Performance Of Long-span Bridges Research Articles

Wind-Induced Performance of Long-Span Bridge with Modified Cross-Section Profiles by Stochastic Traffic

The presence of traffic on a slender long-span bridge (SLB) deck has two types of primary impacts: (1) modification of the bridge cross-section profiles, which may influence the flutter derivatives and in turn, wind-induced aeroelastic loads acting on the bridge; and (2) additional dynamic loads acting on the bridge including dynamic interactions from the vehicles. As compared to the investigations on the impact of traffic as external dynamic loads, those on the impact from the modification of bridge cross-section profiles are rather rare. A scaled bridge section model with vehicle models distributed on the bridge section has been tested in the wind tunnel laboratory. With the FDs obtained from the wind tunnel experiments of various modified bridge cross-section profiles by stochastic traffic, the present study is to numerically evaluate the impact on the wind-induced performance of the long-span bridge, such as the buffeting response and fatigue damage accumulation.

Optimization of complex dampers for the improvement of seismic performance of long-span bridges

This paper presents a new vibration control method for long-span bridges using a complex damper system. The complex damper system has a simple mechanical configuration with oil and elastoplastic dampers, which are velocity and displacement dependent in absorbing vibration energy, so as to produce various damping forces against the external forces according to its parameter setting. The oil damper dissipates vibration energy for relatively frequent and small vibration amplitudes as in small-to-moderate earthquakes, whereas the elastoplastic damper system works for rare and large amplitude vibrations such as strong seismic events. In order to obtain the optimal performance of the damper, the preference-based optimization technique is applied. A numerical model is established for the complex damper system, and the response characteristics and effectiveness of the proposed system are presented through numerical simulations. Numerical results show that the proposed complex damper system can significantly improve the seismic performance of long-span bridge structures with the combined damping mechanism that is much more effective than the single conventional passive damper system.

Research on seismic safety, retrofit, and design of a steel cable-stayed bridge

After the 1995 Great Hanshin Earthquake, Japanese design specification of highway bridges was revised and many piers and bearing supports have been retrofitted. Large span bridges such as arch, truss, and cable-stayed bridges located in bay area of Kobe city also suffered damages from this earthquake. Therefore the investigation of seismic performance of long span bridges has been conducted for large earthquake. The Aratsu bridge constructed in 1987 is a steel cable-stayed bridge of 345m length, continuous three spans, and single plane of stay cables. The seismic performance of this bridge was examined by nonlinear time history analyses using tri-linear back bone and hysterecis loops. Furthermore fiber model analysis and FE analysis are successfully used to check the behaviors of this bridge. According to the analysis of the target bridge, weak members for large earthquake have been clarified. Install of damper and displacement restrainer, and strengthening of components of bearing supports are proposed retrofit countermeasures. The behavior of retrofitted bridge satisfies the criteria of design specification of highway bridges.

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.

大型構造物の安心・安全を支える最新の技術トレンド 長大橋の耐震性向上方法について

大型構造物の安心・安全を支える最新の技術トレンド 長大橋の耐震性向上方法について

139 低速風洞について

Consideration of wind-resisting properties constitutes one of the key factors in design of long and large structures. As well as the static strength analysis, the dynamic effects of the wind must be taken into consideration in the windresisting design for structures. A wind tunnel is be used for testing the resistance and the aero-dynamic performance of long span bridge, high rise building, steel and offshore structures.etc.This paper describes the outline of the low-speed wind tunnel facility for research and development of aerodynamic stabilities.

The influence of topography on the dynamic wind loading of long span bridges

The importance of topography upon the design loading and aerodynamic performance of long span bridges is discussed using recent model studies as illustrations. The studies include the topographic simulation of the local terrain, vital to the prediction of the aerodynamic performance of the subject bridges.

The influence of topography on the dynamic wind loading of long span bridges

The importance of topography upon the design loading and aerodynamic performance of long span bridges is discussed using recent model studies as illustrations. The studies include the topographic simulation of the local terrain, vital to the prediction of the aerodynamic performance of the subject bridges.