Frp Composite Reinforced Concrete Flexural Members Experimental Study Of Bearing Capacity Analysis Of Numerical Simulation

The reinforced concrete (RC) beam has poor anti-crack property---the crack start early at a low load level, expand quickly with load to a troublesome width in the service stage, as a result its rigidity and durability are weakened and spanning ability limited. In order to improve the RC beam's performance, the new FRP composite reinforced concrete beam(called as FRPCRC beam in acronym) based on fracture mechanics according to literature【22】【47】【51】is proposed, which contains ectally bonded anti-crack reinforcing FRP layers as well as embedded steel rebars. Massive tests and studies make it clear that the crack expanding (in depth and width) is effectively constrained in the NFRPCRC beam, the ultimate carrying capacity is promoted to a level times higher than that of the RC beam, the beam's after-cracking rigidity is enhanced obviously in comparison with the RC beam and the failure ductility also improved. For the sake of exploring its anti-crack reinforcing mechanism and simulating its mechanical behavior under load, the NFRPCRC beam is modeled and analyzed with finite elements, which reveals qualitatively a general law that the ectally bonded anti-crack reinforcing layer could effectively reduce the stress intensity factor at the crack tip near the compressive concrete area, in turn take from the crack width and beam deflection. In addition, the FRPCRC beam's carrying-capacity ultimate state is studied with finite elements in combination with tested data.The finite-element analysis on the NFRPCRC beam with artificially introduced cracks shows the ectally bonded reinforcing layer could provide a pair of closing forces for a crack , so dramatically reduce the crack-tip stress intensity factor and the crack width, and cause a much smaller beam deflection than that of a comparing RC beam at the equal load level. Besides, the crack-closing forces increase directly with the thickness of the ectally bonded reinforcing layers of the same material, but contrarily the layer stress decreases with that parameter, which means a bigger thickness would have stronger positive influence on the beam performance. The analysis also tells that, as far as two kinds of reinforcing FRP layers of different materials but with the same axial rigidity are concerned, the layer with a higher elastic modulus works in a sharper stress state than the layer with a lower one while the other geometry, material and load conditions are kept the same, that implies the higher the layer elastic modulus is, the harder the layer works.The core content of the thesis could be summarized as: forming the method of modeling and analyzing the FRPCRC beam as a plane-stress problem with finite elements and giving the judging criterion of the carrying-capacity ultimate state; successfully conducting the numerical simulation of the ultimate state of the FRPCRC beam to get results agreeing well with the tested data and prove the reasonability of the modeling concept and judging rule. The modeling and analyzing method not only provides an effective quantitative way to the exploration of the new structure, but makes a beneficial reference for the simulation of the ultimate state of the conventional RC beams.The experimental and analytic work comes to the conclusion that the FRPCRC beam with hard-steel rebars(without yielding points) has a higher ultimate carrying capacity than those with mild-steel rebars(with yielding points) and corresponds to a higher load level in the same deflection, which is recommended as the optimal scheme in application.