THERMAL RESPONSE OF BRIDGES

Interest in the control of ice on highway structures has resulted in a number of demonstration projects to investigate the effectiveness of both active and possive techniques to control the problem. Few of these experiments have incorporated any prelimiary thermal modeling in their feasibility studies and, as a result, have met with mixed success. Research was initiated to develop, verify, and document a thermal model applicable to highway structures. This program would allow the design engineer to conveniently estimate the thermal performance of proposed ice control devices in a specific environment. The thermal model was developed and verified by simulating the thermal response of an instrumented bridge to within a mean deviation of 2.1 F (1.2 C) over a 12-day period of severe winter weather. The model is general since standad heat-transfer correlations rather than inferred correlations from the data were used. The utility of the simulation is demonstrated in a study of the effect that insulation would have on the freezing characteristics of a bridge. Insulation would reduce the number of freeze-thaw cycles by 34 percent and the total time frozen by 15 percent. Experimental results indicated that modifying the surface radiative characteristics can induce even larger reductions for the site investigated.