Numerical Analysis of Fiber Reinforced Polymer-Confined Concrete under Cyclic Compression Using Cohesive Zone Models

This paper examines the mechanical behavior offiber reinforced polymer(FRP)-confined concrete under cyclic compression using the 3D cohesive zone model(CZM).A numerical modeling method was developed,employing zero-thickness cohesive elements to represent the stress-displacement relationship of concrete potential fracture surfaces and FRP-concrete interfaces.Additionally,mixed-mode damage plastic constitutive models were pro-posed for the concrete potential fracture surfaces and FRP-concrete interface,considering interfacial friction.Furthermore,an anisotropic plastic constitutive model was developed for the FRP composite jacket.The CZM model proposed in this study was validated using experimental data from plain concrete and large rupture strain(LRS)FRP-confined concrete subjected to cyclic compression.The simulation results demonstrate that the pro-posed model accurately predicts the mechanical response of both concrete and FRP-confined concrete under cyc-lic compression.Lastly,various parametric studies were conducted to investigate the internal failure mechanism of FRP-confined concrete under cyclic loading to analyze the influence of the inner friction plasticity of different components.

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.

PEELING-OFF PHENOMENON IN FRP STRENGTHENED CONCRETE BEAMS DUE TO THERMAL RESIDUAL STRESS

Peeling-off phenomena in FRP strengthened concrete beams are investigated in this paper. Based on the beam theory and the fracture mechanics, a new theoretical model is proposed to analyze the peeling-off behavior near FRP-concrete interfaces, which is governed by residual thermal stresses. Numerical examples are presented to provide a clear insight into the failure mechanism. Some suggestions are provided for the optimal design of FRP strengthened structures.

Flexural Behavior of FRP-Reinforced Concrete Composite Member

Concrete Filled FRP （Reinforced Polymeric Plastic） Tubes （CFFT） and Reinforced Concrete Filled FRP Tubes （RCFFT） are known to have the capability to enhance structural performance in terms of structural stability, ductility, as well as chemical resistance when compared with conventional concrete members. In this study, the authors evaluate the structural performance of the CFFT and the RCFFT through flexural tests for the purpose of applying the members as flexural ones. Moreover, the compressive behavior of the CFFT and the RCFFT members was investigated to examine their confinement effects. Based on the experimental and analytical results of the compressive behavior of the members, equations for estimating the ultimate compressive strengths of the CFFT and the RCFFT were proposed. In addition, the degree of improvement on the flexural performance of the RCFFT member strengthened by the FRP was analyzed from the flexural tests.

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.

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.

State of the art review on the production and bond behaviour of reinforced geopolymer concrete

Geopolymer is produced through the polymerization of active aluminosilicate material with an alkaline activator,leading to the formation of a green,inorganic polymer binder.Geopolymer concrete(GPC)has become a promising low-carbon alternative to traditional Portland cement-based concrete(OPC).GPC-bonded reinforcing bars offer a promising alternative for concrete structures,boasting excellent geopolymer binder/reinforcement bonding and superior corrosion and high-temperature resistance compared to Portland cement.However,due to differences in the production process of GPC,there are distinct engineering property variations,including bonding characteristics.This literature review provides an examination of the manufacturing procedures of GPC,encompassing source materials,mix design,curing regimes,and other factors directly influencing concrete properties.Additionally,it delves into the bond mechanism,bond tests,and corresponding results that represent the bond characteristics.The main conclusions are that GPC generally has superior mechanical properties and bond performance compared to ordinary Portland cement concrete(OPC).However,proper standardization is needed for its production and performance tests to limit the contradictory results in the lab and on site.