Apparatus to Restrain the Freezing of a Bridge Road Surface and Evaluation of Its Performance

An apparatus that restrains the freezing of bridge surfaces has been designed. This apparatus can be installed for existing bridges and those under construction. A sheet-like heating body is bonded to the lower surface of the upper deck of a box guilder, and the inside surfaces of both side walls are covered with heat-insulating layers to prevent energy loss. Heat is restrictively supplied to the upper-floor slab, while using the closed space for heat storage. As the lower-floor slab receives long wave radiation from the river and ground, the temperature of the lower floor contributes to the rise in temperature of the closed space. The energy supplied to the upper-floor slab should be sufficient such that the temperature of the bridge surface equals the access-road surface. The Nakatagiri-Bashi Bridge was chosen to evaluate the performance of the proposed apparatus, which installed 14 thermocouples at the middle section of the bridge and at surface. To determine the minimum electric power required to eliminate the difference in surface temperature between bridge and access road (ΔT), simulation with heat transport and radiation balance equations was carried out for the 38cm upper floor and 7cm asphalt pavement. The apparatus raised the bridge surface temperature by 1.4°C and 2.8°C for 50 and 100 W/m² heat supplies, respectively. If 50 W/m² is supplied to a heating length and width of 267 m and 5.0 m, respectively, for 10 hours per day, electricity cost is 231 USD/d (0.23 USD/kWh). However, if the proposed apparatus includes a solar power unit and operated during the day, running costs can be minimized.