Out-of-plane behavior of URM arching walls with modern blast retrofits: Experimental results and analytical model

A series of framed unreinforced masonry (URM) infill walls were retrofitted with modern materials to evaluate the abilities of these materials to mitigate blast effects. The walls were constructed from traditional and alternative masonry materials to assess the applicability of using a wood-fiber fly ash material for infill construction. The walls were tested in the laboratory under static conditions and were evaluated using several criteria: energy absorption, out-of-plane load resistance, out-of-plane deformability, and the reduction of masonry debris scatter upon collapse. Due to the presence of the surrounding frame structure, all of the walls in this program experienced some form of an arching mechanism. The use of a spray-on polyurea material was found to be highly effective in improving URM energy absorption and reducing masonry fragmentation. Infill walls retrofitted with a combination of fiber-reinforced polymer (FRP) grids and polyurea material were found to fail prematurely due to a lack of anchorage between the strengthened walls and surrounding structure. A simplified analytical model to estimate the ultimate out-of-plane capacity for FRP strengthened URM arching walls was developed. The analytical model was empirically calibrated using test data from this work as well as previous studies. The model predictions agree well with the experimental results reported in this paper.