Abstract
Due to the poor seismic performance, strengthening of masonry structures is always a significant problem worthy to study. It has been proven that the bearing capacity of existing masonry buildings can be enhanced greatly with efficient strengthening measures. An experimental program was conducted to investigate seismic performance of un-reinforced masonry (URM) walls strengthened b,y reinforced mortar (RM) cross strips. Eleven walls were tested under horizontal low-cyclic load, simultaneously with a vertical constant load on the top face. Three URM walls were tested as reference. The other eight walls were externally strengthened with 40 and 60 mm thick of RM cross strips on one or both faces. Test results showed that externally strengthening with RM cross strips was an efficient way to enhance the seismic performance of URM walls. The failure modes were divided into shear failure and shear-compression failure. All the tested walls did not collapse until the test ended, while many diagonal cracks and few vertical cracks appeared on mortar strips. After strengthening, the shear capacity of the strengthened walls increased by at least 38.2%, and the reinforcement ratio was noted to be the key factor to influence the shear capacity with positive correlation. Besides, RM cross strips did improve deformation capacity greatly.
Highlights
Masonry has been used as a building technique for thousands of years
reinforced mortar (RM) cross strips strengthening composite wall consisted of an original un-reinforced wall, cross mortar strips and reinforcement bars
With the increasing of horizontal loading, first crack appeared on the overlay mortar, and it is in a direction perpendicular to the diagonal steel bars, which showed that the RM strip resisted mainly axial load
Summary
Masonry has been used as a building technique for thousands of years. From the Medieval period, a great variety of masonry typologies were studied and applied [1,2]. The FRP materials are bonded diagonally, vertically or horizontally on the surface of walls, which has been proven to enhance the seismic capacity of masonry structures [26,27,28,29,30,31]. Compared to traditional surface retrofitting with mesh reinforcement cement mortar, the X-shaped RM cross strips were smeared or sprayed on the diagonal region of the masonry wall, the position of high principal stress under in-plane load. The end of these diagonal steel bars was connected to the masonry wall with special adhesives In this way, RM cross strips and URM wall compose an integrated member to resist the earthquake. Half-scale masonry walls strengthened by reinforced mortar cross strips were tested under horizontal low-cyclic load.
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