Search

Vision-based systems are promising tools for displacement measurement in civil structures, possessing advantages over traditional displacement sensors in instrumentation cost, installation efforts and measurement capacity in terms of frequency range and spatial resolution. Approximately one hundred papers to date have appeared on this subject, investigating topics like system development and improvement, the viability on field applications and the potential for structural condition assessment. The main contribution of this paper is to present a literature review of vision-based displacement measurement, from the perspectives of methodologies and applications. Video-processing procedures in this paper are summarised as a three-component framework: camera calibration, target tracking and structural displacement calculation. Methods for each component are presented in principle, with discussions about the relative advantages and limitations. Applications in the two most active fields, bridge deformation and cable vibration measurement, are examined followed by a summary of field challenges observed in monitoring tests. Important gaps requiring further investigation are presented, e.g. robust tracking methods, non-contact sensing and measurement accuracy evaluation in field conditions. [ABSTRACT FROM AUTHOR]

Structural temperature is an important form of loading for bridges, particularly for long-span steel structures. In this study, the temperature distribution of the Humber Bridge in the United Kingdom is investigated using numerical simulation and field measurements. A two-dimensional fine finite-element model of a typical section of the box girder of this long-span suspension bridge is constructed. The time-dependent thermal boundary conditions are determined using field meteorological measurements with external surface heat-convection coefficients varying according to differing local wind speeds they experience. Preanalysis is adopted to determine the initial thermal condition of the model, then transient heat-transfer analysis is performed and the time-dependent temperature distribution of the bridge is obtained, leading to numerical temperature data at different locations in different times that are in good agreement with the measured counterparts. The vertical and transversal temperature differences (TTDs) of the box girder are also investigated. Both measured and numerical results show that the transversal temperature variation across the streamlined girder is significant. The effects of the box-girder shape, pavement of the upper webs, and bridge orientation on the TTD are finally investigated. [ABSTRACT FROM AUTHOR]