Experimental And Numerical Investigation On Seismic Performance Of Stone Masonry Joints Under Cyclic Lateral Loads

Stone masonry structures are the traditional housing typologies in South-Coastal regions of China.But the seismic behavior of stone masonry structures is significantly influenced by the failure of stone masonry joints.Thus,it is of great importance to evaluate the seismic performance and develop prediction models of stone masonry joints under lateral loads.The main research work and achievements of this thesis are summarized as follows:(1)Experimental study was conducted to evaluate the seismic performance of stone masonry joints under cyclic lateral loads.The test parameters include: normal stress,strength-and type-of mortar.The experimental results were evaluated in terms of hysteretic behavior,deformation characteristics and shear failure mechanisms of the specimens.The test results showed that the shear behavior of the joints was characterized in four stages,i.e.,elastic stage,crack propagation stage,shear strength degradation stage and frictional sliding stage.From the damage pattern,it was affirmed that all the specimens were failed in shear-sliding mode.The rectangular in shape hysteretic(Shear Stress-Displacement)behavior for all the tested specimens highlighted the significantly better energy dissipation characteristics of stone masonry joints.It was also found that the shear strength of the specimens increased with increase in normal stress and mortar strength.(2)The vertical deformation characteristics of the stone masonry joints were analyzed for all the specimens.During the loading process,vertical compression was primarily due to crushing of mortar and stone wedges inside the joints.The compression corresponding to the peak load was not more than 0.95 mm,while the average compression at the termination of loading was 11.88 mm.Further,it was also found that the compression of the joints increased with increase in horizontal displacement,number of loading cycles,and normal stress.Under the same loading condition,greater the normal stress resulted in larger compression.On the other hand,the compression of the masonry joints decreased with the increase in mortar strength.(3)Mechanical prediction models for shear strength and shear stiffness for the stone masonry joints were proposed based on experimental and theoretical study.A simplified multi-linear(non-linear four-line)hysteretic restoring model for shear stress versus shear displacement was established.The mechanical prediction models proposed can be conveniently to estimate the three stages of the vertical deformation of the joints.Formulations to estimate the equivalent vertical stiffness is also developed.The proposed prediction models were verified and validated against the experimental results.Therefore,the proposed models found to be contributed for a better understanding of the seismic performance of stone masonry structures specifically the stone masonry joints.(4)A finite-element(FE)model for stone masonry structures was established using the micro-scale modelling technique.The proposed multi-linear hysteretic restoring model for shear stress versus shear displacement for the stone masonry joints was adopted in the FE model.The proposed modelling technique was validated with the experimental results and it was found to be effective in estimating the lateral load behavior of masonry structures.Therefore,the proposed numerical modelling technique can provide a basis for the seismic-performance assessment of stone masonry structures.