An experimental study of temperature effect on modal parameters of the Alamosa Canyon Bridge

Damage detection techniques have been proposed to exploit changes in modal parameters and to identify the extent and location of damage in large struc tures. Most of such techniques, however, generally neglect the environmenta l effects on modal parameters. Such environmental effects include changes i n loads, boundary conditions, temperature, and humidity. In fact, the chang es due to environmental effects can often mask more subtle structural chang es caused by damage. This paper examines a linear adaptive model to discrim inate the changes of modal parameters due to temperature changes from those caused by structural damage or other environmental effects. Data from the Alamosa Canyon Bridge in the state of New Mexico were used to demonstrate t he effectiveness of the adaptive filter for this problem. Results indicate that a linear four-input (two time and two spatial dimensions) filter to te mperature can reproduce the natural variability of the frequencies with res pect to time of day. Using this simple model, we attempt to establish a con fidence interval of the frequencies for a new temperature profile in order to discriminate the natural variation due to temperature. Copyright (C) 199 9 John Wiley & Sons, Ltd.