Long-span Continuous Girder Bridge Research Articles

Seismic response study of multi-span continuous beam bridges near faults considering permanent displacement attenuation effects

The fling-step effect caused by near-fault ground motion induces a step-like permanent displacement of the ground surface, which decays sharply with increasing fault distance, leading to varying degrees of ground motion at each supporting point of the bridge structure. In this context, multi-span long-span bridges exhibit echelon displacement of the main beam and a more complex internal force response compared to ordinary bridges. To investigate the seismic response characteristics of multi-span long-span continuous girder bridges under near-fault ground motion, this study is based on the permanent displacement attenuation model. The main bridge of the Hongyazi Yellow River Bridge in Shizuishan City, consisting of 16 spans, is taken as the research object. Using OpenSees software, a finite element model for the dynamic analysis of the multi-span long-span continuous girder bridge was established, and its structural dynamic characteristics were compared with the natural vibration test of the actual bridge. Based on simulated ground motions that consider the permanent displacement attenuation effect and spatial variability, the seismic response of the key components of the near-fault multi-span long-span continuous beam bridge is examined. The results indicate that under near-fault ground motion considering the attenuation effect of permanent displacement, the main girder of multi-span long-span bridges frequently deviates from the axis in different directions, ultimately resulting in residual deformation of the main girder post-earthquake. The permanent displacement attenuation effect increases the maximum bending moment response at the pier bottom and causes uneven internal force distribution in the bridge. Ignoring this effect can lead to overestimation of bearing deformation.

Structural Health Monitoring of Long-Span Continuous Girder Bridge: System Implementation and Data Analysis

Long-span bridges are the key component of the human transportation system, linking communities over vast obstacles. To ensure the safe operation of long-span bridges, structural health monitoring (SHM) is perhaps the most effective solution. This study takes a 430[Formula: see text]m four-span continuous girder bridge as an example and systematically presents an implementation example of the SHM system on the bridge regarding monitoring items, sensor placement, and sensor parameters. The monitoring data including operational load and bridge response are analyzed and the statistical rules of these monitoring data are presented. Besides, the modal parameters of the girder are tracked from long-term vibration monitoring data. Furthermore, the correlations between structural temperature and bridge response are analyzed, and the correlation formulas between bridge modal frequency, static responses, and structural temperature are finally given. The analysis results reveal significant seasonal variations in the responses of the continuously monitored girder bridge, offering valuable insights for data-driven assessment and early warning systems for bridges.

Effects of friction pendulum bearing wear on seismic performance of long-span continuous girder bridge

To clear the wear effect of friction pendulum bearings (FPBs) on the seismic performance of multiple long-span continuous girder bridges, the rapid sliding performance test of the FPBs was carried out to get the wear degree of the modified poly tetra fluoroethylene (PTFE) wear plates. Taking a 6×110 m long-span continuous girder bridge as the engineering background, the seismic response of the bridge with different wear degrees of the FPBs was analyzed. The results show that the modified PTFE wear plate of the FPBs was severely worn in the rapid sliding performance test, and the friction coefficient was first increased to 0.09 and then decreased to 0.016. When the maximum displacement was reached, the bearing collided with the limitation block. Moreover, the internal forces of the critical pier were increased, and the bottom of the piers entered plasticity due to the wear of the FPBs. Due to the change in the seismic performance of the bridge, it is suggested that the rapid sliding performance of FPBs should be tested to ensure the structure safety of the long-span continuous girder bridge in rare earthquakes.

Seismic response analysis of long-span continuous girder bridge considering fluctuating friction of bearing

Under the combined action of horizontal and vertical earthquakes, separation-pounding of bridge beam ends and bearings occurs, which adversely affects the overall mechanical behaviour of any bridge. Based on D'Alembert's principle, this study proposes a theoretical analysis method to verify the separation of bridge beam ends and bearings, which is substantiated by the measured data. A three-span continuous steel-box-girder bridge was selected as the research object, and finite element models (FEMs) using the bilinear bearing and friction bearing models were established. The numerical models were verified by comparing the simulation results with the theoretical calculations. A comparative study on the seismic response of continuous girder bridges with different bearing models was conducted, and it was found that the friction bearing model is better for simulating the whiplash effect of long-span continuous girder bridges. The results indicate that the peak pounding force generated by the separation of the beam end and bearing is 1.74 times the weight of the beam end. Moreover, the whiplash effect causes the tension and compression stress states of the side span of the main beam to reverse and drastically reduce the compressive stress of the middle span by 70%. Finally, it is recommended that the friction bearing model which is able to realistically simulate the seismic response of the bridge more accurately be used to simulate bearings with large axial force fluctuations.

Key Construction Monitoring Technology for Long-Span Continuous Girder Bridge

This paper integrates a monitoring practice for the construction of a long-span continuous girder bridge to explore strain measurement and geometric shape control technology. In doing so, the actual stress of the bridge in the cantilever-construction stage is identified, and the influence of ambient temperature on the geometric shape control of the main girder is eliminated. According to linear creep theory, a strain correction method based on the superposition principle is proposed to remove the strain induced by concrete shrinkage and creep. By identifying the pattern of the solar thermal effect on the main girder geometry, a double in-situ measurement interpolation method is proposed to predict the adjusted value of formwork erection elevation. The results show that the deviation between the measured and corrected stress values on the root section of the main girder under the maximum cantilever state of the main girder is 16%–23%, which verifies the necessity of strain correction. The corrected values of measured stress on each controlled section are essentially identical to the calculated values, and both have consistent change patterns throughout the construction process, which verifies the validity of the strain correction method. During the cantilever-construction stage, the vertical deformation of the main girder owing to the solar thermal effect is parabolic and significant; hence, the main girder geometry should be measured prior to sunrise. The double in-situ measurement interpolation method can effectively eliminate the adverse effects of solar thermal when lofting the vertical formwork elevation in a non-ideal period.

Study on Residual Displacement of FPB bearing in Long-span Continuous Girder Bridge

Based on the principle of mechanical equilibrium, the theory of FPB with residual displacement is analyzed. This analysis derives the stiffness and equivalent damping ratio of FPB with residual displacement, and constructes the hysteretic model with residual displacement according to the existing hysteretic model of FPB. Through midas/civil modeling and analysis, the influence of different friction coefficients on the residual displacement of FPB is studied. When the friction coefficient is small, the distribution of residual displacement of FPB bearings is directional; the positive residual displacement is positively correlated with the friction coefficient, and the negative residual displacement gradually changes to the direction of seismic wave input with the increase of friction coefficient, first decreases and then increases. The positive and negative residual displacements after aftershocks are the same as those after main shocks, and their variation with friction coefficient is related to aftershocks intensity. By analyzing the hysteretic curves of different residual displacement bearings, the correctness of theoretical analysis is proved. At the same time, it is concluded that the larger the residual displacement, the more vulnerable the bearings are to instability, which leads to the failure of the main beam. The study of residual displacement can provide theoretical basis for selecting friction coefficient and controlling residual displacement in FPB design.

Stability safety assessment of long-span continuous girder bridges in cantilever construction

Stability safety assessment of long-span continuous girder bridges in cantilever construction

Shaking Table Test of a Long-Span Continuous Girder Bridge

Compared with middle-span bridges, seismic response of long-span bridges is more complicated, and so is seismic design. For example, influence of high order modes is obvious, as well as multi-support excitation, all kinds of nonlinear factors and soil and structure interaction (SSI). It is necessary to study on seismic behavior of a long-span continuous girder bridge. With the help of shake table array and substructure test technology, study on seismic performance of a long-span continuous girder bridge has been done and some useful conclusions have been got.

Shaking Table Test of a Long-Span Continuous Girder Bridge

Compared with middle-span bridges, seismic response of long-span bridges is more complicated, and so is seismic design. For example, influence of high order modes is obvious, as well as multi-support excitation, all kinds of nonlinear factors and soil and structure interaction (SSI). It is necessary to study on seismic behavior of a long-span continuous girder bridge. With the help of shake table array and substructure test technology, study on seismic performance of a long-span continuous girder bridge has been done and some useful conclusions have been got.

Experiment Research and Numerical Simulation of an Innovative Seismic Isolating System Designed for Long-Span Continuous Girder Bridges

To enhance the earthquake resistance capacity of long-span continues bridge, theory and design of a new seismic isolating system are proposed based on the utilization of improved carbon structural steel material. Pseudo-static test result of the damping tenon, one essential energy dissipation component, proved the system’s excellent characteristic of consuming earthquake energy. Comparative experiments of three models reflect the working stability of the damping tenon confronted with different stimulation. Finite Element simulation further validates accuracy of the experiment and helps analyzing the material’s elastic and plastic developing status due to different load steps. Finally, this new seismic isolating system is recommended to long-span continues girder bridge designed on the basis of high level earthquake resistant standard.

Seismic Performance of Continuous Girder Bridges Using Cable-sliding Friction Aseismic Bearing

This paper reports on the study of the performance of a new seismic control device named as cable-sliding friction aseismic bearing (CSFAB), which combines a conventional aseismic bearing with restrainer cables to dissipate earthquake energy and at the same time to control the displacement of girder to an acceptable value. A twodimensional long-span continuous girder bridge model was developed and analyzed in the study. Considering the influence of different site conditions, the model was subjected to three historic ground motion records applied to different (A,B,C,D) site conditions specified in the USGS site classification. Compared with conventional aseismic bearing, the effectiveness of the CSFAB in controlling the girder displacement and limiting the shear force and bending moment demands on the bridge piers was assessed. Furthermore, study considering different fixed pier heights was conducted and the results showed that with the decrease of height or increase in stiffness of piers, CSFAB was to be more effective.