Zhuojin Pipe Fitting Co., LtdConcrete Lateral Pressure During Top-Lifting Construction of Rectangular Steel Tube Concrete Columns
Overview and Engineering Context
The study by Wu Honggang, Li Jing, Xia Chengxin, Tian Xuesong, and Zhang Quan, published in Cement, Issue 8, 2025, pages 151–153, addresses a practical construction challenge: the concrete lateral pressure exerted on the walls of rectangular steel tube concrete columns during top-lifting construction. This research involves collaboration between Qingdao Urban Construction Group, Qingjian Infrastructure Development, Shandong University, Shandong Provincial Engineering Construction Standard Cost Center, and Shandong Huayi Steel Structure Co., Ltd. The top-lifting construction method is widely used in the construction of tall buildings and bridges, where the structure is lifted upward from the top rather than being constructed from the ground up.
Top-Lifting Construction Method and Lateral Pressure Problem
In the top-lifting construction method, the steel structure is assembled at ground level and then lifted upward by hydraulic jacks mounted on a fixed lifting frame. The concrete is poured into the steel tube as the structure is lifted, and the lateral pressure exerted by the fresh concrete on the steel tube walls must be carefully controlled to prevent tube deformation or failure.
The lateral pressure of fresh concrete is influenced by several factors, including the concrete's slump, unit weight, pouring rate, temperature, and the presence of internal transverse diaphragms. In the case of rectangular steel tube concrete columns with internal transverse diaphragms, the diaphragms act as obstacles that impede the flow of concrete, leading to localized pressure buildup that can exceed the values predicted by conventional lateral pressure formulas.
The following table presents the key parameters and their effects on lateral pressure:
| Parameter | Effect on Lateral Pressure | Practical Consideration |
|---|---|---|
| Concrete slump | Higher slump increases pressure | Control slump within 100-160 mm range |
| Pouring rate | Faster rate increases pressure | Limit rate to prevent excessive pressure |
| Temperature | Higher temperature increases pressure | Use cooling measures in hot weather |
| Transverse diaphragm spacing | Closer spacing increases pressure | Optimize spacing for structural and construction needs |
| Lifting height | Higher lifting increases dynamic effects | Monitor pressure during lifting operation |
Field Measurement Results and Pressure Variation Patterns
The researchers conducted on-site measurements to monitor the lateral pressure and tube wall deformation during the top-lifting process of a rectangular steel tube concrete column with internal transverse diaphragms. The measurements revealed that the lateral pressure is not uniform but varies dynamically with the lifting height and the position of the concrete surface relative to the transverse diaphragms.
When the concrete surface reaches a transverse diaphragm, the pressure increases sharply as the concrete is forced to flow around or over the diaphragm. The diaphragm acts as a partial barrier, creating a hydrostatic pressure buildup above the diaphragm level. As the lifting continues and the concrete level rises above the diaphragm, the pressure gradually decreases as the concrete flows past the diaphragm.
The tube wall deformation measurements showed that the rectangular tube walls deflect outward under the lateral pressure, with the maximum deformation occurring at the mid-span of the bay between transverse diaphragms. The deformation is elastic and recovers after the concrete hardens and the lateral pressure is released, but excessive deformation during the fresh state could lead to permanent distortion if the tube wall yield strength is exceeded.
Dynamic Lateral Pressure Formula
Based on the field measurement data, the researchers proposed a formula for calculating the maximum dynamic lateral pressure of steel tube concrete columns with transverse diaphragms during top-lifting construction. The formula incorporates the effects of concrete unit weight, slump, pouring rate, temperature, and the geometric configuration of the transverse diaphragms.
The dynamic lateral pressure is expressed as a function of the static lateral pressure modified by a dynamic coefficient that accounts for the lifting operation. The dynamic coefficient is determined empirically from the field measurements and varies with the lifting speed and the distance between transverse diaphragms.
The proposed formula provides a practical tool for engineers to predict the maximum lateral pressure during top-lifting construction and to verify that the steel tube walls have adequate stiffness and strength to resist the applied pressure without excessive deformation. The formula should be used in conjunction with the relevant design codes, such as GB 50010 for concrete structure design and GB 50017 for steel structure design, to ensure that the tube wall thickness and stiffener configuration are adequate.
Quality Control and Construction Recommendations
The control of concrete lateral pressure during top-lifting construction requires a systematic approach involving material selection, construction sequencing, and real-time monitoring. The following measures are recommended:
- Concrete mix design should target a slump of 100 to 160 mm, with a unit weight of approximately 2400 kg/m³, to minimize lateral pressure while maintaining workability for placement within the steel tube.
- The pouring rate should be limited to prevent excessive pressure buildup, with a recommended maximum rate of 0.5 to 1.0 m/h depending on the tube dimensions and diaphragm spacing.
- Real-time pressure monitoring using pressure gauges or strain gauges mounted on the tube walls should be conducted during the pouring and lifting operation, with predetermined alarm thresholds to trigger rate reduction or pouring cessation if excessive pressure is detected.
- The lifting speed should be coordinated with the pouring rate to ensure that the concrete surface does not rise too rapidly relative to the lifting frame, which could create additional dynamic effects.
- The tube wall thickness should be verified to have adequate stiffness to limit lateral deformation to acceptable limits, typically not exceeding 1/200 of the tube width or 10 mm, whichever is smaller.
Engineering Practice and Reflections
The top-lifting construction method offers significant advantages for the construction of tall structures, including reduced need for temporary supports, improved working conditions at height, and faster construction cycles. However, the concrete lateral pressure during the simultaneous pouring and lifting operation presents a unique challenge that requires careful management.
The presence of internal transverse diaphragms, which are essential for the structural integrity of the steel tube concrete column, introduces additional complexity to the lateral pressure problem. The diaphragms create localized pressure concentrations that can exceed the values predicted by simple hydrostatic models. Engineers must account for these localized effects in the design of the tube wall and stiffener configuration.
The field measurement approach adopted in this study provides valuable empirical data that can be used to calibrate analytical models and improve the accuracy of lateral pressure predictions. Future work should focus on developing more sophisticated numerical models that incorporate the interaction between the concrete flow, the transverse diaphragms, and the tube wall deformation.
In conclusion, the control of concrete lateral pressure during top-lifting construction of rectangular steel tube concrete columns is a critical aspect of construction safety and quality. The proposed dynamic lateral pressure formula, based on field measurements, provides a practical tool for engineers to predict and manage the lateral pressure during the lifting operation. Attention to concrete mix design, pouring rate control, real-time monitoring, and tube wall stiffness verification is essential for successful implementation of the top-lifting construction method. The research findings contribute to the development of safer and more efficient construction practices for steel tube concrete structures.