Alternative approach to compute shear amplification in high-rise reinforced concrete core wall buildings using uncoupled modal response history analysis procedure

Abstract

The seismic response of the high-rise reinforced concrete (RC) wall structures is really complicated as several vibration modes other than the fundamental mode normally contribute significantly to the response-commonly recognized as 'higher mode effects'. Response spectrum analysis (RSA) procedure, which can account for higher mode effects, is usually employed to compute the seismic design demand for the high-rise structures. Recent studies show that the inelastic seismic force demands obtained from the rigorous nonlinear response history analysis procedure are much larger than the seismic force design demands obtained from the code-based RSA procedure for the high-rise RC wall structures. Though, the nonlinear response history analysis procedure is widely accepted for its ability to provide the most accurate estimate of nonlinear seismic responses, the obtained responses are generally so complex that it is quite difficult for engineers to grasp the overall picture of the responses and gain some insight into them and use them to understand the cause of high seismic demands. Another important issue related to the nonlinear seismic response prediction of the high-rise RC wall structures is the realistic and accurate numerical modeling of RC walls. In this study, a simplified but reasonably accurate procedure called the uncoupled modal response history analysis procedure is used to interpret the complex nonlinear behavior of high-rise RC wall structures. Moreover, a finite element model based on modified compression field theory is employed for accurate numerical modeling of RC walls by incorporating the axial-flexure-shear interaction. This study, by making use of a better computer modeling approach and an in-depth analysis by modal decomposition, aims to resolve some of the unanswered questions regarding realistic prediction of nonlinear seismic demands of high-rise structures. KEYWORDS finite element modeling, higher modes, high-rise, modal decomposition, RC core wall buildings, uncoupled modal response history analysis procedure

A modified response spectrum analysis procedure to determine nonlinear seismic demands of high‐rise buildings with shear walls

“…In consistence with the FIGURE 7 The cyclic modal pushover curves versus the hysteretic response of idealized nonlinear single-degree-of-freedom (SDF) systems (representing an ith vibration mode) under one ground motion previous studies, [14][15][16] this observation reconfirms that the use of same response modification factor (R) for each vibration mode, as prescribed in the standard RSA procedure, is not appropriate. Figure 8 shows the envelopes of individual modal contributions to story displacements, interstory drift ratios, story shears and story overturning moments obtained from the UMRHA procedure, for all three case study buildings.…”

“…However, this procedure requires to perform the multimode pushover analysis of an inelastic structural model and, therefore, can also be viewed as a simplification of the modal pushover analysis (MPA) proposed by Chopra and Goel. [13] More recently, Ahmed and Warnitchai [14] and Mehmood et al [15,16] applied the uncoupled modal response history analysis (UMRHA)…”

“…This shows the efficiency of this approach in decomposing the complex nonlinear dynamic response of buildings into individual modal contributions. Further details of this procedure and its validation can be seen in Chopra and Goel, [13] Ahmed, [18] Ahmed and Warnitchai, [14] and Mehmood et al [15,16] 3.2 | From the UMRHA procedure to the modified response spectrum analysis procedure-the basic concept…”

Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

“…These studies have shown that the UMRHA procedure is able to provide accurate predictions of story shears, story overturning moments, interstory drifts, and floor accelerations. Further details of this procedure and its validation can be seen in Chopra, Chopra and Goel, Ahmed, Ahmed and Warnitchai, Mehmood et al, and Najam and Warnichai . The modal cyclic pushover curves of case study rocking wall (shown in Figure ) are idealized using the suitable bilinear FS hysteretic model and the UMRHA procedure is performed to obtain the individual modal contributions as well as the combined response.…”

“…These studies have shown that the UMRHA procedure is able to provide accurate predictions of story shears, story overturning moments, interstory drifts, and floor accelerations. Further details of this procedure and its validation can be seen in Chopra, [46] Chopra and Goel, [25] Ahmed, [42] Ahmed and Warnitchai, [43] Mehmood et al, [44,45] and Najam and…”