Title:analysis Of The Influence Of Masonry Mortar St Rength On The Compression-shear Behavior Of Brick And Stone Pagoda Substructures

The diamond-shaped pagoda is one of the traditional buildings with a long history and cultural value.It is prone to damage due to natural disasters such as earthqu akes.The seismic resistance of the diamond-shaped pagoda is an important factor in determining whether it can be preserved permanently.A synthesis of quasi-static tests and numerical simulations was employed in this investigation to evaluate the hysteresis features and breakdown modes of brick tower substructure models built with varying mortar strength under compression-shear loading conditions.The crack propagation patterns in the substructure of the pagoda were investigated,and the relationship between mortar strength and structural seismic resistance was explored.The main work and conclusions are as follows:(1)A scaled-down model of the Xuanzang Pagoda substructure was designed and fabricated,using two different strengths of traditional mortar for construction.Low-cycle repeated loading tests were conducted to observe the failure phenomena of the specimens and analyze the failure mechanisms.The results showed that when the mortar strength was below 1 MPa,the hysteresis characteristics,energy dissipation capacity,and ductility of the model were affected,leading to premature cracking and localized shear-sliding failure at the corners.The mortar’s strength being raised to more than 1 MPa,the structural bearing capacity,energy dissipation capacity,and ductility were all augmented,resulting in an increase in stiffness.Compression-shear failure was the mode of failure.(2)A segregated modeling approach was employed to establish a numerical model of the substructure of the ancient pagoda.The numerical model’s parameters were established through material tests,and the model’s precision was shown by comparing it to experimental data.To investigate the effect of mortar strength on the pagoda substructure’s failure mechanism,different mortar strength conditions were simulated.Comparative analysis revealed that the mortar strength primarily caused a change in the crack propagation angle,resulting in a variation in the structural failure mode.When the mortar strength was low,premature cracking occurred on various surfaces of the structure,leading to crack penetration and localized shear-sliding failure as the dominant failure mode.When the mortar strength increased to a range of 1 MPa to 4 MPa,cracking in the structure was significantly delayed,cracks were distributed more widely,and the brick tower experienced overall compression-shear failure.The numerical model’s parameters were established through material tests,and the model’s precision was shown by comparing it to experimental data.To investigate the effect of mortar strength on the pagoda substructure’s failure mechanism,different mortar strength conditions were simulated.(3)Considering the influence of different mortar strengths on the failure modes of brick and stone pagodas,the study investigated the variation of the load-bearing capacity of the pagoda masonry structure under vertical compressive stress for different mortar strength conditions.The results showed that when the mortar strength was between 0 and 3 MPa,the normal stress coefficient increased proportionally with the compression-shear ratio.When the mortar strength was increased within 1 MPa,the rate of increase in the normal stress influence coefficient was higher.However,when the strength increased beyond 3 MPa,the normal stress influence coefficient initially increased and then decreased with the compression-shear ratio.Based on the results of numerical simulations,an expression for the normal stress influence coefficient of the pagoda masonry constructed with low-strength mortar was fitted.