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UBC Theses and Dissertations

In-plane shake table testing of gravity load designed reinforced concrete frames with unreinforced masonry infill walls Centeno, Jose


Common construction practice before modern seismic design codes appeared allowed designing columns lap splices located above the slab in each floor or above the foundation. The lack of lap splices and the shear reinforcement was in the form of stirrups with 90-degree bends and spaced at half the depth of the frame member. As a result, the section at the base of these columns is unconfined and susceptible to shear failure or to a premature failure of the lap splices before yielding of the longitudinal bars. The masonry infill walls used as partitions were often ignored by design engineers since such walls were considered as nonstructural architectural elements. However, lessons learned from past earthquakes and from several tests performed have shown that those walls tend to interact with the bounding frame when the structural system is subjected to moderate or severe earthquake ground motions. The first part of an experimental testing program carried out at the University of British Columbia (UBC) in Vancouver, Canada tested the performance of 1/2 scale Gravity Load Designed Reinforced Concrete (GLDRC) frames with unreinforced masonry walls. This testing program consisted of one monotonic loading test on an infilled frame and two series of shake table tests, one on an infilled frame and one on a bare frame with the UBC Earthquake Engineering Research Facility (EERF) unidirectional shake table. It was concluded from these tests that the interaction with the unreinforced masonry wall stiffens the frame, reduces the deformations, and allows dissipating energy through nonlinear response for several cycles of deformation. It was determined that the governing failure mode for the masonry wall was shear sliding for monotonic and dynamic loading. There was consistent evidence of local lateral deformations at the base of the gravity load designed columns due to construction cold joints and inadequate lap splices that may result in shear failure of the base of the column due to the interaction with the masonry infill during a severe earthquake.

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