Experimental And Numerical Research Of Durability Of FRP-high Strength Concrete Joints Under Aggressive Exposure Conditions And Sustained Loads

With the rapid development of the economy of China, there are more and more coastal and offshore constructions, such as harbor, wharf, cross-sea bridge and subsea tunnel, are build. But many of these reinforced concrete structures have been corroded badly under the aggressive marine environment, especially in the northern China. The aggressive conditions include freeze-thaw cycle, wet-dry cycle, corrosion by chlorine ion, etc. Compared with constructing a new bridge or harbor after demolishing the broken one, rehabilitating and strengthening cost less funds, energy resources and is more environmentally friendly. As a light-weight and high-strength polymer material with outstanding durability, carbon fiber reinforced polymer/plastic(CFRP) is extremely suitable for strengthening of structures in marine environment. Because of the small porosity, the freeze-thaw durability of high strength concrete is much better than common concrete. It has been widely used in wharf, shipyard, seawall and cross-sea bridge. However, the strength of the concrete used in previous research on the durability of FRP-concrete joint was mostly about 35 to 45MPa. The durability design of high strength conrete structure strengthened by FRP hasn't any experimental basis. So durability research of FRP-high strength concrete is needed for the long-term use of coastal and offshore constructions.Supported by National Natural Science Foundation of China, this paper conduct following researches:1) the change of ultimate load, load-global slip curve, etc. of CFRP-high strength concrete interface under freeze-thaw cycle and sustained load; 2) the change of ultimate load, load-global slip curve, etc. of CFRP-high strength concrete interface under freeze-thaw, wet-dry cycle and sustained load; 3) study the debonding behavior of CFRP-high strength concrete interface after degradation by finite element software.The experimental data shows that the durability of CFRP-high strength concrete is much better than CFRP-common concrete. Neither 450 freeze-thaw cycles nor 300 freeze-thaw cycles combined with 120 wet-dry cycles caused evident degradation. But the load end of the interface debonded under sustained load. A finite element model was built, which can simulate the direct shear test well. The depersion degree of ultimate load and effective adhesive length from the simulation is much smaller than that from experiment. Besides, the trend of the ultimate global slip, whose accurate value is difficult to measure in experiment, is very distinct.