Damage Diagnosis On Vibration Mode Analysis For Reinforce Concrete Beam

The separate finite element model of the reinforce concrete beams (RCB) is established, including: the healthy RCB, RCB with local cast of the concrete, RCB with local hollow in the concrete, RCB with local crack, RCB with local descending of the reinforce steel bar's elasticity modulus, RCB with local looseness of the reinforce steel bar and reinforce concrete and so on. The felting relation about the reinforce steel bar and reinforce concrete is simulated and stiffness matrixes and mass matrixes of every RCB are presented in the model. As a result, the vibration characteristic parameters of the RCBs can be calculated using the model.The numerical value simulation calculation is carried through on the vibration characteristic parameters of the healthy RCB and the RCB with different local damage using the model, including: nature frequency, displacement mode ship, strain mode ship, curvature mode ship and so on. The relation of the vibration characteristic parameters and the local damage occurring, position and extent is studied. The amount relation of the vibration characteristic parameter and the local damage extent is fitted according to different damage forms.Based on the theory of combination beam, the formula of nature frequency is deduced for the free RCB. Based on calculus of variation, the approximate formula of lower rank nature frequencies is deduced for the free RCB with local dilapidation of concrete. The academic formula of the strain frequency response function is deduced for the healthy free RCB and the geometry figure is protracted for the formula.The healthy RCBs and the RCBs with local looseness of reinforce steel bar and reinforce concrete are designed and manufactured. After vibration characteristic parameter being tested for the manufactured healthy RCB, the shared concrete is wiped off from the manufactured healthy RCB and the RCB with local cast of the concrete is received. For simulating the RCB with local crack, one crackle is sawed on the manufactured healthy RCB.The vibration mode ship is tested for the manufactured healthy RCB, the RCB with local cast of the concrete and the RCB with local looseness of reinforce steel bar and reinforce concrete. And vibration characteristic parameters of the RCBs are received. The result of testing, numerical simulation and theoretical calculation is basically uniform and the correctness and reliability are validated.The nature frequency of RCB is the basis that is used to judge whether the local damage happens or not because it will distinctly descend after being damaged. The curvature mode ship and strain mode ship are sensitivity parameters of the local damage position for RCB and their absoluteness diversification can be used for making sure the position of the local damage nicety exactly. The norm of the absoluteness diversification can be used for the local damage ration discrimination in RCB because the relation between it and damage extent is monotone.