DEVELOPMENT OF SEISMIC DESIGN AND ANALYSIS METHOD FOR RC FRAMES WITH INFILL WALLS

Low-rise RC frames with Infilled walls are widely used in many areas around the world including Thailand. It is well known that the presence of infill walls can have adverse effects on the seismic response of the frame due to infillframe interactions. Despite their widespread usage, clear design strategies to prevent undesirable failure modes due to the infill-frame interactions are not normally given in design codes. Typically, these frames are designed based on elastic analysis without considering the infill walls. It is well recognized that structures designed with elastic analysis may result in uncontrolled inelastic response. Together with complexed infill-frame interactions, theses RC frames may develop undesirable, and potentially dangerous, failure modes such as soft-story mechanism and brittle shear failure. The undesirable response modes can be mitigated by controlling the response mechanism and using realistic inelastic internal force distribution for design. This paper proposes a practical design method for RC with infilled frames. The method focuses on controlling failure mechanism of the frame. The inelastic internal force distribution is obtained from push-over analysis using a structural model that can capture infill-frame interactions. By ensuring that the frame develops a pre-selected mechanism and preventing all the undesirable local failures, the RC frame with infill walls can be one of the most seismically robust structural systems for low-rise structures.