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

Mechanical performance of steel fibre reinforced rubberised concrete for flexible concrete pavements

This work aims to develop materials for flexible concrete pavements as an alternative to asphalt concrete or polymer-bound rubber surfaces and presents a study on steel fibre reinforced rubberised concrete (SFRRuC). The main objective of this study is to investigate the effect of steel fibres (manufactured and/or recycled fibres) on the fresh and mechanical properties of rubberised concrete (RuC) comprising waste tyre rubber (WTR). Free shrinkage is also examined. The main parameters investigated through ten different mixes are WTR and fibre contents. The results show that the addition of fibres in RuC mixes with WTR replacement substantially mitigates the loss in flexural strength due to the rubber content (from 50% to 9.6% loss, compared to conventional concrete). The use of fibres in RuC can also enable the development of sufficient flexural strength and enhance strain capacity and post-peak energy absorption behaviour, thus making SFRRuC an ideal alternative construction material for flexible pavements

Bond of textile-reinforced belite calcium sulfoaluminate cement mortar to concrete substrate

The fast aging of existing building stock requires effective and sustainable strengthening solutions. Textile-reinforced mortars (TRM) have already proved to be very effective as well as versatile retrofitting solutions for reinforced concrete and masonry structures. TRMs can enhance the load bearing capacity of reinforced concrete structures; however, current TRM systems are based on standard Portland cement-based binders, which largely contribute to global human-induced CO2 emissions. This work, for the first time, explores the use of belite calcium sulfoaluminate (BCSA) binder for carbon textile reinforcement through a cross-disciplinary study combining structural engineering and materials science. An experimental study was carried out on concrete block members with externally bonded strips of carbon textile-reinforced mortars, similar to a typical TRM retrofitting system for concrete beams. The textiles were embedded in an ordinary Portland cement-based (OPC) binder or in a BCSA-based binder to compare the bond behaviour to the concrete substrate. The tests revealed a superior bond between the BCSA mortar and the concrete, as well as outstanding adhesion to the textiles achieved using the BCSA binder, with performance levels largely surpassing those measured in their counterparts that used the OPC-based binder. Scanning Electron Microscopy, X-ray diffraction, and thermogravimetric analyses were used to understand this behaviour difference and it was concluded that the ettringite phase is responsible for the enhanced performance in the studied system. The results of this study suggest that BCSA binders have the potential to be a more effective and “greener” alternative to the standard binders based on Portland cement in TRM strengthening applications

Optimal Fair Computation

A computation scheme among n parties is fair if no party obtains the computation result unless all other n-1 parties obtain the same result. A fair computation scheme is optimistic if n honest parties can obtain the computation result without resorting to a trusted third party. We prove, for the first time, a tight lower bound on the message complexity of optimistic fair computation for n parties among which n-1 can be malicious in an asynchronous network. We do so by relating the optimal message complexity of optimistic fair computation to the length of the shortest permutation sequence in combinatorics

Textile-reinforced mortar (TRM) as retrofitting material of masonry-infilled RC frames

The contribution of masonry infills to the seismic resistance of existing reinforced concrete structures is significant, both before separation of the infill from the surrounding frame occurs and during large cycles of imposed deformations near collapse. Strengthening of this type of structures usually aims at increasing the resistance and deformation capacity of the frame itself, setting aside the contribution of infills as a source of strength reserve. An alternative route at improving the performance of existing building structures, while avoiding the drawbacks of the approach above, is to convert masonry infilling to a more reliable source of resistance by guaranteeing its contribution over the whole spectrum of structural response. This is sought and examined experimentally in the present study, by employing the very promising technique of textile-reinforced mortars (TRM). The application of TRM is examined in this study on nearly full-scale as-built and retrofitted 3-storey masonry infilled frames, subjected to cyclic loading. The results of the tests are presented and discussed along with the presentation of an analytical model accounting for the TRM contribution to the global response. Finally, the results of the numerical analyses, which were carried out after the implementation of the model to the open-source software OpenSees, are being compared to the experimental results

Retrofitting masonry infills in substandard RC structures via TRM jackets

The paper a technique based on textile-reinforced mortar (TRM) jacketing is presented for the retrofitting non-seismically reinforced concrete masonry-infilled frames. The efficiency of TRM jacketing was experimentally examined by testing two, as-built and retrofitted, 2:3- scaled, three-storey frames subjected to in-plane cyclic loading. The test results showed a considerable increase in resistance, deformation capacity and (initial) stiffness of the retrofitted specimen compared to that of the as-built one and provided strong evidence on the efficiency of the proposed technique

Seismic retrofitting of a three-storey masonryinfilled RC frame with textile-reinforced mortar (TRM)

The effectiveness of using textile-reinforced mortar (TRM) as a means of improving the mechanical behaviour of reinforced concrete (RC) or masonry elements has been experimentally verified in the recent past. In this study TRM was employed for the first time in the case of substandard masonry-infilled RC frames representing structural detailing of the 60s-era in Southern Europe. For this purpose cyclic tests on two nearly full-scale three-storey RC frames were conducted. The structure was subjected to a linear pattern of cyclically alternating forces through servohydraulic actuators. The performance of the retrofitted specimen was compared to the performance of the unretrofitted companion specimen. The test results demonstrate that the proposed strengthening technique considerably enhances the lateral strength, the lateral stiffness and the deformation capacity of the frame. An analytical model to simulate the response of TRM retrofitted masonry-infilled RC frames is also provided

Seismic strengthening of masonry-infilled RC frames with TRM: Experimental study

This paper presents a technique for retrofitting nonseismically reinforced concrete (RC) masonry-infilled frames with textile-reinforced mortar (TRM) jacketing. In the present study the application of TRM is examined on nearly full-scale, as-built and retrofitted, three-story frames, subjected to in-plane cyclic loading. The results of testing a 2:3 scale, as-built frame representing typical structures with nonseismic design and detailing characteristics and of a companion frame retrofitted via TRM jacketing are presented and compared in terms of the efficiency of the proposed technique to enhance the strength and deformation characteristics of substandard infilled frames

In-Plane Behavior of a Three-Storey Masonry- Infilled RC Frame

Past research and practice has shown that masonry infilling of non-seismically designed reinforced concrete frames is a decisive parameter for their seismic response and more so during the early stages of deformation. It seems, therefore, that there would be much to gain if strength and deformation capacity of masonry infilling could be enhanced, modifying its character towards that of a structural element than the current non-structural one. To that end, a research effort, part of which is reported in this paper, was undertake investigating the possibility of converting masonry infilling to a reliable structural element employing innovative composite materials. A three-storey, RC plane frame – representing a scaled portion of a prototype existing structure – was constructed and infilled with masonry to serve as control specimen. The structure, tested under cyclic lateral loading up to failure, showed a stable response at the early stages of loading, with early cracking in masonry which accelerated during the subsequent loading cycles up to the initiation of shear cracking at the top end of one of the ground floor columns. Test results support the possibility of developing an alternative route for strengthening masonry-infilled frames: that of turning the infill to an actual structural element. This may be accomplished through the enhancement of strength and deformation capacity of the infills via suitably anchored, externally-bonded reinforcement and the provision of appropriate measures to guarantee relative monolithicity at frame-infill interface, provided that steps to exclude damage in the surrounding frame members (mainly the columns) are taken in advance