Experimental and numerical investigation on vertical temperature gradient of concrete-filled steel tubular arch under sunlight

To investigate the effects of diameter and inclination on the vertical temperature gradient (VTG) of concrete-filled steel tubular (CFST) arches, this study conducted temperature field tests on three CFST segment specimens with diameters of 426 mm, 750 mm, and 1000 mm, as well as an arch specimen with inclination angles varying from 48.76° to −48.76°. 2D and 3D numerical simulation models were developed to analyze the impact of diameter, wall thickness, inclination and orientation. The results indicate that as the diameter increases, the internal temperature becomes more uniform, forming a constant temperature zone in the middle of the VTG, with linear increases in temperature differences at the top (T₁) and bottom (T₂). Beyond approximately 600 mm in diameter, the VTG stabilizes. The maximum T₁ of the three segment specimens were 15.37 ℃, 22.40 ℃, and 23.81 ℃, respectively. Inclination affects the solar incidence angle and intensity, causing T₁ to vary along the arch span, proportional to solar intensity. The maximum difference of T₁ in the arch specimen reached 10.87 ℃. Wall thickness showed minimal effect on the VTG. The proposed VTG pattern was applicable to arches with various orientations and can assist in evaluating thermal effects in CFST arches.