Experimental Research On Seismic Behavior Of Masonry Pagoda Walls Strengthened By Hoop Reinforcement

Due to the limitations of the techniques and materials of ancient buildings, wind and rain erosion and earthquake damage, most of our existing masonry pagodas have varying degrees of damage; they are needed to be reinforced or repaired, to resist the seismic action in future long-term protection. So far, many masonry pagodas were reinforced by steel. However, the reinforcement can effectively improve the seismic performance of masonry pagoda or not, as well as the mechanism of reinforcing steel and the masonry pagoda body are not clear. In view of the above, some studies about the seismic behavior of masonry pagoda walls strengthened by hoop reinforcement have been done in three aspects of theoretical analysis, numerical simulation and experimental research in this paper.(1) According to study of the selected masonry pagoda construction, four1/8scale single-layer masonry tower theoretical models with different constructions and reinforcement conditions were designed. Finite element analysis models were established by separate modeling approach, then the boundary conditions and loading method as same as the pseudo-static test were simulated for the nonlinear finite element analysis. The numerical simulation results show: walls which parallel with the horizontal force were shear failure mode; walls which vertical with the horizontal force were bending failure mode; hoop reinforcement was in the tension and compression alternating stress state in the action of cyclic loading.(2) With the analysis of the selected masonry pagoda construction and theoretical analysis model, four1/8scale test models were made by small bricks which be special manufactured. The models were grouped by whether the masonry tower have floor or not, and in every group only one with reinforced by hoop reinforcement, the other as compared one. By testing of low reversed cyclic loading, the studies of the seismic behavior of masonry pagoda walls strengthened by steel hoops were carried out. The results show that ultimate bearing capacity of no-floor wall strengthened by hoop reinforcement, increased by22.5%in the positive loading and increased by47.5%in the reverse loading than unstrengthened no-floor wall; ultimate bearing capacity of floor wall strengthened by hoop reinforcement, increased by13.2%in the positive loading and increased by31%in the reverse loading than unstrengthened floor wall. Whether reinforced or not, cracking load and ultimate load of the walls with floor were increased significantly than the no-floor walls. The ductility coefficient of the floor wall strengthened by hoop reinforcement were increased by approximately51.7%,100%than the no-floor wall strengthened by hoop reinforcement and unstrengthened floor wall. Hysteresis loops of the walls strengthened by hoop reinforcement were fuller than the unstrengthened walls, and energy dissipation capacity enhanced.(3) Based on the test results and theoretical analysis of brick wall models in reciprocating horizontal load under different conditions, the model of computing shear capacity of the masonry pagoda wall strengthened by hoop reinforcement was established, and the initial formula of shear capacity of the masonry pagoda wall strengthened by hoop reinforcement were got.The experimental and theoretical analysis of single-layer brick wall strengthened by hoop reinforcement show that, the restraint effect of hoop reinforcement can effectively improve the seismic performance of masonry pagoda. The seismic performance and law of masonry pagoda wall under the combination of different vertical pressure and different prestress level reinforcement need to be further explored.