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.
Plastic dilation rate characteristic of concrete confined with steel tube
- Authors: Piscesa, Bambang , Attard, Mario , Samani, Ali Khajeh
- Date: 2017
- Type: Text , Conference paper
- Relation: 14th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2017; Barcelona, Spain; 5th-7th September 2017 p. 436-446
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- Description: The use of external confining devices to confine concrete has become widely used. One of the purposes is to gain additional concrete strength and ductility. Although there are many types of external confining devices, in this paper, the attention is limited to the use of the steel tube as an external confining device. One of the main objectives of this research is to study the plastic dilation rate behavior of concrete-filled-steel-tube (CFST) columns. The experimental data for the plastic dilation rate is extracted, and compared with the authors concrete plasticity model. In the authors’ previous research, the calibration of the plastic dilation rate model was based on confined concrete tested under both active and passive confinement using FRP wraps. Since the behavior of the steel tube and the FRP materials are different, the author’s plastic dilation rate model needs to be re-evaluated for CFST columns. Comparisons of the extracted experimental plastic dilation rates with the model prediction for CFST specimens with normal strength concrete show good agreement and requires no adjustment in the formulation. However, for a specimen with 80 MPa concrete, the proposed formulation shows slightly lower plastic dilation rates. More experimental data for CFST using high strength concretes is required for further investigation. For the sake of completeness, the overall response of two CFST specimens is also evaluated using an in-house three-dimensional non-linear finite element analysis (3D-NLFEA) using the author’s proposed plasticity formulation for confined concrete.
Refined plasticity model for concrete stress-strain relationship part I : Prediction of peak stress and residual stress
- Authors: Piscesa, Bambang , Attard, Mario , Samani, Ali Khajeh
- Date: 2014
- Type: Text , Conference paper
- Relation: 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23) p. 149-154
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- Description: A refined plasticity model for concrete stress-strain relationships is proposed. The proposed failure surface has the ability to evolve its form based on empirical formulation in which being extracted from the experimental results via the frictional driver parameter (). Two main features are highlighted in this paper such as the peak stress prediction and residual stress prediction of the proposed model. In this paper the comparison of proposed models with experimental results weighted on uniaxial-triaxial compression in axial direction. In the next part of the research a non-associative flow rule in which has an inclusion of size effect to be applied in the constitutive driver is proposed and experimental comparison in both axial and lateral direction is discussed.
- Description: A refined plasticity model for concrete stress-strain relationships is proposed. The proposed failure surface has the ability to evolve its form based on empirical formulation in which being extracted from the experimental results via the frictional driver parameter (
Refined plasticity model for concrete stress-strain relationship part II : Inclusion of size effect
- Authors: Piscesa, Bambang , Attard, Mario , Samani, Ali Khajeh
- Date: 2014
- Type: Text , Conference paper
- Relation: 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23) p. 155-160
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- Description: This article will discuss about the implementation of size effect into the proposed plasticity model by adjusting the plastic potential function or flow rule. A new parameter (
Lateral strain of confined concrete incorporating size effect
- Authors: Samani, Ali Khajeh , Attard, Mario
- Date: 2012
- Type: Text , Conference paper
- Relation: 22nd Australasian Conference on the Mechanics of Structures and Materials, ACMSM22; Sydney, Australia; 11th-14th December 2012; published in From Materials to Structures: Advancement through Innovation; p. 357-361
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- Description: The lateral and axial strain relationship plays an important part in predicting the confinement of confined columns. Measuring lateral strains in compressive experiments proves to be difficult which mean few reliable results are available. A lateral strain versus axial strain model is proposed based on the supposition that the concrete behaves linear elastically in the early stages of loading, nonlinear hardening up to the peak stress after which the inelastic lateral strain vary linearly with the inelastic axial strain. The lateral to axial inelastic strain ratio is shown to be a function of the lateral confinement level and related to the failure mechanism. Moreover, size effect is also discussed from the lateral strain versus axial strain perspective.
A new model for confined concrete
- Authors: Samani, Ali Khajeh , Attard, Mario
- Date: 2010
- Type: Text , Conference paper
- Relation: 21st Australasian Conference on the Mechanics of Structures and Materials p. 227-232
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- Description: Analytical models for the stress-strain relationship of confined and unconfined concrete in compression are required for modeling the structural behavior of the reinforced concrete structural elements. The presented paper reviews the widely used models by Attard & Setunge (1996) and Binici (2005) and compares them with test results on uniaxial and triaxial tests with different specimen heights and widths and concrete strength. The variation of peak stress and corresponding strain, as well as the residual stress level, under confinement are compared with experimental results and discussed. A new analytical model is introduced which tries to address the limitations in previous models. The proposed model is capable of predicting the behavior of normal strength as well as high strength concretes.
Size effect in confined concrete
- Authors: Attard, Mario , Samani, Ali Khajeh
- Date: 2010
- Type: Text , Conference paper
- Relation: 21st Australasian Conference on the Mechanics of Structures and Materials p. 221-226
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- Description: Compressive size effect tests have been mainly conducted on uniaxial compression tests. However, softening in concrete happens not only in uniaxial compression but also under triaxial compression. The present study shows that the post-peak compressive fracture energy per unit area, is influenced by the level of confinement in triaxial loading. The results estimated from the literature show an increasing fracture energy with increasing confinement until a limit is reached, at a confinement ratio of about 10 to 20% after which it decreases until it becomes zero. The fracture energy, the specimen height, aspect ratio and the confinement level is shown to influence the softening behavior of both uniaxially and triaxially loaded concrete. A new stress strain model is proposed for unconfined and confined concrete. The proposed model takes account of size effects dependent on specimen height and aspect ratio. The model is compared to experimental data and shows excellent agreement.