Seismic Shear Forces in Shear Walls of a Medium-Rise Building Designed by Response Spectrum Analysis
According to ASCE7-05, response spectrum analysis (RSA) procedure can be used to determine the seismic demands of the structures for the seismic design of any type of structures. However, this design procedure has been found to be inappropriate for medium-rise and high-rise buildings. This paper is aimed at verifying the RSA procedure prescribed in the current Thai seismic design code which is based on ASCE7-05 and proposing appropriate modification to the design shear force from RSA procedure. A 16-story medium-rise reinforced-concrete core-wall case-study building was first designed based on RSA procedure and then the non-linear response history analysis (NLRHA) was performed to determine the more accurate seismic demands of the structure. The results show that seismic shear demand of the shear wall from non-linear analysis is about 2 times the shear capacity of the wall designed by RSA procedure. This could lead to shear failure in the shear walls designed by RSA procedure. To avoid shear failure in the shear wall elements, the shear demands in the wall elements designed by RSA procedure needs to be amplified by a factor of 2, which is equivalent to reducing the response modification factor R = 5.5 in ASCE7-05 to R = 2.75 (for shear force in the shear wall only).