Research on hydration heat effect and influence parameters of concrete filled steel shell composite pylon

Due to the large volume and significant hydration heat of concrete filled steel shell composite (CFSSC) pylons, concrete cracking during the hydration heat process can hinder the normal operation of the CFSSC pylons. To investigate the temperature field, thermal effect and influencing parameters of hydration action in CFSSC pylons, a research is conducted based on the Longgun River Bridge's CFSSC pylon. Upon verifying the consistency between simulation and measured results, a comparative analysis is conducted on the temperature field and thermal effect of the CFSSC pylon and concrete pylon. The effects of five parameters, including the final cement heat release, peak time of hydration rate, initial temperature, ambient temperature, and insulation layer thickness, are analyzed. The results indicate that the maximum temperature of the CFSSC pylon reaches 73.47 degrees C, with a maximum temperature difference of 40.75 degrees C. The maximum strain of concrete is 160 mu epsilon, the area and the depth of the cracking risk reachs 20 m2 and 24.5 cm. The surface temperature of the CFSSC pylon is 3.9 degrees C higher than that of the concrete pylon, and the tensile stress on the top surface of the CFSSC pylon's concrete is 1.09 MPa higher and 1.24 MPa lower on the sides compared to the concrete pylon. Applying lateral constraints to the top surface of the CFSSC pylon could reduce the cracking risk significantly. Adjusting each parameter reduces the concrete temperature difference by up to 20 % to 45 %. After proposing an optimization schemes, the maximum temperature is reduced by 14.25 degrees C and the maximum temperature difference is reduced by 29.58 degrees C. The cracking area is less than 0.5 m2, and the crack depth is less than 5.5 cm. Based on the preceding analysis, this paper could offer invaluable guidance for the design and construction of CFSSC pylons.