Seismic response of multistory reinforced concrete frame with vertical mass and stiffness irregularities

Abstract

Irregular buildings behave differently as compared with regular buildings. Seismic design codes have quantified the irregularities in terms of magnitude only ignoring the effect of irregularity location. In the present study, a single parameter to quantify mass, stiffness and strength irregularity in terms of both magnitude and location is proposed on the basis of the dynamic characteristics of the building. Furthermore, building models with different types of irregularity with variation in magnitude and location of irregularity are analyzed by subjecting them to an ensemble of 27 ground motions to create a seismic response databank. In the analysis, the torsional effects generated due to irregularities in the building systems (as per EC 8:2004 provisions) are included. On the basis of regression analysis conducted on this seismic response databank, equations to estimate seismic response parameters such as fundamental period, maximum roof displacement and maximum inter-story drift ratio etc. are proposed for the irregular buildings in terms of the proposed irregularity index. Finally, applicability of the proposed equations is discussed in brief, and these equations are validated for 2D and 3D building models.Mmodel name, M rmass ratio, S rstiffness ratio, ST rstrength ratio.

Seismic behavior of multistory RC building frames with vertical setback irregularity

“…The proposed index effectively captures the variation of vertical irregularities (mass, stiffness and strength) as compared with the code‐defined approaches (Varadharajan et al ., ). Therefore, the authors propose the use of this index to represent building frame setback irregularity as well.…”

“…In a first companion paper (Varadharajan et al, 2012b), the authors proposed a parameter called 'irregularity index' to quantify different types of vertical irregularities (mass, stiffness and strength). The proposed irregularity index was based on dynamic characteristics of the buildings and was more efficient in capturing vertical irregularities as compared with the code approaches (Varadharajan et al, 2012b).…”

Least Favorable Probability of Failure for 5- and 10-story RC Frame Structures with Vertical Irregularities

“…The first aspect is the assessment of the seismic control effect of the vertical irregularity limit parameters in the seismic design codes [Das and Nau, 2003;Jeong et al, 2012;Pirizadeh and Shakib, 2013;Habibi and Asadi, 2013;Shakib and Pirizadeh, 2014]. The second aspect is the analysis of the seismic response demand of the vertically irregular structures [Choi, 2004;Chintanapakdee and Chopra, 2004;Athanassiadou, 2008;Basu, 2009;Lee 2011;Sehgal et al, 2011;Kirac et al, 2012;Sadashiva et al 2012;Zhou et al, 2011b;Mondal and Tesfamariam, 2014;Varadharajan et al, 2014]. The third aspect is to propose simplified methods to assess seismic performance and control measures for seismic design [Fragiadakis et al, 2006;Men et al, 2008;Sarkara et al, 2010;Zhou et al, 2013c].…”

Incremental dynamic collapse analysis of RC core‐wall tall buildings considering spatial seismic response distributions

“…Most of all, the focus has been concentrated on fragility analysis of the structures with moment‐frame system. In this case, several studies were conducted to establish fragility curves and performance levels in plan‐regular RC frame structures whereas other studies were performed to evaluate probabilistic responses of plan‐irregular buildings . The literature review also indicates that a number of researchers performed fragility analysis of the buildings in which RC shear walls were used as main seismic force‐resisting system.…”