Study On Seismic Performance And Post-Earthquake Retrofitting Technology Of Stone Masonry Walls

Stone masonry structures are the commonly and widely distributed building typologies specifically in the rural areas of Southeast China.In most of the stone buildings,all the structural members were of granitic stone,rendering the structures more vulnerable under earthquakes.Thus,it is of great theoretical and social significance to carry out investigations on the earthquake-disaster prevention theory and strengthening options of stone masonry buildings.Experimental investigations and theoretical analysis were conducted in this thesis,focusing mainly on understanding the shear behavior of stone masonry-walls constructed with different construction methods,followed by the assessment of the seismic performance of stone masonry-walls with openings,and the corresponding strengthening techniques to enhance the shear behavior were studied.The primary research contents and conclusions are summarized as follows:(1)A total of fifty stone masonry double-shear specimens with different construction methods were tested under combined vertical compression and horizontal monotonic loading,to investigate the shear behavior of the bed joints.Three different construction methods were involved in the test program,i.e.,dry laid stone masonry with coarse blocks,wet laid stone masonry with coarse blocks,and dry laid stone masonry with machine-cut blocks.The influence of construction method on the shear mechanism,failure mode,and shear stress-displacement relationship of stone masonry were studied.Based on the experimental and theoretical results,empirical expressions to predict the shear strength of stone masonry with different construction methods were proposed.(2)Pseudo-static tests were carried out on five dry laid stone masonry-wall specimens.The influence of vertical compression and opening arrangement on the failure mode,shear strength and seismic performance of the specimens were investigated.From the experimental results it was found that the failure of the stone masonry-wall was dominated by X-shaped diagonal stepped cracks.The hysteretic curve of the intact stone masonry wall showed a plump shape while those of the walls with opening showed remarkable pinching.The strength,stiffness and energy dissipation of the stone masonry-walls with opening were significantly lower than those of the intact stone masonry-wall.(3)Subsequently,to evaluate the strengthening options twenty-one stone masonry specimens with embedded polymer mortar into the bed joints were tested using double shear method.Test results showed that,the proposed strengthening technique effectively enhanced the shear strength and deformation capacity of thestone masonry-wall.The maximum strength and the corresponding deformation of the specimens with polymer mortar was found to be about 39.3% and 96.8% higher than those of the control specimens.Theoretical expressions to estimate the shear strength of stone masonry walls with embedded polymer mortar into the joints was proposed based on the double shear test results.(4)Further,the seismic performance of four strengthened stone masonry-wall specimens,which were previously damaged were tested to evaluate the effectiveness of embedding polymer mortar into the joints.Test results showed that the strengthened specimens observed a shear strength close to that of the undamaged ones,while the ultimate deformation capacity of the strengthened specimens was increased by about 16% compared to that of the undamaged specimen.The adopted strengthening technique was found to be easy to handle and suitable for the immediate strengthening of stone masonry-walls in the aftermath of earthquakes.(5)Based on the experimental results on the shear behavior of bed joints and seismic performance of the stone masonry-walls,the shear failure mechanism and shear strength of the bed joints and the stone masonry-walls were analyzed.Furthermore,empirical expressions were proposed for predicting the shear strength of stone masonry-walls with different construction methods and opening types.(6)On the basis of test results,a three-stage skeleton-curve model and hysteretic rules for the dry laid stone masonry-walls were proposed and a restoring force model was established.