Thermal Field Analysis of Rectangular Steel Tube Concrete Columns Under Solar Radiation in Super High-Rise Construction

Literature Overview

The study by Zhou Ting, Yang Huijie, Liu Hongbo, and Yan Xiangyu, published in Industrial Construction (2016, Vol. 46, No. 11, pp. 29-32), investigates the temperature field distribution within rectangular steel tube concrete (RCFST) columns during the construction phase of super high-rise buildings. Funded by the Tianjin Municipal Commission of Urban Construction Science and Technology Project (2015-3), this research addresses a practical construction challenge that has received insufficient attention in structural engineering literature.

The authors, from Tianjin University's School of Architecture, School of Building and Civil Engineering, and Tianjin University Architectural Design and Research Institute, focus on the non-uniform thermal environment experienced by large-section steel tube concrete columns exposed to direct solar radiation during construction.

Core Technical Findings

The research establishes several critical quantitative findings regarding temperature distribution:

The temperature gradients within the cross-section are driven by differential solar absorption on exposed faces versus shielded faces, combined with the thermal mass of the concrete core. The steel tube acts as a heat conduit, but its thermal diffusivity is insufficient to equalize temperatures across large cross-sections within the timescale of a construction day.

Thermal Stress Implications and Structural Analysis

From a metallurgical and structural perspective, the temperature gradients identified in this study have direct implications for:

• Thermal stress development: The coefficient of thermal expansion for structural steel is approximately 12×10⁻⁶ /°C. A 35.6°C differential across a 1000 mm cross-section can generate significant thermal stresses that may interact with construction loads.
• Differential concrete shrinkage: Non-uniform concrete curing temperatures affect hydration rates, potentially creating internal residual stresses that compound long-term shrinkage cracking.
• Steel tube distortion: Although elastic at these temperature levels, cyclic thermal loading over multiple construction days may contribute to fatigue accumulation in the steel tube walls.

The finding that temperature extremes increase with cross-section size but with diminishing returns beyond 1000 mm is practically significant. It suggests that for columns with cross-section dimensions exceeding 1000 mm, the marginal benefit of thermal mitigation measures decreases, and engineers should consider the cost-benefit ratio of shading or insulation strategies.

Engineering Practice Recommendations

Based on the thermal field data presented, the following engineering countermeasures are recommended for super high-rise construction projects:

1. Shading strategy: Install temporary shading screens on the sun-exposed faces of steel tube concrete columns during peak solar hours, particularly for columns with cross-sections exceeding 800 mm.
2. Construction scheduling: Schedule concrete placement during early morning or late afternoon when solar radiation intensity is lower, reducing the initial thermal asymmetry.
3. Instrumentation: Deploy thermocouple arrays at representative locations within large-section columns to monitor actual temperature differentials during construction.
4. Finite element thermal-structural coupling: Incorporate measured temperature fields into structural analysis models to assess combined thermal-mechanical response.

Key Questions and Reflections

This study raises several questions that warrant further investigation:

• How do the thermal gradients identified affect the bond strength between steel tube and concrete during the critical early-age period?
• What is the cumulative fatigue effect of daily thermal cycling over a multi-year construction program?
• Can the thermal analysis framework be extended to consider wind-induced convective cooling effects that may create additional temperature asymmetries?

The research methodology, combining experimental measurement with numerical simulation, provides a robust basis for the conclusions drawn. However, the study is limited to the construction phase and does not address long-term thermal effects during service life, which may involve different temperature boundary conditions.

Study Insights and Implications

This literature contributes to the growing body of knowledge on construction-phase thermal effects in complex structural systems. For engineers involved in super high-rise projects, the findings underscore the importance of considering environmental loading conditions that are often overlooked in conventional structural design. The thermal field data presented should be incorporated into construction methodology plans, particularly for projects in regions with intense solar radiation. The diminishing returns beyond 1000 mm cross-section provide a practical threshold for prioritizing thermal mitigation resources.