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Showing 4 results for Frp Sheets

M. Reza Esfahani,
Volume 6, Issue 3 (9-2008)

In this paper, the effect of cyclic loading on punching strength of flat slabs strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets is studied. Experimental results of ten slab specimens under monotonic and cyclic loading are analyzed. Eight specimens were strengthened with CFRP sheets on the tensile face of the slabs and the two other specimens were kept un-strengthened as control specimens. The width of CFRP sheets varied in different specimens. After the tests, the punching shear strength of specimens under cyclic loading was compared with those with monotonic loading. The comparison of results shows that cyclic loading decreases the effect of CFRP sheets on punching shear strengthening. This decrease was more for the specimens with a larger value of reinforcing steel ratio. Therefore, it can be concluded that for specimens with large reinforcing steel ratios, cyclic loading may completely eliminate the effect of CFRP sheets on shear strengthening of slabs.
A.r. Rahai, M.m. Alinia, S.m.f Salehi,
Volume 7, Issue 1 (3-2009)

Concentric bracing is one of the most common lateral load resistant systems in building frames, and are

applied to many structures due to their manufacturing simplicity and economics. An important deficiency in the

bracing members is their irregular hysteretic loops under cyclic loading. In order to overcome this problem, it is

advised to restrain braces against buckling under compression, since buckling restrained frames dissipate a large

amount of energy. One method to restrain braces against buckling is to cover them with concrete. A proper covering

can prevent the core from buckling and provide similar capacities whether in tension or compression which would

produce regular hysteric curves. In this study, the behavior of buckling restrained braces (BRB) has been investigated

by considering different types of surrounding covers. The steel core is encased in concrete with different coverings. The

covering types include steel tubes, PVC pipes, and FRP rolled sheets. Experimental and numerical analyses were

implemented. According to the results, PVC pipes and FRP sheets are suitable alternatives to steel pipes. Furthermore,

the behavior of several types of steel cores was assessed since, applying steel with high ductility promotes the energy

dissipation of the brace. Finally, the effect of the separating layer between the steel core and the concrete on the

performance of bracing was evaluated.

M. Z. Kabir, A. Hojatkashani,
Volume 10, Issue 4 (12-2012)

The aim of current study is to investigate the effect of Carbon Fiber Reinforced Polymer (CFRP) composites on the fatigue

response of reinforced concrete beams. 6 reinforced concrete (RC) beams from which 3 were retrofitted with CFRP sheets, were

prepared and subjected to fatigue load cycles. To predict and trace the failure occurrence and its growth, a small notch was

induced at the middle span in bottom surface of all RC specimens. At the certain points, strains in concrete and CFRP were

measured in each cycle. The upper limit of applied load was considered at the level of design service load of bridges. In addition,

strain measurements facilitated to the calculation of interfacial shear stresses between concrete substrate and the CFRP layer.

The variation of such stresses through load cycles has been presented and discussed. Also, a discussion on possibility of the local

debonding phenomenon resulted from such interfacial stresses was presented. Load–deflection curves, strain responses and

propagation of tensile cracks provided an insight on the performance of the CFRP strengthened beams subjected to different

cycles of fatigue loading. Variation of load-deflection curves through fatigue load cycles depicted stiffness degradation which

was discussed in the research.

A.r. Sattarifar, M.k. Sharbatdar, A. Dalvand,
Volume 13, Issue 4 (12-2015)

In this paper, an experimental study has been conducted on strengthening of reinforced concrete (RC) connections by FRP sheets. The innovation of this research is using narrow grooves on critical regions of connection to increase the adherence of FRP sheets and prevent their early debonding. Therefore, four RC connections were made and tested under a constant axial load on the column and an increasing cyclic load on the beam. The first specimen, as the standard reference specimen, had close tie spacing in ductile regions of beam, column and panel zone based on seismic design provisions, and the second specimen, as the weak reference specimen did not have these conditions in all regions. Two other weak specimens were strengthened using two different strengthening patterns with FRP sheets one by ordinary surface preparation and the other with surface grooving method for installing FRP sheets on the connection. The results showed that ultimate load and ductility of the weak specimen compared to standard specimen decreased 25% and 17%, respectively. The shear failure and concrete crushing were prevented in the ductile regions of the beam and panel zone in both strengthened specimens. Also, it was observed that early debonding of FRP sheets was prevented in the strengthened connection with grooving pattern and so had desirable ductility and bearing capacity similar to the standard specimen.

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