Effectiveness of Some Strengthening Options for Masonry-Infilled RC Frames with Open First Story

摘要

Strengthening of masonry-infilled reinforced concrete (RC) frame buildings with an open first story is needed because of the inherent irregularity in such buildings resulting in their poor performance as observed during several past earthquakes. In the present study, several strengthening schemes were evaluated for their effectiveness in improving the performance of such buildings, based on nonlinear analyses of typical RC frames. Instead of using predetermined multiplying factors for designing the first-story members for higher forces as recommended in some national codes, a rational method was developed for the calculation of the required increase in strength of open first-story columns. Other strengthening schemes studied were providing additional columns, diagonal bracings, and lateral buttresses in the open first story. Code methods were found to increase only lateral strength (and not the ductility) of such frames; whereas, some of the alternate schemes studied were found to improve both lateral strength and ductility for improved seismic performance.