Direct displacement-based design of special concentrically-braced frames in near-fault regions

The effect of near-fault earthquakes on the effective period of special concentrically-braced frames is studied in this paper. The effective period is one of the most important parameters in direct displacement-based design. Given the effective period, the design base shear of structure can be obtained. Since the braced frames have high stiffness, an appropriate category of near-fault earthquakes for structures with high stiffness is established in this paper and the relations are presented to determine the pulse period and peak ground velocity. Sixteen near-fault accelerograms are simulated by the proposed methodology and applied to 16 one-storey special concentrically-braced frames. The results show that the behaviour of frames subjected to earthquakes with magnitude <6 is quite different from that of earthquakes with magnitude >6. The effective period depends on pulse period, peak ground velocity, ductility and design displacement. Two expressions are suggested to determine the effective period of two types of special concentrically-braced frames (X-braced and Inverted V-braced frame) according to these parameters.