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The existing infilled reinforced concrete (RC) buildings' poor energy performance is responsible for a significant part of the energy consumption in the European Union (EU). In addition, recent earthquakes showed the seismic vulnerability of the existing RC buildings that were not designed according to modern codes, where several casualties, collapses, and economic losses were reported. Around 40% of the EU buildings are located in seismic regions and designed with substandard safety requirements, of which 65% need both energy and seismic retrofit. New strategies are necessary to simultaneously improve the energy efficiency and seismic vulnerability of new constructions. Apart from the modern seismic and energy codes, new materials are being developed by the construction industry that can play a significant role in the next few decades. Based on this motivation, this paper aims to study the efficiency of using textile-reinforced mortar (TRM)-based solutions to improve the seismic behavior of masonry infill walls made of lightweight and energy-improved masonry blocks. This holistic strategy is designed for new constructions. For this, eight strengthened energy-improved infill walls were subjected to flexural strength tests to validate the TRM efficiency using a low-strength and a high-strength textile mesh and study the effect of using connectors. All the tests consisted of applying a monotonic out-of-plane tests were performed through a one-point load approach. The results will be presented in terms of out-of-plane force–displacement responses, flexural stress, and damage evolution. Lastly, a state-of-the-art discussion is carried out to analyze possible relationships between the textile mesh tensile strength and the flexural strength of the walls. [ABSTRACT FROM AUTHOR]

Currently, the upgrade of existing reinforced concrete (RC) buildings focuses only on energy retrofitting measures due to the current policies promoted in the scope of the European Green Deal. However, the structural deficiencies are not eliminated, leaving the building seriously unsafe despite the investment, particularly in seismic-prone regions. Moreover, the envelopes of existing RC buildings are responsible for their energy efficiency and seismic performance, but these two performance indicators are not usually correlated. They are frequently analyzed independently from each other. Based on this motivation, this research aimed to perform a holistic performance assessment of five different types of masonry infill walls (i.e., two non-strengthened walls, two walls with seismic strengthening, and one wall with energy strengthening). This performance assessment was performed in a three-step procedure: (i) energy performance assessment by analyzing the heat transfer coefficient of each wall type; (ii) seismic performance assessment by analyzing the out-of-plane seismic vulnerability; (iii) cost–benefit performance assessment. Therefore, a global analysis was performed, in which the different performance indicators (structural and energy) were evaluated. In addition, a state-of-the-art review regarding strengthening techniques (independent structural strengthening, independent energy strengthening, and combined structural plus energy strengthening) is provided. From this study, it was observed that the use of the external thermal insulation composite system reduced the heat transfer coefficient by about 77%. However, it reduced the wall strength capacity by about 9%. On the other hand, the use of textile-reinforced mortar improved the strength and deformation capacity by about 50% and 236%, but it did not sufficiently reduce the heat transfer coefficient. There is a need to combine both techniques to simultaneously improve the energy and structural energy performance parameters. [ABSTRACT FROM AUTHOR]

During the last years, some experimental efforts were conducted in order to evaluate the in-plane cyclic behaviour of infilled reinforced concrete frames considering and not openings. From the experiments, it was observed that the openings reduced infill panels’ stiffness, strength and energy dissipation capacity. In the literature, there are different numerical approaches to predict the infill panels expected behaviour with and/or without openings when subjected to in-plane demands. The experimental data are of full importance to calibrate the numerical models and evaluate their accuracy. A good calibration of the numerical models could result on a better and accurate safety assessment of the existing buildings and designing of the new ones. The main aim of this article is to evaluate the capacity of a simplified double strut model to represent the cyclic behaviour of infilled reinforced concrete frames with and without openings using the software OpenSees. The five infilled reinforced concrete frames tested by different authors and with different configurations will be simulated. Details from each specimen modelling will be provided along the article, and the accuracy of this numerical modelling approach will be evaluated in terms of force–displacement hysteretic curves. Additionally, a state-of-art review regarding the in-plane tests will be presented containing the main characteristics of the specimens and conclusions performed by each author. [ABSTRACT FROM AUTHOR]

One of the main challenges in earthquake risk mitigation is the assessment of existing buildings not designed according to modern codes and the development of effective techniques to strengthen these structures. Particular attention should be given to RC frame structures with masonry infill panels, as demonstrated by their poor performance in recent earthquakes in Europe. Understanding the seismic behaviour of masonry-infilled RC frames presents one of the most difficult problems in structural engineering. Analytical tools to evaluate infill-frame interaction and the failure mechanisms need to be further studied. This research intends to develop a simplified macro-model that takes into account the out-of-plane behaviour of the infill panels and the corresponding in-plane and out-of-plane interaction when subjected to seismic loadings. Finally, a vulnerability assessment of an RC building will be performed in order to evaluate the influence of the out-of-plane consideration in the building response. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Experimental study on the effect of the openings in the out-of-plane behavior of infills in RC buildings. • Full-scale tests of horizontal hollow clay bricks, with a central window and the remaining one with a central door. • The openings reduced the maximum strength of 30% for undamaged panels, and it occurred for lower displacement demands. • The increase of the opening area did not affect the peak load but reduces the energy dissipation capacity. This research work aims to present an experimental study concerning the effect of the openings in the out-of-plane (OOP) behaviour of masonry infills in RC buildings. The experimental campaign comprises the OOP testing of three full-scale infill walls made up of horizontal hollow clay bricks, two of them with a central window and the remaining one with a central door. One of the specimens with a central opening was first subjected to a previous in-plane test and, after that, the damaged wall was subjected to an OOP test. All the tests consisted of applying a loading–unloading-reloading history of imposed displacements in the OOP direction through a uniformly distributed load. An innovative setup was used and adapted for each wall typology. The results are presented in terms of OOP force–displacement responses, damage evolution, relative stiffness and energy dissipation capacity. Finally, the test results are compared to each other to assess the effect of: i) the area of the opening; and ii) the previous damage. It was found that the openings reduced the maximum strength of 30% for undamaged panels, and it occurred for lower displacement demands. The increase of the opening area did not affect the peak load; however, it reduced their energy dissipation capacity significantly. The energy dissipation capacity reduced from 42% to 70%. [ABSTRACT FROM AUTHOR]

Following the strong earthquake on April 25, 2015 in Nepal, a team from the University of Porto, in collaboration with other international institutions, made a field study on some of the most affected areas in the capital region of Kathmandu. One of the tasks was the study of a high-rise settle of buildings that were damaged following the earthquake sequence. A survey damage assessment was performed to a 15-storey infilled reinforced concrete structure, which will be detailed in the manuscript. Moreover, ambient vibration tests were carried out to determine the natural frequencies and corresponding vibration modes of the structure. The main aim of this manuscript is to present a numerical study concerning the influence of the masonry infill walls in the structure seismic response. For this, three numerical models were built discriminating the situations with and without damage and nondamaged infill walls. Validation and calibration of the numerical model was ensured by comparing the numerical frequencies with those obtained from ambient vibration tests. In addition, linear elastic analyses were carried out, using real accelerograms from the Gorkha earthquake to assess and quantify the major differences between the models in terms of inter-storey drifts ratios, inter-storey shear forces and seismic loadings. [ABSTRACT FROM AUTHOR]

The primary objective of this manuscript is to present a systematic review of experimental studies regarding infill masonry walls out-of-plane (OOP) behaviour. An extended database was built containing information from each experimental campaign and specimen tested. Parameters such as geometric dimensions, material and mechanical properties, test setups and loading protocols and test results were collected. A systematic review methodology s conducted with the aim of filter the more relevant work in this field. For the analysis of each parameter in the infill wall OOP performance, three different groups were defined: as built specimens, specimens with previous in-plane damage and retrofitted specimens. Comparisons were drawn between the specimens of each group to assess the impact of those parameters on the panel response. Empirical relationships were proposed to predict the infill panels OOP capacity according to the aspect ratio, panel slenderness, percentage of masonry units’ voids, masonry properties and previous in-plane drift. The results demonstrated that previous damage caused by in-plane tests that reached a maximum drift until 1.25% can reduce about 70% the OOP capacity of the panel, changing the failure mode of the panel that can result in fragile collapses. It was also observed that the parallel flexural strength parallel to the horizontal bed joints can increase the panel OOP maximum strength until 5 times. [ABSTRACT FROM AUTHOR]

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. • Experimental and numerical assessment of in-plane behavior of masonry infilled walls. • Experimental assessment of the effect of the openings in the in-plane behavior of infilled RC frames. • Experimental assessment of the effect of the textile-reinforced mortar strengthening in the in-plane behavior of infilled RC frames. [ABSTRACT FROM AUTHOR]

The primary objective of this work is to present a experimental analysis of textile-reinforced mortar based strengthening solutions to prevent the out-of-plane (OOP) collapse of masonry infills in RC buildings. The experimental campaign comprises the OOP testing of five full-scale infill walls made up of horizontal hollow clay bricks, two of them unstrengthened and the remaining three strengthened, with and without prior damage. All the tests consisted in the application of a semi-cyclic (loading–unloading-reloading) history of imposed displacements in the OOP direction by means of a uniformly distributed load. The mechanical properties of the adopted materials are characterized and presented. The results will be presented in terms of OOP force–displacement responses, deformed shapes, damage evolution and energy dissipation capacity. In the end, the tests' results are compared to each other to assess the effectiveness of the selected strengthening techniques and to provide a support towards the choice of the best strategies for future further investigations and applications. [ABSTRACT FROM AUTHOR]

• A review of the experimental testing of strengthening solutions of infill walls was performed. • Different strategies can be adopted: disconnection of the panel from the frame adopting energy dissipation or the effective strengthening based on different techniques. • All the techniques revealed interesting results, in terms of increase the deformation capacity of the panels. • All the techniques are effective if the strengthening material is bonded or anchored to the panel and to the surrounding frame. The masonry infill walls' seismic behaviour is being characterized by extensive damages and out-of-plane (OOP) collapses due to combined in-plane and OOP loading demands. Several efforts are being made to develop efficient strengthening strategies to reduce their seismic vulnerability and in particular to prevent the panels' collapse. The present manuscript aims presenting retrofit and strengthening strategies to improve the infill masonry walls seismic performance, with particular attention to the prevention of the OOP collapse. Retrofit and improvement of infill walls seismic behaviour is a complex subject, since it cannot be disconnected from their effect on the overall building response. It is paramount to assume that the strengthening should be effective under seismic actions in the plane of the infill wall and under transverse loadings. A systematic review was carry out focusing the major findings and observations made by each author are presented. For each technique, a summary table is provided containing the details regarding the strengthening strategy adopted, major results and observations. [ABSTRACT FROM AUTHOR]

Highlights • Seismic vulnerability assessment of RC infilled structures due to mainshock-aftershock impacts. • Study of a RC bare frame, full infill with and without out-of-plane behaviour. • The seismic vulnerability assessment methodologies for undamaged and damages structures is presented. • Undamaged structures: Higher seismic vulnerability of infilled RC structures considering combined in-plane and out-of-plane behaviour. • Damaged structures: higher vulnerability of bare frame structures. Abstract The primary objective of this manuscript is to present a numerical study regarding the mainshock-aftershock damage assessment of infilled reinforced concrete (RC) structures. For this, an 8 storey building was built in the OpenSees software considering different modelling strategies: (i) RC structure without infill masonry walls; (ii) RC structure with infill walls considering only the in-plane behaviour; and (iii) RC structure with infill walls considering the combined in-plane and out-of-plane non-linear behaviour. Two different approaches are proposed to assess the seismic vulnerability of undamaged and damaged structures due to mainshock-aftershock sequences. Both methodologies are described throughout the manuscript. Incremental dynamic analysis were carried out to achieve fragility curves for different damage states of the structures. A comparison between the undamaged and damaged structures’ fragility curves will be presented and discussed which will allow to assess the effect of the mainshock-aftershock. Furthermore, the effect of the infill walls presence and the consideration of the combined in-plane and out-of-plane behaviour will be discussed. [ABSTRACT FROM AUTHOR]

• Experimental tests on TRM-strengthened infilled frames under OOP loading. • Analysis of dynamic properties of the TRM-strengthened infills. • Comparison of response with and without IP damage and with and without strengthening. • Database of experimental tests on TRM-strengthened infilled frames under OOP loading. • Analysis of predictive equations for OOP strength of TRM-strengthened infills. In existing Reinforced Concrete (RC) buildings, the out-of-plane (OOP) collapse of masonry infills can be a significant issue for resulting damage and life safety in case of earthquake. Quite recently, research works from the literature have studied possible strengthening strategies to reduce the vulnerability of the infill panels due to OOP loading. Among these techniques, the use of Textile Reinforced Mortars (TRM) as an innovative reinforcing plater has rapidly become very popular, due to its good compromise between costs of intervention and effectiveness, along with its durability properties. Nevertheless, still quite few studies exist on this topic to experimentally prove the TRM effectiveness on masonry infills, above all in case of pre-existing in-plane (IP) damage. Even fewer studies in the literature are currently devoted to the prediction of the OOP strength of TRM-strengthened infills, despite the necessity to quantify the beneficial effect of the strengthening solution in a force-based safety check. This work shows the experimental outcomes of four full-scale infilled frames under OOP loading, with or without a TRM-based strengthening technique and with or without previous IP damage. First, a look insight the effect on dynamic properties of the TRM strengthening strategy is reported and commented. Then, the (cyclic) IP and (half-cyclic) OOP pseudo-static testing results are shown and compared to each other to analyze the effect of the IP damage on the OOP response with and without strengthening. Lastly, the very few predictive proposals for OOP strength of TRM-strengthened specimens have been analyzed, based on a dedicated collected database, to lastly provide some suggestions for future design tools for TRM applications on infills. [ABSTRACT FROM AUTHOR]

• Out-of-plane tests of infill masonry walls with concrete blocks. • Assessment of the impact of previous damage. • Analysis of the effectiveness of using TRM strengthening to improve the OOP behaviour. • Tested walls results were compared with data available in the literature with different masonry units. Masonry infill walls are widely spread over the reinforced concrete buildings due to different demands. The buildings' thermal energy efficiency is a top priority nowadays since many of the existing building stock comprises buildings with low energy performance. The buildings' external envelope is undergoing a transformation with the vertical hollow concrete blocks' appearance with high thermal and acoustic demands. However, recent evidence from a strong earthquake shows that the masonry infill walls are quite vulnerable to out-of-plane loadings and were responsible for many casualties, injuries and economic losses. Based on that, this work's main objective is to study the out-of-plane (OOP) behaviour of masonry infills made with vertical hollow concrete blocks. The experimental campaign comprises the OOP testing of three full-scale infill walls made up of these masonry units, one of them as-built without previous damage, one with previous damage due to an earlier in-plane test and the third one retrofitted. All the tests consisted of applying the loading–unloading-reloading history of imposed displacements in the OOP direction through a uniformly distributed load. The results will be presented in terms of OOP force–displacement responses, damage evolution and energy dissipation capacity. The test results are compared to assess the previous damage effect and the retrofit technique's effectiveness. A final study is presented concerning the masonry unit and slenderness effect with other literature results. [ABSTRACT FROM AUTHOR]