# A Review of the Performance of Infilled RC Structures in Recent Earthquakes
## 5 Conclusions and Recommendations  
This manuscript presented the typical damage observed in RC structures due to earthquakes. The damages were divided into ten types, for which some examples are shown. From that damage list, it was found that eight of them were related to primary elements, one related to secondary elements and finally, one related to the 'non-structural' elements (infill panels). The definition of each damage type was supported by field evidence in several post-earthquake damage survey assessments. It was observed that the proper design and detailing of the RC beam-column joints and the plastic hinges regions of the columns are mandatory for a good performance of the structure. In the absence of adequate seismic design, jacketing (with steel, CFRP or RC) can be considered to avoid shear failure. It was observed that the infill panels played a critical role in the seismic behaviour of the RC structures and presented strong interaction with the RC elements. On the one hand, when distributed in-plan and in-elevation uniformly, the infill walls can positively contribute to the global behaviour of the structure. However, when some irregularities are observed, the infill panels can potentially develop essential failure mechanisms such as soft-storey or torsion. On the other hand, at a local level, it was observed that depending on the disposition, the openings can lead to stress accumulation in certain parts of the columns for which they were not designed to support and the consequences to shear failure (short-column) occurrence. Four different types of local damage can occur due to the in-plan loading demands, namely the detachment of the panel from the envelope frame (for lower seismic demands), diagonal cracking, sliding cracking and corner crushing. Finally, the OOP collapse revealed to be the most critical failure since it is prone to risk in terms of life safety and very important concerning the loss estimation. The OOP collapse vulnerability is dependent on the level of damage caused by the in-plane seismic demand, panel slenderness, boundary conditions and panel support conditions. It was observed that the collapse occurred most often in the intermediary levels of the buildings. Their retrofitting need to be considered, for example, using reinforced plaster. The reinforcement mesh must be connected to the RC elements through steel connectors to prevent the wall's collapse. Future investigations are needed to characterise the interaction between the in-plane and OOP behaviour interaction of the masonry infills when subjected to earthquakes. Most of the damages and poor performance of the RC building are related to the not inadequate implementation of the codes demands in terms of detailing and designing the RC elements. The transversal reinforcement design of the RC beam-column joints and columns must be improved to prevent shear failures. A brief literature review was provided concerning the impact of the infill walls in the economic loss estimation after the last major earthquakes. The costs related to the infills, on average, are equal to 50% of the repair costs of the buildings, highlighting the paramount importance of the infill walls in the seismic loss assessment of RC buildings. A case study was presented in which the seismic vulnerability of a soft-storey building configuration was performed. After that, four strengthening solutions were proposed and tested to reduce the seismic vulnerability. It was concluded that using strengthening solutions at the storey where it is located, the vertical irregularity (absence of masonry infill walls) is enough to reduce or even eliminate the soft-storey mechanism. Therefore, this strategy can be efficient and can be adopted in existing buildings with this type of problem, which is quite common worldwide. The strengthening solutions were quite efficient, reducing the maximum inter-storey drift ratio up to 90% and improving the energy dissipation capacity up to three times.