Seismic Performance of the Buckling-Restrained Brace Central Buckle for Long-Span Suspension Bridges

2018 ◽  
Vol 12 (05) ◽  
pp. 1850015 ◽  
Author(s):  
Wei Guo ◽  
Jianzhong Li ◽  
Nailiang Xiang
Keyword(s):  
Seismic Performance ◽  
Design Procedure ◽  
Suspension Bridges ◽  
Preliminary Design ◽  
Viscous Dampers ◽  
Buckling Restrained Brace ◽  
Long Span ◽  
Parametric Analyses ◽  
Yield Force ◽  
Central Buckle

In this paper, a novel central buckle composed of buckling-restrained braces (BRBs) is developed for long-span suspension bridges, and its preliminary design procedure is presented. Seismic performance of suspension bridges equipped with BRB central buckles is investigated and compared with those with conventional central buckles (e.g. rigid or flexible central buckles). Furthermore, the effect of BRB yield force, as well as the effectiveness of BRB central buckles combined with viscous dampers, is evaluated using parametric analyses. The results indicate that the BRB central buckle is more effective than other central buckles in reducing both the longitudinal girder displacements and force demands on towers during an earthquake. Furthermore, the combination of BRB central buckles and viscous dampers is a superior option for mitigating the seismic response of long-span suspension bridges.

Compositive Optimal Control for the Seismic Response of a Long-Span Triple-Tower Suspension Bridge

2018 ◽  
Vol 18 (08) ◽  
pp. 1840009 ◽  
Author(s):  
Hao Wang ◽  
Yifeng Wu ◽  
Ben Sha ◽  
Wenzhi Zheng ◽  
Yuqi Gao
Keyword(s):  
Optimal Control ◽  
Suspension Bridge ◽  
Suspension Bridges ◽  
Seismic Responses ◽  
Viscous Dampers ◽  
Analytic Hierarchy ◽  
Expansion Joints ◽  
Elastic Links ◽  
Long Span ◽  
Floating System

In the design of super-long-span suspension bridges, the floating system is commonly adopted. However, this system may lead to the excessive earthquake-excited longitudinal displacement (LD) at the end of the main girder, which in return could result in pounding damage at expansion joints. In this paper, Taizhou Bridge, the triple-tower suspension bridge with the longest main span in the world, is taken as an example to demonstrate the effectiveness of three different approaches (elastic links, viscous dampers, and their combination) of mitigating the possible excessive LD. The finite element code ABAQUS is used to build the numerical model of the bridge and calculate the dynamic characteristics as well as the seismic responses. Then, 24 cases with different parameters of elastic links and viscous dampers are investigated and it is observed that the mitigation effect of the 24 cases varies significantly with different parameters. To obtain the optimized mitigation effect for seismic responses, including the LD of the girder, the LD and shear force of all towers, in the 24 cases, the modified analytic hierarchy process (AHP) method is introduced to realize the compositive optimal control of the triple-tower suspension bridge. Results show that the 24th case is the optimal one in which the LD of the girder is reduced significantly while the inner force of towers does not get excessive increase.

scholarly journals Fragility-Based Improvement of System Seismic Performance for Long-Span Suspension Bridges

2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Guanya Lu ◽  
Kehai Wang ◽  
Wenhua Qiu
Keyword(s):  
Seismic Performance ◽  
Fragility Curves ◽  
Suspension Bridge ◽  
System Level ◽  
Suspension Bridges ◽  
Fragility Function ◽  
Long Span ◽  
Damage Indices ◽  
Composite Damage ◽  
Demand Models

In this study, a procedure is developed to evaluate and improve the seismic performance of long-span suspension bridges based on the performance objectives under the fragility function framework. A common type of suspension bridge in China was utilized in the proposed procedure, considering its approach structures according to earthquake damage experience and fortification criteria. Component-level fragility curves were derived by probabilistic seismic demand models (PSDMs) using a set of nonlinear time-history analyses that incorporated the related uncertainties such as earthquake motions and structural properties. In addition, one step that was covered was to pinpoint the capacity limit states of critical components including bearings, pylons, and columns. The stepwise improved seismic designs were proposed in terms of the component fragility results of the as-built design. Results of the comparison of improved designs showed that the retrofit measure of the suspension span should be selected based on two attributes, i.e., displacement and force, and the restraint system of the approach bridges was a key factor affecting the reasonable damage sequence. Necessarily, from the comparison of different system vulnerability models, the mean values of earthquake intensity of system-level fragility function developed by the composite damage state indices were used to assess the overall seismic performance of the suspension bridge. The results showed that compared to the absolutely serial and serial-parallel assumptions, the defined composite damage indices incorporating the thought of component classification and structural relative importance between the main bridge and approach structures were necessary and were able to derive a good indicator of seismic performance assessment, hence validating the point that the different damage states were dominated by the seismic demands of different structures for the retrofitted bridges.

Mechanics Characteristics Study for Cable-Stayed-Suspension Bridges

2011 ◽  
Vol 243-249 ◽  
pp. 1817-1825
Author(s):  
Jing Qiu ◽  
Rui Li Shen ◽  
Huai Guang Li
Keyword(s):  
Finite Element ◽  
Suspension Bridge ◽  
Simulation Method ◽  
Suspension Bridges ◽  
Preliminary Design ◽  
Structural System ◽  
Long Span Bridges ◽  
Long Span ◽  
Element Simulation ◽  
Mechanics Characteristics

As a composite structure, the cable-stayed-suspension bridge is characterized by relatively new structure, great overall stiffness and long-span capacity, which has been proposed for the design of some extra long-span bridges. In order to research further into the mechanics characteristics of this type of structural system, the proposed preliminary design of a cable-stayed-suspension bridge with a main span of 1800m is analyzed by means of finite element simulation method. The advantages on overall stiffness in the cable-stayed-suspension bridge are summarized in comparison with the three-span suspension bridge and the single-span suspension bridge. Then, the reasons for the fatigue of the longest suspension cables in the cable-stayed-suspension bridge are also discussed in this paper.

Preliminary design of very long-span suspension bridges

2000 ◽  
Vol 22 (12) ◽  
pp. 1699-1706 ◽  
Author(s):  
Paolo Clemente ◽  
Giulio Nicolosi ◽  
Aldo Raithel
Keyword(s):  
Suspension Bridges ◽  
Preliminary Design ◽  
Long Span

High-Performance Computer-Aided Optimization of Viscous Dampers for Improving the Seismic Performance of a Tall Steel Building

2018 ◽  
Vol 763 ◽  
pp. 502-509
Author(s):  
Shan Shan Wang ◽  
Stephen Mahin
Keyword(s):  
Seismic Performance ◽  
Earthquake Engineering ◽  
High Performance ◽  
Optimization Design ◽  
Nonlinear Dynamic Analysis ◽  
Design Procedure ◽  
Optimization Procedure ◽  
Viscous Dampers ◽  
Safety Level ◽  
Fluid Viscous Dampers

Using fluid viscous dampers (FVDs) has been demonstrated to be an effective method to improve seismic performance of new and existing buildings. In engineering applications, designs of these dampers mainly rely on trial and error, which could be repetitive and labor intensive. To improve this tedious manual process, it is beneficial to explore more formal and automated approaches that rely on recent advances in software applications for nonlinear dynamic analysis, performance-based evaluation, and workflow management and the computational power of high-performance, parallel processing computers. The optimization design procedure follows the framework of Performance Based Earthquake Engineering (PBEE) and uses an automatic tool that incorporates an optimization engine and structural analysis software: Open System for Earthquake Engineering Simulation (OpenSEES). An existing 35-story steel moment frame is selected as a case-study building for verification of this procedure. The goal of the retrofit design of FVDs is to improve the building’s seismic behavior that focuses on avoiding collapse under a basic-safety, level-2 earthquake (BSE-2E). The objective of the optimization procedure is to reduce the building’s total loss under a BSE-2E event and optimal damper patterns will be proposed. The efficiency of the optimization procedure will be demonstrated and compared with a manual refinement procedure.

Dynamic Characteristics Analysis and Parametric Study of a Super-Long-Span Triple-Tower Suspension Bridge

2012 ◽  
Vol 256-259 ◽  
pp. 1627-1634 ◽  
Author(s):  
Jia Wen Zhang ◽  
Wen Hua Guo ◽  
Chao Qun Xiang
Keyword(s):  
Dynamic Characteristics ◽  
Suspension Bridge ◽  
Torsional Stiffness ◽  
Mode Shapes ◽  
Suspension Bridges ◽  
Box Girder ◽  
Long Span ◽  
Steel Box Girder ◽  
Elastic Restraints ◽  
Central Buckle

Based on the Taizhou Yangtze River Bridge, a 3D finite element model is developed to establish its deformed equlibrium configuration due to dead loading. Strating from deformed configuration,a modal analysis is performed to provide the frequencies and mode shapes. The study focuses on the effects of the vertical, lateral and torsional stiffness of the steel box girder, the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. The results show that, variation of vertical, lateral and torsion stiffness of stiffening girders have effects on the vibration frequency in corresponding directions only and have little effects in other directions. The elastic restraints have a more significant effect on the dynamic characteristics than the central buckle, and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span tripletower suspension bridges.

Post-Critical Behavior of Suspension Bridges Under Nonlinear Aerodynamic Loading

2015 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea Arena ◽  
Walter Lacarbonara ◽  
Pier Marzocca
Keyword(s):  
Reduction Process ◽  
Design Parameters ◽  
Suspension Bridges ◽  
Long Span ◽  
Fold Bifurcation ◽  
Speed Up ◽  
The Stability ◽  
Parametric Analyses ◽  
Bifurcation Behavior ◽  
Nonlinear Aerodynamic

The limit cycle oscillations (LCOs) exhibited by long-span suspension bridges in post-flutter condition are investigated. A parametric dynamic model of prestressed long-span suspension bridges is coupled with a nonlinear quasi-steady aerodynamic formulation to obtain the governing aeroelastic partial differential equations adopted herewith. By employing the Faedo–Galerkin method, the aeroelastic nonlinear equations are reduced to their state-space ordinary differential form. Convergence analysis for the reduction process is first carried out and time-domain simulations are performed to investigate LCOs while continuation tools are employed to path follow the post-critical LCOs. A supercritical Hopf bifurcation behavior, confirmed by a stable LCO, is found past the critical flutter condition. The analysis shows that the LCO amplitude increases with the wind speed up to a secondary critical speed where it terminates with a fold bifurcation. The stability of the LCOs within the range bracketed by the Hopf and fold bifurcations is evaluated by performing parametric analyses regarding the main design parameters that can be affected by uncertainties, primarily the structural damping and the initial wind angle of attack.

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