Zhuojin Pipe Fitting Co., LtdJacking Construction Technology for Steel Tube Concrete Columns
Literature Overview
The paper by Tian Wei, Yang Weibo, and Zou Xiande, published in Construction Technology in 2022, presents a comprehensive study of the jacking construction method for steel tube concrete columns in super-high-rise buildings. This technique involves pouring high-performance self-compacting concrete from the bottom of a steel tube column and using pumping pressure to raise the concrete to the desired height without vibration. The research was supported by the China State Construction Research Project (CSCEC-2019-Z-22) and the China Construction Eighth Engineering Division Research Project (2019-2-08). The method addresses significant challenges in the construction of ultra-tall buildings, including the reduction of high-altitude work, decreased labor intensity, and shortened construction schedules.
Technical Characteristics and Process Flow
The jacking method for steel tube concrete columns represents a departure from conventional concrete placement methods that rely on crane-bucket delivery and mechanical vibration. In the jacking method, a sealed steel tube column serves as both a structural element and a pumping conduit. High-performance self-compacting concrete (SCC) is introduced at the base of the column, and pumping pressure is used to displace the concrete upward through the column cross-section to the target elevation.
| Technical Parameter | Typical Value or Requirement | Engineering Significance |
|---|---|---|
| Concrete compressive strength | C60 to C100 | Must withstand jacking pressure and service loads |
| Concrete flowability (funnel time) | 20 to 35 s | Ensures self-compacting behavior without vibration |
| Concrete filling height per lift | 3 to 8 m | Limited by column height and pump pressure capacity |
| Jacking pressure | 0.5 to 2.0 MPa | Must overcome friction and hydrostatic pressure |
| Pumping rate | 20 to 50 m³/h | Depends on column cross-section and lift height |
| Maximum column diameter | 1.5 to 2.5 m | Affects pressure distribution and filling uniformity |
| Concrete temperature during pouring | 15 to 30°C | Critical for SCC workability and strength development |
The process flow begins with the installation and alignment of the steel tube column, followed by the sealing of the bottom joint to create a pressure-tight boundary. The SCC is then pumped into the bottom of the column at a controlled rate and pressure, gradually displacing the concrete upward. The filling process is monitored through pressure gauges and level sensors, and the pump is shut off when the target elevation is reached. After a specified curing period, the top seal is removed, and the column is ready for the next structural stage.
Jacking Pressure Calculation and Steel Tube Burst Verification
A critical aspect of this technology is the accurate calculation of the jacking pressure required to raise the concrete to the target height. The pressure must overcome the hydrostatic head of the concrete column, the friction resistance between the concrete and the inner surface of the steel tube, and any additional resistance from the concrete's yield stress. The paper presents a systematic approach to pressure calculation that accounts for all these factors.
The steel tube column must also be verified against bursting failure under the internal concrete pressure. This is particularly important for columns with large diameter-to-thickness ratios, where the hoop stress induced by internal pressure can approach or exceed the yield strength of the steel tube. The verification involves calculating the hoop stress using thin-walled pressure vessel theory and comparing it with the allowable stress of the steel material, with appropriate safety factors.
| Verification Item | Calculation Method | Acceptance Criteria |
|---|---|---|
| Hoop stress | σ_h = p × D / (2t) | σ_h ≤ f_y / γ, where γ is the safety factor |
| Longitudinal stress | σ_l = p × D / (4t) | σ_l ≤ f_y / γ |
| Combined stress (von Mises) | σ_vm = √(σ_l² + σ_h² - σ_l × σ_h) | σ_vm ≤ f_y / γ |
| Local buckling resistance | Elastic buckling pressure per EN 1993-1-6 | p_burst > 1.5 × p_jacking |
Quality Control Points
The quality control of the jacking process is essential to ensure the structural integrity of the completed column. Key quality control points include the verification of the bottom seal integrity before pumping begins, continuous monitoring of pumping pressure and rate during the filling process, and post-pour inspection of the column for voids, segregation, or incomplete filling. Non-destructive testing methods such as ultrasonic testing and impact-echo methods may be employed to verify the internal quality of the concrete within the steel tube.
The paper emphasizes that the self-compacting property of the concrete is critical to the success of the jacking method. Unlike conventional concrete, SCC must flow and fill the entire cross-section of the column without mechanical vibration, relying solely on gravity and pumping pressure. This places stringent requirements on the concrete mix design, particularly regarding the balance between flowability, viscosity stability, and segregation resistance.
Study Insights and Implications
The jacking construction technology for steel tube concrete columns represents a significant advancement in the construction methodology for super-high-rise buildings. By eliminating the need for crane-bucket concrete delivery at extreme heights, the method reduces safety risks associated with high-altitude work and improves construction efficiency. From a materials and manufacturing perspective, the technology places unique demands on both the steel tube fabrication and the concrete mix design, requiring close coordination between structural engineering, materials science, and construction engineering disciplines. Engineers involved in such projects should pay particular attention to the pressure verification calculations and the quality control protocols to ensure that the completed columns meet design requirements.