Experimental Analysis of Temperature Gradient Patterns of Concrete-Filled Steel Tubular Members

Concrete-filled steel tubes (CFSTs) have been applied widely as the main members in bridge structures; however, the temperature gradients have not been studied sufficiently. To fill this gap, a long-term experimental and analytic study was conducted on four CFST members with different inclinations and orientations. Then a systematic 2-step approach with curve fitting and extreme value analysis (EVA) was proposed to establish the most unfavorable vertical temperature gradient (VTG) and transverse temperature gradient (TTG) patterns with the extreme temperature differences (TDs) in a 100-year return period. The curve fittings show that both VTG and TTG profiles can be described by two piecewise functions with multiple parabolas. And EVA shows that TDs in positive VTG, negative VTG, and positive TTG all fit the Weibull distribution well, while the TDs in negative TTG all fit the Gumbel distribution better. Comparison analysis shows that the Chinese specification underestimates the temperature gradients of CFST bridges. The proposed temperature gradient patterns are more suitable for probabilistic limit-state design for thermal effect calculations of CFST bridges than the Chinese specification.