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Ghoddousi P.,Iran University of Science and Technology | Ahmadi R.,Building and House Research Center | Sharifi M.,Iran University of Science and Technology
Canadian Journal of Civil Engineering | Year: 2010

The main objective of this study is to derive an analytical model for the pullout behavior of hooked-end steel fiber. The pullout behavior of hooked-end steel fiber comprises a component due to interfacial bond stress at the fiber-matrix interface and a component due to mechanical anchorage at the hook end of the fiber. To study the first component, the effects of hooks on the distributions of the force and stresses along the fiber length are analyzed. Then these results are used, with the concept of bond shear stress versus slip relation between fiber and matrix, to obtain a force component due to the interfacial bond. After that the required theoretical relations are obtained to determine the component due to the mechanical anchorages. Finally, the model is validated with two existing experimental results on the hooked-end steel fiber pullout. The results show that the proposed model is able to estimate the pullout behavior of hooked-end steel fiber. Source


Ghoddousi P.,Iran University of Science and Technology | Ahmadi R.,Building and House Research Center | Sharifi M.,Iran University of Science and Technology
International Journal of Civil Engineering | Year: 2010

Superior performances of Self-Compacting Concrete (SCC) in fresh state to achieve a more uniform distribution encourage the addition of fibers in concrete which is a motivation for structural application of fiberreinforced concrete. Fiber addition reduces the workability of Self-Compacting Fiber Reinforced Concrete (SCFRC). To provide required workability of the SCFRC, more paste is needed in the mixture. Therefore, the coarse aggregate content shall be adjusted to maintain its workability. The purpose of this study is to drive a model for estimating the aggregate contents for SCFRC. This model is based on constant covering mortar thickness theory. In this paper, all parameters which are participated in coarse aggregate content are discussed and presented in a relation. Then another relation is developed for predicting the void volume in the fibrous concrete. These relations are combined and a mathematical relation is deduced for predicting the coarse volume content in the function of the fiber factors. Proposed model is validated by conducting a rheological test. The result shows that the proposed model is simple, applicable and can be used as starting point in practical project. Finally in order to complete the proposed model, another relation has been derived that can show the interaction of parameters involved in SCFRC rheology behavior. Source


Ahmadi R.,Building and House Research Center | Ghoddousi P.,Iran University of Science and Technology | Sharifi M.,Iran University of Science and Technology | Bahreh V.M.,Sharif University of Technology
Journal of Zhejiang University: Science A | Year: 2011

This paper presents a precise solution to predict the behavior of steel fiber reinforced concrete (SFRC) under the four point bending test (FPBT). All the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a realistic stress-strain model is used for concrete behavior in compression, a linear response is considered for the uncracked tension region in a concrete constitutive model, and an exponential relationship is proposed as a stress-crack opening in the crack region which requires two parameters. Then the moment capacity of the critical cracked section is calculated by using these forces and satisfying equilibrium law at the section. Parametric studies are done on the behavior of SFRC to assess the sensitivity of the solution. Finally, this solution is validated with some existing experimental data. The result shows the proposed solution is able to estimate the behavior of SFRC under FPBT. © 2011 Zhejiang University and Springer-Verlag Berlin Heidelberg. Source


Ahmadi R.,Building and House Research Center | Rashidian O.,Iran University of Science and Technology | Abbasnia R.,Iran University of Science and Technology | Mohajeri Nav F.,Iran University of Science and Technology | Usefi N.,Iran University of Science and Technology
Shock and Vibration | Year: 2016

An experimental test was carried out on a 3/10 scale subassemblage in order to investigate the progressive collapse behavior of reinforced concrete (RC) structures. Investigation of alternative load paths and resistance mechanisms in scaled subassemblage and differences between the results of full-scale and scaled specimens are the main goals of this research. Main characteristics of specimen response including load-displacement curve, mechanism of formation and development of cracks, and failure mode of the scaled specimen had good agreement with the full-scale specimen. In order to provide a reliable numerical model for progressive collapse analysis of RC beam-column subassemblages, a macromodel was also developed. First, numerical model was validated with experimental tests in the literature. Then, experimental results in this study were compared with validated numerical results. It is shown that the proposed macromodel can provide a precise estimation of collapse behavior of RC subassemblages under the middle column removal scenario. In addition, for further evaluation, using the validated numerical model, parametric study of new subassemblages with different details, geometric and boundary conditions, was also done. © 2016 Rasool Ahmadi et al. Source


Ahmadi R.,Building and House Research Center | Ghoddousi P.,Iran University of Science and Technology | Sharifi M.,Iran University of Science and Technology
International Journal of Civil Engineering | Year: 2012

The main objective of this study is to drive a simple solution for prediction of steel fiber reinforced concrete (SFRC) behavior under four point bending test (FPBT). In this model all the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a bilinear elastic-perfectly plastic stress-strain response for concrete behavior in compression, a linear response for the un-cracked tension region in a concrete constitutive model, and an exponential relationship for stress-crack opening in the crack region which requires two parameters.Then the moment capacity of the critical cracked section is calculated by applying these assumptions and satisfying equilibrium lawat critical cracked section. After that, parametric studies have been done on the behavior of SFRC to assess the sensitively of model. Finally the proposed model has been validated with some existing experimental tests.The result shows that the proposed solution is able to estimate the behavior of SFRC under FPBT with simplicity and proper accuracy. Source

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