503
BEHAVIOUR OF AEROCRETE INFILLED RIBBED WALL PANELS
SUBJECTED TO INPLANE LATERAL LOA,DING
Or. N.C1I1THARANjAN
Assistant Professor
Structures Division
College of Engineering
Anna Universi ty
Madras - 600 025
SOUTH INDlA
R.SUNOARARAjAN
Q.I.P.Research Scholar
Structures Oivision
College or Engineering
Anna Unlversity
Madras - 600 025
SOUTH INOIA
G.SIVARAMAN
Visiting Faculty
Structures Division
College of Engineering
Anna University
Madras - 600 025
SOUTH INDIA
P.OEVAOAS MANOHARAN
Lecturer
Structures Oivision
College of Engineering
Anna University
Madras - 600 025
SOUTH INOIA
ABSTRACT
This article enumerates the experimental study on the behaviour of precast.
Aerocrete infilled ribbed wall panel when subjected to lateral Inplane loads.
Manufacture of Inflll panels, cross rlbs and the assembly of IndividuaI elements
to form the wall panels are brlefed. To slmulate the slte condltlons panels
wlth or wlthout openlng were tested. To ease castlng assembJlng and testlng
the selected panels were of half scale model. Formatlon of Inltlal cracks,
lateral deformatlons and the progresslve fallure pattern of the test samples
etc. were observed durlng the tests. From the observed rosette readlngs
principal stresses were caJculated and the crack patterns of the Infllled panels
at different load leveIs were Identlfled and compared wlth actual crack patterns
observed on test samples.
INTRODUCTlON
Industriallsalon in bullding techniques only could satlsfy the growlng demand
of the public for houslng. Large panel prefabricatlon technlques are unsultable
for developlng countrles IIke Indla. To a certaln extent semi large panel
prefabrlcatlon technlque proved to be versatlle. Scarclty of conventlonal
materiaIs leads to the Innovatlon of unconventlonal materiais for houslng.
One such attempt Is the development of a hlgh strength IIght welght material
called 'Aerocrete' (1).
EarJler studies revealed (2) the sultablllty of thls
504
material for the precast elements. It is proposed to develop a prefabrication
technique using the light weight material Aerocrete, for mass housing schemes.
The system consist of the following
i) Prefabricated column elements.
li) Prefabricated horizontal rib elements.
iii) Prefabricated panel elements.
These precast elements are cast seperately and the complete
will be assembled at site using bolts and nuts or by grouting.
wall panel
AEROCRETE
The flow line production of Aerocrete (Figure 1) is identical to that of lime
based Microporite (3). The ingredients used are similar to that of conventlonal
amated concretes. The addltion of air entraining agents were eliminated
hecause the porous structure could be obtained in the mix due to voids left
by the use of excess water than that Is required for chemical reaction. The
optimum quantity of asbestos powder added fo r this cement based water cured
material is 30 percent by weight of cement used. The suggested cement,
sand ratios were 1: 1, 1:2, and 1:3 respectively. The Inelastic behaviour of
thls material could be mathematically represented by a thlrd degree equatlon
as shown in Table 1. When the Asbestos content (s) was 30 the value of 'K'
in table 1 reduced to zero and the stress straln relationship was identlcal to
that of normal concrete (4). The mechanical properties of Aerocrete with
30 percent asbestos content were obtalned from controlled test samples and
compared with that of normal concrete In Table 2. The bond stress of
Aerocrete at inclpient slip was far above the co de speclfied (5) value of bond
stress for normal concrete of comparable strength (Figure 2). The variation
of modulus of elasticity of Aerocrete was idealised as in Figure 3. Earlier
studies (6) revealed that by providing chicken mesh caging aggregate interlock
force could be induced and the ductllity of reinforced Aerocrete flexural
members could be increased. Therefore this material is used for the present
study.
MANUFACTURE OF TEST SAMPLES
The general survey of layouts reveal that the wldth and helght of a room In
precast bulldlng vary from 2500 to 5000 mm and the thlckness of the wall
vary from 100 to 300 mm. The overall dlmenslon of the selected panel are
3000 mm x 3000 mm and are tested as half scale models. The detalls of wall
panels are shown in Figure 4. It conslsts of four vertical rlbs and four
horizontal rlbs of slze 100 mm x 50 mm. The Inflll panels are of slze
500 mm x 500 mm wlth skin thlckness 20 mm and a pherlferal rlb of slze
450 mm x 100 mm x 20 mm wlth central holes for connectlng the inflll
panels wlth the rlbs (7) .
MateriaIs
Aerocrete Is used for the manufacture of rlbs and panels. 100 mm x 100 mm
x 10 G weld mesh and 26 G hexagonal chlcken mesh are used as relnforcement
for Inflll panels (Figure 5.a). For vertical and horizontal rlbs four number of
6 mm dlameter mlld steel rods are t led wlth 3 mm diameter mlld steel
stlrrups at 100 mm c/c In addltion to a layer of 26 G chlcken mesh Introduced
505
ADDI TIVES
81 N DER
'CEM ENT ON
ASSES TOS
WASTE
POWDER
CEMENT
KlINKER
..c.,EROCAETE SAIo4Pl(
BONO
'sr:'
STRESS 41 INCIPtENT SLIP ] . ')s "'/".,m 2
90NO STAES5 Ar INCIPtENT $LlP
P(RIo4IS$I BLE
AEROCREiE
AUTOCLAVE CURED
5 T RESS
~.H N/mm 2
AS PER
15 L5'-1'6N / ~1
FINISHED
PRODUCT
WATER CURED
STEAM CURED
BONO
tO
-I
SLlP ''''
FIG 1. FLOW LI N E PRODUCT ION
AEROCRETE
OF
ml'rl.10
FIG2 , BONO SLIP
\g~ I
/
RELATIONSHIP
ISSO
'!to
f~
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INfTlAl TANGENT 10400UlUS.
TAN6ENT
MODUlUS . , }
A.~ STR(SS lEvH
~
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• ~
ti
t
,I
0.003
0.004
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FIG3,VARIATION OF MODULUS OF ELASTICITY
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506
OF
TABLE: J. COMPARAT IVE STUOY OF THE OUCfI L1TY
AEROCRETE ANO NORMAL CONCRETE
Ic,
REGION OA
REGION AS
NORMAL WEIGHT CONCREr'E
AS AVAILASlE FROM EARlIER
WORKS (IN FPS UNITS)
AEROC RETE
(IN METRIC UNITS)
REGJONS
lé{2(-~L)_~)2 +-k (k))}
(o
Eo
Eo
whfreb - l . 551-0.1215S +0.0059 S2
S,(WEIGHT OF ASBESTOS P<M'DER/
WE1GHT OF BIN DER USED) 100
Ip
Ic, fc {l-Z (Ec-Eo)} whort
te, I~ {l-Z (Ec -Eo )} whert
Z,
0·5
---
0·002Ic·- 0·45
REGION OC
fé - 115·~
fc ,
ESO '
3 +- 0 . 002f~
fe -1000
Ic' 0·2
TABLE: 2. MECHANICAL PROPERTIES
CUSE
CYlI N DE R
COMPRESS IVE COMPRESSIVE
STRE SS
STRESS
OC
OF
INDIRECT
CUSE SPlI T
TENSllE
STRESS
Dtc
OCy
((o
k
O· 5
and
ESO- E O
0.2 f é
UNIAXIAl COMPRESSION TEST
I -
Z,
and
E50 - (O
E50 '
I~ {2 (k(o
le
AEROCRETE
TENSllE
DIAGONAL
CYlINDER
SPlIT TENSIUE SPlIT TENSllE
STRESS
STRESS
CT"ld
i'}
TESTS
MODULUS CF
RUPTURE
PRISM SPlIT
TENSllE
STRESS
CT"br
Cítb
Dtcy
~ W Q <> Q
li
AEROCRETE
NWC
1· 0
1· 0
0·82
0·60
0 ·05
0·09
NWC : NORMAL WEIGI;IT CONCRETE
NON' DIMENSIONAlISED .
CF
0 · 14
0 ' 07
COMPARABlE
0 · 11
0 · 07
2
2
0 ·30
0'11
STRENTH. VAlUES
t.
~
0·12
0 · 13
ARE
.-
--
.
507
to slmulate aggregate Interlock force.
castlng the samples.
Detachable wooden moulds are used for
Manufacture of Infill panels
The relnforcement deta!ls can be seen from figure 5.a. The castlng Is done
in two stages. The skln of the panel Is cast flrst uslng mould for skln
(Figure 5.b). After flnlshlng the panel skln (Figure 5.0.) the mould for slde
rlbs are kept In posltlon (Figure 5. .::) and the castlng of the rlbs are completed
(figure 5. d). After 24 hours slde forms are removed and the samples are
water cured by ponding water Inside the trough. (Figure 5.d).
Manufacture of wall panel
The steel relnforcement cage for the vertical and horizontal rlbs were
fabrlcated in the same way as advocated for the proto and the connectlon at
the junctlon of vertical and horizontal rlbs are made by extendlng 6 mm
dlameter m!ld steel rods In both dlrectlons at the junctlons. Thus the system
conslst of four horizontais and four verticais wlth nine openlngs to recelve the
Inflll panels (Figure 5, e). A layer of chlcken mesh Is wound over the
relnforcement to Induce aggregate Interlock force. The base relnforcement
conslst of two numbers of 16 mm R.T.S. at bottom and two numbers of 12
mm R.T.S. at top and sldes wlth 6 mm m!ld steel two legged stlrrups at
150 mm c/c. The vertical rods from the edge rlbs are anchored well In the
base beam and the base beam Is used for anchorlng the speclmen In the test
bed.
Precast Infllled ribbed panels are placed in posltlon In the openlng of the
steel gr!lls (Figure 5.e) and the connectlng bolts are Introduced connectlng
the rlb relnforcement and the precast panels to prevent the seperatlon of the
panels and the rlbs under normal condltlon. Ribs are cast uslng Aerocrete
and base beam Is cast uslng normal concrete. Four numbers of 40 mm
dia meter holes are provlded in the base beam for anchorage purposes.
for Induclng wlndow or door openlngs one or two pane I are left durlng
castlngs. The samples are wter cured for 28 days and tested for lateral
Inplane loading.
TESTING
Totally three numbers of half scale model for rlbbed precast wall panels
wlth door or wlndow openlng and wlthout openlng are tested to Inplane lateral
loads to study the effect of lateral deformatlon of the panels durlng assembly
due to lack of fltness uneven settlement of foundatlon at slte etc. These
panels are anchored to the test bed uslng vertical bolts and nuts (Figure 5.f).
Load is appl!ed through hydraul!cally operated 30T jack and the load Is
measured uslng a cal!brated 20T provlng rlng.
Lateral deformatlons are
measured uslng dlsc type displacement meters flxed at selected polnts uslng
rectangular straln roset tes (Figure 5. f).
...
508
(a)
Reinforcement
(b) Panel
(e)
Ribs
(d)
Finished
Figure. 5. Manufacture
Finished
(f) Test
(e) Steel Grill For Wall Panel
Of
••
skin
Finished
Product
Set up
Test Samples
509
Testlng of rlbbed wall panel deslgnated l-H:
The over-al\ dimenslon of thls panel wlthout openlng was 1550 mm x 1550 mm
The flrst crack appeared at the bottom most pane I near the load face at
20 KN load (Figure 6.a). At about 20 KN the panel started cracklng and as
load is Increased the number of panels cracked also Increased. At about
0.76 of the ultlmate load leveI the panel started seperatlng from the rlb
(Figure 6.b). At thls stage the column started cracklng. At the ultlmate load
leveI (55 KN) predomlnent cracks were observed at the topmost and
Intermediate jolnts In the f1rst row of the panels. The observed lateral
deformatlon ( t::.cr = 1.37 mm) of the topmost polnt at the cracklng load leveI
was only 10.5% of the deflectlon ( t::. = 13.02 mm) at the ultlmate load
leveI. It Is evldent from figure 7 that untll the pane I seperated from the rlb,
the lateral deformatlon was linear. At about 0.76 of the ultlmate load leveI,
the composlte actlon was lost and large deformatlon was exhlblted. The load
deformatlon curve for the topmost panel polnt Is shown In figure 8. The
inltlal stlffness of the sample was 20 KN/mm and reduced to 2.44 KN/mm
at the ultlmate load leveI. The stlffness degradatlonwas gradual upto cracklng
leveI and beyond whlch It was hlgher which may be due to the Ineffectlveness
of the composlte actlon of the panels and rlbs (Figure 9).
The tenslle and compresslon principal stress contours for the test sample
at the cracklng load leveI and at the ultlmate load leveI are plotted In
figure 10 and figure 11. The thick and doted IInes Indicate the tenslle and
compresslve principal stress cont,?urs respectlvely.
Tl").e maxlmum principal
tenslle stress reached is 15 N/mm In the lower most panel near the loading
face which agrees wel\ wlth the observed fallure pattern. The hlghly stressed
topmost ~anel experlenced a maxlmum compresslve principal stress of
12 N/mm
as antlclpated.
Due to the difference In rlgldlty of the rlb
members, the m~lmum compresslve principal stress experlenced by the rlbs
are only 3 N/mm .
The flrst crack appeared at the hlghly stressed bottom corner panel due
to tenslle stress and the panels were Intact upto 0.76 times the ultlmate load
levei, beyond whlch vertical cracks are Induced in the rlbs. The typlcal struct
actlon of the Inflll panels are evldent from the dlrectlon of propogation of
cracks (Figure 6.c). The final fallure was due to the formation of hinge at
the junction between the column and base (Figure 6.a).
Testlng of rlbbed wall pane} deslgnated 2-H:
The dimenslon of the test sample Is the same as that of earlier one except
for a window openlng of slze 450 mm x 450 mm provided by ellmlnatlng one
infllI pane I. The flrst crack appeared at the topmost corner polnt at 20 KN
load leveI as In the earller sample. The ultlmate capacity of the sample was
only 77 percent of that of the ealier sample whlch may be due to reduction
of 11 percent of panel are a due to the wlndow openlng. At about 35 KN the
panel started seperatlng. At ultimate load leveI predomlnent cracks were
appeared at the corners of the openlng (Figure 6.d). The lateral deformation
at the topmost polnt for the test sample at the cracklng levei was 2.5 times
that of the panel without openlng for the same load leveI, whlch Is due to
redution In stlffness. The deflectlon ( t::.= 8.38 mm) at the load levei (35 KN)
when the pane I started seperatlng is only 60 percent hlgher than that for the
earller sample ( t::.= 5.0 mm) at the same stage (Figure 12). The maximum
deflection ( t::. = 15.45 mm) at the ultlmate load levei (Pu' = 42.5 KN) Is only
510
•
)
..
/.'",
/
.... .
.
/',;
Ir
V
, io'(a) Craek
Pattern Of (5ample l-H)
(b) Pane! 5eperation (5ample l-H)
(d) Craeking
(Sample 2-H)
(e) 5trut Action (Sample l - H)
-'C_
I
..
;:J "\
;':!
"
".......
'-'I
'\"
','
!Jt
\.
..
""----'
"
.:::'~
- , _:_-.:;::... ~-
(e)Failure
-
Mode (Sample 2-H)
•
(f) Te 5 t ed
Figure.6 Tested
Wall
.
5a m p I e , 2· H
Panels
511
19 percent hlgher than that of the pane I wlthout openlng. Referrlng to
figure 8 and figure 9 it Is evldent that the Inltlal stlffness (11.1 KN/mm)
reduces to (1.09 KN/mm) near the ultlmate load levei due to the
Ineffectlveness of the panel after the formatlon of the cracks.
The principal stress contours (tenslle and compresslve) at the cracking
and at the ultlmate load leveis are shown In figure 13 and figure 14. The
observed crack patterns In the test samples agreed well wlth the principal
tenslle stress contours at the cracklng levei. The compressive principal stress
contours identlfled the hlghly stressed polnts. As antlclpated the panels are
stressed more than the ribs due to the distlnct seperatlon of the panels from
the rlb (Figure 6.d).
The lateral deformatlons are linear upto the cracklng levei. The flrst
cracks appeared at the hlghly stressed top corner loadlng polnt. The Inflll
panels exhlblted typlcal strut actlon and the final fallure was due to the
formatlon of hlngs on the vertical column at the base (Figure 6.e). The tested
sample can be seen from figure 6.f.
Testiog of rlbbed wall panel deslgnated 3-H:
The dimenslon of the test sample Is the same as earller samples except for
a door openlng of slze 450 mm x 950 mm by ellmlnatlng two panels and one
cross rlb. The flrst crack load (15 KN) Is only 75 percent of that of panel
wlthout openlng. Due to the reductlon of panel area by 22 percent the
ultlmate load (P , = 35 KN) Is reduced to 64 percent of that of sample
wlthout openlng. u As the load Increaseá beyond the cracklng leveI predomlnent
cracks are observed on the panel near the loadlng face (Figure 6.g). From
figure 15 It Is evldent that the deflectlon (ll cr' = 2.54 mm) at the cracklng
levei Is 1.85 times that for the panel wlthout openlng. Beyond the cracklng
stage the deformatlons are large compared to the earller samples because of
the reduced panel are a and stlffness. The deflectlon (ll u' = 16.9 mm) at the
ultimate load leveI (P , = 35 KN) Is 1.3 times that of the sample wlthout
openlng. The stlffnessu degradation (Figure 9) calculated from figure 8 shows
Its sensltlveness to load due to the reduced panel area.
~ ~:~l'~
.:
(9)
-.
. ~:'.
,
~--
I
.
Panel Seperation
(Sample 3-H)
(h) Failure
Mode
(Sample 3-H)
Figure.6. (contd) Tested Wall panels
512
P.
%
%
z
z
~
z
~ 1000
~
~
o
x
~
w.
t r----ill-t
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O'S
o.sr
1"
Q.
s-J.-_
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PA,NEL
Q . 3~
•
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BASE
la
OEFORMATION IN 101M
15
FIG . 7 LATERAL DEFORMATION OF INFILLED
WA LL PANEL WITHOUT OPENING
7-
4 ·1m m
I
...
WITHOUT OP[tWiC,
SO
~'00
~
40
~ii',\f.:""rNOOW
~~OOR
~
~
OPENrNG
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o
~ 80
~
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õ fiO
OOOR OP[NING(n·2"/.OP[HING I
z
I
z
o
<
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WIHOOW OPENING(l1""/.OPENING)
§'O
WITHOUT OPENING
z
~ 20
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15
FIG :
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FIG.l0 PRINCIPAL STRE5S CONTOURS
FOR THE PANEL lH AT CRACKING
LOAD LEVEL
, ..... "
t
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FIG ,ll PRINCIPAL STRESS CONTOUR FOR
lHE PANEL l-H NEAR ULT I MATE
LOAD LEVEL
- - TENSll E
_
_
o.
PRINCIPA.lSTRESS
COMPRESSIVE PRINCIPAL STRESS
513
O· 2L Pu' O.L 7Pu' 0.71 Pu'
...~
O
soo
5
10
IS
DEFORMATrON IN 104M
FIG: 12 MATERIAL DEFORMATION OF
INFILLED WALL PANEL WITH
WINDOW OPENING
Flv: 13 PRINCIPAL STRESc; CONTOUR FOR THE
PANEL
2-H AT CRAlKING LOAD LEVEL
-joo~~_P
0· 5M
0 ·5104
-DOO R
OPENlriG
/
0·5 M
0'5M'
.
FIG: 14
PRINCIPAL STRESS CONTOUR FOR THE
PANEL 2H AT ULTIMATE LOAD LEVEL
S
'"
o
c
BASE
la
15
OEFOR104ATION IN MM
FIG : 15
MATERIAL DEFORMATION OF
INFILLED WALL PANEL WITH
DOOR OPENING
,[]
FIG: 16
PRINCIPAL STRESS CONTOUR FOR
THE PANEL 3 H AT CRACKING LOAD
LEVEL
FIG: 17 PRINCIPAL STRESS CONTOUR FOR THE
PANEL 3-H FOR ULTIMATE LOAD LEVEL
- - TENS ILE
PRINC:P.U STRESS
-----COMPRES SIVE
PRINCIPAL
STRESS
514
The principal stress contours (Figure 16) at cracklng levei clearly agrees
with the observed crack patterns on the test panels. The tenslle stress
contour near the ultimate levei (Figure 17) agrees well wlth the crack patterns
at the ultlmate levei.
Because of the large openlng the flrst crack appeared at lower load
leveI.
As load increases subsequent panels started cracklng and at the
ultimate levei the top horizontal rlb seperated pulllng out the vertical column
of the door openlng (Figure 6.h). As in the earlier case the fallure of the
sample is due to the fallure of the column wlth panels In tact with the ribs
and wlth deep and distinct cracks extendlng both faces.
CONCLUSION
From the limited tests the following conc\usions are arrived at:
1)
Considerlng the high strength and light weight
Aerocrete (1) Is sul table for thls suggested system.
the newly developed
2)
The observed crack pattern on the panels are comparable with principal
tenslle stress contour at the cracklng levei.
3)
The panels behaved monolythically with the rlbs upto 75 percent of the
ultimate load levei.
4)
The panels became ineffectlve only after its seperatlon from the rlbs.
5)
The stl ffness degradatlon after the cracklng are large.
6)
The reductlon In ultimate capacitles due to the openlngs are not so
serious.
7)
The fallure of the system Is only due to the failure of the vertical rlbs.
8)
Even at the ultlmate levei the bolted jolnts are In tact.
9)
The regaln of the originai shape of the panels on release of the load
Indicates the good behavlour of the material and the system adopted.
ACKNOWLEDGEMENT
The authorit les of Anna Universlty are thanked for providing the facllitles to
carry out this experimental study.
REFERENCES
1)
Devadas Manoharan,P., 'Further Investlgatlon On the Development Of
Microporites', A M.E. Thesls approved by the Anna Unlverslty, Madras
India, July, 1982, pp. 57 to 67 and 101 to 197.
2)
Sivasankaran,N.G., 'Development of Aerocrete - A Llght Welght High
Strength Concrete', A M.E. Thesls approved by the Anna Unlverslty,
Madras, India, August 1984, pp. 1 to 101.
fIi'
515
3)
Chitharanjan,N., 'Development of Light Welght Concrete and thelr
appllcation to Reinforced Flexural Members'. A Ph.D. Thesis approved
by the University of Madras, Madras, India, May 1980, pp. 1 to 481.
4)
Kent, D.e. and Park, R., 'Flexureal Members With Confined Concrete',
journal Of Structures Divislon, ASCE, Vol.97, ST 97, july 1971,
pp. 1969 - 1990.
5)
............................•.• , Indian Standards Code Of Practlce for Plaln and
Reinforced Concrete (Thlrd Editlon), I.S. 456 - 1978, Indian Standards
Institution, New Delhl, September, 1977, p. 148.
6)
Chltharanjan,N., Sundararajan,R., and Devadas Manoharan,P., 'Development
and Appllcation of Aerocrete wlth Non-metalllc Flbres', Proceedings of
the Internatlonal Symposlum of Flbre Relnforced Concrete, Vol. lI,
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7)
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