Application of Drucker-Prager Plasticity Model for Stress-Strain Modeling of FRP Confined Concrete Columns

Department of Building and Construction, City University of Hong Kong, China
Procedia Engineering 01/2011; 14:687-694. DOI: 10.1016/j.proeng.2011.07.088

ABSTRACT Existing research works have identified that Drucker-Prager (DP) plasticity model is capable of modeling the stressstrain behavior of confined concrete. However, the accuracy of the model largely depends on the adequate evaluation of its parameters that determine the yield criterion, hardening/softening rule and flow rule. Up to date, most research works mainly focus on the first two criteria. The plastic dilation angle is the major parameter that governs the DP flow rule. This paper addresses the plastic dilation properties of concrete for FRP confined circular concrete columns under the theoretical framework of DP model in the commercial software ABAQUS. Through careful analyses of test results for FRP confined concrete columns, it is found that the plastic dilation angle is a function of axial plastic strain and the lateral stiffness ratio. A simple model for the plastic dilation angle is subsequently developed. With the implementation of this model, the finite element analysis results fit well with the experimental stress-strain curves for columns with both low and high confinement.

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    ABSTRACT: An important application of FRP composites is as a confining material for concrete, in both the seismic retrofit of existing reinforced concrete columns and in the construction of concrete-filled FRP tubes as earthquake-resistant columns in new construction. Reliable design of these structural members necessitates clear understanding and accurate modeling of the stress–strain behavior of FRP-confined concrete. To that end, a great number of studies have been conducted in the past two decades, which has led to the development of a large number of models to predict the stress–strain behavior of FRP-confined concrete under axial compression. This paper presents a comprehensive review of 88 models developed to predict the axial stress–strain behavior of FRP-confined concrete in circular sections. Each of the reviewed models and their theoretical bases are summarized and the models are classified into two broad categories, namely design-oriented and analysis-oriented models. This review summarizes the current published literature until the end of 2011, and presents a unified framework for future reference. To provide a comprehensive assessment of the performances of the reviewed models, a large and reliable test database containing the test results of 730 FRP-confined concrete cylinders tested under monotonic axial compression is first established. The performance of each existing stress–strain model is then assessed using this database, and the results of this assessment are presented through selected statistical indicators. In the final part of the paper, a critical discussion is presented on the important factors that influenced the overall performances of the models. A close examination of results of the model assessment has led to a number of important conclusions on the strengths and weaknesses of the existing stress–strain models, which are clearly summarized. Based on these observations, a number of recommendations regarding future research directions are also outlined.
    Engineering Structures 01/2012; · 1.77 Impact Factor
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    ABSTRACT: Concrete dilation is one of the main parameters that controls the stress–strain behaviour of confined concrete. Several analytical studies have been carried out to predict the stress–strain behaviour of concrete encased in fibre-reinforced polymer (FRP), which is crucial for structural design. However, none of these studies have provided a simple formula to determine the dilation parameter that is always required in the finite element (FE) material modelling of concrete. This paper presents a simple empirical model predicting the confined concrete dilation parameter within the theoretical framework of a Karagozian and Case type concrete plasticity model. A set of 105 FRP-confined specimens with different unconfined concrete strengths (f′c) and confinement moduli (E1) was analysed using the LS-DYNA program. The model predictions of the confined ultimate strength (f′cc), confined ultimate axial strain (ℰcc) and confined ultimate hoop strain (ℰh) were compared with the corresponding experimental database results for each specimen. In addition, the model axial and hoop stress–strain curves of each specimen were developed and compared with the corresponding experimental ones. The proposed model was able to predict stress–strain curves of the test specimens quite well .The proposed model was able to predict f′cc with mean errors (M) and standard deviations (SD) of 2.6% and 10.7%, respectively. Similarly, the model predicted ℰcc with M and SD values of 0.3% and 29.0%, respectively. Finally, the model was less successful in predicting ℰh with M and SD values of 13.7% and 26.3%, respectively.
    Engineering Structures 07/2014; · 1.77 Impact Factor

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