| Due to the fact that historical buildings were usually constructed without considerations of their aseismic functions,after years of weathering and erosion,which contributed to serious deterioration of the structural material,most of their masonry structures are insufficient in terms of their aseismic performance.As a result,there exist great hidden safety hazards if those buildings should come into use,and therefore,it is necessary to implement seismic reinforcement for them.This study analyses the aseismic performance of historical masonry structures after reinforcement and further studied,the potential causes of collapse and the damage mechanism of the masonry structure during the earthquake.The main works are as follows:(1)Based on the previous experiments,the author uses ABAQUS to model and calculate the single-sided concrete wall reinforced brick wall components,through which the author analyzed the figures of the thickness and the horizontal reinforcement ratio of the conctere wall,the change of the axial compression ratio of the brick wall,and single and double face plate reinforcement on the seismic bearing capacity.And the relevant reinforcement suggestions are given based on these figures and analysis.(2)Referring to the masonry structure of historical buildings in Nanjing built in the Republic of China period,the author conducted a calculation example of two-story unreinforced masonry structure and used the PKPM software to assess.The result shows,it fails to meet the standard of seismic,and aseismic reinforcement is necessary.We made two designs for aseismic reinforcement according to the standard.The final scheme is determined after analysis and comparison.(3)A finite element model was built in ABAQUS to analyze the influence of the rigidity of the floor on the natural frequency of the masonry structure.The natural frequencies of the structures with a rigid floor and with a flexible floor showed differences.The modal analysis shows that additional ring beams and structional columns slightly improves the initial stiffness of the structure;the natural frequency of the structure strengthened by single panel wall between ring beam structural column and single panel wall is not obviously increased.(4)The VUSDFLD subroutine that controls the deletion of failure units was implemented in Fortran,while the models of the unreinforced and reinforced masonry structures has been simulated under different working conditions.The results show that additional ring beams and structural columns can improve the seismic resistance of masonry structure in the frequent and moderate earthquakes,while the probability of collapse was still relatively high in rare earthquakes.With the rare earthquake,the masonry structure strengthened by single-sided concrete wall has been severely damaged but no collapse,which achieved the fortified purpose;Compared with that of the single-sided concrete wall,the damage of masonry structure strengthened by double-sided concrete wall decreased.(5)Through regression analysis,the vulnerability fitting equation of masonry structure before and after reinforcement is obtained and the vulnerability curve is drawn.According to the vulnerability curve,the collapse probability of unreinforced masonry structure under rare earthquake is 87.3%,and the collapse probability of reinforced masonry structure under rare earthquake is 3.9%.The seismic capacity of the structure is significantly improved.The CMR value of the unreinforced masonry structure is 0.625,and the CMR of the reinforced masonry structure is 2.098.Compared with the unreinforced masonry structure,the CMR of the masonry structure strengthened by single-sided concrete slab wall is significantly higher,and the safety reserve of the structure against collapse is higher. |
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