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

Analytical modeling of masonry-infilled RC frames retrofitted with textile-reinforced mortar

This paper proposes an analytical approach for modeling the behavior of textile-reinforced mortar (TRM)-strengthened masonry-infilled reinforced-concrete (RC) frames under seismic loading. The model falls into the discrete diagonal-element type and is based on the use of single-strut and single-tie elements to represent the infill panel. It builds on the results of past experimental studies by the writers, in which the application of TRM jacketing was effective for seismic retrofitting of masonry-infilled RC frames. The model is implemented in a nonlinear finite-element code, with the parameters of the diagonal elements being determined from a series of tests on TRM coupons and masonry specimens. The results of the numerical analyses are compared with the experimental data of cyclic tests on 3-story masonry infilled RC frames (as-built and after retrofitting). The model developed in this paper adequately accounts for the TRM-strengthening contribution to the global response of masonry-infilled frames

New School, New Job, New Life: Supporting the Transition of Student Affairs Graduate Assistants

Student affairs professionals have a responsibility for the professional development of graduate assistants (GAs) in the department as these positions are marketed as first professional positions. While prior literature has addressed the transition of graduate students into graduate school, there is little about the transition process for students with graduate assistantships in student affairs. Student transitions are important as they may set the tone for their first professional experience and ongoing professional development. Four key themes emerged from the voices of the graduate student participants in this study as they described their transition process into a GA position. First, they viewed the GA experience as a professional opportunity. Second, their sense of belonging was dependent on their perceived contribution to the department or division. Third, relationships mattered as they navigated the transition into their GA role. And finally, self agency (individual action) was apparent as they became engaged in their own success

SU(N) Gauge theories for large N

86 σ.Μία εισαγωγή στις θεωρίες βαθμίδας για μεγάλο Ν όπως αυτή διαμορφώθηκε από την εργασία του G. t' Hooft. Περιγραφή της διακριτοποίησης στο Lattice και εφαρμογή της ανάλυσης των θεωριών βαθμίδας για μεγάλο Ν στα πλαίσια του Lattice. Ανάφορά των σύγχρονων τεχνικών του θερμοδυναμικού μοντέλου, του μοντέλου Eguchi-Kawai, των φερμιονίων Wilson και των τεχνικών απομείωσης όγκου.This volume is a basic introduction to large N gauge theories and the parallel development of the Lattice formalization from Wilson and others. A particular attention to the technics that introduce results of large N to Lattice simulations. The modern techniques widely used in Lattice this days presented like the Eguchi-Kawai model, the volume reduction techniques, the twisted E-K, the factorization properties and the basic principles that lead to the Monte Carlo simulations of the Lattice.Δημήτριος Θ. Κούτα

Bond between textile-reinforced mortar (TRM) and concrete substrates: experimental investigation

This paper presents an extended experimental study on the bond behaviour between textile-reinforced mortar (TRM) and concrete substrates. The parameters examined include: (a) the bond length (from 50 mm to 450 mm); (b) the number of TRM layers (from one to four); (c) the concrete surface preparation (grinding versus sandblasting); (d) the concrete compressive strength (15 MPa or 30 MPa); (e) the textile coating; and (f) the anchorage through wrapping with TRM jackets. For this purpose, a total of 80 specimens were fabricated and tested under double-lap direct shear. It is mainly concluded that: (a) after a certain bond length (between 200 mm and 300 mm for any number of layers) the bond strength marginally increases; (b) by increasing the number of layers the bond capacity increases in a non-proportional way, whereas the failure mode is altered; (c) concrete sandblasting is equivalent to grinding in terms of bond capacity and failure mode; (d) concrete compressive strength has a marginal effect on the bond capacity; (e) the use of coated textiles alters the failure mode and significantly increases the bond strength; and (f) anchorage of TRM through wrapping with TRM jackets substantially increases the ultimate load capacity

Tensile capacity of FRP anchors in connecting FRP and TRM sheets to concrete

This paper investigates the effectiveness of carbon fiber spike anchors as a means of anchoring externally bonded (EB) fiber-reinforced polymers (FRP) and textile reinforced mortar (TRM) sheets into concrete. The investigation employs experimental work, which includes reinforced concrete (RC) columns strengthened with various configurations of EB FRP and TRM sheets connected to RC footings via carbon fiber spike anchors. The fiber spikes have two parts: the anchor part and the fan part. The anchor part is a bar-type dowel component that is epoxy pre-impregnated and inserted into epoxy filled holes within the footing. The fan part was impregnated in-situ and fanned out over and bonded to the EB reinforcement of the column. The connections were tested by pulling the columns upwards, thus applying tensile forces to the connection system. The direct tensile capacity of the anchors was determined for a number of vari- ables including the size and number of anchors, the bonding agent and the type and amount of EB rein- forcement. It is concluded that, with appropriate anchorage into concrete, the carbon fiber spike anchor is an effective anchorage system, and therefore, could be used in a range of strengthening applications to prevent premature delamination of FRP and TRM sheets from concrete surfaces

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

Out-of-plane response of masonry walls strengthened using textile-mortar system

The out-of-plane response of masonry walls strengthened with textile-reinforced mortar (TRM) is experimentally investigated in this work. Medium-scale three-point bending tests were carried out on 18 specimens comprising a set of 9 single-wythe and 9 double-wythe brick masonry walls. Key investigated parameters involved the textile reinforcement ratio, the textile material, the coating of the textile reinforcement with epoxy resin, and the wall thickness. Experimental results suggest that TRM significantly increase the load bearing capacity of masonry walls. The amount of reinforcement utilised affects both the strength and deformation characteristics of the corresponding specimens, while it may alter the failure mode. Resin coating on the textile is found to be beneficial for the performance of the TRM overlays

Bond between TRM versus FRP composites and concrete at high temperatures

The use of fibre reinforced polymers (FRP) as a means of external reinforcement for strengthening the existing reinforced concrete (RC) structures nowadays is the most common technique. However, the use of epoxy resins limits the effectiveness of FRP technique, and therefore, unless protective (thermal insulation) systems are provided, the bond capacity at the FRP-concrete interface will be extremely low above the glass transition temperature (Tg). To address problems associated with epoxies and to provide cost-effectiveness and durability of the strengthening intervention, a new composite cement- based material, namely textile-reinforced mortar (TRM) has been developed the last decade. This paper for the first time examines the bond performance between the TRM and concrete interfaces at high temperatures and, also compares for the first time the bond of both FRP and TRM systems to concrete at ambient and high temperatures. The key parameters investigated include: (a) the matrix used to impregnate the fibres, namely resin or mortar, resulting in two strengthening systems (TRM or FRP), (b) the level of high temperature to which the specimens are exposed (20, 50, 75, 100, and 150 °C) for FRP-reinforced specimens, and (20, 50, 75, 100, 150, 200, 300, 400, and 500 °C) for TRM-strengthened specimens, (c) the number of FRP/TRM layers (3 and 4), and (d) the loading conditions (steady state and transient conditions). A total of 68 specimens (56 specimens tested in steady state condition, and 12 specimens tested in transient condition) were constructed, strengthened and tested under double- lap direct shear. The result showed that overall TRM exhibited excellent performance at high temperature. In steady state tests, TRM specimens maintained an average of 85% of their ambient bond strength up to 400 °C, whereas the corresponding value for FRP specimens was only 17% at 150 °C. In transient test condition, TRM also outperformed over FRP in terms of both the time they maintained the applied load and the temperature reached before failure

New School, New Job, New Life

Student affairs professionals have a responsibility for the professional development of graduate assistants (Gas) in the department as these positions are marketed as first professional positions. While prior literature has addressed the transition of graduate students into graduate school, there is little about the transition process for students with graduate assistantships in student affairs. Student transitions are important as they may set the tone for their first professional experience and ongoing professional development. Four key themes emerged from the voices of the graduate student participants in this study as they described their transition process into a GA position. First, they viewed the GA experience as a professional opportunity. Second, their sense of belonging was dependent on their perceived contribution to the department or division. Third, relationships mattered as they navigated the transition into their GA role. And finally, self agency (individual action) was apparent as they became engaged in their own success