Study On The Scismic Evaluation Of Masonry Structures In Rural Areas Based On Push-over

Masonry structure is widely used in our country because of the population,land,economic development and other restrictions,especially has been widely applied in the construction of villages and towns in the countryside.The research shows that,most of the rural masonry structure can not meet the requirements for seismic resistance.The secondary disasters such as houses collapsed have far more serious under seismic action,and the masonry structure has become the most common form of the damaged structures.Therefore,it has practical significance to analyze the seismic response characteristics and evaluate the bearing capacity of masonry structure,which could reduce the damage and ensure the safety of life and property.Study of seismic analysis based on the performance is the mainstream ideology in the field of earthquake engineering.It is widely used in engineering practice of the frame structure,reinforced concrete structure and high-rise building,and the study on seismic behavior of masonry structure is relatively less.In this paper,a three-dimensional finite element model of masonry structure was established through ABAQUS analysis software.Then the seismic response of structural damage,crack distribution and load displacement curve under seismic action were obtained based on Push-over analysis method.Furthermore,the seismic performance of the structure was evaluated based on the story drift by combining the capacity spectrum method.The main conclusions can be drawn as follows:(1)In this paper,the loading mode of Push-over analysis method is the inverted triangular distribution pattern.Push-over analysis is an important means for the evaluation of the seismic performance of buildings,and the loading model has great influence on the calculation results.Research shows that,the masonry structure focuses on the first mode of vibrationunder under the action of earthquake,and the effect by the high modes can be neglected.Compared with the present level of load patterns,the inverted triangular distribution pattern can be applicated well in the seismic response analysis whose first mode of vibration is dominant.It also can approximate inertial envelope the actual distribution of the force along the height of structure during earthquake.(2)Putting forward the criteria for the classification of the masonry structure seismic performance levels.By summing up the damage characteristics and damage mechanism of masonry structure in rural areas,we can konw that the masonry structure building materials are brittle with poor connection,so it is easy to be damaged in the complex stress and insecure connection parts.According to code for seismic design of buildings at home and abroad,combined with existing research results,based on the analysis of damage of the masonry structure,the level of performance of masonry structure is divided into normal,moderate damage,safety gear.Using the drift angle as the quantitative index for seismic evaluation,and the performance of inter story displacement angle are given.(3)Determining the static elastic plastic analysis model of masonry structure.Compared with the present masonry structure elastic-plastic model and combined with the characteristics of the masonry structure to determine the finite element model the structure of material constitutive relation.According to the ABAQUS analysis software to test the masonry walls by Push-over analysis method,based on the test data of existing masonry walls,and use the finite element model,material constitutive relationship and horizontal loading pattern in this paper.Simulating the crack distribution,ultimate load and displacement,the viscous damping coefficient and the stiffness value of feature points of the masonry wall,then calculated the error between finite element analysis and experimental results to prove the accuracy and reliability of this analysis model.(4)Estimating the seismic performance of masonry structure in rural housing assessment.Using ABAQUS analysis software to establish the finite element model of masonry buildings in rural areas,analysis on seismic performance with Push-over method based on the material constitutive model and the lateral load pattern.The analysis of structural damage shows that,the injury of longitudinal wall is greater than that with cross wall under the earthquake;the underlying structure damage is greater than the upper because of the low strength grade of the mortar.The crack distribution shows that,cracks are mainly concentrated in the stairwell and the walls with the stress concentration,and the crack is similar to X due to lack of struts structure measures;at the same time,since the longitudinal wall openings for "weak shear wall,the wall between windows" failure is obvious.When the main load-bearing components are transverse wall,the maximum inter story displacement angle is 1/501,the structure will not collapse;and when the main load-bearing components are longitudinal walls,the maximum inter story displacement angle is 1/223,collapse occurs and the structural does not satisfy seismic fortification requirements.(5)Analysing the influence of structural material parameters and seismic measures on the structural seismic performance.Based on the evaluation results of the seismic performance,combined with the seismic damage of masonry structure mechanism,use the above model as the initial model to compare the difference between different models with different strength grade of the mortar and different parameters setting method.The results show that,when the mortar strength grade is increased from M7.5 to M10,the ultimate damage will decrease by 2.1%;the maximum story drift angle under the basic fortification intensity earthquake and rare earthquake will decrease by 24.2%and 30.5%,the structure will not initiate collapse.When the beam is set up,the degree of structural damage will decrease by 10.9%;the maximum story drift angle under the basic fortification intensity earthquake and rare earthquake will decrease by 30%and 45.1%,the seismic capacity will be significantly higher than before.When the mortar strength grade is increased and the beam is set up,the structural damage degree will decrease by 17.4%,and the maximum story drift angle under the basic fortification intensity earthquake and rare earthquake will decrease by 45.7%and 63.2%,the structure will have a good stability which can meet the seismic requirements.It turns out that it is significant to improve the seismic capacity of masonry structure by lifting the strength mortar grade and setting the ring beam.