Shaking table tests on a 5-storey unreinforced masonry structure strengthened by ultra-high ductile cementitious composites

Abstract

Multi-storey unreinforced masonry structures have been widely used as residential building structures in China during the decade of 1970–1980. Recent earthquake events have shown that these buildings may exhibit severe damages due to their relatively brittle seismic resistance mechanism. The use of ultra-high ductile cementitious composites (UHDCC) layers can be an attractive minimal-disturbance strengthening option for masonry structures resulting in low intervention costs and quick construction. UHDCC is a high-performance engineered cementitious composite that offers a tensile strain capacity higher than 5%, thus significantly improving the low tensile strength and ductility of the masonry wall. To investigate the seismic behavior of UHDCC-strengthened masonry structures, shaking table tests were carried out on two three-dimensional 5-storey masonry structures including a conventional test structure (CS) and a strengthened test structure (SS). The results show that the proposed strengthening method can effectively improve the seismic performance of multi-storey unreinforced masonry structures due to the excellent cohesion achieved between the existing masonry walls and the UHDCC external strengthening layers. The strengthened method changes the damage state of masonry structures from shear failure to a more ductile failure, and the strengthened masonry walls can exhibit a multi-cracking response. The initial natural period of the SS specimen was found 0.58 times that of the CS specimen. The base shear and maximum roof drift of the SS specimen are 4.8 and 3.4 times that of the CS model, respectively. This study provides reference results for the application of UHDCC layers to strengthen multi-storey unreinforced masonry structures.