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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP301_07

Date: 

March 16, 2015

Author(s):

Ahmed M. Abd El Fattah and Hayder A. Rasheed

Publication:

Symposium Papers

Volume:

301

Abstract:

Fiber reinforced polymers (FRP) is an attractive material to the field of strengthening and confining new and existing structures. FRP is usually used to wrap columns to increase the ultimate strength and strain of the concrete through confinement. Existing columns typically have spiral steel reinforcement (SS) in the section when wrapped with FRP. The nature of the problem becomes totally different since there are two systems with different behavior engaged in confinement. Several models were proposed to depict the behavior of the FRP alone in confining concrete. On the other hand, the literature has limited studies assessing the behavior of FRP and SS working on confining concrete simultaneously. This paper proposes a model addressing the two materials engagement in circular columns. The development of the effective lateral confinement pressure is based on Lam and Teng model for FRP action and Mander Model for SS action. It also introduces the force eccentricity as a new parameter that plays an important role in estimating the amount of confinement involved. Hence, the level of strength and ductility vary based on the eccentricity. The proposed model considers the fully confined curve as an upper bound curve with zero eccentricity and the unconfined curve as a lower bound curve with infinite eccentricity. In between these two curves, infinite numbers of stress-strain curves can be generated based on the eccentricity. Generalization of the moment of area approach is utilized based on proportional loading, finite layer procedure and the secant stiffness approach, to achieve equilibrium points of P-e and M-f diagrams up to failure. Finally the model is validated by showing good conservative correlation to experimental data.


Document: 

SP301_01

Date: 

March 16, 2015

Author(s):

Donna Chen and Raafat El-Hacha

Publication:

Symposium Papers

Volume:

301

Abstract:

This paper explores the investigation using finite element methods of experimentally tested hybrid FRP-UHPC (Ultra-High Performance Concrete) beams under flexural loading. A combination of mesh sensitivity and cohesive element parameter studies were performed through validation with experimental data. Good correlation was found between experimental findings and the finite element method, though higher stiffness was found in the latter case. It was found that an overall mesh size of 12.5 mm (0.50 in) was suitable for use in the model in order to allow for proper convergence. For the parameters at the GFRP-UHPC interface, it was found that a bond-slip ratio of 5 along with a bond strength of 5 MPa (0.725 ksi) were the best fit to experimental data and should be used in future studies. Additional investigation into the incorporation of considerations to allow for more damage accumulation in the finite element model was recommended.


Document: 

SP301

Date: 

March 16, 2015

Publication:

Symposium Papers

Volume:

301

Abstract:

Editor: Riadh Al-Mahaidi

This CD contains 8 papers that were presented at a session sponsored by Joint ACI-ASCE technical commttee 447 at the ACI Fall Convention, October 2011 in Cincinnati, Ohio. The papers cover the modeling for strengthening for flexure, shear, torsion, and confinement of concrete. Where applicable, the papers cover comparisons of modeling results with experimental tests performed around the world.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-301


Document: 

SP301_05

Date: 

March 16, 2015

Author(s):

R. Hawileh, J. A. Abdalla , M. Z. Naser , and M. Tanarslan

Publication:

Symposium Papers

Volume:

301

Abstract:

This paper presents Finite Element (FE) model to predict and analyze the cyclic loading response of reinforced concrete (RC) beams strengthened in shear with Carbon Fiber Reinforced-Polymer (CFRP) and Near-Surface Mounted (NSM) reinforcement. Four FE models were developed based on experimental tests conducted in a previous study. The first specimen was unstrengthened to serve as a control beam while the other two beams were strengthened with NSM CFRP bars with different spacing arrangements. The last beam specimen was strengthened with larger diameter CFRP bars. The developed FE models employed different nonlinear constitutive material modeling laws and techniques such as concrete cracking, steel yielding, bondslip between CFRP bars and epoxy resin, and debonding between the epoxy resin and concrete surfaces. The predicted and measured load-deflection response envelop curves along with the associated hysteresis loops for each specimen were used as platforms to validate the accuracy of the developed models. The results indicate that there is a good match between the predicted results and measured data. It is concluded that the developed FE model is a suitable tool to predict the behavior of such strengthening systems when subjected to cyclic loading and could be used in lieu of expensive experimental testing especially in design-oriented parametric studies.


Document: 

SP301_02

Date: 

March 16, 2015

Author(s):

Fadi Oudah and Raafat El-Hacha

Publication:

Symposium Papers

Volume:

301

Abstract:

Finite Element Method (FEM) models of Reinforced Concrete (RC) beams strengthened in flexure using prestressed Near-Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) subjected to quasi-static loading were developed and presented in this paper. One un-strengthened RC beam and four RC beams strengthened using NSM CFRP prestressed to various prestress levels were modeled. Comparisons of the load-deflection behaviors between the FEM models and the experimental test results indicate the good agreement in the loading branch. However, differences in the stiffness exist once the beams are unloaded. It seems that the concrete damage variables in tension and in compression play a paramount role in the response of the beams under cyclic loading. The possible modifications to the developed FE model are outlined as well as the future needed research.


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