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- Seismic Vulnerability and Parametric Study on a Bare Frame Building in NepalPublication . Dumaru, Rakesh; Pinheiro Rodrigues, Hugo Filipe; Furtado, André; Varum, HumbertoThe influence of the infill masonry walls in the structural response of reinforced concrete (RC) structures when subjected to earthquakes is not considered in Nepal National Building code and Indian Standard code. Field observations carried out after the 25th April Gorkha earthquake in Nepal reinforce the importance of the infill walls, namely, through the significant increasing of the structural stiffness and by the possibility of introducing unexpected mechanisms that can cause extensive damages or even the collapse of the structure. This article focuses on the study of an existing bare frame, representative of the Nepalese RC buildings, which was modeled and calibrated with data results collected from ambient vibration tests. Initially, a parametric study was conducted with the aim of evaluating the influence of parameters, such as concrete strength and elasticity modulus, slab thickness, and columns cross section in the natural frequencies of the building. The influence of the infill masonry walls in the structural response was evaluated through the modeling of three different numerical models with different disposition of the infill panels from the calibrated existing structure. The seismic vulnerability assessment was performed through non-linear static pushover and dynamic analysis. The results will be presented and discussed in terms of base maximum inter-storey drifts and maximum base shear.
- Mainshock-aftershock damage assessment of infilled RC structuresPublication . Furtado, André; Rodrigues, Hugo; Varum, Humberto; Arêde, AntónioThe 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.
- Out-of-plane behavior of masonry infilled RC frames based on the experimental tests available: a systematic reviewPublication . Furtado, André; Rodrigues, Hugo; Arêde, António; Varum, HumbertoThe 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.
- Seismic fragility assessment of revised MRT buildings considering typical construction changesPublication . Dumaru, Rakesh; Rodrigues, Hugo; Varum, HumbertoThe present study investigates the vulnerability assessment of the prototype revised Mandatory Rule of Thumb (MRT) buildings initially designed and detailed for three storeys bare frame building; later modified through variable number of storeys (three, four, and five) and different arrangement of infill walls (bare frame, soft-storey, irregular infilled, and fully infilled). The application of infill walls increases the fundamental frequencies, stiffness, and maximum strength capacity, but reduces the deformation capability than the bare frame building. The vulnerability was also reduced through infill walls, where the probability of exceeding partial-collapse and collapse damage reduced by 80% and 50%, respectively. Furthermore, the increased in storeys (three to five) also increases the failure probability, such that partial-collapse and collapse for fully infilled increases by almost 55% and 80%, respectively. All obtained results and discussions concluded that the structural sections and details assigned for MRT building is not sufficient if considered as bare frame and soft-storey. And increase in number of storeys causes building highly vulnerable although the infill walls were considered.
- Seismic assessment of a school building in Nepal and analysis of retrofitting solutionsPublication . Rodrigues, Hugo; Furtado, André; Vila-Pouca, Nelson; Varum, Humberto; Barbosa, André R.Recent earthquakes highlighted the vulnerability of some infilled reinforced concrete structures due to the presence and distribution of the infill masonry walls. Buildings such as school buildings and residential buildings are typically not designed considering the contribution of the infill panels to the structure strength and stiffness, when these are subjected to earthquakes. The lack of consideration of the infill panel results in observed poor performance and structural collapses. This manuscript presents a numerical study of a school in Nepal, representative of those existent in the country. Non-linear numerical analyses were carried out to assess the seismic vulnerability in terms of peak inter-storey drifts. In addition, results will be presented and discussed in terms of peak inter-storey drift profiles and peak base shear. Results from a seismic vulnerability assessment of the pre-earthquake structure indicate that the presence of the infill panels in the original structures were responsible for the development a soft-storey mechanism, combined with torsion. Following the seismic vulnerability assessment, four different retrofit solutions were tested and compared with the results of the original structure to gain an understanding on the structural efficiency of each proposed solution. The retrofit solutions proposed revealed to be efficient and reduce the seismic vulnerability. The retrofit solution showing best results correspond to the ones in which reinforced concrete column jacketing was employed.
- Calibration of a simplified macro-model for infilled frames with openingsPublication . Furtado, André; Rodrigues, Hugo; Arêde, AntónioDuring 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.
- Simplified macro‐model for infill masonry walls considering the out‐of‐plane behaviourPublication . Furtado, André; Pinheiro Rodrigues, Hugo Filipe; Arêde, António; Varum, HumbertoOne 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.