Theoretical and Experimental Analysis of GFRP Bridge Deck under Temperature Gradient

The temperature difference between the top and bottom of a glass fiber reinforced polymer (GFRP) composite deck, ∼65°C (∼122°F) , is nearly three times that of conventional concrete decks ∼23°C (∼41°F) . Such a large temperature difference is attributed to the relatively lower thermal conductivity of GFRP material. In this study, laboratory tests were conducted on two GFRP bridge deck modules (10.2 and 20.3 cm deep decks) by heating and cooling the top surface of the GFRP deck, while maintaining ambient (room) temperature at the deck bottom. Deflections and strains were recorded on the deck under thermal loads. Theoretical results (using macro approach, Navier-Levy, and FEM) were compared with the laboratory test data. The test data indicated that the GFRP deck exhibited hogging under a positive temperature difference (i.e., Ttop > Tbottom , heating test; Ttop and Tbottom are temperatures at top and bottom of the deck, respectively) and sagging under a negative temperature difference (i.e., Ttop < Tbottom , cooling test). Deflections of the deck increased with an increasing magnitude of temperature difference. Typically in the field, tensile strains are induced in the top surface of GFRP deck when exposed to sunlight. Based on the field data, for a temperature gradient of 20°C (36°F) at the deck top and 5.6°C (10°F) at the deck bottom, the induced thermal stress was about 0.6 MPa (90 psi) . However, for a critical temperature gradient of 39°C (70°F) the induced thermal stress on GFRP decks is 6.2 MPa (900 psi) .