Textile Reinforced Mortar Strengthening Research Articles

Empirical Equations for Modelling Yarn–Mortar Debonding in TRM-Strengthened Masonry Walls Subjected to Out-of-Plane Loading

The effectiveness of textile-reinforced mortar (TRM) strengthening of masonry walls largely depends on the bond between the constituent materials. Finite element analysis (FEA) can provide valuable insights on the effect of the parameters affecting the bond; however, detailed FEA is computationally intensive. To alleviate this, we develop novel empirical equations to estimate effective textile fibre properties, thus implicitly accounting for yarn and mortar debonding. As a result, 3D finite element simulations of strengthened wall specimens are simplified and accelerated. The proposed scheme is calibrated using load–displacement paths derived from experimental data, and the simulated failure modes are compared against the experimental ones demonstrating perfect agreement. A parametric analysis is conducted, exploring the impact of the mechanical ratio of TRM reinforcement and the axial wall load on the effectiveness of TRM strengthening. We demonstrate that low values of mechanical reinforcement, corresponding to natural fibres, give rise to an 8-fold increase in the capacity of unreinforced walls. The findings draw conclusions about the efficacy of TRM strengthening in masonry structures, and provide valuable insights for optimising TRM reinforcement, considering different fibre materials and axial loads in masonry structures.

Finite Element Analysis of Axially Loaded RC Walls with Openings Strengthened Using Textile Reinforced Mortar for Sustainable Structures

Sustainable solutions in the building construction industry promotes the use of innovative materials such as textile reinforced mortar (TRM) as a strengthening technique resulting in a reduced life-cycle cost. This paper presents a nonlinear finite element analysis (FEA) of TRM strengthened RC walls with cut-out openings under axial loading. FEA models were developed and validated with two experimental tests from the literature. Subsequently, a parametric study was performed to investigate the contribution of TRM in strengthening RC walls considering various opening sizes, types, numbers and orientations of window openings, and TRM strengthening configurations. The parametric study results revealed that strengthened models with smaller opening sizes had higher axial strength enhancement. Furthermore, the increase in the axial load capacities of walls with door and window openings were 34 and 26%, respectively, as compared to the corresponding control ones. TRM was more effective with a lower opening aspect ratio (Ho/Lo). In addition, confining the wall piers with U-shaped TRM jackets was the most effective configuration in improving the walls’ axial strengths with maximum enhancements of 16 and 22% as compared to the models strengthened with side-bonded sheets and strips, respectively. Finally, the axial strengths of the FEA models were also compared with the existing empirical solution and showed reasonable correlation with an average discrepancy of 15%.

Prediction of Ballistic Limit of Strengthened Reinforced Concrete Slabs Using Quasi-Static Punching Test

The formulas available in the literature for predicting the projectile impact response of reinforced concrete (RC) targets are generally developed based on the results of impact tests. Recently, however, in order to avoid performing involved and challenging projectile impact tests, the impact response of RC targets was predicted using the quasi-static punching response of RC slabs. In this paper, the concept is extended to concrete slabs strengthened with textile-reinforced mortar (TRM) or carbon fiber-reinforced polymer (CFRP) sheets externally bonded to the concrete surface. In 16 groups, 96 slabs of 600 × 600 × 90 mm size were cast and tested under quasi-static and impact loads. The slabs were reinforced with two types of reinforcement: ϕ8@100 mm and ϕ4@25 mm. The singly and doubly reinforced concrete slabs with rebar spacing of 100 mm were strengthened using externally bonded CFRP and TRM on the back side of the slab specimens. Two mixes of concrete, representing normal and high-strength concretes, were used. The results of the present study reveal that the CFRP and TRM strengthening of RC slabs enhanced the energy absorption in punching by 57–130% and 20–59%, respectively. The use of WWM in singly and doubly reinforced slabs also resulted in a 30–42% and 41–63% increase in energy absorption in punching, respectively. An earlier proposed model was modified to incorporate the influence of strengthening (CFRP and TRM) in the estimation of the projectile perforation energy of the strengthened RC slabs with the help of energy absorbed in their quasi-static punching. This perforation energy was then employed for predicting the ballistic limit of CFRP- and TRM-strengthened slabs. The predictions show good agreement with the experimentally observed ballistic limits.

Flexural Behavior of Textile Reinforced Mortar-Strengthened Reinforced Concrete Beams Subjected to Cyclic Loading

Textile-reinforced mortar (TRM) is used to strengthen reinforced concrete (RC) structures using a textile and inorganic matrix. TRM is a part of textile-based composites; the basic structural behaviors, application methods, and methodologies for the extension of actual structures in TRM were studied. However, structural behavior and performance verification which depict the long-term service situation and fatigue is limited. Therefore, this study, verified the flexural behavior of TRM-strengthened beams and their fatigue performances using carbon- and alkali-resistant (AR) glass textiles through 200,000 load cycles. TRM-strengthened beams were applied to an optimization strengthening method which consisted of whether the textile was straightened. According to the test results, the strengthening efficiency of TRM-strengthened beams when subjected to cyclic loading was lower than that of the monotonic loading, except for the straightened carbon textile specimen. The average efficiency of the AR-glass textile (straightened and non-straightened) and carbon (non-straightened) was 0.86 compared to the TRM-strengthened beam subjected to monotonic loading in terms of flexural strength. In the case of deflection, the average efficiency of the AR-glass textile type was similar to the monotonic loading test results, while that of the non-straightened carbon textile was improved. The Ca-S specimen that was used to straighten the carbon textile showed a reliable structural performance with a strength efficiency of 0.99 and a deflection efficiency of 0.97 compared to the monotonic load test. Therefore, TRM strengthening using a straightened carbon textile is expected to be sufficient for the fatigue design of TRM-strengthened beams.

Experimental study on pre-damaged RC beams shear-strengthened with textile-reinforced mortar (TRM)

An experimental investigation of pre-damaged reinforcement concrete (RC) beams strengthened in shear with textile-reinforced mortar (TRM) is reported in this paper. Eight RC beams, including a control beam and seven beams strengthened with U-shaped TRM jacket, were constructed and tested under four-point bending monotonic load. The investigated parameters included (a) the reinforcement ratios of carbon textiles, (b) the pre-damaged degrees of the RC beam before strengthening, and (c) the levels of the sustaining load on RC beams during the strengthening process. The test results indicated that (1) TRM strengthening could completely restore the mechanical properties of the pre-damaged RC beams, and the shear capacity of the beams was increased by 18.32–67.45% after strengthening. (2) The shear capacity of the pre-damaged strengthened beams was smaller than that of the non-damaged strengthened beams with identical strengthening scheme. 3 As the sustaining load on the beams to be strengthened increased, the failure of the specimens changed from shear-compression mode to diagonal-tension mode, and the shear capacity of the strengthened beams decreased. Finally, a modified model was proposed to predict the shear capacity of TRM-strengthened beams based on the current code. This model considered the effects of the pre-damaged degree and the sustaining load level.

Experimental and numerical assessment of confined infill walls with openings and textile-reinforced mortar

This work's primary objective is to present an experimental campaign, comprised of three full-scale in-plane tests. It was assessed the effect of the openings (central window) and of using textile-reinforced mortar strengthening. The slenderness is also studied by comparing the results herein obtained with other test existing in the literature. The masonry infill walls were built with horizontal hollow clay bricks. All the tests consisted of applying cyclic (loading-unloading-reloading) history of imposed displacements in the in-plane direction employing a top horizontal load. The mechanical properties of the adopted materials are characterized and presented. The results will be presented in terms of in-plane force-displacement responses, damage evolution and energy dissipation capacity. A literature review of numerical modelling approaches to simulate the masonry infill walls seismic behaviour was provided after that. In the end, the experimental tests were simulated in the software OpenSees through a simplified modelling approach. The openings reduced the in-plane maximum strength and energy dissipation capacity by about 40% and 18%, respectively. On the other hand, the textile-reinforced mortar increased the initial stiffness, maximum peak strength and energy dissipation capacity by about 31%, 15% and 38%, respectively.

Flexural strengthening of RC beams with textile-reinforced mortar composites focusing on the influence of the mortar type

This paper presents an experimental study on the flexural strengthening of reinforced concrete (RC) beams with externally bonded layers of textile-reinforced mortar (TRM), as a means of improving their flexural response. The main aim of this study was to investigate the effect of the mortar type in the performance of TRM strengthening system, while varying the type of the textile and the number of the textile layers. In total, nine medium-scale RC beams were manufactured and tested as simply supported under 4-point bending. One beam was tested as-built without strengthening and served as control specimen. The rest of the beams were first strengthened with different configurations and then were subjected in monotonic bending. The parameters under investigation included: a) the mortar type (two different mortars were used, M1 and M2), b) the number of strengthening layers (three versus six), and c) the type of the textile (basalt-fibre with small mesh-size versus glass-fibre textile with large mesh-size). The main difference between mortars M1 and M2, was the use of synthetic polymers as additives in mortar M1. It was overall concluded that there is a strong influence of the mortar type on the flexural capacity increase, on the flexural stiffness response after yielding, as well as on the failure modes. Combined effects between the different type of mortars and the rest of the investigated parameters were also revealed.

A simplified design approach for predicting the flexural behavior of TRM-strengthened RC beams under cyclic loads

This paper proposes a simplified design approach to predict the flexural behavior of reinforced concrete (RC) beams strengthened by high-performance textile reinforced mortar (TRM) under cyclic loads. Based on the experimental results, the effect of main factors on the beams as well as the effectiveness and reliability of TRM strengthening layer under cyclic loads were examined as per ACI 437 method. The reinforcement ratio of the original RC beams, the textile reinforcement ratio of TRM layer, and the interface bond between the original beam and TRM layer, all have significant influence on the flexural behavior and failure modes of TRM-strengthened beams. The simplified models based on the fib model and the Architectural Institute of Japan (AIJ) standard were suggested to predict the flexural capacity of the strengthened beams. These were also used to evaluate the flexural curve of the beams while employing simplified calculation models of the deflection capacities of the RC beams. The results verified that the simplified capacity curve model presented good accuracy to evaluate the TRM-strengthened RC beams.

Impact of the Textile Mesh on the Efficiency of TRM Strengthening Solutions to Improve the Infill Walls Out-of-Plane Behaviour

Different retrofitting techniques have been developed and proposed to prevent the masonry infill walls (MIW) out-of-plane collapse. Many other authors confirmed that these types of elements are vulnerable when subjected to earthquake loadings, leading to several casualties and economic losses. Based on this, the present manuscript comprises an experimental campaign of flexure strength tests on small masonry walls to discuss the efficiency of textile-reinforced mortar (TRM) strengthening solutions to improve their out-of-plane behaviour. For this, eighteen flexural strength tests parallel to the horizontal bed joints were carried out. Nineteen masonry infill walls made with hollow clay horizontal brick, eight non-strengthened and the remaining ones strengthened with TRM. The tests were performed according to the EN 1052-2 standard. In this study, the effect of textile mesh (weak or strong) is analysed in parallel with the efficiency of the strengthening solutions. The results are presented and discussed in terms of force-displacement response parameters and damages observations. From the tests, it was observed that the TRM strengthening improved the flexural strength capacity up to 54% and the out-of-plane deformation ability about 7.18 times.

A detailed micro-modelling approach for the diagonal compression test of strengthened stone masonry walls

The aim to retrofit and preserve the monumental stone masonry buildings due to their historical and cultural relevance is accompanied by the necessity of understanding the behaviour of the unstrengthen structure, as well as its behaviour after the strengthening systems are applied. There is scarce information related to the mechanical properties of stone masonry buildings and even less regarding the assessment of these characteristics in numerical models. Therefore, simulating the force displacement variation and the stress-strain distribution of stone masonry loaded in diagonal compression is a challenging issue. This work contributes to this topic by developing two detailed micro non-linear 3D models. The first model was designed for an unreinforced masonry (URM) wall and the second one was developed for a strengthened URM wall. For this purpose, a commonly used seismic strengthening system, referred to as reinforced plastering mortar (RPM) or textile reinforced mortar (TRM) was applied on the wall. All the components of the TRM strengthening system and the interfaces between the system and the stone masonry wall were considered in the numerical model. The structural responses of the models were analysed and compared and the TRM system effectiveness in increasing the in-plane load resistance and ductility of stone masonry walls was highlighted.

Flexural Behavior of Fire-Damaged Prefabricated RC Hollow Slabs Strengthened with CFRP versus TRM.

In this paper, carbon fiber reinforced polymer (CFRP) and textile reinforced mortar (TRM) strengthening techniques were proposed to retrofit and strengthen fire-damaged prefabricated concrete hollow slabs. A total of six slabs, from an actual multi-story masonry building, were tested to investigate the flexural performance of reinforced concrete (RC) hollow slabs strengthened with TRM and CFRP. The investigated parameters included the strengthening method (CFRP versus TRM), the number of CFRP layers, and with or without fire exposure. One unstrengthened slab and one TRM strengthened slab served as the control specimens without fire exposure. The remaining four slabs were first exposed to ISO-834 standard fire for 1 h, and then three of them were strengthened with CFRP or TRM. Through the four-point bending tests at ambient temperature, the failure modes, load and deformation response were recorded and discussed. Both CFRP and TRM strengthening methods can significantly increase the cracking load and peak load of the fire-damaged hollow slabs, as well as the stiffness in the early stage. The prefabricated hollow slabs strengthened by CFRP have better performance in the ultimate bearing capacity, but the ductility reduced with the increase of CFRP layers. Meanwhile, the TRM strengthening technique is a suitable method for the performance improvement of fire-damaged hollow slabs, in terms of not only the load capacity, especially the cracking load, but also the flexural stiffness and deformation capacity.

Experimental Study of Flexural Behavior of Reinforced Concrete Beam Strengthened with Prestressed Textile-Reinforced Mortar

In this study, nine specimens were experimentally tested to analyze the strengthening efficiency of textile-reinforced mortar (TRM) and the difference in flexural behavior between prestressed and non-prestressed TRM-strengthened reinforced concrete beam. The test results show that TRM strengthening improves the flexural strength of TRM-strengthened reinforced concrete beams with alkali-resistant-(AR-) glass textile as well as that with carbon textile. However, in the case of textile prestressing, the strengthening efficiency for flexural strength of the AR-glass textile was higher than that of the carbon textile. The flexural stiffness of AR-glass textiles increased when prestressing was introduced and the use of carbon textiles can be advantageous to reduce the decreasing ratio of flexural stiffness as the load increased. In the failure mode, textile prestressing prevents the damage of textiles effectively owing to the crack and induces the debonding of the TRM.

TRM strengthening of masonry arches: An experimental investigation on the effect of strengthening layout and textile fibre material

The effectiveness of the textile reinforced mortar (TRM) strengthening technique on clay brick masonry arches is investigated. Eight half-scaled specimens were subjected to static monotonic loading applied at the quarter length of the span until failure. Experimental parameters comprised the number of TRM layers, the textile fibre material, and the strengthening layout, i.e., application in either the intrados or the extrados. The experimental results are discussed in terms of the resulting failure mechanisms and conclusions are drawn with regards to the strength and deformability achieved through each strengthening strategy.

Comparison between TRM and FRP strengthening systems at preventing buckling failure of brick masonry walls

Fibre Reinforced Polymer (FRP) and Textile Reinforced Mortar (TRM) have been studied, compared and applied to strengthen brick masonry walls. The comparison of their performance against second order bending effects is addressed in this paper for the first time. Experimental and analytical data from previous researches and new analytical data for TRM cases are summarised, ordered and systematically compared to analyse the structural response of strengthened brick masonry walls. The results show a similar performance for both systems in terms of load bearing capacity and in-plane response. However, TRM strengthened cases showed greater lateral deformation than FRP ones.

In-plane and out-of-plane testing of unreinforced masonry walls strengthened using polymer textile reinforced mortar

Details of an experimental program investigating the structural performance of unreinforced masonry (URM) walls strengthened using two different types of polymer textile reinforced mortar (TRM) is presented. The experimental program involved full scale reversed cyclic in-plane and out-of-plane testing of TRM strengthened URM walls. The testing was performed in two series, with series 1 involving in-plane testing of two (03) pier-spandrel assemblages representing part of a perforated URM wall and series 2 involving out-of-plane testing of three (03) slender walls having no penetrations. To replicate the physical characteristics of historic masonry materials, vintage solid clay bricks and a low strength hydraulic cement mortar were used for construction of the test walls. Numerous structural characteristics pertaining to the seismic behaviour of TRM strengthened historic URM walls were investigated and then compared to those obtained from corresponding as-built tested URM walls. In general, strengthened walls exhibited a ductile behaviour until the polymer textile ruptured in a brittle manner. The strength increment due to TRM strengthening was observed to range from 128% to 136% when the URM test walls were loaded in-plane and from 575% to 786% when the URM test walls were loaded out-of-plane, with a notable increment in deformation capacity and ductility.

Effect of CFRP and TRM Strengthening of RC Slabs on Punching Shear Strength

The paper presents experiments involving punching of RC slabs strengthened using externally bonded carbon fiber reinforced polymer (CFRP) sheet and textile reinforced mortar (TRM). Twelve RC slab specimens of two concrete grades (39.9 and 63.2 MPa) and employing two strengthening schemes (CFRP and TRM) were tested. Specimens were supported on two opposite edges. Experimental load-displacement variations show two peak loads in strengthened slabs and one peak followed by a plateau in control. Second peak or the plateau corresponds to the combined action of aggregate interlock and the dowel action of back face rebars and strengthening layers. The dowel action of back face rebars and strengthening layers had no role in ultimate punching load (i.e. first peak). Strengthened slabs showed 9-18% increase in ultimate punching load (i.e. first peak) whereas there was significant increase in the second peak load (190-276% for CFRP; 55-136% for TRM) and energy absorption (~66% for CFRP and 22-56% for TRM). An analytical model was also developed for predicting the punching shear strength (first and second peaks) of strengthened slabs showing good comparison with experiments.

Behaviour of soft brick masonry small assemblies with and without strengthening under compression loading

A large percentage of the building stock in India and around the world comprises of non-engineered unreinforced masonry (URM) structures. The performance of these buildings in the past has shown that they are highly vulnerable to failure under seismic loads. Very few studies in the past have focused on behaviour of URM structures made of bricks with low strength and stiffness. Hence, the main objective of this study is to improve the understanding of brick masonry made of low strength and low stiffness bricks and assess the effectiveness of various strengthening schemes namely glass fiber reinforced polymer (GFRP) composites and textile reinforced mortar (TRM) systems. The scope of the study includes the following: (i) experimentally characterising the mechanical properties including stress strain curves for bricks, mortar and prisms cast with various mortar composition under pure compression and (ii) to experimentally assess the performance of masonry assemblies such as prisms and triplets strengthened with GFRP and TRM composites. TRM strengthening involves external application of poly-propylene (PP) grid as reinforcement using cement mortar layers as a matrix. GFRP strengthening is found to increase the strength, stiffness and deformational capacity of masonry prisms made with all grades of mortar. TRM strengthening using PP grid increased the strength, stiffness and deformational capacity of prisms made of low strength mortar but resulted in premature failure in prisms made of high mortar strength. In case of shear triplets, both the GFRP and TRM strengthening increased the strength and stiffness.