A new passive confinement model for the analysis of concrete structures subjected to cyclic and transient dynamic loading

Abstract

SUMMARYThe paper describes an analytical model for reinforced concrete members subjected to cyclic or transient dynamic loading. Model characterization is given in the context of a pseudo-spatial description of the stress state. This comprises a procedure for calculating and continuously updating the transverse confinement stress for a given applied axial strain, thus accounting for the passive confinement which an element of concrete is subjected to within a structural member.Comparison with existing uniaxial models shows that the new formulation takes note of previously neglected effects, such as non-coincident peaks of the steel and concrete stress-strain curves, and Poisson's ratio variation during loading. Moreover, comparison with 3D concrete constitutive relationships indicates that the level of accuracy is comparable, whilst significant computing time saving is achieved by the new model. Model validation is confirmed by comparison with cyclic loading laboratory test results. Finally, two frames with the same overall strength enhancement factor are analysed under earthquake loading; the difference in the response clearly demonstrates that the model accounts for important behavioural characteristics which are hitherto neglected in comparable existing models.

Concrete Subjected to Varying Confinement, I: Experimental Evaluation

“…To account for the variation in confining pressures with dilation, a variable confinement (VC) methodology was developed by Madas and Elnashai (1992) and modified by Kestner et al (1997) and Harries and Kharel (2002). In this method, the axial deformation is incremented and the level of confining stress is determined based on the amount of dilation present.…”

Nonlinear analysis of axially loaded circular concrete-filled stainless steel tubular short columns

“…Madas and Elnashai [29] proposed a passive confinement model for confined concrete in which the concrete confinement varies with the axial strain. They reported that the confinement model given by…”

Concrete Subjected to Varying Confinement, II: Modeling

“…Research has shown that the axial response of concrete is enhanced under the presence of lateral confinement (Mander et al 1988b;Razvi and Saatcioglu 1999;Xiao and Wu 2000;Lam and Teng 2002;Richart et al 1928;Tan and Sun 2006;Candappa et al 2001;Madas and Elnashai 1992;Kestner et al 1997). In particular, confinement provides an increase in compressive strength and deformability.…”

“…The axial response models are based on one of two concepts: 1) the confining pressure is constant (Mander et al 1988a;Razvi and Saatcioglu 1999;Xiao and Wu 2000;Lam and Teng 2002;Richart et al 1928;Tan and Sun 2006;Candappa et al 2001), or 2) the confinement pressure varies with lateral dilation (Madas and Elnashai 1992;Kestner et al 1997). The assumption of a constant level of confinement is based on the assumption that when the concrete dilates the confining material is at yield (Mander et al 1988a;Razvi and Saatcioglu 1999).…”

“…This can occur when fiber reinforced polymers (FRP) or excessive amounts of steel are used. For these applications, variable confinement models, where confining stress changes based on the level of dilation, are more appropriate (Madas and Elnashai 1992;Kestner et al 1997).…”