New M.E. Thesis Submitted from Civil Student

STUDY THE EFFECT OF IRREGULARTY ON SEISMIC RESPONSE OF R.C.C. FRAMED BUILDING By Ritu Gupta,Civil

Abstract
Multistoreyed buildings are most affected by earthquake forces. An asymmetric multistoreyed building in plan is subjected to lateral loads and the eccentricity between the centre of mass and centre of rigidity causes horizontal twisting of structure. To improve the performance of such buildings, shear wall can be provided. The shear walls should preferably be extended from foundation to the top of building.In the present study, comparison between the seismic behavior of symmetrical (rectangular shape) and asymmetrical (L-shape) multistoreyed buildings has been done to decide the optimum position of shear wall. The building considered in the present study are rectangular (R) as well as L-shaped (L) having 7, 15, 20 and 25 storeys each. The analysis has been carried out by Response Spectrum Method using STAAD PRO 2005 (Structural Analysis & Design Software).Five cases having different outer plan dimensions (L*B) are considered for this study and are nomenclatured as case1 to case5.Each case contains are rectangular building of particular plan dimension L*B and few L-shaped buildings having same outer plan dimensions L*B but with different locations of shear wall, with one of them without a shear wall. These subdivision of cases are denoted as R (rectangular), L-0 (L-shaped without shear wall), L-1 (L-shaped with shear wall at grid no. ‘e’), L-2 (L-shaped with shear wall at grid no. ‘f’) and so on. The results are compared in terms of average displacement in X-direction, shear force & quantity of steel and concrete.It is concluded that at 7 storey buildings, no shear wall is located for any case (case1 to case5). So for case1 to case5, L-0 (without shear wall) can also be constructed in place of R shape building. At 15 storey buildings, no shear wall is located for case1 to case3 but in case4, L-6 shows the best performance similarly in case5, L-7 shows the best performance, which shows the position of shear wall. So for case1 to case3, L-0 (without shear wall) can also be constructed in place of R shape building. But for case4 to case5, L-6 & L-7 (with shear wall) can also be constructed in place of R shape building.At 20 storey buildings, no shear wall is located for case1 but case2, L-4 shows the best performance similarly case3, L-5 & case4 or case5, L-6 shows the best performance, which shows the position of shear wall. So for case1, L-0 (without shear wall) can also be constructed in place of R shape building. But for case2 to case5, L-4, L-5 & L-6 (with shear wall) can also be constructed in place of R shape building.At 25 storey buildings, no shear wall is located for case1 but case2, L-3 shows the best performance similarly case3, L-5 & case4 or case5, L-6 shows the best performance, which shows the position of shear wall. So for case1, L-0 (without shear wall) can also be constructed in place of R shape building. But for case2 to case5, L-3, L-5 & L-6 (with shear wall) can also be constructed in place of R shape building.It is also concluded that in such cases geometric changes in not much affected but its affected by storey height.




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