Study On Rotational Deformation And Lateral Stiffness Of Masonry Wall Under Low Cyclic Recurrent Loading

Masonry structure is widely used and retained at this stage.With the innovation of wall materials and the development of construction technology,there is still a large application space for masonry structure.The seismic performance of masonry structures is relatively poor because of the brittleness of masonry materials.Therefore,there is a long way to go in the study of seismic reduction of masonry structures.The non-rotation assumption adopted in the traditional calculation model of lateral stiffness of masonry wall is not consistent with the failure mode of wall in structural earthquake damage.The traditional elastic lateral stiffness considering only flexural and shear deformation in elastic stage cannot truly reflect the effect of wall rotation in elastic-plastic stage.The experimental analysis based on phenomenology is an important technical way to study the rotational deformation of masonry walls.The following work is carried out on the rotational deformation of masonry walls:Based on the investigation of masonry structure,eleven kinds of combinations facade shape of masonry wall with "rectangle","convex" and "L" as basic shapes were summarized,and the basic shapes are used to guide the selection of test specimens.Seven full-scale masonry walls quasi-static test were completed in two batches,in which two rectangular walls were composed of two different height-width ratio cases,and three convex walls were composed of three kinds of constraints of spandrel wall,and two pieces of L-shaped wall were composed of two kinds of constraints of spandrel wall.Based on the basic experimental data,i.e.test phenomenon,hysteresis curves,skeleton curves,ductility and energy consumption indicators,the seismic performance of the test wall was analyzed.From the point of view of theoretical analysis,the possible rotational deformation shapes of masonry walls in shape of rectangular,convex and L-shaped were qualitatively predicted and analyzed,and the correctness of the qualitative prediction analysis was verified by comparing with the rotational deformation shapes in experimental phenomena.An inequality for predicting the relative position of initial horizontal cracks in masonry walls is presented to predict the rotational deformation shape of the walls.Based on the deterioration law of lateral stiffness of walls,the rotation of masonry walls is quantitatively analyzed.The degradation of lateral stiffness after wall cracking is attributed to the occurrence of rotational deformation,and lateral stiffness degradation after wall cracking is defined as equivalent rotational deformation stiffness degradation.The lateral stiffness degradation corresponding to the displacement angle limit of multi-stage seismic performance target is used to evaluate the degree of equivalent rotational deformation stiffness degradation.Through cross-comparison and analysis of pseudo-static test data of seven masonry walls,the difference of degradation degree of equivalent rotational deformation stiffness caused by four factors,i.e.heightwidth ratio,elevation shape,restraint condition and horizontal force direction,is discussed.