# A Review of the Performance of Infilled RC Structures in Recent Earthquakes
## 2 Seismic Behaviour of Infilled RC Structures: Definition of Damage Type  
The Eurocode 8 [8] classifies the structural elements as structural or non-structural. The structural elements are subdivided as primary members (SP) or secondary members (SS). The primary members (SP) are considered part of the structural system that resists the seismic demands, which are modelled in the analysis for the seismic design situation and are fully designed and detailed for earthquake resistance. On the other hand, the secondary elements are not considered part of the seismic resisting system and whose strength and stiffness against seismic actions are neglected. They are not required to satisfy all Eurocode 8 [8] requirements but are designed and detailed to maintain the support of gravity loads when subjected to the displacements caused by the seismic actions.  
The non-structural elements (NS) comprise architectural, mechanical or electrical components, systems and components, which, whether due to lack of strength or the way they are connected to the structure, are not considered in the seismic design as load-carrying elements. As mentioned before, the Eurocode 8 [8] recognises that infill panels are included in this NS elements group.  
Following the last major earthquakes all over the world, different types of damage have occurred (the most representative ones listed above) and affected the RC structures according to post-earthquake survey damage assessments:  
* Damage Type 1: Damage associated with stirrups and hoops (inadequate quantity and detailing, regarding the required ductility);
* Damage Type 2: Damage associated with longitudinal reinforcement detailing (bond, anchorage and lap-splices);
* Damage Type 3: Damage associated with the shear and flexural capacity of elements;
* Damage Type 4: Damage associated with the inadequate shear capacity of structural joints;
* Damage Type 5: Damage associated with strong-beam weak-column mechanism;
* Damage Type 6: Damage associated with short-column mechanism;
* Damage Type 7: Damage associated with structural irregularities (in plan and/or in elevation: torsion, 'weak-storey' and'soft-storey');
* Damage Type 8: Damage associated with bounding;
* Damage Type 9: Damage in secondary elements (cantilevers, stairs, etc.,).
* Damage Type 10: Damage in non-structural elements.  
The first eight damage types are related to the SP members, the ninth is related to SS members and finally, the tenth is associated with the infill walls (NS elements). According  
Figure 1: Location of the post-earthquake damage reconnaissance missions carried out.  
to the post-earthquake damage survey assessment, it can be concluded that there is an interaction among the last five types of damage. Figures 2 and 3 show the schematic layout concerning the damage type and their respective interaction. The damage observed in the different post-earthquake field trips highlighted that the masonry infill walls cannot be considered non-structural or secondary elements and disregarded from the expected building seismic behaviour. According to the observations detailed in the following subsection, the infill walls assume a principal role since they can modify the global structural behaviour.  
The following sub-sections detail some examples of each damage type presented and the significant observations and conclusions extracted from the post-earthquake damage reconnaissance missions.