&e! for %attens.

Q.16) What is $recast concrete! =escri>e the a$$"ications of $recast

concrete structures.Ans. recast Concrete(

• It is "ro!uce! %) castin$ concrete in a reusa%le mol! or OformO ic# is

t#en cure! in a controlle! en+ironment

• T#e structural com"onents are stan!ar!ie! an! "ro!uce! in "lants in a

location a&a) from t#e %uil!in$ site.

• Trans"orte! to t#e construction site an! lifte! into "lace

• T#e com"onents are manufacture! %) in!ustrial met#o!s %ase! on mass

"ro!uction in or!er to %uil! a lar$e num%er of %uil!in$s in a s#ort time at

lo& cost.

A$$"ications of recast Concrete

Drecast concrete is use! e(tensi+el) in %uil!in$ structures, for e.$. structural

frames, 4oors an! roofs, cla!!in$s etc.

Use of recast Concrete in frames(

T#ere are t&o main t)"es of "recast %uil!in$ frame. T#e structura"

frame consists of sla%s, %eams an! columns. :tructural frames are mainl) use!

for oPces, car "arks an! retail !e+elo"ments.

The cross#a"" frame consists of 4oor sla%s an! soli! &alls. It is use! mainl)

for #otels, sc#ools an! #os"itals.


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Use of recast Concrete for &"oors(

Eac# )ear t#e in!ustr) makes a%out 7 million suare meters of "recast 4oor

sla%s. T#ats eui+alent in area to 5= foot%all "itc#es. T#e main t)"es of 4oors

are s#o&n in *$ure %elo&

The reason for their success is(

• ast construction

• Economic "ro!uction

• :tan!ar!ie! crosssection

• ?oo! stren$t# to &ei$#t ratio

• :moot# surface *nis#es

Use of recast concrete in C"addin(

Drecast concrete cla!!in$ ma) %e use! as a structural element.

Ho&e+er, it is use! more freuentl) as a non-structural !ecorati+e faa!e.

T#e %ackin$ concrete is ma!e from an or!inar) mi(, ereas t#e faa!e ma)

consist of a s"ecial mi(, e.$. ite Dortlan! cement. A $reat +ariet) of forms,

!etails an! colours can %e "ro!uce!.

Drecast concrete cla!!in$ is not e(clusi+e to "recast frames. T#e maGorit) is use!

&it# in-situ concrete or steel frames, an! for refur%is#ments.

Q.1?) What are the merits and demerits of $restressed concrete

structures!

Ans. Ad4antaes of Dre-stresse! structures-

o Concrete remains un-cracke!

o Re!uction of steel corrosion

o Re!uce %eam !e"t#s

o

Increases !ura%ilit)o ?oo! for "ressure +essels


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o Hi$# s"an to !e"t# ratio 6e( =75 +s. 2859

o less !ea! loa! an! #ence $reater s"an len$t#s

o Fore economical

=isad4antaes of Dre-stresse! concrete structures-

o Drestressin$ nee!s skille! tec#nolo$). Hence, it is not as common as

reinforce! concrete

o T#e use of #i$# stren$t# materials is costl).

o T#ere is a!!itional cost in au(iliar) eui"ments.

o T#ere is nee! for ualit) control an! ins"ection.

assignment 2 anchal

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