The bridges are one of the most important engineering structures. Determination of the bridge responses during their service life has gained great importance using nondestructive test methods with the changing of aims, usages, environmental conditions, material deteriorations by time, and damages during some dramatical events. This chapter presents the nondestructive experimental measurement test results of the bridges for structural identification. Ten different bridges, which have different type and carrier systems, such as historical masonry arch bridges, long span concrete highway bridges, base isolated bridges, footbridges, steel bridges, and old riveted bridges, are selected for numerical examples. The measurements are conducted under environmental excitations of pedestrian movement, traffic, wind-induced vibration, and the response signals are collected using uniaxial- and triaxial-sensitive seismic accelerometers. Operational modal analysis or ambient vibration tests are performed to extract the dynamic characteristics such as natural frequencies, mode shapes, and damping rations using enhanced frequency domain decomposition method in the frequency domain and stochastic subspace identification method in the time domain. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of all bridge types.
Part of the book: Structural Bridge Engineering