Seismic Performance of a Hybrid Building System Consisting of a Light Wood Frame Structure and a Reinforced Masonry Core

Story limit of residential light wood-frame buildings in the province of British Columbia was raised from four to six in 2009. The increase in height leads to more flexible buildings, potentially requiring the stiffer elevator shaft and stairwell core made from reinforced masonry to reduce building deflection under lateral loads. Guidelines for designing such hybrid buildings connected with ductile connections are currently lacking. As a first step towards achieving this goal a six-story light wood-frame building was designed assuming different scenarios of attachment to a stiffer core. Seismic responses to 10 ground motions of the designed six-story light wood-frame building with and without connection to a reinforced masonry core were obtained through the use of a finite-element modeling procedure through commercial software. A user-developed subroutine to model the hysteretic performance of wood shear walls, masonry core and connections was used in the analyses. Results show that the maximum lateral drift of wood shear-wall subsystem reduces to 79, 62 and 48% on average of that of pure wood structure in hybrid buildings with masonry core designed to 25, 50 and 100% shear resistance of the wood subsystem respectively. It is concluded that seismic design of the wood subsystem in hybrid building can be based on the use of the same seismic force modification factor for light wood frame system published in the the building code.