Quasi-static in-plane testing of FRCM strengthened non-ductile reinforced concrete frames with masonry infills

Performance of fibre reinforced cementitious matrix (FRCM) strengthened non-ductile reinforced concrete frames with hollow concrete masonry infill (RCFMI) subjected to cyclic in-plane loading was experimentally assessed herein. A set of nine two-third scaled one bay-single story RCFMI prototypes were constructed that represented one bay of a low to medium height RCFMI building. Of these specimens, one frame was tested as-built without infill, one frame was tested as-built with infill, and the remainder were retrofitted using different FRCM schemes. The as-built tested frames served as control specimens and represented the baseline collapse risk associated to RCFMI buildings. Three different types of fibre grids (i.e. basalt, carbon, and glass) and three different FRCM configurations were used for retrofitting (i.e. full surface, diagonal bands with varying width). FRCM strengthened test frames exhibited a controlled failure mode characterised by distributed cracking in the FRCM matrix, without any signs of fibre slippage/rupture or deboning noted during the testing. Separation at the un-strengthened infill-frame contact region in FRCM strengthened frames was noted at a lateral drift of 0.4–0.6% and an applied lateral force of 1.2–2.0 times the strength of as-built tested frame. In general, test frames strengthened using diagonal bands with width equal to 1/6 infill diagonal length performed very similar to other configuration and therefore was deemed the most effective configuration. Carbon fabric had the highest strength compared to other fabrics used, but resulted in the lowest strength increment for the RCFMI, whereas Basalt-FRCM strengthened RCFMI exhibited the largest in-plane strength.