Shear strengthening of full-scale RC T-beams using textile-reinforced mortar and textile-based anchors

This paper presents a study on the effectiveness of TRM jacketing in shear strengthening of full-scale reinforced concrete (RC) T-beams focussing on the behaviour of a novel end-anchorage system comprising textile-based anchors. The parameters examined in this study include: (a) the use of textile-based anchors as end-anchorage system of TRM U-jackets; (b) the number of TRM layers; (c) the textile properties (material, geometry); and (d) the strengthening system, namely textile-reinforced mortar (TRM) jacketing and fibre-reinforced polymer (FRP) jacketing for the case without anchors. In total, 11 full-scale RC T-beams were constructed and tested as simply supported in three-point bending. The results showed that: (a) The use of textile-based anchors increases dramatically the effectiveness of TRM U-jackets; (b) increasing the number of layers in non-anchored jackets results in an almost proportional increase of the shear capacity, whereas the failure mode is altered; (c) the use of different textile geometries with the same reinforcement ratio in non-anchored jackets result in practically equal capacity increase; (d) TRM jackets can be as effective as FRP jackets in increasing the shear capacity of full-scale RC T-beams. Finally, a simple design model is proposed to calculate the contribution of anchored TRM jackets to the shear capacity of RC T-beams

Cracking behavior and crack width predictions of FRP strengthened RC members under tension

This paper presents and discusses the experimental results of uniaxial tensile tests of fiber reinforced polymer externally strengthened reinforced concrete (FRP strengthened RC) prisms in terms of crack width and crack spacing. As a non-contact and material independent system for in-time measurement of displacement and strain, the digital image correlation (DIC) technique has been used in this study for investigating the evolution of strains and formation of cracks during uniaxial tensile tests. As a result, the cracks were measured precisely at any load stage. The experimental results of tests performed by authors and other researchers on FRP strengthened RC members in tension are compared to prediction models from code provisions and guidelines (Eurocode 2 and fib 14), and their suitability are analyzed and discussed. The results show the dependence of the behavior and crack characteristics of FRP strengthened RC members to parameters such as wrapping scheme and FRP reinforcement ratios which are not included in design provisions for crack analysis. A new formulation for predicting crack width and spacing in FRP strengthened RC members, calibrated using the experimental results, has been proposed which considers all the main affecting parameters

Textile-reinforced mortar (TRM) versus fibre-reinforced polymers (FRP) in flexural strengthening of RC beams

The aim of this paper is to compare the flexural performance of reinforced concrete (RC) beams strengthened with textile-reinforced mortar (TRM) and fibre-reinforced polymers (FRP). The investigated parameters included the strengthening material, namely TRM or FRP; the number of TRM/FRP layers; the textile surface condition (coated and uncoated); the textile fibre material (carbon, coated basalt or glass fibres); and the end-anchorage system of the external reinforcement. Thirteen RC beams were fabricated, strengthened and tested in four-point bending. One beam served as control specimen, seven beams strengthened with TRM, and five with FRP. It was mainly found that: (a) TRM was generally inferior to FRP in enhancing the flexural capacity of RC beams, with the effectiveness ratio between the two systems varying from 0.46 to 0.80, depending on the parameters examined, (b) by tripling the number of TRM layers (from one to three), the TRM versus FRP effectiveness ratio was almost doubled, (c) providing coating to the dry textile enhanced the TRM effectiveness and altered the failure mode; (d) different textile materials, having approximately same axial stiffness, resulted in different flexural capacity increases; and (e) providing end-anchorage had a limited effect on the performance of TRM-retrofitted beams. Finally, a simple formula proposed by fib Model Code 2010 for FRP reinforcement was used to predict the mean debonding stress developed in the TRM reinforcement. It was found that this formula is in a good agreement with the average stress calculated based on the experimental results when failure was similar to FRP-strengthened beams

Shear strengthening of concrete members with TRM jackets: Effect of shear span-to-depth ratio, material and amount of external reinforcement

An experimental work on reinforced concrete (RC) rectangular beams strengthened in shear with textile reinforced mortar (TRM) jackets is presented in this paper, with focus on the following investigated parameters: (a) the amount of external TRM reinforcement ratio, ρf, by means of using different number of textile layers and different types of textile fibre materials (carbon, glass, basalt); (b) the textile geometry, and (c) the shear span-to-depth ratio, a/d. In total, 22 tests were conducted on simply supported rectangular RC beams under (three-point bending) monotonic loading. The experimental results revealed that: (1) TRM is very effective when the failure is attributed to debonding of the TRM jacket from the concrete substrate; (2) the trend of effective strains for carbon, glass and basalt TRM jackets is descending for increasing values of the TRM reinforcement ratio, ρf, when failure is associated to debonding of the jacket; (3) the effect of textile geometry is significant only for low values of ρf, resulting in variances in the capacity enhancement and the failure modes, and (4) the shear span-to-depth ratio has practically no effect to the failure mode nor to the TRM jacket contribution to the total shear resistance of the RC beams

Textile-reinforced mortar (TRM) versus fiber-reinforced polymers (FRP) in shear strengthening of concrete beams

This paper presents an experimental study on shear strengthening of rectangular reinforced concrete (RC) beams with advanced composite materials. Key parameters of this study include: (a) the strengthening system, namely textile-reinforced mortar (TRM) jacketing and fiber-reinforced polymer (FRP) jacketing, (b) the strengthening configuration, namely side-bonding, U-wrapping and full-wrapping, and (c) the number of the strengthening layers. In total, 14 RC beams were constructed and tested under bending loading. One of the beams did not receive any strengthening and served as control beam, eight received TRM jacketing, whereas the rest five received FRP jacketing. It is concluded that the TRM is generally less effective than FRP in increasing the shear capacity of concrete, however the effectiveness depends on both the strengthening configuration and the number of layers. U-wrapping strengthening configuration is much more effective than side-bonding in case of TRM jackets and the effectiveness of TRM jackets increases considerably with increasing the number of layers

In-plane behavior of cavity masonry infills and strengthening with textile reinforced mortar

The seismic vulnerability of masonry infilled reinforced concrete (rc) frames observed during past earthquakes in some south European countries resulted in losses of human lives and huge repair or reconstruction costs, justifies the need of deeper study of the seismic behavior of masonry infills enclosed in rc frames. Therefore, the main goals of this study are related to: (1) better understanding of the cyclic in-plane behavior of traditional brick infills built in the past decades as enclosures in rc buildings in Portugal; (2) analysis of a strengthening technique based on textile reinforced mortar (TRM) aiming at enhancing the in-plane behavior. To accomplish the objectives, an extensive experimental campaign based on in-plane static cyclic tests on seven reduced scale rc frames with masonry infill walls was carried out. The performance of strengthening of masonry infill based on textile reinforced mortar was also evaluated experimentally. Among the conclusions of this research, it should be stressed that: (1) the presence of infill inside the bare frame could significantly enhance the in-plane stiffness and resistance of bare frame; (2) TRM technique could enhance the in-plane behavior of infilled frames by improving the lateral strength and by reducing significantly the damage of the brick infill walls.The authors would like to acknowledge the Portuguese Foundation for Science and Technology (FCT) for funding the research project ASPASSI – Assessment of the safety and strengthening of masonry infill walls subjected to seismic action (POCI-01-0145-FEDER-016898) (PTDC/ECMEST/3790/2014).info:eu-repo/semantics/publishedVersio

Axial compressive behavior of FRP-confined concrete: Experimental test database and a new design-oriented model

A large number of experimental studies have been conducted over the last two decades to understand the behavior of FRP-confined concrete columns. This paper presents a comprehensive test database constructed from the results of axial compression tests on 832 circular FRP-confined concrete specimens published in the literature. The database was assembled through an extensive review of the literature that covered 3042 test results from 253 experimental studies published between 1991 and the middle of 2013. The suitability of the results for the database was determined using carefully chosen selection criteria to ensure a reliable database. This database brings reliable test results of FRP-confined concrete together to form a unified framework for future reference. Close examination of the test results reported in the database led to a number of important observations on the influence of important parameters on the behavior of FRP-confined concrete. A new design-oriented model that was developed to quantify these observations is presented in the final part of the paper. It is shown that the predictions of the proposed model are in close agreement with the test results and the model provides improved predictions of the ultimate conditions of FRP-confined concrete compared to any of the existing models. © 2013 Elsevier Ltd. All rights reserved.Togay Ozbakkaloglu, Jian C. Li

4, Title and SubtiUe 5. Report Date IS.Porl""'*'i!~C- Structural Qualification Testing of Composite-Jacketed Circular and Rectangular Bridge Columns

The damage and collapse of highway bridges during recent destructive eanhquakes has demonstrated that reinforced concrete bridge columns designed and constructed using older design specifications may suffer from lack of sufficient shear reinforcemem and/or sufficient lap splice length. This summary repon presents an experimental and analytical study on the seismic retrofit of half-scale bridge columns using advanced composite-material (carbon or glass fiber) jackets. I I A structural assessment and qualification-testing program. coupled with a complementary material testing program. were conducted. In order to verify the performance of reinforced concrete bridge columns retrofitted with advanced composite material jackets. cyclic testing of column samples was carried out at the University of Colifomia. Irvine, Structural Test Hall. Twenty-seven half-scale, circular and rectangular columns, with and without lap splices, were built and tested under cyclic loading in both single and double bending configurations. Six different jacket systems were evaluated. All tests conformed to Caltrans guidelines for the Pre-qualificatio