| Unreinforced masonry structures are very vulnerable under seismic action,especially for masonry structures with window openings.Therefore,a strengthening material and strengthening technique need to be proposed to improve the seismic performance of confined masonry walls with window openings.In this study,a hybrid fiber modified reactive powder concrete(HFMRPC)material with good composite action with masonry walls was first obtained through material tests.Then the confined masonry walls with window openings were strengthened or repaired by using HFMRPC coating in several different ways,including single-sided reinforcement,double-sided reinforcement,single-sided coverage in piers,and double-sided coverage in piers.To investigate the effect of HFMRPC coating on strengthening or repairing the confined masonry walls with window openings.Seven half-scale masonry walls with height to width ratio of 1:1 were tested under in-plane quasi-static horizontal loading.The seismic performance including load-bearing capacity,damage mode,crack development,displacement ductility,stiffness degradation,and energy dissipation was compared.It provided a theoretical study basis for later selection of different ways to strengthen or repair the confined masonry walls with window openings.Finally,a simplified analysis method for calculating the shear bearing capacity of confined masonry walls with window openings was proposed based on the theoretical analysis and test results.The main contents and conclusions of this thesis are as follows:(1)The HFMRPC has been formulated based on the design theory of reactive powder concrete(RPC).The best mixing ratio was achieved by adjusting the amount of each matrix material.The positive mixing effect of mixed fibers was ensured by controlling the volume ratio of steel fibers and polypropylene fibers.The best mixture with moderate fluidity,low compressive strength and good bonding ability with the masonry wall was obtained by adjusting the water-cement ratio and the amount of water-reducing agent.(2)The integrity of the specimens was significantly improved,the development of cracks were effectively inhibited by using HFMRPC coating strengthening or repair.Meanwhile,the damage of strengthened or repaired walls was more uniform.The failure mode of unreinforced specimen URMW-1 was a diagonal compression failure,while the failure modes of other reinforced specimens were shear slip failure,except for the failure modes of specimens SPRW-5 and DPRW-6,which were mixed failure modes of shear failure in the spandrels and flexural failure in the piers.(3)The HFMRPC strengthening technique can effectively improve the bearing capacity,energy dissipation capacity and delay the stiffness degradation of the strengthened masonry walls.The ductility and energy dissipation capacity of masonry walls were significantly improved by single-sided coverage in piers and double-sided coverage in piers.The cracking load,peak load and stiffness were significantly improved by double-sided reinforcement.(4)The seismic performance of the post-seismic repaired specimen DRUW-7 was significantly improved by using HFMRPC coating for double-sided repair of the post-seismic damaged specimen URMW-1.The cracking load and peak load of specimen DRUW-7 were lower than those of double-sided strengthened specimen DRMW-3 due to the existing damage of mortar joints and bricks of specimen DRUW-7.However,the difference was not significant.The displacement ductility,peak stiffness and energy dissipation of specimen DRUW-7 were higher than those of specimen DRMW-3.(5)A simplified model was proposed for the shear bearing capacity of confined masonry walls with window openings strengthened by HFMRPC coating by the test results and equivalent diagonal strut concept.By comparing the tested values with the theoretical calculated values,the calculated values were safety and it can be applied to the calculation of the bearing capacity of confined masonry wall with window openings. |
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