Mechanical contribution of exterior parapet walls to the structural resistances of RC building frames

Due to environmental and architectural considerations, the partially infilled exterior walls of reinforced concrete (RC) condominium buildings are typically cast monolithically with the surrounding beams and/or columns. Generally, their mechanical contribution to structural resistance is neglected due to the variety in the opening types and only their weight is considered in the structural design phase. Parapet wall is very common among the various partially infilled exterior walls. In this study, the mechanical influences of the parapet wall on the structural resistances of RC building frames against lateral seismic and progressive collapse failure were investigated. From the nonlinear static pushover and pushdown analyses of seven seismically designed RC building frames, the seismic and column-loss resistances with and without the parapet walls were compared. The analysis results revealed that the presence of parapet walls enhanced both the lateral seismic resistance and the progressive collapse resistance under column loss. The mechanical influences of the parapet walls decreased with increased span length, seismic design force, and number of stories of the RC building frames. For the five-story building frames, the normalized seismic resistance can be enhanced by 22% to 62%, depending on the span length. Moreover, the normalized progressive collapse resistance varies with the span length and the location of the removed column. An increase of 50% to 207% is observed under corner-column loss, and 28% to 162% under side-column loss. However, both the seismic and progressive collapse resistance enhancements may decrease to less than 10% for the fifteen-story building frame. From the variation of the amplification of resistance, it is practically acceptable to neglect the resistance contribution of the exterior RC parapet walls for medium-to-high building frames located in high seismic hazard zones.