INFLUENCE OF SEISMIC ACTION ADJUSTMENTS ON SEISMIC DESIGN AND SAFETY OF RC FRAMES

The experience of Wenchuan earthquake and Lushan earthquake shows that the actual seismic intensity suffered by buildings was often much greater than the code-specified seismic design intensity, which caused very serious damage to buildings. Although the seismic safety margin of buildings in China is in continuous improvement with the updating of seismic design code and seismic hazard map, many experts still believe that to date the seismic safety level of buildings in China is not sufficient yet. Hence, how to determine the reasonable seismic action is important and meaningful to ensure the seismic safety. Based on a series of reinforced concrete frames designed according to the Code for Seismic Design of Buildings (GB 50011-2010), these frames are redesigned with the adjustments of seismic design parameters, including dynamic amplification factor (b_max), seismic action, and dead and live load combination factors. The earthquake-induced collapse analysis is conducted for these frames. Consequently, the influence of the adjustments on the seismic forces, material consumption and seismic safety is discussed. The results indicate that the parameters adjustments make the axial compression ratio for columns increase by about 8%, and the reinforcement ratio for beams and slabs increase by about 6%. For frames whose collapse starts from the bottom story, the parameters adjustments can obviously improve the seismic safety of the frames. However, with the increasing of seismic design intensity, the increased amplitude of seismic safety will decrease slightly.