AN IMPROVED METHOD ON THE DETERMINATION OF COMBINED DESIGN SPECTRUM

Design spectra are basic criteria for seismic design of engineering structures. Appropriately chosen spectra are essential for safety and economic efficiency of structures. To overcome the inherent problems in conventional approaches, relevant ground motion parameters and response spectra are studied by using the ground motion data recorded from the recent worldwide strong earthquakes. The relationships between ground motion amplitudes are evaluated by the weighted average method instead of the arithmetic average method, which introduces a more reasonable calculation of the design ground motion amplitudes. A normalized parameter varying with period (T) is applied when calibrating combined design spectra, and thus the asymptotically incorrect behavior caused by the three individually fixed parameters (PGA, PGV, PGD) in the calibration process of the response spectrum is rectified. Subsequently, the improved design spectrum is compared with those derived from other conventional approaches. The accuracy and reliability of the proposed procedure are examined by the discreteness analysis and validity assessment of ground motion response spectra.