Calculation Method For Dynamic Characteristics And Damage Detection Of The Irregular Continuous Beam Bridge

With the rapid development of transportation and urban construction, the density oftransportation network is increasing. In order to alleviate traffic congestion and enhance thecoordination of transport infrastructure and the surrounding environment, a growing numberof interchanges are applied to the cross-roads. Due to the constraints of topography, linearand space, irregular shaped bridge structures with variable slope, width or curvature areusually set at the connections of the main bridge leading to the ramp line or branch line.Currently, the design theory and method of force characteristics analysis for such bridgestructures is seriously lagging behind its engineering. So far there is no systematic, effectivemethod to calculate the dynamic characteristics and damage identification method.In response to the above issues, based on the continuous box girder bridge project ofChangchun City Fourth Ring Road overpass in the Silicon Valley Avenue T line down0#-4#pier, and combined with Jilin Provincial Communications Department of Science andTechnology Project " Research on the analysis of force characteristics and design methodfor the prestressed concrete bridge(2012-1-7)", the paper carries out the following researchwork in the respects of calculating the dynamic characteristics of continuous beam bridgeand damage recognition.(1) Three finite element models respectively relying on space three-dimensional finiteelement model, grillage finite element model and a single beam finite element model areestablished to calculate the dynamic characteristics of the project. The results based on thedynamic characteristics of the three finite element models are compared.(2) Due to the complexity of the structure and stress state, irregular shaped bridgestructure may need to be modified many times in the design process. If the finite elementmodel is re-established in every modification to calculate the dynamic characteristics, it isbound to greatly consume designers’ energy and reduce design efficiency. In case,perturbation method for solving the dynamic characteristics of the irregular continuous beambridge is presented. Based on the changes in the stiffness and mass matrices of the modifiedstructure and dynamic properties of the reference structure, the dynamic characteristics ofthe modified structure can be calculated by this means. Based on the proposed method, thesensitivity of the design parameters on the dynamic characteristics of the bridge structure is analyzed, and the reasonable proposals are put forward to optimize the design parameters.(3) In order to reduce the workload for computing dynamic characteristics in the designprocess, a dual coordinate free interface modal synthesis method to solve the dynamiccharacteristics of the irregular shaped continuous beam bridge is proposed in this paper. Inthe method, the whole bridge is decomposed into two sub-segment structures as the constantsegment and changeable segment. Based on the several bands of the dynamic characteristicsof the sub-structure and coordination conditions of the interface displacement and force, thedynamic characteristics for the overall structure are calculated. In order to meet therequirements of modifying changeable segment, the method combined of modal synthesisand perturbation method is proposed to solve the dynamic characteristics for the irregularshaped continuous beam bridge. Firstly, the perturbation method is used to solve thedynamic characteristics of the change segment, and then the modal synthesis method is usedto solve dynamic characteristics of the whole structure.(4) During the operational phase of the bridge, sometimes its dynamic characteristicsneed rapid calculation. For this case, the calculation method to solve the irregular continuousbridge dynamic characteristics is proposed based on the idea of segment. By this method, thebridge is divided into several small pieces, and the vibration of each segment is expressed bythe undetermined coefficients. Each undetermined coefficient is solved by the boundaryconditions and constraints, and finally the dynamic characteristics of the overall bridgestructure can be calculated.(5) The model of the continuous irregular shaped beam bridge-vehicle coupled vibrationis established to calculate the bridge dynamic characteristics under the effect of the vehiclewith the modal analysis techniques. And the effects of continuous suspension stiffness, tirestiffness of vehicle parameters and vehicle location on the dynamic characteristics of thebeam bridge under the action of vehicle are explored.(6) Objected to the features of dynamic characteristics of the continuous irregular shapedbridge, structure damage identification method based on the improved particle swarmoptimization RBF neural network is formed and of the applicable structure damageidentification index is proposed. The damage identification method is applied to thenumerical simulation of the project to verify the validity and reliability of the method.