SEISMIC PERFORMANCE OF RC WALL WITH TRUSS TYPE DETAILING

R. Deepak Kumar,1 T. J. Vijay2 and Mr. K. Rajeshkumar3 1PG Student,

2,3 Assistant Professor, PSNA College of Engineering and Technology, Dindigul, Tamil Nadu,

India.

ABSTRACT

This paper presents experimental investigations of

seismic behavior of RCC shear walls reinforced with

steel Truss type detailing. In this experimental study,

wall specimens consisting of X bracing in vertical

direction and these specimens were tested under

medium cyclic load reversals and constant axial load

with the help of hydraulic actuator to examine the

influences of embedded truss detailing on the overall

seismic behavior of the specimens. Totally three shear

walls are casted, from that one is kept as standard

reinforcement and other two walls are strengthened by

using additional truss type detailing. The performance

of the wall specimens in terms of load–deformation

response and cracking patterns are evaluated. Based

on those results, detailed discussion of the influence of

different configurations on the seismic performance of

shear walls with different type of truss type detailing is

observed

Key words: truss type detailing, shear wall, cyclic

loading.

1. Introduction

Load bearing masonry consists of materials which

having the brittle nature. The earthquake causes

different kinds of stresses in a structure such as shear,

tension, torsion, etc., The conventional unreinforced

brick masonry collapses instantly during the sudden

earthquakes. It causes death of people and major

economic losses. To overcome these drawbacks,

reinforced concrete shear walls are adopted. The

designing of shear wall structures are not only for

stable, but also comparatively quite ductile. In safety

terms it means that, during very severe earthquakes

they will not suddenly collapse. They give enough

indicative warnings such as widening structural cracks,

yielding rods, etc., that offers most precious moments

for people to run out of structures, before they totally

collapse. For structural purposes, we consider the

exterior walls as shear-resisting walls. Forces from the

ceiling and roof diaphragms make their way to the

outside along assumed paths, enter the walls, and exit at

the foundation. Reinforced concrete (RC) shear walls

have been widely used in high-rise buildings located in

seismic regions to provide sufficient lateral strength

and stiffness to limit nonlinear responses at service

level earthquakes and to ensure adequate nonlinear

deformation capacity during the design of maximum

considered earthquakes. However the energy

dissipating capacity of the RC shear wall depends on

the detailing of the reinforcement in it. To increase the

energy dissipating capacity the additional arrangement

of truss type detailing is to be provided.

Owing to the combination of advantages of

reinforced concrete structural walls have demon- started

superiorities in strength stiffness and ductility.

Which make them favorable worldwide, Especially in

the high seismic regions the sapling of concrete and

tensile cracks can be effectively reduced according to

the experiment from of diagonal bracings can be

introduced in shear walls as an effective approach to

withstand shear force and improve the energy

dissipation capacity by adding inclined bracings in the

RC walls.

In order to supplement the insufficient ongoing

research on RC structural walls with bracings, especially

that on inelastic behavior under reversed cyclic

loadings, tested five specimens consisting of one steel–

concrete composite structural walls for control and other

four ones with bracings. This paper covers a

comprehensive research involving experimental

investigations. Their test specimens demonstrated

excellent ductility and energy dissipation characteristics,

exhibiting stable behavior at very large deformations

even after many load cycles. However, there were

hardly any experiments on steel–concrete composite

structural walls with bracings. Furthermore, most of

research in the literature just gave general comments on

the performance of steel composite shear walls, without

deeper explorations about the effect of individual

parameters.

2. Test program

2.1. Details of specimens

The experimental program included a total of three

specimens named Control and 4VX, which represented

a series of one fourth scale RC shear walls of common

building. All specimens had the exact same dimension

as illustrated in Fig. 1. The specimen was designed and

constructed following the code provisions of ductile

detailing, as per the code IS: 13920:1993. A size of 600

mm × 60 mm × 1100 mm was adopted for the wall,

which was connected to a concrete head with the

dimension of 800mm × 100mm×100mm and 1000 x

250 x 150 mm of base beam size. The differences

between each specimen were the transverse

reinforcement of the embedded 2vx bracings and the

details of detailing is given in table 2.

Table 1. Materials Properties

S.No Material property Results

1 Compressive strength of concrete 26.8 N/mm2

2 Yield strength of steel 458.2 N/mm2

3 Young’s modulus of steel 215462 N/mm2

4 Young’s modulus of Concrete 23846 N/mm2

Table 2 Details of Specimen

Specimens Element Description of detailing

Common for Control specimen

and 4VX specimens

Vertical portion of wall 4nos of 6mm Diameter

Boundary element 4 No. of 6 mm diameter as main bars and 6

mm diameter of 100 mm c/c in shear

Top beam portion 4 No. of 8 mm diameter as main bars and 6

mm diameter of 100 mm c/c in shear

Bottom beam portion 6 No. of 10 mm diameter as main bars and

6 mm diameter of 100 mm c/c in shear

Control specimen Horizontal portion of wall 7nos of 6mm Diameter

4VX specimen Horizontal portion of wall Four Vertical X bracings

Figure 1. Detailing of Control Specimen

Figure 2. Detailing of 4VX Specimen

2.2 Test setup

Each of the test specimens was subjected to axial

loads and cyclic load reversals to simulate an

earthquake scenario by a double acting 100 kN

capacity electro hydraulic actuator.. A constant axial

load of 20 kN (0.1Agf′c) will be applied by one

hydraulic jack of 100 kN loading capacity with its

end connecting to the concrete head. A load cell will

be attached to the jack to measure reaction force

(Figure 3). This setup is designed to ensure uniform

axial load distribution on the wall cross section area,

and more importantly, to accommodate the horizontal

movement of wall specimens due to lateral

displacements.

The first stage aiming to determine the cracking

displacement Δcr increases by the step of 1 mm for

the first 14 cycles and 2 mm for the after cycles.

After cracking happening in both directions, the cycle

Continues by the same size of step until the yielding

of steel is monitored.

The bottom of the wall was connected to laboratory

strong floor by pre-stressing rods, which aimed to

prevent horizontal movement between wall base and

the strong floor as well as the overturning movement.

One end of actuator was fixed to the reaction walls of

lab. All specimens share the same loading apparatus.

Figure 3. Test Setup

3. Experimental observations and results

3.1. Load–deformation response

Figure 4 and 5 shows the shear force versus lateral

displacement of hysteresis loop of control specimen

and 4VX specimens. Figure 6 shows the skeleton

curve of both control specimen and 4VX specimen.

From the figures 4 and 5, the hysteresis capacity of

the 4VX specimen is behaved high when compare

to control specimen. The ultimate load

Figure 4.Load Deflection Curve of Control Specimen

Figure 5.Load Deflection Curve of 4VX Specimen

Figure 6.Skeleton Curve for various Specimens

was observed as 25.46KN to fail the control

specimen and for 4VX specimens required

30.32KN in the positive loading cycles and at the

negative loading cycles control specimen took 27.5

KN and 4VX specimen took about 30.317 kN, at

same time the ductility behavior of the 4VX

specimen is higher. It deflects up to 9.1 mm but

control specimen deflected only 8.4 mm at the stage

-40

-30

-20

-10

0

10

20

30

-2.00E+01 0.00E+00 2.00E+01 4.00E+01

LOA

D in

kN

DEFLECTION in mm

Control Specimen

-40

-30

-20

-10

0

10

20

30

-1.00E+01 -5.00E+00 0.00E+00 5.00E+00 1.00E+01

LOA

D i

n k

N

DEFLECTION in mm

4VX

-40

-20

0

20

40

-20 -10 0 10 20

LOA

D in

KN

DEFLECTION in mm

SKELETON CURVE

4VX

CONTROL

of failure. The permanent drift at the top the wall

was observed as 4.8 mm for the 4VX specimen and

the 5.2 mm for the Control specimen. It shows that

the permanent deformation of the control specimen

is high when comparing to the 4VX specimen.

Energy absorption Characteristics of the control

specimen at the earlier cycles of the loading, up to

the 8 cycle it shown good and the consecutive

cycles it gets reduced, But compare to 4VX

specimen up to 12 cycles it shown good and the

consecutive cycles it gets reduced. The stiffness of

the specimen were decreased when the 8th

cycle in

the control specimen and for 12th

cycle for the 4VX

specimen. The control specimen took 15 cycles for

the failure where 4VX specimen took 19 cycles for

the failure.

3.2. Cracking pattern

Figure 8 and 9 shows the crack pattern of the

control specimen and the 4VX specimen

accordingly. The crack was observed at the 8th

cycle for the control specimen and the 12th

cycle for

the 4VX specimen. The ultimate width of the

cracks for the control specimen is 3.2 mm and 2.8

mm for the 4VX specimen at the stage of the failure

cycles. The cracks where observed by the means of

crack width microscope. Starting from the crack

propagation itself that same crack is monitored and

the behavior of that crack was studied. The Control

specimens show the crack of 0.2mm at the 8th

cycle

and it is increased with the increased cycle. The

4VX specimens show the crack of 0.1mm at the

starting stage and it is increased with the increased

cycle. The diagonal cracks were observed at the last

three cycles for the control specimen where no

control cracks were observed in 4VX specimen.

The large no of primary and secondary cracks were

observed in the control specimen when compare to

the 4VX specimen.

4. Conclusions

The seismic behavior of the RC shear wall with

truss type detailing was investigated

experimentally. Based on the observation and the

results the following conclusion can be drawn. The

experimental observation showed that 4VX steel

truss type detailing had a beneficial effect on the

shear wall capacity and energy dissipating capacity

of RC shear wall. By adding X shaped bracing in

the vertical direction of this unconventional

detailing model was able to withstand more shear

force under cyclic loading and low amount of the

crack propagation and thereby trending the failure

mode to the flexural failure.

Figure 7. Crack pattern of Control specimen

Figure 8. Crack pattern of 4VX specimen

References

1. Hui Wen Tian, Yuan QiLi and Cheng Yu

(2015), ‘Testing of steel sheathed cold-formed steel

trussed shear walls’, Thin-Walled Structures,

vol.94, No.4, pp.280–292.

10. IS 456 (2000), ‘Plain and Reinforced

Concrete-Code of Practice’, Bureau of Indian

Standards, New Delhi.

2. Omar A. El Azizy, Marwan T. Shedid ,

Wael W. El Dakhakhni and Robert G. Drysdale

(2015), ‘Experimental evaluation of the seismic

performance of reinforced concrete structural walls

with different end configurations’, Engineering

Structures, vol.101, No.3, pp.246-263.

3. Konstantinos I. Christidis, Emmanouil

Vougioukas and Konstantinos G. Trezos (2016),

‘Strengthening of non-conforming RC shear walls

using different steel configurations’, Engineering

Structures, vol.124, No.5, pp.258–268.

4. Wenwu Lan, Jiaxing Ma , Bing Li (2015),

‘Seismic performance of steel–concrete composite

structural walls with internal bracings’, Journal of

Constructional Steel Research Vol.110, No.2,

pp.76–89.

5. Omar A. El Azizy, Marwan T. Shedid ,

Wael W. El Dakhakhni , Robert G. Drysdale

(2015), ‘Experimental evaluation of the seismic

performance of reinforced concrete structural walls

with different end configurations’, Engineering

Structures, Vol.101, No.4, pp.246-263.

6. Xiaodong Ji, Tongseng Leong, Jiaru Qian,

Wuhui Qi, Weibiao Yang (2016), Cyclic shear

behavior of composite walls with encased steel

braces, Engineering Structures, Vol.127, No.3,

pp.117-128.

7. Yuntian Wua, Wei Yang, Yan Xiao, F.

ASCE, F. ACI (2016), ‘Seismic behavior of high

strength concrete composite walls with embedded

steel truss’, Journal of Constructional Steel

Research, Vol.118, No.5, pp.180–193.

8. Yuntian Wu, Dao-yang Kang, Yeong Bin

Yang (2016), ‘Seismic performance of steel and

concrete composite shear walls with embedded

steel truss for use in high-rise buildings’,

Engineering Structures, Vol.125, No.2, pp.39–53.

9. IS 13920 (1993), ‘ Ductile detailing of

reinforced concrete structures subjected to seismic

forces’ Bureau of Indian Standards, New Delhi.