| Accurate prediction of structural performance under earthquake loading is essential for design of structures to achieve life-safety or higher performance objectives. This study investigated the estimation of seismic demands and the factors that determine these demands in steel moment-resisting frame buildings using a series of different approaches.; The first approach employed a single-degree-of-freedom model and used the Coefficient Method (FEMA356) and the Capacity Spectra Method (ATC-40) to estimate the maximum drifts. Although the Coefficient Method generally predicted the maximum drifts well, the Capacity Spectra Method often predicted unconservative maximum drifts. Both methods were re-calibrated to provide accurate median maximum drifts over all period ranges.; In multi-degree-of-freedom (MDOF) building frames, large drifts may result from unstable behavior associated with P-Delta effects and material yielding. To investigate seismic demands on MDOF structures, static and dynamic nonlinear analyses were performed using 1D and 2D MDOF models with various structural parameters. Major findings are: (1) the impact of the P-Delta effects on structural stability changes during an earthquake, (2) the distribution of yielding predicted using dynamic analysis is often different than that predicted using static analysis, (3) 2D strong-column weak-beam frames exhibited a stable response under earthquake loading, (4) as the post-yield tangent stiffness of beam hinges decreased, larger drift concentrations occurred, (5) when beam-end moment releases were introduced, interstory drifts did not change significantly, and (6) as column stiffness increases, the P-Delta stability coefficient and drift concentrations decreased.; Based on the understanding of seismic behavior developed using 1D and 2D models, the seismic performance of 3D steel moment-frame structures was evaluated using a probabilistic approach. The annual probability of exceedence (APE) in member collapse was calculated and compared for the two-way and one-way frames. The two-way frames often had large drift concentrations due to a lack of continuous columns. However the one-way frames typically included large-sized members due to a limited number of seismic frames, which often results in a small plastic rotational capacity and then larger APE in member collapse. The approach presented in this study can be used for decision making for the framing systems in the United States and Japan. |
