A modified constitutive model for FRP confined concrete in circular sections and its implementation with OpenSees programming

OpenSees is a well-recognized open source platform with high compatibility,and it has a well-developed fiber element method to cope with nonlinear structural analysis.Fiber reinforced polymer(FRP)confined concrete can effectively improve the seismic performance of concrete structures.However,sophisticated constitutive models for FRP confined concrete are not available in the current version of OpenSees.In this paper,after reviewing several typical FRP confined concrete constitutive models,a modified constitutive model for FRP confined concrete in circular sections was proposed based on Lam and Teng(2003)’s model with four main modifications including the determination of FRP rupture strain,ultimate condition,envelope shape,and hysteretic rules.To embed the proposed constitutive model into OpenSees is a practical solution for engineering simulation.Hence,the secondary development of OpenSees New UserMat was briefly demonstrated and a set of critical steps were depicted in a flow chart.Finally,with the numerical implementations of a series of FRP confined concrete members covering a wide range of load cases,FRP confinement types and geometric properties,the utility and accuracy of the proposed model compared with Lam and Teng(2003)’s model and new material secondary development in OpenSees were well validated.

A Review of Fibre Reinforced Polymer (FRP) Reinforced Concrete Composite Column Members Modelling and Analysis Techniques

The use of fibre-reinforced polymer(FRP)to confine concrete columns improves the strength and ductility of the columns by reducing passive lateral confinement pressure.Many numerical and analytical formulations have been proposed in the literature to describe the compressive behaviour of FRP confined concrete under both monotonic and cyclic loads.However,the efect of a stress/strain level in the columns has not been well defined because of the lack of well-defined strategies of modeing and oversimplification of the model.This paper reviews the existing FRP combinations and the available numerical and analytical methods to determine the effectiveness of the adopted method.An effort has been made to examine the usage of FRP materials in column applications in exist-ing building regimes and highlights the possible future scopes to improve the use of FRP confined concrete in civil applications.

Unified bearing capacity model of confined concrete column subjected to axial compression

To better study the behavior of confined concrete, this paper presents the basic hypothesis of uhimate equilibrium of confined concrete and the unified yield criteria of confining material. Based on the static equilibrium condition and yield criteria of components, a unified bearing capacity model of confined concrete column is proposed, and a simplified calculating equation of the model is also given. The model captures the character of confined concrete column. Effects of the confinement effect ratio, the lateral confinement ratio, unconfined concrete strength and the properties of confining material on the bearing capacity of confined concrete column are carefully considered. The model may be applicable to the calculation of bearing capacity of steel-confined concrete, concrete filled steel tube and FRP-confined concrete. The predictions of the model agree well with test data.