Biaxial effects in modelling earthquake response of R/C structures

Abstract

Recent studies reveal that R/C structural members subjected to biaxial flexure due to two‐dimensional earthquake excitation can deform much more than would be predicted by conventional one‐dimensional response analysis. The biaxial flexure may therefore have a significant effect on the dynamic collapse process of structures subjected to intense ground motions. The present paper is intended to develop a new formulation of the two‐dimensional restoring force model of R/C columns acted upon by biaxial bending moments, and to discuss the dynamic response properties of R/C structures. The model considered is a two‐dimensional extension of various non‐linear models for one‐dimensional response analysis, including the degrading trilinear stiffness model which is one of the simpler idealizations of the restoring force characteristics of flexural‐failure‐type R/C structures. The modelling validity is then examined by comparison with experimental data on the biaxial bending behaviour of R/C columns. Calculations are made to study the role of different system properties on the influence of inelastic biaxial bending on the dynamic structural response. It is shown that the inelastic biaxial effect is generally significant and, in some cases, critical in the case of R/C structures with stiffness‐degrading properties, while the effect is not so important for the non‐degrading inelastic cases.

Comparative efficiency analysis of different nonlinear modelling strategies to simulate the biaxial response of RC columns

“…A detailed review of the available models is presented in CEB (1996) and Fardis (1991). In addition to the fi ber models (Petrangeli et al, 1999;Taucer et al, 1991;Spacone et al, 1992), other analytical models are available, following the concepts of classical plasticity (Pecknold, 1974), Mroz multisurface plasticity (Takizawa and Aoyama, 1976;Powell and Chen, 1986;Galal and Ghobarah, 2003), Bouc-Wen (Wen, 1976), hysteresis modelling (Romão et al, 2004;Kunnath and Reinhorn, 1990;Casciati, 1989;Wang and Wen, 2000), bounding surface plasticity Fardis, 1991a, 1991b;Bousias et al, 2002), or lumped damage models Florez-Lopez, 2002, 2003;Mazza and Mazza, 2008), among others. The available test results for biaxial bending are not as extensive and the development and calibration is not exhaustive.…”

Nonlinear dynamic analysis of reinforced concrete building structures

“…The biaxial ground motion was found to cause 20-200% larger response than the uniaxial ground motions from columns for which the calculated deflection under uniaxial ground motion exceeded approximately twice the yield deflection. Takizawa and Aoyama (1976) extended the one-dimensional degrading trilinear hysteretic model into a two-dimensional model on the basis of plasticity theories (Ziegler 1959). The proposed model was judged to predict the significant trends of the biaxial behaviour of reinforced concrete test columns.…”

Numerical Modelling of RC Columns Subjected to Biaxial Horizontal Loading and Variable Axial Load

“…It has been also reported that the damages of reinforced concrete (RC) elements caused by earthquakes increased when submitted tomultiaxial excitation (Takizawa et al, 1976, Lejano, 2007.From the axial load-bending interaction diagrams, the yielding and ultimate moment's increases with the level of axial load until the balance point is achieved. The variation of the axial load during an seismic action can change all the hysteretic properties and inelastic response of the RC columns, in particularly the strength, stiffness, and ultimate displacement capacity , CEB, 1996, Bonet et al, 2006.…”