Designing an experimental test on a reinforced concrete frame with polystyrene infill

Frame structures are one of the most common type of structural schemes currently used to resist both gravitational and lateral loading. Façade walls are, in many cases, not needed for the lateral resistance, and hence not detailed accordingly. It is not strange to encounter frame structures with infill walls (typically infilled with unreinforced masonry) which have been conceived by the designer as just frames with added weight. This topic has been widely studied in the case of masonry, and it has been concluded that, in many cases, it leads to non-conservative results, due to the fact that the masonry infill will unavoidably tend to stiffen up the structure if no special detailing is carried out. An interesting new option to use as infill has been developed, which consists of polystyrene foam. This product works as insulation, with only a fraction of the weight of masonry, making it ideal to use as infill in façade walls. As any new product, its structural behavior must be properly studied and tested, in order to develop design guidelines that comply with design codes and pre-defined limit states. Masonry infilled frames were studied as a starting point, and the methods of analysis were suitably adopted for polystyrene infilled frames. A simplified analytical method was carried out for one infilled frame. Then, a finite element analysis was carried out for the same infilled frame, by means of both a static non-linear analysis (pushover analysis) and an elastic analysis. Results were then compared amongst each other in order to quantify the difference between all approaches. Results show that no significant error is made when assuming the polystyrene infill as a non-structural element, regarding low damage limit states. However, there is a significant gain of strength of the structure when considering post-elastic behavior. The results obtained during this research are meant to be compared with the experimental values obtained during the testing of the specimen.