| ABSTRACT:The Bridge Erection Machine is a special construction machinery which can hoist prefabricated reinforced concrete beam on the bridge bearing. The failure or accident of bridge erection machine will cause casualties and huge economic loss, even catastrophic consequences. The girder is one of the most important bearing parts and then its safety is particularly vital; therefore, it has a great practical significance to identify the structural damage of the girder.The judging process of structural damage is analyzed. The security factor subset is built; the definition, formula and judgment are described in detail and the beam model as an example, the security factors are carried on applicability analysis, and then the security factors more suitable for beam structure are found.Cuckoo search algorithm is introduced and improved from the dynamic discovery probability, the step length and the levy flight, and the improved cuckoo search algorithm has a faster convergence speed and a higher precision. And on this basis the cooperative cuckoo search algorithm suitable for high dimensional functions is developed. Then the damage identification is formulated as a constrained optimization problem, and the combination of natural frequency and modal strain energy are used to establish the objective function, which can be identified by the improved cuckoo search algorithm. The simulation results show that the improved cuckoo search algorithm can better identify the damage of structure.The kernel fuzzy means clustering algorithm and the relevance vector machine based on multi-wavelet kernel are presented respectively to establish a damage identification model for the girder of bridge erection machine. The safety factors such as modal strain energy, frequency variation, and the derivative of acceleration are the input vector, the single damage and damages samples were used to identify the damage under noise and without noise, thus illustrating its high accuracy and rapid speed through the simulation results.The large analysis software ANSYS is used to establish the finite element model of girder and its meshing is performed, the aforementioned security factors are used to simulate different damage conditions and analyze them, thus the security factors suitable for the girder are acquired, which can provide a theoretical basis for safety monitoring of large construction machinery. The damage experiments are conducted for the main girder, the rectangular beam is used to simulate the main girder, and then the stiffness tests; the modal tests and the dynamic load tests are finished respectively, the test results and the simulation ones are almost unanimous. |
