| Ancient pagodas integrate the essence of Chinese and overseas architecture,have a unique architectural image,reflect the wisdom of working people in ancient times,and are important cultural heritage buildings.Most ancient pagodas are a high-rise structure,their bodies remain in high pressure stress for a long period of time,and their interiors may have damages and defects,leading to low structural reliability.Therefore,the compression performance and reinforcement method of ancient pagodas need to be evaluated and researched.Based on the damage theory,this paper conducted the compression test and numerical simulation for the substructure model of ancient pagodas,analyzed their mechanical properties and fracture mechanisms,adopted angle steel hoops to confine the compression of structural model,and studied the influence of hoop confinement on the compression performance of ancient pagodas.The main work and conclusions were as follows:(1)Research on masonry mortar and masonry mechanical properties of ancient pagodasFour groups of mortar test blocks were prepared with different water cement ratios and rice milk concentrations,conduct an axial compression test to test its compressive strength,analysis shows that the concentration of rice slurry has the most significant effect on the compressive performance of mortar,and the reasonable mix proportion of sticky rice mortar was determined.The masonry test pieces of ancient pagodas were also prepared to perform axial compression experiments.According to the experimental results,a proposed formula used to calculate the compressive strength of ancient pagodas was put forward after correcting the calculation formula of masonry compression strength in the standard,the mechanical calculation parameters of the ancient pagoda masonry are determined.(2)Experimental research on the mechanical properties of the substructure model of ancient pagodasIn view of the influence of existing damages and defects in pagoda bodies on the compression performance,a substructure model of bricks with three types of dimensions was established by taking the numerical representation of vertical mortar joint as initial defect.The homotaxial compression experiments were performed,and the characteristics of load-displacement,pagoda body deformation and block strain deformation in the model were analyzed.The results indicated that the vertical deformation of pagoda bodies mainly occurred at the earlier stage of load;the tensile and lateral deformation began to increase after the load entered into crack propagation,and the damage first happened at the corner of pagoda top where blocks cracked due to the tension;the damage extended gradually downward with the increase of load;and finally the vertical straight joint was formed at the corner area,resulting in the buckling failure of the model.The analysis of pagoda body damage showed that with the continuous increase of the damage caused by internal defects,both bearing capacity and deformation capacity of the structure reduced,the damage speed of the structure quickened,and serious damage tended to occur.(3)Finite element analysis of the substructure model of ancient pagodasThe compression performance of ancient pagodas was simulated by ABAQUS finite element software,and the influence of damages and defects on the compression performance of ancient pagodas was analyzed by changing damage parameters.The simulation showed that when ancient pagodas were in compression failure,cracks were mainly distributed in the side of arches,and both damage area and damage degree of pagoda bodies continuously enlarged with the increase of pagoda body damage.Under the action of vertical load,the bulging deformation of pagoda bodies occurred horizontally towards the side of arches,and it mainly occurred vertically at the door opening,which would give rise to roof collapse.Tensile deformation mainly occurred horizontally at the corner of pagoda bodies,and with the increase of structural damage,the horizontal and vertical deformation of pagoda bodies weakened,while tensile deformation started to enlarge at the corner.(4)Experimental research on the mechanical properties of hoops confining ancient pagodasCompare the test and numerical simulation results,analyze the mechanical properties of the ancient pagoda after the angle steel hoop restraint damage,the comparison of load-displacement and pagoda body deformation before and after reinforcement was carried out.The results showed that after using angle steel confinement,the form of tensile failure at the edge of pagoda bodies changed,the range of tensile failure reduced,the in tegrality of the model enhanced,and both compressive capacity and deformation capacity improved.Parameter expansion analysis indicated that the increase of both width and thickness of angle steel could improve the bearing capacity of pagoda bodies;the thickn ess of angle steel could be increased when reinforcing ancient pagodas with slight dama ges;and the cross-section width of angle steel could be increased when reinforcing ancient pagodas with serious damages,so as to enhance the anti-cracking capability and ultimate bearing capacity of pagoda bodies. |
