Research On The Seismic Performance Of Masonry Structure Strengthened With External Precast Ring Beams And Constructional Columns

Masonry structure is widely used in our country especially in rural areas due to its convenience in achieving material, simplicity in construction and low cost. The compressive strength of masonry structure is very high while its tensile and shear strength is rather low. At the same time, many of the masonry structures lack seismic precautions, leading to serious damage in earthquake and causing great loss of property and lives. There are a large number of masonry buildings in our country, so it is not appropriate to remove all these buildings and rebuild them. Only by the seismic strengthening can these buildings avoid great damage in the future earthquakes. Researches have indicated that the integrity and seismic performance of masonry structure strengthened with external ring beams and constructional beams is significantly improved. However, this method requires formwork and the pouring of concrete, leading to the complexity of construction, a large quantity of wet operations and long construction period. In view of this matter, a new method of using external precast columns and beams for masonry structure strengthening is proposed. Constructional columns and ring beams can be prefabricated in factories, then transported to the construction site, assembled and then tied to walls by bonding material. As a result, the construction speed becomes fast and the construction time is shortened. A series of researches on this new technology are conducted and the main research works and achievements are as follows:(1) Based on the principle of convenience and fast in construction, the technology of using external precast constructional columns and ring beams for masonry structure strengthening is proposed, including the connection between precast members, the connection between precast members and walls and the construction process.(2) The strengthening effect is studied by ABAQUS. Firstly, the proper analysis method of masonry structure by ABAQUS is sought through checking literature and proved by experimental results. Secondly, five 4-storey models are created, including two unreinforced models and three reinforced models, to make modal analysis and elasto-plastic time history analysis. Modal analysis shows that the vibration mode of reinforced models is corresponding to unreinforced models, but longitudinal and transverse stiffness of reinforced models are increased. Elasto-plastic time history analysis shows that the deformation of reinforced models is decreased while the shear force of walls in reinforced models does not change apparently. The main function of ring beams and constructional columns is to confine the deformation of masonry walls, especially the walls of first floor.(3) Eight buildings are selected to be strengthened with precast ring beams and constructional columns in order to examine the practicability of the new proposed technology. Through the pilot project, it is proved that the proposed technology is feasible and satisfies the basic requirements. At last some problems and suggestions are raised according to the pilot project.