Seismic shear demand on wall segments of ductile coupled shear walls

Abstract

This paper presents the results of nonlinear dynamic analyses carried out on ductile coupled shear walls (CSWs) to investigate the seismic shear demand on wall segments. The objectives of the present study were to evaluate the dynamic amplification and establish a code-format force reduction factor for shear, applicable in Canada. The study considered three Canadian seismic zones (4, 5, and 6), five numbers of storeys (6, 10, 15, 20, and 30), three degrees of coupling (low, medium, and high), and 10 historical earthquake records encompassing a broad range of frequency contents. Overall, 450 analyses were performed. Results indicate that the New Zealand amplification factor βv presently used in Canada overestimates the dynamic amplification. Additionally, the use of the overstrength factor for shear γp for tension walls may underestimate their shear resistance and result in a shear failure. Conversely, the use of γp for compression walls provided a reasonable factor of safety. Finally, for the shear design of CSWs, two alternative approaches are suggested. The first involves the use of a force reduction factor for shear, Rv, including the dynamic amplification factor γd and the overstrength factor γp as follows: Rv = 2.0 for Za > Zv, Rv = 1.0 for Za < Zv, and Rv = 1.3 for Za = Zv, where Za and Zv are acceleration- and velocity-related zonal identifiers. The second approach implies the use of the overstrength factor γp of the compression wall for both walls of CSWs and βv = 1.0.Key words: coupled shear walls, reinforced concrete, degree of coupling, seismic, frequency content, shear demand, dynamic amplification factor, force reduction factor for shear.