Research On Seismic Behavior Of Rough Block Stone Masonry Strengthened Using External Prestressing Technique

Stone is an abundant specialty in coastal southeast of China, especially in Fujian Province, so the country buildings are mostly stone structures in these areas, with strong architectural features and long history. However, it was discovered by survey that few circle beams and constructional columns were adopted, leading to poor seismic capacity of these buildings, which may suffer great damages under strong earthquake. This paper carried out the test of seismic performance on rough block stone masonry walls with external prestressing reinforcement, in order to find suitable methods to improve the seismic capacity of these buildings.Low cyclic loading tests were carried out with seven specimens with external prestressing to investigate the seismic performance of rough block stone masonry wall. For example the loading process, the failure model, the shear strength, hysteresis curves, skeleton curves, deformation capacity, energy dissipation capacity, stiffness degradation rule, etc. The main parameters are external prestressing, reinforcement position and window. The results show that:the failure of the rough stone masonry walls with external prestressing could be divided into three phases, namely elastic stage, adhesion disappearing stage and friction energy consuming stage; Prestressing force not only greatly improve the cracking loads and the ultimate loads of the walls, but also improve their behavior of deformation, ductility and energy consumption evidently, The cracking load and ultimate load of the wall increase with the increasing of the external prestressing force, the external prestressing has changed the destruction form of the wall and the fracture spacing, so that the cracks more uniform and the stone masonry wall has many cracks but do not collapse; the hysteretic behavior and energy dissipation capacity increase first and then decrease with the increasing of the external prestressing force, and reached the maximum under the effect of external prestressing of 0.3MPa;Prestressed reinforcement can delay the wall stiffness degradation, playing the role "two line of defense" of the wall; Compared with external prestressing reinforcement arranged on both ends of the wall and the middle, prestressed reinforcement all arranged on the ends of the wall can increase the cracking load of the wall, but will reduce the ultimate load and the seismic performance of hysteretic behavior, deformation capacity, energy dissipation capacity; window to wall overall performance and seismic performance weakened very obvious. In the actual structure should try to avoid opening a window.According to the test and theoretical analysis, the shear strength formula of rough block stone masonry wall with external prestressing is put forward. The formula can realize smooth transition between rough block stone masonry wall with external prestressing and rough block stone masonry wall without external prestressing, so the formula not only can be used for calculating the shear strength formula of rough block stone masonry wall with external prestressing, but also can be used for calculating the shear strength formula of rough block stone masonry wall without external prestressing.Through the calculate of the typical structure, you can see that in seismic design, The seismic bearing capacity of the structure is ok without any measures when the earthquake fortification intensity is under seven degrees (0.10 g); The seismic bearing capacity of the structure is ok with 0.2MPa external prestressing when the earthquake fortification intensity is eight degrees (0.20 g) and the seismic bearing capacity of the structure is ok with 0.3MPa external prestressing when the earthquake fortification intensity is eight degrees (0.30 g). The seismic bearing capacity of the structure is ok with 0.2MPa external prestressing reinforcement arranged on both ends of the wall and the middle in coastal southeast of China.Combined with the construction experiences and research present situation, This paper summarizes some suggestions of designing and constructing the rough stone masonry structure with external prestressing, which can be used as a reference for masonry structure with external prestressing design and construction and stone structure reinforcement.