Dynamic Test And Modal Analysis Of Prestressed Reinforced Concrete Truss Beam

Stucture of prestressed reinforced concrete truss is used widely, which mainly is used in transfer stories and tussed beam bridges. At persent, its static is researched more, but the dynamic is involved less. It not only provides some guides about dynamics, but also gives some references for overall detection, evalution and health monitoring. The method of modal test based on the ambient excitation is used widely because that it does not damage the stuctures which are detected, does not break stuctures'service and it uses economically and feasiblely. The method can provide dynamical feature parameters and accurate original data file of structure exactly. The dynamic properties of proscenium beam in multi-function studio of Anhui Broadcast & Television Centre, whose structure is prestressed reinforced concrete truss strucrure, is tested in the method in this paper, some modal parameterso of beam are got by comparetion between experiment modal analysis and calculating modal analysis, the quality of proscenium beam is detected from dynamical perspect and the reference data also can be provided for the health monitoring and damage identification of beam in future.The main contents included as follows:(1) The basic theories of modal analysis are discussed briefly in this thesis. Vibration equation of multi-degree-of-freedom system is given in the case of three different damping, and the process of time frequency transforms of each equation is deduced. In addition, several modal parameter identification methods are introduced. Especially, the principle and method of pick-peaking is discussed in detail.(2) Vibration test of proscenium beam in multi-function studio of Anhui Broadcast & Television is described in detail under ambient excitation. The plane frequency and damping ratio is identified by using the pick-peaking method. Test shows:the relevant parameters can be identified by the pick-peaking; the parameters can be considered as one of the bases of judging the construction quality of proscenium beam.(3) The initial finite element model of proscenium beam is established, and the modal is calibrated in terms of measured data. From comparative results, the right reference value can be provided. The model can simulate the proscenium beam well and measure the construction quality. It will offer some valuable dynamic reference for health monitoring and damage identification research in the future.(4) Looking from the paper, the dynamic test plan, test steps, the method to simplify the finite element model and the modifying methods can all service as guidance for dynamic measurement in the same kind of structures.