Study On Design Strategy About The Seicmic Retrofitting Of RC Columns Using FRP Jackets

As a new type of retrofitting materials, fiber reinforced polymer (FRP) has a number of advantages, including:superior to corrosion, ease of installation, high strength to weight ratio, low manpower, virtually unnoticeable after installation, etc. It is confirmed by test results that FRP jackets could effectively increase the ductility of RC columns. In the current design of fiber reinforced most use overall volume-stirrup ratio to control the ductility of column design. However, the working mechanism and failure mode of fiber hoop winding the plastic hinge zone of column is very different from the Stirrup Densification area.The development of this design theory is seriously lagging behind a lot of test work completed.In this paper, study on seismic behavior of FRP strengthened concrete columns and its influencing factors such as species and amount of FRP,Section types of column,concrete strength grade, by the numerical simulation technique using detailed three-dimensional solid finite element models which embodies reinforcement details of retrofitted columns, real material properties. The results show that:It can significantly improve the Seismic Capacity of structures by hoping FRP; Ductility of reinforced columns is decided by concrete strength grade and stirrup ratio, and they have little effect on the ductility of FRP reinforced columns. Ductility of FRP reinforced columns is decided by the amount of FRP; FRP wraping the column plastic hinge zones can effectively improve the seismic performance, close to wrap the full column; The seismic reinforcement effect of FRP wrapped column, circular column and AFRP wrapped column is best, rectangular and CFRP is second. And for the rectangular column, with the aspect ratio increases, the worse effect of seismic reinforcement.Based on these theoretic results and a large test database assembled from an extensive survey of existing studies, detailed analysis the seicmic working mechanism and the factors, different with the purity steel hoop, of FRP jacket RC columns. A analytical model used for predicting the ductile deformation capacity of RC columns retrofitted by FRP jackets is presented, and a design equation is built by regression analysis using the large test database. Proved through the test data calculation, this design equation is more accuracy than the existing formula, and can more accurately reflect the actual ductility. To provide a theoretical basis for revise the relevant provisions of corresponding provisions of china code, and has important reference value of actual seismic retrofit project.