| Summary: |
The presence of infill masonry (IM) walls in reinforced concrete (RC) buildings is very common. However, and even today, in the design process of new buildings and in the assessment of existing ones, infills are usually considered as non-structural elements, and their influence in the structural response is disregarded. The influence of IM walls is recognized to be crucial in the global behaviour and performance of RC framed building structures when subjected to earthquake demands, as confirmed in the poor performance of many buildings damaged in recent earthquakes in Europe (e.g.: L'Aquila/Italy 2009; Lorca/Spain 2011; Emilia-Romagna/ Italy 2012). Many authors recognize the need for the inclusion of IM panels in the numerical models adopted in the seismic assessment of existing buildings and in the design process of new buildings.
The large in-plane shear demands that IM walls may attract, and the associated in-plane damage evolution are likely to increase their out-of-plane vulnerability. The eventual out-of-plane collapse of IM walls can result in serious human injuries and casualties and high economic losses, as experienced in recent earthquakes. The rigorous knowledge of all the aspects related to the behaviour of infilled framed structures, of their components (structural and non-structural elements) and of the phenomena interaction is fundamental to guide the designers in the assessment and strengthening of existing buildings.
Nevertheless, the available knowledge in this regard is still very limited. Thus, the main goals of the research project proposed are: (1) characterization of the IM walls' behaviour when subjected to in-plane and out-of-plane loading; (2) development of innovative retrofit solutions for IM walls; (3) development of a simplified numerical tool for the analysis of the interaction for in-plane and out-of-plane responses of IM walls in RC buildings; (4) calibration of the numerical model, based on  |
Summary
The presence of infill masonry (IM) walls in reinforced concrete (RC) buildings is very common. However, and even today, in the design process of new buildings and in the assessment of existing ones, infills are usually considered as non-structural elements, and their influence in the structural response is disregarded. The influence of IM walls is recognized to be crucial in the global behaviour and performance of RC framed building structures when subjected to earthquake demands, as confirmed in the poor performance of many buildings damaged in recent earthquakes in Europe (e.g.: L'Aquila/Italy 2009; Lorca/Spain 2011; Emilia-Romagna/ Italy 2012). Many authors recognize the need for the inclusion of IM panels in the numerical models adopted in the seismic assessment of existing buildings and in the design process of new buildings.
The large in-plane shear demands that IM walls may attract, and the associated in-plane damage evolution are likely to increase their out-of-plane vulnerability. The eventual out-of-plane collapse of IM walls can result in serious human injuries and casualties and high economic losses, as experienced in recent earthquakes. The rigorous knowledge of all the aspects related to the behaviour of infilled framed structures, of their components (structural and non-structural elements) and of the phenomena interaction is fundamental to guide the designers in the assessment and strengthening of existing buildings.
Nevertheless, the available knowledge in this regard is still very limited. Thus, the main goals of the research project proposed are: (1) characterization of the IM walls' behaviour when subjected to in-plane and out-of-plane loading; (2) development of innovative retrofit solutions for IM walls; (3) development of a simplified numerical tool for the analysis of the interaction for in-plane and out-of-plane responses of IM walls in RC buildings; (4) calibration of the numerical model, based on experimental results, accounting for different aspects, such as, in-plane/out-of-plane interaction, wall typologies, wall/frame contact conditions, retrofitting strategies applied, etc. This will be valuable for the assessment of existing RC buildings and for the safety assessment of the large building stock in Portugal, considering simultaneously the in-plane and out-of-plane response of the IM walls.
The experimental results and conclusions, combined with development and calibration of the numerical models, is expected to contribute significantly to the upgrade of the limited information and knowledge currently available concerning the in-plane/out-of-plane cyclic behaviour of infilled RC framed structures, representative of the existing building structures (as-built or retrofitted). One of the major contributions of this research project proposed, in relation to past studies, is its focus in the study of IM walls behaviour subjected to combined in-plane/out-of-plane demands, better representing the complex behaviour and response of these elements when subjected to earthquakes. It is also pointed out that the topic of IM walls' design and assessment will be specifically addressed in the revision of Eurocode 8 (which will occur in parallel to this research project).
Furthermore, retrofitting solutions will be developed and tested, using innovative materials such as steel elements, textile fibres, Glass/Carbon Fibre Reinforced Polymers (GFRP/CFRP) and High Performance Fibre Reinforced Mortars (HPFRC). The retrofitting solutions to be studied will be designed and detailed considering economic, feasibility for real applications and environmental sustainability concerns. The design objectives of the retrofitting solutions for the IM walls will consider: (i) the stiffness compatibility between the retrofitting system and the existing frame and IM wall system; (ii) a clear definition of the retrofitting objective (in terms of improvement of the in-plane and/or out-of-plane performance of the infill walls); (iii) damage limitation for in-plane demands; (iv) detachment and out-of-plane collapse prevention of the walls for ultimate demand conditions.
Based on the calibrated simplified model for the IM walls, for the "as-built" and retrofitted walls, RC buildings vulnerability can be assessed for different earthquake demand levels, considering the influence of IM walls and including retrofitting solutions. Parametric analyses for the variables influencing the response (frame, IM materials and details, retrofitting system and details) will be developed. This simplified model will allow the evaluation of the benefits of each retrofitting strategy in the seismic performance upgrading of buildings. |