Concrete and Fiber-Reinforced Concrete in a Cage Made of Polymers Reinforced with Fibers

Experimental studies have shown that in steel pipes filled with concrete, there is a rather weak coupling between the concrete and the cage. This is due to the significant difference in the Poisson ratio of steel and concrete, which causes the concrete to separate from the pipe when both materials experience longitudinal deformation, as well as the fact that the shrinkage of the concrete leads to delamination at the contact boundary of the two materials under any loading. As a result, pipe-concrete elements may fail due to steel yield or concrete crushing. This disadvantage is overcome by the use of polymers reinforced with fibers (FRP), that is, the device of a fiberglass or carbon-plastic cage. Increasing the strength of concrete is achieved by fiber reinforcement (glass, carbon or other fibers). Cage out of FRP exhibits elastic properties up to the failure. An overview of the results of experimental studies of concrete specimens FRP cage, including the experiments conducted by the author. The stress and strain formulas based on them can be used to reliability the estimate of the designed structures.