Thermal Gradients and Their Effects on Bending Behavior of Composite Girders with Trapezoidal Profiled Webs

Abstract

Thermal gradient may have significant effect on the bending behavior of the composite girder with trapezoidal profiled web. To quantify such an effect on the thermos-strain action, temperature elevation test and finite element modeling were carried out on the specimens with the flange sensitive to bending and the web possessed adequate buckling resistance. The cross-sectional thermal gradients for different location away from the middle of span were measured using thermocouples and correlated using Boltzmann sigmoid equations. The applicability of finite element model was validated against experiments in terms of the distribution of thermal strain, deflections and axial strains. The axial strain distributions across the flange width and along the longitudinal direction of girder were analyzed in details. The testing and finite element modeling results showed that, the deflections with applied loads near the middle of span subjected to maximum bending moment are notably influenced by the increase of thermal gradient. The maximum axial strains at the upper surface and the lower surface of the bottom flange are obviously influenced by the temperature, especially for the girders with relatively high span-depth ratios or thicker flanges. The thermal gradient at the upper surface of the bottom flange is relatively higher than that on lower surface for every 10°C rise of temperature which meant that the upper surface of the bottom flange connecting trapezoidal profiled webs is more sensitive to thermo-elastic action.