Experimental tests on masonry strengthened with bed joint reinforced repointing

L. Licciardello, J.G. Rots, R. Esposito

Delft University of Technology, the Netherlands

Bed joint reinforced repointing, also known as bed joint reinforcement, is a strengthening method often used in the Netherlands to counteract settlement damage. It consists in the installation of twisted steel bars in mortar joint embedded in high-strength repair mortar. Currently it is of interest to investigate whether this strengthening technique is efficient against induced seismic load, since the gas extraction from the subsoil is causing an increase of the induced seismic events in the region of Groningen, in the northern part of the country.

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 and four-point bending tests on masonry wallets were performed; similar tests on unstrengthened specimens were available from a previous experimental campaign and they were used for comparison. Moreover, small scale pull-out tests were performed to study the interaction between the steel bars and the repair mortar.

The bed joint reinforcement results efficient in reducing crack width and crack length up to the serviceability limit state; the performance of strengthened masonry at near collapse show an increase in terms of ductility and displacement capacity for the wall subject to in-plane loading. The preliminary information obtained for the presented case study provides the ground for further research as well as benchmark for numerical modelling.

Key words: Unreinforced masonry (URM), settlement, induced seismicity, bed joint reinforcement, twisted steel bars, experimental tests