The main objective of this project is to assess the contribution of non-structural masonry walls to the safety of buildings after an unforeseeable event and the definition of procedures to enhance this contribution.

Although the knowledge in structural engineering has advanced enormously in the last decades, structural collapses still occur with significant frequency. These are, in general, a consequence of unexpected loading, design and construction errors or harmful human actions.

Reducing the susceptibility of structures to these unforeseeable events is a key aspect in increasing safety in civil engineering structures. Intensive research has focused on these aspects in the last decade, and it is now clear that a general approach to robustness must be based on risk analysis.

However, it is also clear that less complex formulations must be defined for particular structural typologies, in order to be applicable in current design.

In Portugal, buildings are traditionally erected using a reinforced concrete frame, complemented by reinforced concrete walls, and using non-structural walls built with clay or concrete blocks masonry. In this project, this common building typology is studied from a robustness viewpoint, aiming at defining simple robustness indicators and mitigation solutions specific for these structures.

Recent examples of near collapses in Portugal showed that the non-structural walls can, under extreme events, sustain significant loads, preventing collapse and allowing evacuation and repair. Although significant damage occurred in these cases, no casualties were registered, and the buildings could be used after repair.

To assess the importance of walls in robustness as well as the condition under which such contribution can be considered, different wall panels, composed of masonry walls and reinforced concrete frames, will be analyzed experimentally, to assess their joint performance and its dependence on materials (clay bricks vs. concrete bricks), geometry and continuity between masonry and reinforced concrete frame. Particular attention will be paid to the quality of workmanship on the properties of wall, as the existence of gaps between bricks and between bricks and frame and poor brick arrangement can severely limit the ability of these elements in improving robustness.

Based on the properties of the wall defined experimentally, risk assessment of several typical buildings, considering different non-structural walls, under extreme events, will be performed. The risk analysis will be based on reliability analysis considering an initial damage (modeled through removal of a key-element), considering the non-linear behavior of all components of the structure.

This analysis will give clear indications on the improvement in robustness resulting from the use of non-structural masonry walls, as well as, indicate possible methods to enhance robustness of existing structures.

The second phase of the project focus on the use of recycled aggregates concrete blocks (RACB) walls for improving robustness. The advantages of this solution are: competitive cost, higher sustainability and capacity to increase resistance through the use of ladder reinforcement. The analysis of advantages of this solution will be performed using the same procedure defined for traditional walls. The comparison of results will show the effectiveness and cost efficiency of this solution.

The final step of the project is the development of a guideline on the structural robustness assessment of reinforced concrete buildings with masonry infill, including assessment simplified rules and enhancement procedures for both new and existing structures. At the end of the project, a seminar oining national and international experts will be organized, in order to transpose the obtained knowledge to the community.

The team involved in this project involves experienced researchers in reliability and robustness analysis, strengthening of reinforced concrete structures, recycled aggregated concrete, and experimental analysis of reinforced concrete structures. The two invited consultants are renowned experts on risk assessment and robustness analysis and on recycled aggregate concrete, respectively.