Nonlinear Dynamics Analysis For Cracked Beams With Considering The Effect Of Reinforced Constraints

The crack damage of beam even if the surface crack is difficult to detected withoutcertain load action in most cases. In recent years, the structural damage identificationmethod based on dynamic test technology is widespreadly concerned in theengineering circles. The dynamic characteristics of the beam will change with thecrack damage propagation. In order to gain accurate dynamic parameters of theinverse problem it is necessary to study the effect of crack parameters on dynamicscharacteristics of the beam,which conduce to provide the theoretical basis andfoundation for online detection and safety assessment of engineering structureperformance.Reinforced concrete beam is composed by the two kinds of materials, steel andconcrete, Of which the mechanical properties is different from the components of asingle material medium. Crack of reinforced concrete beam subject to the constraintsof ordinary rebars is not exactly the same as free open crack model in the plainconcrete beam in the service process, which leads to the linear and nonlinear dynamiccharacteristics change of the cracked beam.The main research work covers thefollowing aspects:Chapter1: The research background, research status, research significance andresearch methods of cracked beam dynamics analysis is introducted.Chapter2: Based on the relationship between flexibility rate and crack stressintensity factor, the cracked concrete beam model considering the effect of reinforcedconstraints is established.The characteristic equation of a simple supported crackedbeam is acquired. Considering reinforced constraints effect or not, the former threenatural frequencies with varitious crack depth and position are investigated. Thenumerical analysis shows that the natural frequencies of cracked concrete beamincreases,compared with the case ignoring effects of reinforced constraints and thenatural frequency varies with the crack depth and position.Chapter3: Using nonlinear elasticity mechanics and fracture mechanics theory,and considering the effect of reinforced constraints, the motion equation of crackedbeam is obtained by the energy method. The equation is analyzed using the harmonicanalysis method,and the effect of crack depth, crack location and reinforcedconstraints on the amplitude-frequency response of non-linear free and forcedvibration is discussed. Chapter4: Considering the effect of reinforced constraints, the dynamic responseof cracked beam is solved using the Runge-Kutta method. The linear and nonlinearvibration discipline of cracked beam under a rectangular pulse load is comparativelyanalyzed by the account case. The effect of structural damping, crack parameters, andreinforced constraints on nonlinear dynamic response under the rectangular pulse loadis researched by numerical calculation.The final: The conclusion of this paper is summarized, and dynamics researchtrend of cracked beam considering reinforced constraints effect is introduced.