Theory And Method Of Direct Displacement-based Seismic Design Of Reinforced Concrete Frame Structures

In this paper, the merit and fault of methods of seismic design in current code and new problems appearing in recent years are analyzed, the introduction and developments of performance/displacement (PBSD/DBSD) seismic design is reviewed and the formwork of DBSD is founded. It is believed that two methods-ductility coefficient-based design and capacity spectrum method which are often used in DBSD can only be used in checking the structure displacement after traditional force-based design because the displacement can't control the whole design process and iterative computation is repeated which lead to great amount of work and difficulty in manual design as is often done in current code.Direct displacement-based seismic design is presented in this paper according to these factors. An approximate formula for computing yield story drift of structures is concluded and a proportional vector is introduced to modify the displacement considering the differences in selecting the initial displacement vector and the indefinite computation methods after getting the base shear. It is very important to control the behavior of structures when middle-degree earthquake occurs, so in this paper the following steps will be used: computing the base shear to design the bar arrangement when minor levels of ground motion occurs; selecting the ductility coefficient of structures by users when moderate levels of ground motion occurs; computing the ductility coefficient according to the theory of "damage control" when rare earthquake occurs. By these steps, not only designing the bar arrangement but also controlling the elastoplastic behavior can be done. The validity and the simple computation process of this method is shown by analyzing 10-steoryR. C. frame.