Quantifying panel zone effect on deflection amplification factor

Abstract

Drift is a dominant feature in tall-building design and can dictate the selection of structural systems. Because a reliable estimate of actual drifts is crucial for controlling structural damage, estimating drift considering intricate details seems noteworthy. In order to estimate story drifts during massive quakes, seismic design provisions generally specify a deflection amplification factor (C d ) to amplify elastic design drifts. In most of these codes, the amount of C d is calculated from line-element models without considering panel zone effects, despite the panel zone intensifying the story drift considerably. Therefore, the effect of panel zone on the story drift and C d has been investigated in the current paper. Because C d is independent of the number of stories, 4-story frames, as benchmarks for special steel moment frames, with different thicknesses of the panel zone, are used. The effect of panel zone is provided as a correction factor for C d . The results show that the panel zone should be considered in the analytical models; otherwise, the story drift will be underestimated up to 35%. Finally, a relation has been derived to consider panel zone effects on C d , as a function of the panel zone thickness.KEYWORDS deflection amplification factor, modification factor, nonlinear time history analysis, panel zone, special moment-resisting frames, story drift | INTRODUCTIONAlthough nowadays it is possible to access different earthquake records, the use of this method is not common for designing conventional structures because of complication of performing nonlinear time history analyses. Therefore, the use of simplified methods of analyses to estimate the maximum inelastic response of structures during strong earthquakes is still an important and unavoidable matter. On this basis, in most seismic design provisions, the maximum lateral displacement of structures is estimated by amplifying the drifts computed from an elastic analysis with a deflection amplification factor.The first researches in this field were performed by Veltsos and Newmark [1] and Veltsos et al. [2] They investigated single-degree-of-freedom systems subjected to simple pulses and three earthquakes. They found that in the range of small frequencies (frequencies less than 0.38 Hz), the maximum displacement of an elastic-perfectly plastic system can be considered identical with the maximum displacement of an elastic system having stiffness equal to the initial stiffness of the elastic-perfectly plastic system. These observations caused the formation of the equal displacement. In addition, it was obtained that in the range of high and relative high frequencies, the maximum inelastic displacement of the elastic-perfectly plastic system is remarkably greater than the maximum displacement of the corresponding elastic system is. [3] After that, many researches have been performed, in which the effects of record properties, soil type, P-Δ effects, ductility, and the indexes of hysteretic curve on the ratio of inelastic displacement to the elasti...