Experimental study on anchoring of FRP-strengthened concrete beams

Bond enhancement for NSM FRP bars in concrete using different anchorage systems

Effect of concrete strength and longitudinal reinforcement arrangement on the performance of reinforced concrete beams strengthened using EBR and EBROG methods

A critical performance aspect of FRP retrofitted concrete elements is the bonding of the FRP sheet to the concrete surface. In general, the performance is limited by the debonding of the loaded FRP sheets from the concrete surface. One method to delay debonding and enhance the capacity is the use of FRP anchors which interlock the FRP sheet to the concrete body. FRP anchors are made of rolled FRP fibres epoxied into in predrilled boreholes. There are a considerable number of studies on FRP strengthening methods available, and also FRP anchors attract more attention of the research community recently. However, to date FRP anchors were tested in a system together with the FRP sheet attached to the concrete, inhibiting the development of general design models. Moreover, the anchor behaviour was never tested for cyclic loads, though most applications are for seismic retrofitting schemes and cyclic shear loading generally results in reduced load capacity due to fatigue failure. To overcome the deficit in knowledge, shear tests on various FRP anchors were carried out. For these tests, FRP anchors were installed in concrete specimens on a separating steel section. The FRP anchor was then directly loaded to determine the capacity of the isolated component. This paper describes the testing approach and procedure. Details on the experimental results for static tests are presented and an outlook on seismic tests is given.

Impact of anchored holes technique on behavior of reinforced concrete beams strengthened with different CFRP sheet lengths and widths

Bond efficiency of EBR and EBROG methods in different flexural failure mechanisms of FRP strengthened RC beams

A design guideline for shear strengthening of pre-cracked reinforced concrete (RC) beams using steel plates has been presented in this research by modifying the available shear capacity formulas. An experimental investigation was also carried out in order to validate the proposed guideline. Total five RC beams were fabricated, among which four beams were pre-cracked in shear by applying preloads. Two of the cracked beams were then strengthened with adhesive bonded steel plates while the rest two were strengthened with bolted steel plates. Variation was made in plate depth and bolt layers. The shear performance of the strengthened beams was evaluated by testing the beams to their ultimate capacity. Experimental results indicated that the shear capacity, ductility and stiffness of the pre-cracked beams increased significantly after strengthening with continuous steel plates. The shear capacity varied from 131% to 201% for strengthened beams compared to the control beam. Deeper plates offered better shear performance than the shallower plates. Modification of the existing formulas by introducing preload factors for estimating the shear capacity of the strengthened beams showed a good agreement with the experimental shear capacity.

A total of six beams have been tested to investigate the influence of FRP sheet on the mechanical behavior of concrete beam with different FRP sheet width. In addition, the failure mode of the concrete beam and FRP reinforced concrete beams were also studied by numerical simulation method named Realistic Failure Process Analysis (RFPA). The results indicate that, the loading capacity is increased and maximum deflection of the concrete beam is also increased with the increasing of the FRP sheet width. Moreover, the interfacial debonding easily propagates along the interfacial concrete layer at a load that is below the estimated maximum strength of the FRP-strengthened structure. The maximum strength of the FRP sheet in the experiment was not achieved due to the adhesive layer between the concrete and FRP sheet was not strong enough compared with the numerical simulation result. It showed that the FRP sheet width was considered to be an important factor influence the failure mode and load capacity. So does the interface between the concrete and FRP plate.

One reinforced concrete coupling beam and two strengthened reinforced concrete coupling beams by bolted steel plates are analyzed by nonlinear finite element method. Two-dimensional finite element model is employed with material nonlinearities and geometrical nonlinearities. A special ring region, which simulates the slip effect between concrete and steel plates, is developed an incorporated into the numerical analysis model. The load-displacement relationship, cracking/crushing type and steel plates internal are compared and found to be in good agreement with those in test.

Structural assessment of corroded self-consolidating concrete beams

This paper presents a three-dimensional nonlinear finite elemental analysis about the reinforcement concrete beams strengthened by bolting steel plate. The contact effects between the steel plate with reinforced concrete beam surface was simulated by developing the contact elements. The effect of strengthening is analyzed and the effects of the deformation and stress distribution of anchor bolt on the failure mode were investigated. It is declared that this strengthening method can obviously improve the capacity and stiffness of beam, and the flexural deformation of anchor bolt is key problem inducing the failure of strengthened beam. This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

Shear performance of bolted side-plated reinforced concrete beams

Finite element modelling of concrete cover separation failure in FRP plated RC beams

In the present paper, the results of an experimental campaign concerning the failure due to intermediate crack-induced (IC) debonding of RC beams strengthened with FRP composites are presented. Both CFRP plates and sheets have been adopted for strengthening. The simply-supported beam scheme with a multiple-load distribution has been adopted in order to have a loading condition the more close possible to the real cases. During the tests, mid-span deflection, compressive strain, mean tensile elongation, crack opening and FRP strains along the beams have been measured. The effect of the FRP reinforcement on flexural strength and ductility has been studied. Moreover, the IC debonding type of failure has been identified from the FRP strain distribution profiles. The IC debonding occurs where the FRP strain is high and a gradient of it (associated with shear stresses along the interface according to classical beam theory) is also present. Finally, the comparison with the theoretical prediction of the FRP strain distribution at IC debonding failure is presented. It is shown that the strengthening with FRP sheets is more effective than adopting pultruded plates, because: i) the anchorage surface is much greater, being equal to the beam width; ii) the debonding surface is more irregular and, consequently, the mode II fracture energy is greater. The role of the amount of the longitudinal steel reinforcement on the FRP strain at IC debonding is also discussed.

The success of most of strengthening or retrofitting technologies for concrete structures by using external bonded FRP sheets depends highly on the interface bond between the FRP sheets and concrete substrates. This paper reviews current studies on evaluating the bond properties of FRP sheet–concrete interfaces and, in particular, focuses on several newly developed bond models for describing the bond characteristics of FRP sheet–concrete interfaces under various loading conditions. This paper also gives several examples that apply these interfacial bond models to the design of different retrofitting cases. Analytical solutions are discussed that consider the local interfacial delamination and slip behaviour, which can improve the prediction of strength and deformation performances, as well as clarify the failure mechanisms of concrete members upgraded with FRP composites. Moreover, the improvement in structural performance of retrofitted concrete members is discussed by relating them to the optimum microscopic properties of the interface bond and the properties of retrofitting materials.

This special issue of the Journal of Composites for Construction, on “Recent International Advancements in FRP Research and Application in Construction,” contains selected topics presented at the Second International Conference on FRP Composites in Civil Engineering CICE 2004 , which was held at The University of Adelaide, Australia. CICE 2004 was also the first official conference of the International Institute for FRP in Construction IIFC , which was founded in 2003 and became cosponsor of the Journal in 2005. This special issue, along with its companion special issue to be published in Construction and Building Materials Vol. 21 , is a direct result of the efforts and dedication of the members of the IIFC. The 13 papers contained in this special issue have been developed to allow a thorough presentation of a diverse range of innovative topics by researchers from Asia, Europe, the United States, and Australia/New Zealand. The first paper in this special issue is by Feng et al. and introduces an innovative large-span FRP woven web roof structure. It is followed by a paper written by Taljsten and Blanksvard on the use of cement based agents for the bonding of CFRP to concrete as an alternative to traditional epoxy adhesive bonding. The next four papers are on the topic of bond and interfacial stresses between FRP and concrete. The first, by Thamrin and Kaku, is on the bond behavior of internal longitudinal CFRP reinforcement in concrete beams. The remaining three papers in this group are on the interfacial behavior of externally bonded FRP to concrete in strengthening applications, including a paper by Dai et al. on the dowel resistance between FRP sheets and concrete for application in the design of spalling prevention; the use of an innovative electronic speckle pattern interferometry technique to infer an interface bond-slip relationship by Cao et al., and a paper by Lu et al. on a novel finite-element model that considers the complex interfacial behavior to simulate the intermediate crack debonding process in beams.