DIRECT DISPLACEMENT-BASED SEISMIC DESIGN METHOD BASED ON RELATIVE RELIABILITY CONCEPT

Based on the average reliability level of structures designed according to the current Chinese force-based codes, a relative reliability theory was established and a specific method for Direct Displacement-Based Design (DDBD) is presented. In this method, for any seismic performance objective, the expected seismic risk level is always transformed into a frequent earthquake to calculate relative reliability, which is expressed in a ratio with the reliability of structures designed according to the current codes. This method preserves the reliability level of current codes and avoids complex calculations. After presenting the method, it is demonstrated that the base shear calculated by the DDBD method is theoretically equal to current code method for frequent earthquakes, so the section bearing capacity expression in current codes is adopted for the DDBD method, and a modified coefficient is introduced to account for errors in actual calculation. Finally, two examples are analyzed to identify the method’s effectiveness and advantages compared to the current force-based method.