Performance of unreinforced masonry strengthened with bed joint reinforced repointing

Bed joint reinforced repointing is a strengthening method often used in the Netherlands to counteract settlement damage. This strengthening technique consists of cutting a slot in the mortar joint and installing twisted steel bars embedded in a high-strength repair mortar. Due to the increase in seismic activities, triggered by gas extraction in the region of Groningen (northern part of the Netherlands), it is of interest to investigate whether this strengthening technique is efficient against seismic load. In order to characterize the performance of the bed joint reinforced repointing using twisted steel bars, an experimental campaign was conducted at Delft University of Technology. A quasi-static cyclic in-plane test on a full-scale wall was performed; similar tests on unstrengthened specimens were available from a previous experimental campaign [1][2] and were used for comparison. Moreover, small scale pull-out tests were performed to study the interaction between the steel bars and the repair mortar. By comparing the response of unstrengthened and strengthened masonry specimens, it is observed that the use of bed joint reinforced repointing can provide an increase in terms of ductility and displacement capacity, but not in terms of force capacity. Regarding the serviceability limit state, a reduction in crack width and an increase of load at onset of cracking were observed. The preliminary information obtained for the presented case study provides the ground for futher research as well as benchmark for numerical modelling.