Dynamic performance is an important consideration in long-span bridge design. Owing to its flexibility and low damping, various types of vibration from different sources of excitation could occur during the lifetime of a long-span bridge. This paper reviews important studies and developments on long-span bridge vibration mechanism and control under wind, seismic, traffic and human-motion excitations. Types of vibration commonly observed on the long-span bridge are discussed from the viewpoint of structure engineering. Discussion for each subject is commenced by describing the vibration mechanism followed by the survey on observed phenomena in many long-span bridges associated with the type of vibration. The paper also describes the engineering solutions adopted as countermeasures for each type of bridge vibration problem.

Driving velocity, natural frequency of vehicle and natural frequency of bridge are the main contributing factors to vibration of a vehicle when passing a bridge. By separating contributions of the first two factors, one can estimate the natural frequency of a bridge indirectly from vehicle acceleration response when it crosses a bridge. In this paper, we apply this concept to estimate the bridge fundamental frequency indirectly using the response of a passing instrumented vehicle. The paper first describes analytical formulation and finite element simulation to demonstrate the feasibility of the method. Afterwards, it describes an experimental verification as a proof-of-concept of the method on a full-scale simply-supported short span bridge by using a light commercial vehicle instrumented with accelerometer. Dynamic responses of the vehicle while passing the bridge are recorded and analyzed. Spectra analysis of the vehicle responses reveal that the first natural frequency of the bridge can be estimated with reasonable accuracy when the vehicle moves with constant velocity. The concept of indirect frequency estimation is useful for assessment of short and medium span bridges where permanent instrumentation and routine visual inspection can be too costly. In this method, one can use inspection vehicle instrumented with vibration sensor to conduct periodic measurements by passing the vehicle over several monitored bridges and estimate their fundamental frequencies. When significant change in frequency is detected, detail inspections can be further conducted to investigate the possible damage on the bridge.

This paper discusses the development of bridge monitoring in Japan. Firstly, the background of the development of bridge monitoring is described. The need for monitoring was originally influenced by geographical conditions. Due to the fact that Japan is prone to natural disasters and has a severe environment for deterioration; monitoring of the environment and loading conditions with respect to natural hazards has been conducted for several decades. In the last decade, bridge monitoring has extended its function as an instrument for an efficient stock management. Based on the accumulation of bridge stock and concentrated construction in former years, many bridges in Japan are expected to have serious deterioration problems within the next decade. The second part of the paper describes the concept of bridge monitoring as an essential part of risk reduction. To improve bridge safety, monitoring technologies for risk and vulnerability are implemented. In this concept, structural health monitoring serves as a tool for vulnerability monitoring. The third part of the paper outlines strategies implemented for bridge monitoring in Japan. They are categorised into three main groups according to the purpose of monitoring: natural hazard and environment condition, effective stock management, and failure prevention. Examples of bridge monitoring systems that implement these strategies and the lessons learned from monitoring experiences are also presented in this paper.