Thermal Analysis Analysis of Long Buildings for Elimination of Expansion joints Department of Civil Engineering, Datta Meghe College of Engineering, Airoli, Navi Mumbai 400708 ABSTRACT
In view of demanding arhiteture and present Industrial trend! long strutures without any expan expansio sion n joint joint is "e "eomi oming ng a ne neess essit ity y of the proj projet et## As per Indian Indian Standa Standard rd ode! ode! IS$ %&'()***! "uildings longer than %&m shall "e analy+ed for the thermal stresses and appropriate measures shall "e ta,en during fixing the strutural system# -owever! IS odes are silent in terms of proess to follow in suh ,ind of designs# To worsen the situation! there are no guidelines availa"le with the design engineers to arrive at design temperature temperature value that should "e onsidered in wor,ing out thermal stresses#
.n$ladded three multilevel ar par, "uildings are seleted here in order to study the effet of temperature temperature load with respet to length of "uilding# Buildings onsidered are of length approx# /*m! 0'*m and )%*m# Initially all the three "uildings are analy+ed and designed for gravity loads in presene of earth1ua,e fores# Then same models are applied with temperature load of 0** 0** C un unif ifor orml mly y on all all floo floors rs## Analy nalysi siss and and desi design gn is arr arrie ied d out out agai again n in pres presen ene e of temperature load and results are ta"ulated# Effet of temperature load on overall defletion! hori+ontal shear in shear ores! axial fores in "eams! axial 2 "ending stresses in sla"s are reviewed losely in "oth the ases# Reinforement onsumption in all load arrying elements vi+# flat sla"! "eams! olumns and shear walls is alulated for all the "uildings with and without temperature loads# 3raphs are plotted to ompare the results#
1
I4TR56.CTI54
As a standard pratie based on !" ode, e#pansion $oints are usuall% provided ever% after 4&m length in ase of long buildings' (hese e#pansion $oints affets the e#eution of )or*, onstrution se+uene, faade design -in ase of dr% ladding. AC/ ladding and also at as a soure of lea*age in monsoon during life span of buildings' E#pansion $oint as used throughout this report refers to the isolation or separation $oint provided )ithin a building to allo) ad$oining segments to e#pand and ontrat individuall% in response to temperature hanges )ithout adversel% affeting the buildings strutural integrit% or servieabilit%' (emperature variation indues stresses in a struture, if the struture is restrained' (hese stresses var% )ith the magnitude of the temperature hange2 large temperature variation an result in substantial stresses that must be aounted for in design, )hile lo) temperature hanges ma% result in negligible stresses' Elongation aused b% temperature variation an simpl% be )or*ed out b% using relation3 5 6 # 5 # t here, 5
6 Elongation due to temperature variation
6 Co9effiient of thermal e#pansion of onrete -:':E 90; onsidered here
5
6 5ength of building
t
6 Design temperature hange
Design temperature hange is t)o third of the differene bet)een the e#treme values of the normal dail% ma#imum and minimum temperatures i'e' <.=-409<& >as per Martin and Aosta,1:70?' Martin and Aosta arbitraril% hose the t)o9third fator to aount for the fat that the temperature at )hih the building is ompleted )ould statistiall% not be at the ma#imum or minimum dail% temperature, but some)here bet)een the t)o' @alues of ma#imum and minimum temperature an be referred from Meteorologial department of the it%' As a ase stud%, data for Mumbai it% )as referred to arrive at the value of design temperature hange' asiall%, buildings an be divided into three separate ategories3 •
Cladded buildings )ith ontrolled temperature li*e, ommerial offies, shopping malls, et'
•
Cladded buildings )ithout temperature ontrol li*e residential buildings, !ndustrial estates, shools, olleges, et'
•
Bn9ladded buildings li*e stadiums, sport omple#es, multi9level ar par*s, et'
<
Different effet an be seen in the strutural design of buildings oming under above ategories due to variation in seasonal as )ell as da% and night time temperature variation' 7ACT5RS A77ECTI43 E89A4SI54 :5I4T
ollo)ing fators generall% govern the neessit% of the e#pansion $oint in the building3 1' Dimensions and onfiguration of building <' Design temperature hange =' /rovision for temperature ontrol 4' (%pe of frame &' (%pe of onnetion )ith the foundations ;' "%mmetr% of stiffness against lateral loads 7' Material of onstrution B.IL6I43 6ESCR9TI54
As desribed at the beginning of this paper, three idential buildings intended to be used as par*ing strutures )ithout e#ternal faade are onsidered in this parametri stud%' Number of floors, strutural framing at all floors, imposed loads and lateral load parameters are e#atl% same in all the three buildings' Effets of temperature as varied )ith the length, three different lengths are onsidered vi' 80m, 1;0m and <40m )ith onfiguration as round F 7 floors F terrae' eing a par*ing struture, ramps onneting all the floors, passenger elevators and ar lifts are onsidered as a funtional re+uirement' ()o stairases are provided for ever% 80m length of building' As the struture is proposed to be a multi9level ar par* building )ithout an% e#ternal faade, )ind loads )ill not govern the design of building' Gene, struture is anal%ed for earth+ua*e load as lateral fore in addition to imposed loads along )ith onstant temperature load of 10 0 C' All strutures are onsidered as HCC flat slab strutures )ith =00mm thi* flat slab and &00mm thi* drop panels from 5evel 1 to (errae' round floor is onsidered as grade slab supported on plinth beams having sie =00 # 7&0mm' All the strutural sies are )or*ed out based on hand alulations made for ontributor% area, imposed loads and self )eight of struture' 5ateral loads are mainl% intended to be shared b% shear ores' (hese shear ores are formed b% =
providing HCC shear )alls around ar lifts, passenger elevators and stairases' Mehanial, eletrial and plumbing servies are intended to be arried )ithin a shafts provided in these shear ores' ()o )a% ramp )ith gradual slope of 1 in 8'4 is provided at the entre of ever% 80m streth of building to failitate inters store% movement of ars' (able 1 desribes the important features of these buildings3 Ta"le 0 I uilding eatures
1' <' =' 4' &' ;' 7' 8' :' 10' 11' 1<' 1='
(%pe of "truture Earth+ua*e Jone Hesponse redution fator !mportane fator 5a%out Number of floors round floor height /ar*ing floor height E#ternal )alls !nternal )alls 5ive load Materials "eismi anal%sis
14'
Design /hilosoph%
1&' 1;' 17 18' 1:' <0'
"ie of e#terior olumn "ie of interior olumn (hi*ness of shear )all "ie of beams lat slab thi*ness Drop panel thi*ness
Multi9store% pin $ointed frame !!! & 1 As sho)n in igure 1, < K = 8 - F 7 ='0m ='0 m 1'
As per "/ <4, lause =&'4'1 of E#planator% Gandboo* of !ndian "tandard ode of pratie for /lain and Heinfored Conrete -!" 4&;91:78 follo)ing load ombinations are used onsidering 5imit state of ollapse for designing the building against thermal variation3 0'7& -1'0& Dead 5oad F 1'7 5ive 5oad F 1'4 (emperature 5oad 1'4 Dead 5oad F 1'4 (emperature 5oad A4AL;TICAL SI<.LATI54S = 6ESI34
"trutural anal%sis arried out using C"! soft)are Etabs :'7' uildings having variable floor plates are seleted for this stud%' 1' Columns and beams modeled as line elements <' "hear )all and flat slabs modeled as finite shell elements 4
=' (emperature load assigned to the floor plate. slabs' Computer aided design soft)are LHCDC from "9ube utureteh )as used to design various strutural elements' ased on anal%sis and design results, various graphs are plotted to disuss the effet of temperature variation )ith respet to the length of building' !n addition, building )as designed for earth+ua*e loads as per !" 18:=3<00<' As the base shear alulated for )ind fores )as lesser than base shear alulated for earth+ua*e, )ind fores and their ombinations have been omitted from this stud%'
ig' 1'
MDE5 ! -80m long M5C/ building'
ig' <'
MDE5 !! -1;0m long M5C/ building'
ig' ='
MDE5 !!! -<40m long M5C/ building &
RES.LTS A46 6ISC.SSI54
!nitiall%, all the three buildings are anal%ed and designed )ith e#pansion $oint )ithout appliation of temperature load' 1;0m long building )as divided into t)o separate strutures isolated b% e#pansion $oints -modeled as ph%sial gap in floor plate' "imilarl%, <40m long building )as divided into three separate strutures isolated b% e#pansion $oints' All belo) listed parameters are )or*ed out for these three buildings of 80m, 1;0 and <40m lengths' (o eliminate the e#pansion $oints, all three buildings are then loaded )ith temperature load of uniform 100 C' At the same time, separate strutures in 1;0m and <40m long building )hih )ere isolated b% e#pansion $oint are stithed together eliminating gap left in previousl% as a e#pansion $oint' All buildings are onsidered as uildings )ith Dual s%stemsO, )ith Dutile shear )alls and speial moment resisting frames -"MH as per !" 18:= -/art 1 3 <00<, lause ;'4'<' ollo)ing parameters are studied and ompared on anal%ing and designing all the three models for temperature loads in addition to gravit% and lateral loads3 i'
Elongation of flat slab
ii'
Design shear in shear )alls
iii'
Heinforement onsumption in olumns K shear )alls
iv'
A#ial tension in beams due to temperature load
v'
Design a#ial tension in beams
vi'
Heinforement onsumption in beams
vii' Ma#imum a#ial stress in flat slab @s' Modulus of rupture viii' Heinforement onsumption in flat slab indings against ever% parameter are desribed in detail in follo)ing sessions along )ith their graphial representation' i#
Elongation of flat sla"(
E#treme top right orner of ever% model applied )ith temperature load is seleted for omparing elongation e#periened b% flat slab under ambient temperature ondition' Hesults are tabulated in table < for all three buildings' ig' 4 sho)s the graphial representation of inrease in length of building at ever% floor on eah side along its length' rom this graph, it is lear that higher the length of building e#pansion e#periened b% floor plate )ill be higher' !t also observed that e#pansion inreases in all the three building to)ards terrae as ompared )ith levels belo)' Ta"le ) I Elongation of flat slab under basi load ase of temperature load
;
Story
(errae 5evel 7 5evel ; 5evel & 5evel 4 5evel = 5evel < 5evel 1
CASE 0 $ /*<
CASE ) $ 0'*<
CASE > $ )%*<
9oint
.8
.;
9oint
.8
.;
9oint
.8
.;
1;; 1;; 1;; 1;; 1;; 1;; 1;; 1;;
=': =': =': =': ='8 ='7 ='; ='0
1': 1'8 1'8 1'8 1'8 1'8 1'7 1'&
1<:= 1<:= 1<:= 1<:= 1<:= 1<:= 1<:= 1<:=
8'0 7'8 7'; 7'4 7'0 ;'4 &'& 4'<
1': 1'8 1'8 1'8 1'7 1'7 1'; 1'4
18<< 18<< 18<< 18<< 18<< 18<< 18<< 18<<
1< 1< 11 10 : 8 7 &
< < < < < < < 1
7ig# % I E#pansion of building under a effet of temperature load
ii# 6esign shear in shear walls along length(
/ier /1 -(op most pier of e#treme left shear ore as highlighted in ig' & is seleted as a sample pier in ever% model to stud% the effet of temperature load in design of shear )alls' /ier /1 is initiall% designed in all three models )ithout temperature load in e#istene of e#pansion $oint' Hesults are tabulated for these ases' (hen same pier /1 is designed in all three models applied )ith temperature load eliminating e#pansion $oints' Again results are tabulated as sho)n in (able = and graph is plotted omparing inrease in design shear due to temperature load as sho)n in ig' ;'
7
7ig# & I /art plan of e#treme left shear ore in all models
Ta"le > I Design shear fore in pier /1
Case
! I 80m !!91;0m !!!9<40m
9ier I6
/1 /1 /1
?ith temperature Critial load 6esign
?ithout temperature Critial load 6esign
om"i
shear @4
om"i
shear @4
1'4D5F1'4(emp 1'4D5F1'4(emp 1'4D5F1'4(emp
;:78 1<=;& 148<&
1'<-D5F559E+P 1'<-D5F559E+P 1'<-D5F559E+P
<0:7 <0:7 <0:7
7ig# ' I Design shear fore in pier /1
rom the obtained results, it an be onfirmed that shear fore attrated b% shear )alls of bottom stories loated at e#treme end of the building inreases )ith the inrease in length of building' (o aommodate this inreased shear, thi*ness of shear )alls need to be inreased as per inreased length of building as presented in ig' 7 belo)'
8
Case 1 I 80m
Case < I 1;0m
7ig# I @ariation in thi*ness of
Case = I <40m
ore )all as per length
iii# Reinforement onsumption in olumns = shear walls(
No diret impat )as observed on reinforement onsumption in olumns and shear )all due to temperature loads' Although the reinforement onsumption in ase 1, i'e' "hortest building is found to be high amongst all three, it )as $ustifiable in vie) of restrited thi*ness of shear )alls in ase 1' or ase < and ase =, shear )all thi*ness is inreased in order to fulfill the re+uirement of shear along length of building' As a result of )hih, overall reinforement onsumption in shear )all is marginall% redued in these ases' !n absene of temperature load, e#pansion $oint e#ists in Case < and Case= reating e#atl% idential buildings as Case 1' Gene, for ase )ithout temperatureO, Case < model omprises < Case 1 buildings plaed ne#t to eah, )hereas Case= model omprises = Case 1 buildings plaed ne#t to eah other -separated b% e#pansion $oints' (his allo)s *eeping reinforement onsumption onstant in all the three ases )ithout temperature load' Ta"le % I Heinforement onsumption in olumns and shear )alls Case
Length
Case 1 Case < Case =
80 1;0 <40
Steel onsumption ?ithout ?ith temperature temperature
1&8'0 1=4'= 1=='<
1&;'0 1&;'0 1&;'0
iv# Axial tension in "eams(
ig' 8 sho)s the graphial representation of inrease in ma#imum a#ial tension in beam along its length for basi load ase of temperature loads' As the length of building inrease, marginal inrease :
in a#ial tension is observed in beams' (able & sho)s the tabulated results of a#ial tensile fore e#periened b% beams along the length of building' Ta"le & I A#ial tension in beams due to Case
Case 1 Case < Case =
temperature load
Length
80 1;0 <40
1&8'0 1=4'= 1=='<
7ig# / I Ma#imum a#ial tension in beam v# 6esign axial tension in "eams(
igure : represents the a#ial fore e#periened b% beam for all the design load ombinations inluding lateral loads' hen buildings are anal%ed )ithout onsidering effet of temperature loads, design a#ial fore is some)here in the range of <00 QN' hereas if the same buildings are anal%ed after appl%ing temperature loads, a#ial fores in beams inreases up to 1<00 QN' -e'g' eam 1 in ritial load ombination' !t learl% indiates that the building anal%ed )ith temperature load arries heavier a#ial tension in beams as ompared )ith buildings )ithout temperature load' Go)ever, no measure variation )as found in a#ial fores )ith respet to inrease in length of the buildings'
10
7ig# I Ma#imum design a#ial tension in beam
vi# Reinforement onsumption in "eams(
igure 10 represents the inrease in reinforement onsumption in beams for all the three models )ith and )ithout temperature loads' "eleted beams -beam 1 at ground floor, t%pial floor and terrae floor )ere designed using t)o design approahes, vi' "imple bending theor% and i9a#ial bending theor% )ith a#ial fores -similar to olumns sub$eted to tension F moments' !n vie) of signifiant inrease in a#ial tension, these beams shall not be designed onl% for bending' Effet of a#ial tensile fore must be ta*en into onsideration during beam design' As a result, about 1
Ta"le ' I A#ial tension in beams due to
Case
Case 1 9 80m Case < 9 1;0m Case = 9 <40m
temperature load
Reinforement Consumption ?ith ?ithout temperature
temperature
<=0'= <<=': <<4'8
<04'& 178'1 177'7
Inrease
1<'; <&'7 <;'&
11
7ig# 0* I Heinforement onsumption in beams
vii#
igure 11 represents the ma#imum a#ial tensile stress in a t%pial flat slab middle strip at (errae floor level due to temperature load' !t learl% indiates that the stress level inreases )ith length of the building' "trutural designer has to *eep a tab on this value as it should not e#eed be%ond modulus of rupture given b% e+uation3 Modulus of Hupture 6 0'7&S T-* (able 7 desribes ma#imum a#ial tension e#periened b% flat slab middle strip along )ith alulation of a#ial tensile stress' Ta"le I A#ial tensile stress @s' Modulus of rupture
Case Case 1 Case < Case =
5ength UmU 80 1;0 <40
Ma#' a#ial tension due Ma#' A#ial (ensile Moduls of to temperature load *N "tress N.s+'mm Hupture N.s+'mm 74< <'47 4'4= 101; ='=: 4'4= 1047 ='4: 4'4=
7ig# 00 I A#ial tensile
stress @s' Modulus of rupture
1<
viii#
Reinforement onsumption in flat sla"
igure 1< represents the inrease in reinforement onsumption in flat slab at t)o different levels' 5evel 1 )as seleted representing normal loading onditions of t%pial par*ing floor, i'e' 100mm thi* floor finish F servies F 5ive load of <'&Qpa' (o stud% the similar effet, terrae floor )as also onsidered having additional imposed load due to )aterproofing' !n both the ase, it is observed that reinforement onsumption goes on inreasing )ith inrease in length of building' verall inrease is found to be about 1
Case Case 1 Case < Case =
5ength UmU 80 1;0 <40
Heinforement Consumption V level 1 ithout temperature )ith temperature &7'1& ;=': 100'&; 118'88 1&0'11 188'== Ta"le I Heinforement onsumption in
Case Case 1 Case < Case =
5ength UmU 80 1;0 <40
R inrease at level 1 11'81 18'<< <&'4;
flat slab at (errae
Heinforement Consumption V terrae ithout temperature )ith temperature &7'=8 ;;'0; 10&'<= 1<8'4< 1&='&& <00';&
R inrease at terrae 1&'1= <<'04 =0';7
7ig# 0) I Heinforement onsumption in lat slab
C54CL.SI54
1=
(he behaviors of multistoried ar par* building e#posed from all sides )ithout an% ladding, )ith K )ithout temperature loads for various lengths have been studied in present sope of )or*' (his stud% has learl% highlighted effet of temperature load in strutural design of individual element and overall strutural s%stem' asiall%, inrease in length of building be%ond permissible limit of 4&m as per !" 4&; 3 <000, impats on strutural siing, design shear in shear )alls at e#treme ends and reinforement onsumption in bending elements li*e beams and floor slabs' !t is also found that the floor beams plaed along the length of building e#perienes heav% a#ial tension in addition to shear fore and bending moments' !t beomes mandator% in this ase to design the beam as per olumn design theor% )hih onsiders effet of a#ial fore F unia#ial or bia#ial bending' As a result, perentage reinforement inreases in ase of beam design sub$eted to temperature loads' !n ase of flat slabs, effet of temperature load )as found to be as same in ase of beams' Column strips. middle strips e#perienes heav% a#ial tension in addition to bending moments due to thermal variation' !f this a#ial tension generates tensile stress more than modulus of rupture of onrete, there )ill al)a%s be possibilit% of haphaard ra*s on surfae of slabs )hih ma% lead to partial. full ollapse of flat slab'
RE7ERE4CES
1.
Expansion joints in Buildings,O (ehnial Heport No' ;&, National Aadem% of "ienes, ashington D'C', 1:74 prepared b% the "tanding Committee on "trutural Engineering of the ederal Constrution Counil
2.
Malolm W' "' Girst, M'A"CE, Thermal Loading of Concrete Roofs O, April 1:80
3.
"/ 3 <4 I 1:8=O, E#planator% Gandboo* on !ndian "tandard Code of /ratie for /lain and Heinfored onrete
4.
/feiffer, Mihael W' and Dar)in David, oint design for Reinforced concrete !uildings O "M Heport No' <0, Bniversit% of Qansas Center or Hesearh, 5a)rene, Q", De 1:87
".
B# $11% & 'art 2( , ritish "tandard Code of /ratie for speial irumstanes published in 1:8&, amended in Wul% <001 14
).
Ed)ard ' Na)%, D'Eng', /'E', C'Eng, *oints in Concrete Construction(+ Conrete Constrution Engineering Gandboo*, "eond edition,
,.
-# 3414 1//",O !ndian "tandard ode of pratie for Design and !nstallation of $oints in uildings
$.
0C- committee 224.3r/"O, Woints in Conrete onstrution' Amerian Conrete !nstitute, armington Gills, M!, <00&, pp 1944
/.
-# 4") & 2%%%O, !ndian "tandard ode of pratie for /lain and Heinfored onrete
1%. Wames M' isher, "'E', Expansion joints here+ hen and oO, April <00& 11.
ill ashion and Na%an (rivedi, *Temperature and shrin5age stud6 for 3%%m long !uilding O or M.s' (ishman "pe%er !n for their pro$et in G%derabad, !ndia
12. Mohammed !+bal, D'", /'E', "'E', Es+' *7esign of expansion joints in 'ar5ing structures(+ 8cto!er 2%1% 13. *Considerations in Expansion oint s6stem selection(+ b% (eh (opi series of EH!E ME(A5
"/EC!A5(!E", August <010 14. AC!
Committee =18'<011' Building code re9uirements for structural concrete and
commentar6, AC! =18911' Amerian Conrete !nstitute,
armington Gills, M!
1". Expansion joint:h6 Bother XO % Davo Constrution Materials in Ma% <007 1). /aul
Millman, Hobert Qilup A'M'A"CE and C' Allin Cornell, M'A"CE, 7esign
Temperature for #tructural Elements O, April 1:80 1,. Maria Anna /ola*, Thermal 0nal6sis of Reinforced Concrete #hells O, April 1:80 1$. ilig, Q' 1:;0, Expansion joints -n structural concreteO, Mamillan, 5ondon 1/. Jdene*
/' aant and Maurie ' Qaplan, Conrete at Gigh (emperature3 Material
/roperties and Mathematial modelsO, 1::; 2%. Wa* Emanuel, 'A"CE K Charles M' (a%lor, A'M'A"CE , 5ength I (hermal
stress relations
for omposite bridgesO 21. He%nolds,
C'E' 1:;0' Reinforced Concrete 7esigner;s and!oo5 , ;th ed' Conrete
/ubliations, 5ondon 22. 5e)eren,
A'C' 1:07'
-1:,&1<9&14
1&
23. Mann,
'C' 1:70. Expansioncontraction joint locations in concrete structures ' !n
/roeedings of s%mposium on Designing for the effet of Creep, shrin*age, and (emperature in Conrete "trutures, "/9<7 24. /CA'
-1:8<' Building mo=ements and joints( , /ortland Cement Assoiation, "*o*ie, !5,
;4pp 2". /CA' -1::< Woint 7esign for Concrete igha6s and #treet 'a=ements( ,
/ortland Cement
Assoiation, "*o*ie, !5, 1=pp 2). Merrill, '"' 1:4=, 're=ention and control of crac5ing in Reinforced Concrete Buildings(,
Eng Ne)s9Heord, 1=1, :19:=
1;
