Experimental investigations on masonry structures using external prestressing techniques for improving seismic performance

Based on previous failure characteristics of masonry structures under earthquakes, and due to the fact that a considerable number of masonry structures have been built around the world, a strengthening strategy for improving seismic performance of masonry structures is adopted and justified in this paper, namely, the external prestressing technique. The principle of this strategy is to tension the prestressing tendons located on both sides of the walls in order to increase the in-plane shear strength and simultaneously to improve the out-of-plane bending resistance of masonry walls, thus allowing an overall improvement of masonry structures under seismic loadings. In addition, this strategy enables multi-level-prestressing to be applied to the walls at different floors, thus allowing optimized compressive prestress in the structure along the building height. In order to validate the effectiveness of this technique, shaking table model tests were conducted. The experimental results showed that, after introducing vertical prestressing to the walls with the proposed technique, the failure mode of the tested masonry structures was influenced, and the torsional resistance was improved significantly. Furthermore, the prestressing also improved the energy dissipation capacity of the walls and enhanced the overall stiffness of the masonry structure.