Seismic Performance of Hybrid R/C Columns Laterally Confined by Carbon Fiber Reinforcing Plastic Tube Which Has the Dual Function of Stay-in-place Formwork and Transverse Reinforcement

摘要

This paper summarizes test results and discusses the earthquake-resisting performance, such as lateral strength, ductility and energy absorption capacity, of R/C columns laterally confined by carbon fiber reinforcing plastic tube, namely CFRP tube. The CFRP tubes have the dual function of stay-in-place formwork and transverse reinforcement. In addition to above dual function, CFRP tube is light and is hardly likely to corrode, namely its durability is superior. As the transverse bending stiffness of the wall of CFRP square tube is likely to be lack, it must be examine that transverse expansion or deflection happen or do not due to lateral pressure by fresh concrete under construction of test specimens. However, circular CFRP tubes are not concerned with its problem. Although CFRP tubes are not structural members by themselves, they will turn into important seismic resistance member by the combination of CFRP tubes and conventional R/C columns.Total four column specimens are provided and their column sections are square type only. The specimens whose sizes are 250 mm square and 1000 mm height are about one-third or half scale model. Therefore, shear span to depth ratio is 2.0. Concrete cylinder strength is about 32 MPa and longitudinal reinforcement ratio, namely, ratio of total area of longitudinal reinforcement to gross area of section in columns is 2.44% which is close to the upper limit. These R/C column specimens were tested under the combination of cyclic lateral forces and constant axial load in order to investigate their seismic behavior.As a result of this study, the advantages of the CFRP tubes were recognized. Therefore, if the cost of the CFRP tube will be degraded in the near future, this proposed method will be widely accepted in the field of hybrid concrete structures.