Dynamic Performance Of Bridge Research Articles

Static and Dynamic Performance Analysis of Cable-Stayed Bridges with Cables Damaged Fire

Cable-stayed bridges have been widely used in large-span bridge engineering because of their large span capacity and novel structure. The frequent traffic of vehicles transporting flammable and explosive materials has increased the incidence of bridge fires. After being burned, the cable-stayed bridge will suffer from varying degrees of damage, which affects its performance. Therefore, mechanical analysis and evaluation of the fire-damaged cable-stayed bridge are necessary. Due to the development of technology, the structural analysis of cable-stayed bridges has gradually shifted from experimental methods to numerical simulation or artificial intelligence methods, and from local performance research to holistic research. In this paper, a fire accident in the Sifangtai Bridge in Harbin, China, is taken as a case study. Finite element software and damage theory calculation methods were used, and the static and dynamic performances of the bridge under the condition of cable fire damage were analyzed. The results show that the variation of cable force during the movement of vehicle load along the bridge is relatively small, within the range of 7% to 12%. The fusing of the upper cables of the bridge tower has the greatest impact on the deflection of the beam, while the fusing of lower cables has the same impact on the deflection of the entire bridge as the undamaged state. Near the fused cables, cable forces change significantly, increasing by over 20%. As the degree of damage increases, the increase in deflection of the beam becomes more pronounced. The impact of different degrees of cable damage on the dynamic performance of cable-stayed bridges is reflected in quantitative changes. As the degree of cable damage and the amount of fusing increase, the change in structural frequency becomes more pronounced. This paper not only provides technical support and a theoretical basis for the performance analysis of cable-stayed bridges damaged by fire, but it also improves the research content of combining static and dynamic performance, which provides important reference values for similar research in the future.

Advanced Model of Spatiotemporal Mining-Induced Kinematic Excitation for Multiple-Support Bridges Based on the Regional Seismicity Characteristics

In the paper, an advanced model of spatiotemporal mining-induced kinematic excitation (SMIKE) for multiple-support bridges exposed to mining-induced seismicity is proposed. The uniqueness of this model results from the possibility of its application in any region of mining activity, as it is based on empirical regression functions characterizing such regions. In the model, the loss of coherency resulting from the scattering of waves in the heterogeneous ground, the wave-passage effect originating in different arrival times of waves to consecutive supports, and the site-response effect depending on the local soil conditions are taken into account. The loss of coherency of mining-induced seismic waves is obtained by applying a random field generator based on a spatial correlation function to produce time histories of accelerations on consecutive structure supports based on an originally recorded shock. The deterministic approach is used to account for temporal wave variability. The proposed SMIKE model is applied to assess the dynamic performance of a five-span bridge under a mining-induced shock recorded in the Upper Silesian Coal Basin (USCB), Poland. The first model’s parameter (space scale parameter) is identified on the basis of regression curves defined for the USCB region. The estimation of the second parameter (the mean apparent wave passage velocity) is based on discrete experimental data acquired via the vibroseis excitation registered in the in situ experiment. The impact of the model application on the dynamic performance of the bridge is assessed by comparing the dynamic response levels under SMIKE excitations, classic uniform excitations, and the “traveling wave” model—accounting only for the wave passage effect. The influence of wave velocity occurs to be crucial, modifying (either amplifying or reducing, depending on the location of the analyzed point) the dynamic response level up to a factor of two. The introduction of the space scale parameter changes the results by 20% in relation to the outcomes obtained for the “traveling” wave only.

Air void and ring gap effect on CFST arch bridges dynamic performance

Many old concrete-filled steel tube (CFST) arch bridges constructed using common concrete, the fluidity before initial setting and dry shrinkage during use create ring gaps at the interfaces of concrete core column (CCC) and spiral welding tube (SWT), and air voids in CCC. Also, unfavorable conditions of nature increase the number of gaps and voids, create more serious defects, decrease arch rib stiffness, and even change the dynamic properties of the whole bridge structure. Therefore, a finite element analysis (FEA) verified by scale-model experiments on CFST arch bridge rib members with air void and ring gap composite defects was conducted to determine the tangential stiffness of the structure. Secondly, the natural vibration and frequency of the whole bridge were analyzed using tangential stiffness and the influences of various defects on the dynamic performance of bridge was investigated. Therefore, a novel trans-scale determine system was developed for the detection of the tangential stiffness of bridges with composite defects in CFST ribs, so as to evaluate the influences of these defects on the dynamic performance of bridges. This study can provide a strong foundation for the maintenance repair of CFST arch bridges.

Dynamic Load Allowances Corresponding to Different Responses in Various Sections of Highway Bridges to Moving Vehicular Loads

Dynamic load allowance (DLA) is an important index used in design and evaluation of dynamic performance of highway bridges to moving vehicular loads. In many codes, DLAs of different responses in various sections are not distinguished. To facilitate a rational design and objective evaluation, the quantitative relationships of DLAs corresponding to different responses in various sections are systematically studied using both theoretical derivation and numerical simulation. According to results of theoretical derivation, for simply supported girder bridges, DLA of deflection is almost 20% higher than that of bending moment in the mid-span section. According to results of numerical simulation, for continuous girder bridges, DLA of negative (upward) deflection is 20% higher than that of positive deflection, and DLA of negative bending moment is 40% higher than that of positive bending moment in critical cases. These significant differences cannot be ignored. Finally, the contributions of high modes to different dynamic responses in various sections are investigated. Based on the recommended approach to considering these differences, the dynamic performance of bridge can be designed and evaluated in a simple yet rotational way.

Optimal Placement of Wireless Sensor Nodes for Bridge Dynamic Monitoring Based on Improved Particle Swarm Algorithm

The issue of optimal placement of wireless sensor networks (WSNs) is one of the major challenges for dynamic monitoring of bridges. It should be solved based on combining the effective monitoring of the dynamic performance of a bridge with the energy consumption of WSNs. Thus, the relationship between the bridge modal and the energy consumption of wireless networks is derived. Optimizing sensor location is achieved by using the improved wavelet particle swarm algorithm, which overcomes the disadvantage of the conventional particle swarm algorithm by applying mutation operator to the selected particles with certain small probability. Based on the comparison between the ANSYS simulation results and the measured bridge data, as well as the energy distribution diagram of WSNs, the proposed method is shown to reflect the dynamic performance of the test bridge well. Moreover, the method effectively controls the energy consumption of WSNs and achieves reasonable optimization effects. Therefore, this method can be used for dynamic monitoring of wireless sensors in various bridge types.

Coupled Vibration Analysis of Vehicle-Bridge System for Jinsha River Bridge

Numerical simulation model to analyze the coupling vibration between vehicle and bridge established in this paper, upon the engineering background of Jinsha River Bridge. The finite element commercial software, ANSYS, is employed to set up the dynamic analysis model and to compute its natural vibration characteristics. Then CRH3 special refined model is built with SIMPACK, a multi-body dynamics commercial software. Considering the factors like track-rail irregularity, the dynamic performance of bridge and driving comfort level are obtained. The analysis results of coupled vibration demonstrate that bridge bears sufficient stiffness due to its satisfying vibration performance; the safety in operation of vehicle meets the requirement with the comfort index of "good". All the results not only provide reference for design, but also work as the theoretical basis for future design of similar bridges. The paper is deemed a s evidence of the priority of bridge-vehicle model by finite element method and multi-body dynamics method. The process of modeling turns to be stylized, which avoids the unnecessary programming for individual project.

Unified approach to predict the dynamic performance of transportation system considering wind effects

Natural hazards, including the wind hazard and others, threaten the integrity of the modern society. A transportation system usually consists of roadways, bridges and related vehicles. Harsh environmental conditions, caused by such as wind, exist in the real world frequently and affect the dynamic performance of the transportation system through their interactions. Long-span bridges are usually the backbones of transportation lines. In windy conditions, the information about the dynamic performance of bridges and vehicles considering full interactions of environmental factors is very essential for people to assess the overall operational conditions and safety risks of the transportation lines. Most of existent approaches target specifically at several isolated tasks considering partial interaction effects. In order to improve the understanding of these related-in-nature problems integrally as well as the consistency of different approaches, a unified approach to integrally predict the dynamic performance of long-span bridges and vehicles under wind is introduced. Such an approach can be used as a general platform to predict the dynamic responses of vehicles and bridges under various situations through adopting both commercial and in-house software. Dynamic interaction effects can be fully considered automatically for each situation. An example of a prototype bridge in US is given for the purpose of demonstration.