SEISMIC RESPONSE OF FLEXIBLY SUPPORTED COUPLED SHEAR WALLS

Results from seismic analyses performed on 20-story ductile coupled-sh ear-wall models designed for Montreal, Canada, are presented. A two-di mensional model was used to idealize the structure including the suppo rting ground. Allowances were made for nonlinearities not only in the walls and the coupling beams, but also in the soil and foundation elem ents. The soil foundation was modeled by equivalent massless springs ( hangers), located at the base of the structures, allowing for inelasti c bearing of the soil and loss of contact (uplift) of base from suppor ting soil. The stiffnesses of massless foundation springs were obtaine d using the soil properties that were derived on the basis of strain-d ependent shear moduli of real borings. The study showed that the model is capable of tracing the response of coupled shear wall, taking into account the soil-structure interaction effects. Results showed that a llowing for foundation flexibility lengthened the fundamental period b y a maximum of 33%; it amplified deflections by a maximum of 81%. Howe ver the stresses in the walls and the coupling beams attenuated partic ularly in lower stories. Finally, no substantial variations were obser ved in the rotational ductility demands of the coupling beams.