C 1 in Displacement Coefficient Method for Taiwan to Estimate Maximum Inelastic Displacement Demands of Existing Structures

The coefficient C 1 in the displacement coefficient method of FEMA-273/356 is the modification factor to relate the expected maximum displacements of elasto-plastic inelastic SDOF systems to displacements calculated for linear response. It permits the estimation of maximum inelastic displacements from maximum elastic displacements for structures with known lateral strength (usually, the existing structures). Recently, an improved C 1 has been presented in FEMA-440 because it was shown that the C 1 in FEMA-273/356 underestimates the maximum inelastic displacement demands of structures significantly. However, the improved C 1 in FEMA-440 was derived from the earthquake ground motions recorded in California. In addition, it was mentioned in FEMA-440 that “caution should be used when extrapolating the results presented in the report for ground motions and site conditions that differ”. Because the characteristics of earthquakes occurred in Taiwan are different from those occurred in California, the coefficient for used in Taiwan needs to be modified. The objective of this paper is to propose appropriate C 1 for use in Taiwan.