Study of seismic-responses and semi-active control of Taizhou Bridge under multi-support excitation

PurposeIn order to make sure of the safety of a long-span suspension bridge under earthquake action, this paper aims to study the traveling wave effect of the bridge under multi-support excitation and optimize the semi-active control schemes based on magneto-rheological (MR) dampers considering reference index as well as economical efficiency.Design/methodology/approachThe finite element model of the long-span suspension bridge is established in MATLAB and ANSYS software, which includes different input currents and semi-active control conditions. Six apparent wave velocities are used to conduct non-linear time history analysis in order to consider the seismic response influence in primary members under traveling wave effect. The parameters α and β, which are key parameters of classical linear optimal control algorithm, are optimized and analyzed taking into account five different combinations to obtain the optimal control scheme.FindingsWhen the apparent wave velocity is relatively small, the influence on the structural response is oscillatory. Along with the increase of the apparent wave velocity, the structural response is gradually approaching the response under uniform excitation. Semi-active control strategy based on MR dampers not only restrains the top displacement of main towers and relative displacement between towers and girders, but also affects the control effect of internal forces. For classical linear optimal control algorithm, the values of two parameters (α and β) are 100 and 8 × 10–6 considering the optimal control effect and economical efficiency.Originality/valueThe emphasis of this study is the traveling wave effect of the triple-tower suspension bridge under multi-support excitation. Meanwhile, the optimized parameters of semi-active control schemes using MR dampers have been obtained, providing relevant references in improving the seismic performance of three-tower suspension bridge.

Seismic Analysis of Hybrid System Bridge of Multi-Span Continuous Girder and Arches

The Chengdong Hanjiang Bridge in Ankang City is a multi-span continuous beam-arch combination system bridge of (75+2×125+160+2×125+75) m, and its site is located in the earthquake zone. Calculation model based on Midas / Civil finite element software process analysis method is applied to seismic response analysis using power. At the same time, in order to influence the travelling wave effect and the seismic isolation system on the internal force of the bridge structure, corresponding finite element models were established and calculated with time history analysis. The finite element model under non-uniform excitation uses the “Large Mass Method” (LMM) for analysis and calculation under different wave velocity multi-point excitations. The results show that after considering the traveling wave effect, the displacement and bending moment of the control section of each hole increase, and the internal force of the fixed pier increases. When the wave velocity is 600m/s, the traveling wave effect strengthens the seismic response of the structure the most. With the increase of the wave velocity, the seismic response of the structure gradually approaches the seismic response under uniform excitation. After the friction pendulum seismic isolation support is used, it is fixed. The bending moment of Pier No.32 has been reduced by 80%, the stiffness of the whole bridge is more balanced, the forces of each pier are relatively close, and the isolation effect is good.

Seismic Response of Long Span Continuous Rigid-Framed Steel Arch Bridge

This paper investigates seismic responses of Xinguang Bridge, a 3-span continuous rigid-frame and steel-truss arch bridge. Earthquake excitation input is a key issue for the seismic analysis. This paper uses a finite element method to study the traveling wave effect on Xinguang Bridge and its interaction with the dynamic properties of the bridge under the condition of two steps and two levels probability. The seismic response of the bridge under the coincident earthquake excitation is also analyzed. Comparisons show that the seismic response of the long-span bridge by considering the traveling wave effect is much different from that under consistent earthquake excitation. The influence of the shear wave speed on the seismic response of the long span continuous bridge is also explored and the shear wave speed is found to greatly affect the wave shape and magnitude of the time-history of the longitudinal displacement at the crown of the main arch of the bridge. It is concluded that traveling wave effect and shear wave speed of ground have significant influences on the seismic response of the long span continuous rigid-framed and steel-truss arch bridge.

Traveling Wave Effect Analysis on Fabricated Box Girder Bridge Based on ANSYS

This paper analyzed the seismic response of fabricated box girder bridge considering the traveling wave effect based on ANSYS. Take a multi-connected continuous girder bridge over sea island as the research object, consider the effect of pile-soil interaction, the internal force and deformation characteristics of substructure, coping and expansion joint of the bridge are analyzed under the traveling wave effect. Traveling wave effect have some influence on the internal force and deformation of substructure and coping, but the influence is not so strong. Meanwhile the relative displacement of expansion joint and collision force of beam end are influenced significantly, and the risk of girder falling is increased.

Traveling Wave Resonance and Simplified Analysis Method for Long-Span Symmetrical Cable-Stayed Bridges under Seismic Traveling Wave Excitation

The seismic responses of a long-span cable-stayed bridge under uniform excitation and traveling wave excitation in the longitudinal direction are, respectively, computed. The numerical results show that the bridge’s peak seismic responses vary significantly as the apparent wave velocity decreases. Therefore, the traveling wave effect must be considered in the seismic design of long-span bridges. The bridge’s peak seismic responses do not vary monotonously with the apparent wave velocity due to the traveling wave resonance. A new traveling wave excitation method that can simplify the multisupport excitation process into a two-support excitation process is developed.

Large-Span Cable-Stayed Bridge Seismic Response Analysis Considering Traveling Wave Effect

In this paper, three-tower cable-stayed bridge Jinan Jianbang as the researched object, is to built to two models of the bridge with piles and without piles using the finite element software , and is made dynamic characteristic analysis. Meanwhile it is compared the control force of and the elastic response spectra and time history analysis under different conditions.At the same time ,bridge model without pile is excitated by multi-point for traveling wave effect analysis. The results show that pile-soil effects make more greater impact on forces of large span structures, and traveling wave effect on the adverse effects of large-span cable-stayed bridge shoule be considered in the seismic design.

Research on Longitudinal Seismic Response of Continuous Welded Rail on Bridge with High-Pier and Long-Span

Longitudinal seismic responses of CWR on bridges with high-piers and long-spans under uniform excitation and traveling wave effect were studied. Results are shown as follows: Under seismic action, rail longitudinal forces near beam joints increase greatly than rail expansion forces (due to beam expansion); Designing CWR on bridges with high-piers and long-spans needs to consider influences of traveling wave effect and wave spreading derection; With the increase of the apparent velocity of seismic waves, rail longitudinal force tends to decrease; We suggest that designing of CWR on bridges crossing high-intensity earthquake zone should consider impact of seismic action, and establish a reasonable check method.

Damper Optimization for Long-Span Suspension Bridges

Long-span suspension bridges are becoming prevalent globally with the rapid progress in design methodologies and construction technologies. Although with apparent progress, the balance between excessive displacement and inner forces, under dynamic loads, is still a main concern because of increased flexibility and low structural damping. Therefore, effective controllers should be employed to control the seismic responses to ensure their normal operation. In this chapter, the combination of the analytic hierarchy process (AHP) and first-order optimization method are formulated to optimize seismic response control effect of the Runyang suspension bridge (RSB) under earthquakes, considering traveling wave effect. The compositive optimal parameters of dampers are achieved on the basis of 3-dimensional nonlinear seismic response analyses for the RSB and parameters sensitivity analyses. Results show that the dampers with rational parameters can reduce the seismic responses of the bridge significantly, and the application of the AHP and first-order optimization method can lead to accurate optimization effects.