The Fatigue Behaviour Of Crane RC Beams Strengthed By CFRP

The capability of many structures are influenced as for the service time become longer and the function of the structures changed, which need to be strengthened in order to meet the further use requirement. Strengthened with Carbon Fiber Reinforced Polymer laminate (CFRP)as a new way for strengthen, is widely used today. And the specifications for design had given in order to popularize this technology, but with a deficiency of no rules for fatigue strength as for the few research results. In this article, we discuss the detail of the fatigue design for structure strengthened with CFRP.For study, one control beam and three CFRP strengthened beams were tested under fatigue condition with the test parameters of strengthen degree and load level on the beams. During the tests, the strain of the steel, concrete, CFRP and deflection of beams were surveyed by DH3818 after certain cycles as the load was increase, and the dynamic data were collected by DHDAS when fatigue load processing. So we can realize the mechanical performance of the beams during its whole life.The change of the beam's stiffness can reflect the work ability of the beam. Based on the technical specification for strengthening structures with CFRP and correlative conclusion got from other studies and tests, the flexural stiffness of the damaged crane beam were calculated ,and the change of the stiffness during the fatigue cycle were analyzed as the parameter of cycle time.The service life is an another important field which attract many attention in engineering. Based on the test results, the fatigue life of the damaged crane beam was analyzed from the stress of the steel and the residual stiffness of the beams. The S-N curves of steel in the test and some other similar tests were got by regressive analysis. And the declining curve of stiffness and criterion for judge the damage degree of the beam were also gained in the article.The study demonstrates the feasibility of using unidirectional CFRP fabric in the rehabilitation and strengthening of RC structures with respect to fatigue performance. The main results obtained from the tests are: the stress of steel is limited, the stiffness is heightened, and the performance of beam is improved.