Investigation on the fiber based approach to estimate the axial load carrying capacity of the circular concrete filled steel tube (CFST)
- Authors: Piscesa, Bambang , Attard, Mario , Suprobo, Priyo , Samani, Ali Khajeh
- Date: 2017
- Type: Text , Conference paper
- Relation: International Conference of Applied Science and Technology for Infrastructure Engineering 2017, ICASIE 2017; East Java, Indonesia; 5 August 2017; published in IOP Conference series: Materials Science and Engineering Vol. 267, p. 1-9
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- Description: External confining devices are often used to enhance the strength and ductility of reinforced concrete columns. Among the available external confining devices, steel tube is one of the most widely used in construction. However, steel tube has some drawbacks such as local buckling which needs to be considered when estimating the axial load carrying capacity of the concrete-filled-steel-tube (CFST) column. To tackle this problem in design, Eurocode 4 provided guidelines to estimate the effective yield strength of the steel tube material. To study the behavior of CFST column, in this paper, a non-linear analysis using a fiber-based approach was conducted. The use of the fiber-based approach allows the engineers to predict not only the axial load carrying capacity but also the complete load-deformation curve of the CFST columns for a known confining pressure. In the proposed fiber-based approach, an inverse analysis is used to estimate the constant confining pressure similar to design-oriented models. This paper also presents comparisons between the fiber-based approach model with the experimental results and the 3D non-linear finite element analysis.
A lateral strain plasticity model for FRP confined concrete
- Authors: Piscesa, Bambang , Attard, Mario , Samani, Ali Khajeh
- Date: 2016
- Type: Text , Journal article
- Relation: Composite Structures Vol. 158, no. (2016), p. 160-174
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- Description: This paper presents a plasticity constitutive formulation for actively and passively confined concrete. The loading surface is based on Menetrey and Willam's model with an additional frictional driver parameter. The frictional driver parameter controls the prediction of the peak stress and the residual stress level. The proposed flow rule has a plastic dilation rate control parameter which is a function of the restraining device or the local lateral modulus. A non-constant plastic dilation rate formulation is proposed to improve the prediction of the lateral strain behaviour of concrete. The proposed plastic dilation rate formulation is able to model plastic volumetric compaction caused by the use of very stiff confining devices, as well as the initial plastic compaction after the onset of localized cracking. Furthermore, the formulation is able to distinguish between active and passive confinement by monitoring the local lateral modulus. The accuracy of the proposed plastic dilation rate formulation is verified by comparison with experimental results for specimens subjected to either active or passive confinement from a variety of concrete strengths. The comparison between the proposed plasticity model and the experimental results for concrete under passive confinement (specimens with FRP confining material) was excellent. © 2016
Lateral behavior of concrete
- Authors: Samani, Ali Khajeh , Attard, Mario
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Civil and Environmental Engineering Vol. 5, no. 11 (2011), p. 533-538
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- Description: Lateral expansion is a factor defining the level of confinement in reinforced concrete columns. Therefore, predicting the lateral strain relationship with axial strain becomes an important issue. Measuring lateral strains in experiments is difficult and only few report experimental lateral strains. Among the existing analytical formulations, two recent models are compared with available test results in this paper with shortcomings highlighted. A new analytical model is proposed here for lateral strain axial strain relationship and is based on the supposition that the concrete behaves linear elastic in the early stages of loading and then nonlinear hardening up to the peak stress and then volumetric expansion. The proposal for the lateral strain axial strain relationship after the peak stress is mainly based on the hypothesis that the plastic lateral strain varies linearly with the plastic axial strain and it is shown that this is related to the lateral confinement level.