Development of R and Cd Factors for the Seismic Design of AAC Structures

The seismic force-reduction factor (R) specified in seismic design codes is intended to account for energy dissipation through inelastic deformation (ductility) and for structural over-strength. The factor (R) is based on observation of the performance of different structural systems in previous strong earthquakes, on technical justification, and on tradition. For structures of autoclaved aerated concrete (AAC), the force-reduction factor (R) and the corresponding displacement-amplification factor (Cd) must be based on laboratory test results and numerical simulation of the response of AAC structures subjected to earthquake ground motions. The proposed factors must then be verified against the observed response of AAC structures in strong earthquakes. The objectives of this dissertation were: (1) to present a general procedure for selecting values of the factors (R) and (Cd) for use in the seismic design of structures; and (2) using that procedure, to propose preliminary values of the factors (R) and (Cd) for the seismic design of AAC shear-wall structures. The general procedure is based on comparing the predicted ductility and drift demands in AAC structures, as functions of the factors (R) and (Cd), with the ductility and drift capacities of AAC shear walls, as observed in quasi-static testing under reversed cyclic loads. Nonlinear numerical simulations are carried out using hysteretic load-displacement behavior based on test results, and using suites of natural and synthetic ground motions from different seismically active regions of the United States.