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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

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.

DOI:

10.14359/51687995


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.

DOI:

10.14359/51688002


Document: 

SP301_03

Date: 

March 16, 2015

Author(s):

Young-Min You, Ashraf Ayoub, Sang-Wook Bae, and Abdeldjelil Belarbi

Publication:

Symposium Papers

Volume:

301

Abstract:

The structural response of reinforced concrete (RC) girders strengthened with fiber reinforced polymer (FRP) composites in shear is investigated in this study, using a rationally-developed three-dimensional finite element model that was calibrated through comparison with test results. Analysis of reinforced concrete structures dominated by shear requires careful consideration in selecting the appropriate elements and material models. This task is more prominent in RC girders strengthened with FRP composites due to the difficulties of characterizing the corresponding properties and failure modes. Thus, the novel attributes of the proposed model is in the description of the three-dimensional constitutive material laws for each component. In the proposed model, the softening behavior of concrete under a triaxial state of stress was accounted for. The effect of the out-of-plane stress behavior of the FRP-concrete interface was carefully evaluated, which currently cannot be measured during experiments. In addition, the use of mechanical anchors to improve the bond behavior was properly simulated. Furthermore, the damage mechanism and progression of failure were carefully monitored. The model was shown to provide a good level of correlation with experimental data, and could therefore be used to conduct extensive parameter studies.

DOI:

10.14359/51687998


Document: 

SP301_04

Date: 

March 16, 2015

Author(s):

Yashar Moslehy, Moheb Labib, T. R. S. Mullapudi, and Ashraf Ayoub

Publication:

Symposium Papers

Volume:

301

Abstract:

Fiber-reinforced Polymer (FRP) started to find its way as an economical alternative material in civil engineering from the early 1970s. The behavior and failure modes for FRP composite structures were studied through extensive experimental and analytical investigations. While research related to the flexural behavior of FRPstrengthened elements has reached a mature phase, studies related to FRP shear strengthening is still in a less advanced stage. In all proposed models to predict the shear capacity, the constitutive behavior of concrete and FRP was described independently. The true behavior, however, should account for the high level of interaction between the two materials. In this research, new constitutive relations for FRP-strengthened reinforced concrete elements subjected to pure shear are developed. In order to generate these relations, large-scale tests of a series of FRPstrengthened reinforced concrete panel elements subjected to pure shear are conducted. The University of Houston is equipped with a unique universal panel testing machine that was used for this purpose. These constitutive laws are implemented into fiber-based finite element models to predict the behavior of externally bonded FRP strengthened beams. The newly developed model proved to provide a good level of accuracy when compared to experimental results.

DOI:

10.14359/51688001


Document: 

SP301_08

Date: 

March 16, 2015

Author(s):

R. Kalfat and R. Al-Mahaidi

Publication:

Symposium Papers

Volume:

301

Abstract:

The increasing demand to strengthen existing infrastructure has resulted in growing popularity of advanced fiber composite materials (FRPs) applied to reinforced concrete (RC) members as externally bonded reinforcement. Although FRPs contain very high tensile strengths, premature debonding usually prevents the material from reaching its full potential. Research is currently underway to address this shortcoming by the provision of anchorages to the ends of FRP reinforcement. Bi-directional fiber patch anchors have been found to be one of the most effective anchorages available, which are particularly suitable in shear strengthening applications. The ongoing need for verification of the various influencing parameters such as anchor size, spacing and fiber thickness have inspired further numerical and experimental studies resulting in the present work. The paper will investigate the effect of such parameters highlighting key relationships that may be applied for future use in anchorage strength models.

DOI:

10.14359/51688008


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