Study On Seismic Performance Of Masonry Structure Strengthened By Reinforced Concrete Beam And Column

After the Tangshan Earthquake (1976), a large number of masonry buildings in Beijing and Tianjin were strengthened by reinforced concrete beam and column to improve their seismic performance and those building are still widely existed and used nowadays. However, the real seismic performance of those houses cannot be estimated accurately. So it is necessary to study the seismic performance of masonry structure strengthened by ring-beam and constructional column.According to the Codes, a full size model of masonry structure of two-floor and single bar was designed. And the model was built using fired common brick and hand mixing mortar. After the model was finished, it was strengthened by ring-beam and column, using the strengthened method in Code. During the construction, material performances, such as concrete compressive strengthen, fired common compressive strengthen, mortar compressive strengthen and masonry compressive strengthen, were tested to ensure the material performance can meet the codes.In order to know the seismic performance better, the dynamic characteristics was tested, including the period, modal and damping ratio. And the hammer method was used to test the dynamic characteristics. To verify the result of test, ANSYS was used to analyze the modals of this structure.Pseudo-dynamic testing was used to study the response time histories of displacement, velocity, acceleration and resilience of the strengthened model in7degree rare earthquake. Besides, strain of steel was collected in the test. Result shows that the earthquake resistant behavior is fine because vibration of the structure is quite gentle and no visible cracking was found after the testing. The door opening and the window opening, which are often destroyed severely, perform well because of the constraint of ring-beam and constructional column. Besides, time-history analysis was carried, using ANSYS, to study the seismic performance.After the pseudo dynamic testing, pseudo static testing was conducted to study the ultimate bearing capacity, the ultimate displacement and the cracking process. The rigidity degeneration is obvious in the testing. At the end of the testing, the brick wall quit job and the load was born by ring-beam and column, and the rigidity degeneration was quite gentle. Fractures are mainly near the door or window hole of the longitude wall and the beam-column joints. After the testing quite wide fractures appeared, but there were no wall collapse. It means that the integrality of the structure is fine and the ring-beam and column constraint the structure well.