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Title: Evaluating the Dynamic Characteristics of Retrofitted RC Beams

Abstract

The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to movemore » toward the location of the damage in each case.« less

Authors:
; ;  [1]
  1. Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)
Publication Date:
OSTI Identifier:
21148926
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1020; Journal Issue: 1; Conference: 2008 seismic engineering conference: Commemorating the 1908 Messina and Reggio Calabria earthquake, Reggio Calabria (Italy), 8-11 Jul 2008; Other Information: DOI: 10.1063/1.2963780; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BEAMS; BENDING; CARBON FIBERS; COMPRESSION STRENGTH; DAMAGE; DUCTILITY; ENGINEERING; FLEXIBILITY; LOADING; NONDESTRUCTIVE TESTING; REINFORCED CONCRETE

Citation Formats

Ghods, Amir S., Esfahani, Mohamad R., and Moghaddasie, Behrang. Evaluating the Dynamic Characteristics of Retrofitted RC Beams. United States: N. p., 2008. Web. doi:10.1063/1.2963780.
Ghods, Amir S., Esfahani, Mohamad R., & Moghaddasie, Behrang. Evaluating the Dynamic Characteristics of Retrofitted RC Beams. United States. doi:10.1063/1.2963780.
Ghods, Amir S., Esfahani, Mohamad R., and Moghaddasie, Behrang. Tue . "Evaluating the Dynamic Characteristics of Retrofitted RC Beams". United States. doi:10.1063/1.2963780.
@article{osti_21148926,
title = {Evaluating the Dynamic Characteristics of Retrofitted RC Beams},
author = {Ghods, Amir S. and Esfahani, Mohamad R. and Moghaddasie, Behrang},
abstractNote = {The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.},
doi = {10.1063/1.2963780},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1020,
place = {United States},
year = {Tue Jul 08 00:00:00 EDT 2008},
month = {Tue Jul 08 00:00:00 EDT 2008}
}
  • For many long years, steel reinforcements have been considered as the only tool for concrete confinements and studied widely, but nowadays application of Fiber Reinforced Polymer (FRP) as an effective alternative is well appreciated. Many bridges have been constructed in the past that are necessary to be retrofitted for resisting against the earthquake motions. The objective of this research is evaluation of nonlinear behavior of RC bridge piers. Eight RC bridge piers have been modeled by ABAQUS software under micromechanical model for homogeneous anisotropic fibers. Also the Bilinear Confinement Model by Nonlinear Transition Zone of Mirmiran has been considered. Thenmore » types and angles of fibers and their effects on the final responses were evaluated. Finally, effects of retrofitting are evaluated and some suggestions presented.« less
  • A finite element (FE) analysis model of interface layer is established for the pre-stressed CFS-GFS hybrid strengthened beams. An elastic solution for the interfacial stress in the adhesive layer of the retrofitted beams is developed as well. The analytical results were compared with the FE results of interfacial stresses in the beams with different thickness of the adhesive and the fibre sheet. Different heights of Cracks in the interfacial layer of the concrete beam are considered in FE Model. Analysis results show the strengthening pattern is of excellent interface performance and the strength of the fiber sheet can be effectivelymore » utilized. The results also indicate the shear and normal stresses in the interfacial layer of the concrete beam release at the locations of the cracks and reach the maximal value before the concrete cracked. The shear and normal stresses in the adhesive layer increase abruptly, and the cracks in the adhesive layer then appear. The axial stresses of hybrid fiber sheet near the cracks decrease locally at the sites of the concrete cracks.« less
  • The mechanical characteristics of the interface with hollow imperfections for reinforced concrete (RC) beams strengthened with Carbon-Glass fiber sheet is discussed, which is a new hybrid strengthening method. By establishing the constitutive equations of different materials, three interfacial models including imperfection dimension, imperfection location and imperfection amount are simulated using nonlinear finite element method. The shear stress and normal stress of glue layer, the first principal stress of concrete at the end of the interface and the stress distributions of different strengthening modes are analyzed. The results show that the shear stress of glue layer is sensitive for imperfection dimensionmore » and significantly increases with the imperfection dimension. However, the first principal stress of the concrete at the end of the interface marginally decreases with the imperfection dimension.« less
  • This paper presents results and discussions on an experimental study conducted to relate the rate of widening of corrosion cracks with the pattern of corrosion cracks as well as the level of steel corrosion for RC beams (153 x 254 x 3000 mm) that were corroded whilst subjected to varying levels of sustained loads. Steel corrosion was limited to the tensile reinforcement and to a length of 700 mm at the centre of the beams. The rate of widening of corrosion cracks as well as strains on uncracked faces of RC beams was constantly monitored during the corrosion process, alongmore » the corrosion region and along other potential cracking faces of beams using a demec gauge. The distribution of the gravimetric mass loss of steel along the corrosion region was measured at the end of the corrosion process. The results obtained showed that: the rate of widening of each corrosion crack is dependent on the overall pattern of the cracks whilst the rate of corrosion is independent of the pattern of corrosion cracks. A mass loss of steel of 1% was found to induce a corrosion crack width of about 0.04 mm.« less
  • In this study, a reliability-based method for predicting the initiation time of reinforced concrete bridge beams with load-induced cracks exposed to de-icing salts is presented. A practical model for predicting the diffusion coefficient of chloride ingress into load-induced cracked concrete is proposed. Probabilistic information about uncertainties related to the surface chloride content and the threshold chloride concentration has been estimated from a wide review of previous experimental or statistical studies. Probabilistic analysis to estimate the time to corrosion initiation with/without considering the effect of the load-induced cracks on the chloride ingress into concrete has been carried out. Results of themore » analysis demonstrate the importance of considering the effect of the load-induced cracks for correct prediction of corrosion initiation in RC bridge beams exposed to chlorides.« less