B UILDINGS
7.3 E VALUATION OF R ESULTS AND P ROPOSED D RIFT L IMITS
7.3.3 Variation of aspect ratio of wall panel
From the previous two sections, it is observed that the inelastic behaviour of the wall-slab assemblages started at a very low drift level and the tensile damage reaches it maximum value between drift levels of 0.08% and 0.17% considering the variation in the thickness of wall and slab.
In this section, the influence of wall-panel aspect ratio on the attainment of tensile damages is investigated and the lateral drift levels for maximum damages at three different locations of the wall-slab assemblage are presented. As the floor slabs tend to partition the structural wall into a number of panels, the aspect ratio of each panel tends to affect the local behaviour in the vicinity of each wall-slab junction. In this study, walls of 3 m, 5 m, and 10 m in length (Lw) and
Model at the base of shear wall
at the junction region in wall
at the junction region in slab
at maximum lateral load capacity
at maximum lateral drift WSM_TS1
WSM_TS2
WSM_TS3
WSM_TS4
Figure 7.6: Comparison of tensile damage at different drift levels with variation in slab thickness.
0.13% 0.12% 0.21%
%
0.79%
%
3.33%
%
0.10% 0.09% 0.31%
%
0.79%
%
3.33%
%
0.11% 0.14% 0.23% 0.82%
%
3.33%
%
0.09% 0.17% 0.23% 0.83% 3.33%
0 IS c od e d rif t lim it
D Lateral drift (%)0.10.20.30.40.50.60
IS c od e d rif t lim it
C Lateral drift (%)0.10.20.30.40.50.60
IS c od e d rif t lim it
A
Ten sile Dam ag
e 0.2
0.4
0.6
0.8
1.0
1.2 Lateral drift (%)0.10.20.30.40.50.6
IS c od e d rif t lim it
B Lateral drift (%)0.10.20.30.40.50.60 (a)(b)(c)(d) Wall baseWall junctionSlab
Lateral drift (%)
0.030.060.090.120.150 Lateral drift (%)
0.030.060.090.120.150 Lateral drift (%)0.030.060.090.120.150
Ten sile Dam ag
e 0.4 0.2
0.6
0.8
1.0
1.2 Lateral drift (%)0.030.060.090.120.150 Details at A Details at B Details at C Details at D (e)(f)(g) (h) Figure 7.7: Variation of tensile damage atdifferent locations ofwall-slab assemblage byvaryingthe thickness of floor slab; (a) 100 mm, (b) 120 mm, (c) 200 mm, (d) 250 mm, (e) details at A, (f) details at B, (g) details at C and (h) details at D.
2 m, 3 m, and 5 m, in effective panel height (hs) between the floor slab are analyzed. Each pair of wall length and effective panel height corresponds to different wall panel aspect ratios (hs/Lw), namely (a) 0.5, (b) 0.67, (c) 1 and (d) 1.25. Although not considered as an independent parameter in earlier studies, wall length appears to be an important parameter affecting response of shear walls.
As shown in the following sections, for the walls that have the same aspect ratio but different wall lengths (WSM_AR2 and WSM_AR4) the deformation characteristics can be quite different.
Variation of lateral drift levels with respect to maximum damage at different locations of the assemblage for different wall panel aspect ratio is shown in Figure 7.8. The drift level considering the maximum damage at the base of the base of the shear wall varies between 0.1% and 0.18%, while it varies between 0.08% and 0.11% in the wall at the junction region of the assemblage.
Figure 7.8: Variation of drift levels with respect to maximum damage at different locations of the assemblage for different wall panel aspect ratio.
For all the five models, the tensile damage starts at the base of the shear wall but reaches its maximum value in the shear wall at the junction region (Figure 7.9). For the maximum damage, the observed drift level is less for the shear wall at the junction region as compared to the drift level at the base of the wall. For the slab at the junction region, the maximum tensile damage depends on the length of the shear wall panel. Models WSM_AR1, WSM_AR2, and WSM_AR3 have the same length of wall as 3 m but the aspect ratio varies due to different heights of wall panel between the floors. Since the model WSM_AR1 is squat in nature, the observed drift level is more as compared to other models. As the wall length increases, the lateral drift of the shear wall gets reduced. For models WSM_AR3, WSM_AR4 and WSM_AR5, the lengths of shear wall are 3 m, 5 m and 10 m,
140 Chapter 7 - Drift Criteria for RC Shear Wall Buildings Model at the base of
shear wall
at the junction region in wall
at the junction region in slab
at maximum lateral load capacity
at maximum lateral drift WSM_AR1
WSM_AR2
WSM_AR3
WSM_AR4
WSM_AR5
Figure 7.9: Comparison of tensile damage at different drift levels with variation in aspect ratio of wall panel.
0.11% 0.09% 0.56% 0.90% 3.33%
0.101% 0.090% 0.310% 0.794% 3.33%
0.18% 0.114% 0.251% 0.93% 2%
0.13% 0.09% 0.15% 0.89% 2%
0.10% 0.08% 0.14% 0.84% 2%
respectively, and the lateral drifts observed from the maximum damage in the slab are 0.25%, 0.15%, and 0.14%, respectively. The lateral shear capacity is achieved at almost same drift level for all models.
From Figures 7.10a, 7.10b, and 7.10c, it is observed that the maximum damage is achieved at very low drift level at the base and junction region of shear wall, while the slab at the junction region shows the maximum damage at the higher drift ratio. This is because the length of the wall is same for the three models (WSM_AR1, WSM_AR2 and WSM_AR3). As the length of the wall is increased the drift ratio for maximum damage gets reduced (Figures 7.10d and 7.10e). At the lower drift ratio, cracks start developing at the base of the shear wall first and then in the junction region;
thus, no significant damage level is observed (Figures 7.10f, 7.10g, and 7.10h). The cracks in the slab region develop at a very high drift level as compared to that for shear wall. The wall length is found to be the most significant parameter affecting the drift level of the structure. As the length of the shear wall is increased for models WSM_AR4 and WSM_AR5, it is observed the cracks in the slab region start at a lower drift and also the tensile damage reaches its maximum value at lower drift ratio (Figures 7.10i and 7.10j). The drift level varies between 0.08% and 0.18% for the observed maximum tensile damage at the two locations of the shear wall, i.e. at the base and the wall-slab junction region.