| Fiber reinforced polymers (FRP) is a new building material, which has been used wildly in strengthening concrete structures due to its high strength, light weight, convenient construction. At present, the researches and the applications have been mature in America and Japan. In China, the study of FRP has been developed since the end of last century, and the technology of strengthening concrete structures with bonding exterior FRP is the focus of study. In this paper, combined with the key program 'Research on the application of new technologies and new methods in strengthening bridge structures' in Liao Ning province, a series of tests about the basic theories and long time behavior of FRP strengthening concrete structures have been completed, and many conclusions have been obtained.1. Experiments on uniaxial tensile of CFRP and GFRP are carried out, in which the tensile strength, Young's modulus and ultimate deflection of FRP are measured. The influence on tensile behavior caused by different adhesives is analyzed, and the standardization problem on tensile test methods is discussed.2. Based on 123 specimens results of the shear bond test of FRP and concrete, the failure characteristics of bond test are described, and the relationship of bond strength and bond slip is discussed. The calculation formula of bond strength of FRP and concrete is established according to experiment results and former conclusions, and the comparison is carried out among calculated results, test results, and results from other formula.3. Based on the bond test for 33 concrete specimens and GFRP and bending test for 15 beams strengthening with GFRP, surface preparation of concrete, type of epoxy adhesives, thickness of adhesives, hardening time of adhesives, cure condition after strengthening are considered, and the effect on concrete structures strengthening with GFRP causing by construction behavior was analyzed.4. Based on the fast freeze-thaw test, the alkaline test, the water immersion test and the wet-thermal test of FRP, the influence on FRP mechanics behavior caused by aggressive environments are studied, and the causes of degradation of FRP behavior are simply analyzed.5. These problems that the influence of bond behavior among FRP layers caused by the freeze-thaw action, and bond behavior between FRP and concrete experienced freeze-thaw-III-action are studied by test. In addition, the influence on integral structures by freeze-thawaction and wet-thermal condition is considered.6. The creep behavior of carbon fiber reinforced polymers is studied, and the regularity between time and creep deflection is analyzed. Creep model is established by statistic analysis, as well as the influence on engineering practice and prestressing bonding FRP technique induced by creep behavior of CFRP is analyzed.
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