Abstract: To develop an effective software for finite element (FE) model updating of bridges, the interface technology between VC++ and MATLAB was investigated firstly, and then a software for updating FE model of bridges, named Doctor for Bridges (version 1.0) was developed. Finally, a model ofconcrete-filled steel tube arch bridge was applied to verify the performance and effectiveness of the proposed software.
Abstract: The structural reliability analysis is the widely accepted method for bridge safety assessment. Identification the subset of significant failure modes is the most important part of system reliability estimation. In this paper, a stage critical strength branch and bound algorithm is proposed for the failure mode identification of bridge systems. The innovative method is implemented in the combination with the finite element package ANSYS and the MATLAB procedure. The suggest method is applied to a concrete filled steel tubular (CFST) arch bridges. The results reveal various combinations of the failure modes in significantly reduced time and efforts in comparison to the previous permutation method. Additionally, the suggested method can be used for the verification of the system reliability with more specific predictions of the failure mode.
Abstract: For long span arch bridges, the traveling wave effect is an important aspect on seismic response of structure which cannot ignore. The Big Mass Method was used to analyze the seismic response of a half-through CFST arch bridge under both uniform and non-uniform excitations. The results showed that the traveling wave effect caused by non-uniform excitation led to more obvious seismic response in both internal forces and displacements. The skewback section was most dangerous. The waveform of internal forces caused by non-uniform excitation was quite similar to that caused by uniform excitation, but the amplitude of the latter is bigger than the former. It can conclude that the traveling wave effect would cause the unsynchronized vibration to the structure elements which led to the lager responses.
Abstract: Field measurement was conducted on the evaluation of dynamic amplification factors (DAF) for four existing T-girder bridges. Both ambient vibration testing and vehicle impact testing were carried out on the bridges. Ambient vibration testing is relatively easier to conduct and can provide detailed vibrating information of the structure. However vehicle impact testing is indispensable to obtain the impact factor of the traffic load. The measured vibration frequencies matched well to those of calculated values. This means that the finite element model may enable good predictions of the actual behavior of the bridge. The measured DAF for these bridges located in the interval [1.05, 1.22].
Abstract: Based on the characteristics of existing structures, the analyses were presented for an effect on the resistance of existing structures by using deterministic loads and stochastic loads. The calculating equations of the normal distribution and logarithmic normal distribution resistance under the deterministic proof load and the stochastic proof load were presented. Some valuable conclusions have been obtained for the calculating reliability of the existing structures. Based on the conclusions, time-dependent reliability model of the existing bridges was updated, the time-dependent reliability indices were solved with time integrated-discretized approach, and finally the numerical examples were presented.
Abstract: A novel stabilization diagram method was presented for sensor placement in structural health monitoring of bridges. The aim of the method is to select the optimal locations which can achieve the best identification of modal frequencies and mode shapes. A single parents genetic algorithm was adopted to optimize the sensor locations from a set of coordinate positions. Five fitness functions taken as the objective function are proposed based on effective independence, modal assurance and modal energy criterion, in which the combined fitness functions can obtain more comprehensive properties to reduce the noise interference. The proposed method puts forward a universal way for sensor placement of the civil engineering structure. The effectiveness of the method was proved by a simply supported beam and a continuous beam bridge in the An Longquan interchange overpass.
Abstract: In construction stage, a large buffeting response would endanger construction safety and quality for a long span concrete-filled steel tube (CFST) arch bridge. Developing the study on buffeting security is indispensable to CFST arch bridge in construction stage. Combining random vibration analysis of structure with modern probability theory, taking an actual large span CFST arch bridge as example, dynamic reliability of buffeting responses research and analysis is developed, which is based on the buffeting analysis on time domain at the longest cantilever construction stage. The paper gives quantitative valuation on wind-vibration safety performance of the bridge in construction phase and offers a new thought and reference for homologous project.
Abstract: The vehicle-bridge coupling vibration of girder bridge has been widely investigated. But most of previous work focused on the influencing factor of the vibration, such as traveling speed of vehicle, deck surface roughness and vehicle-bridge frequency ratio etc. Taking the box girder bridges of different span number with 20m single span length for example, applying the separated iterative method to multi-sample analysis the vehicle-bridge coupling vibration. The study considered the influence of the vehicle, traveling speed and the random deck surface roughness and then took the average value of the sample to discuss the influence of the span number on the dynamic responses. Results show that the continuous girder form can effectively decrease the dynamic responses of the equal span girder bridge than the simple-supported form. But the influence of the span number on the responses of equal span continuous girder bridge is not obvious.
Abstract: Based on the nonlinear dynamic time history analysis, a multi-span RC highway bridge with high damping rubber bearings was studied, to investigate the damping ratio and seismic performance of the bridge and high damping rubber bearings compared with the rubber bearings. Results show that the application of high damping rubber bearings can reduce the seismic response of substructures of the bridge under longitudinal and transversal seismic excitations to some extent. But what is more important is that high damping rubber bearings wont suffer shear and displacement failure which may happen on rubber bearings. As a result, the pounding response and residual displacement can be dispelled.