Zhuojin Pipe Fitting Co., LtdSteel Tube Arch Installation Method for Rainbow Bridge
Literature Overview
This technical paper by Du Diansuo, Wang Ketai, and Li Zhitao from the 18th Engineering Bureau of the Ministry of Railways, Unit 5, documents the installation methodology and construction control for the 3168-meter steel tube arch of the Rainbow Bridge main span in the Tianjin Development Zone. Published in Railway Standard Design in 1998, this paper represents a valuable record of early Chinese steel tube-concrete arch bridge construction practice. Although the paper is relatively concise, it captures essential aspects of the construction technology that remain relevant to modern steel tube arch bridge projects.
Installation Methodology and Construction Control
The installation of a 3168-meter steel tube arch represents a significant engineering challenge requiring careful planning of temporary works, erection sequences, and construction monitoring. The following table outlines the key aspects of the installation methodology:
| Construction Phase | Key Activities | Critical Control Points |
|---|---|---|
| Foundation preparation | Pier construction, bearing pad installation | Verticality, elevation accuracy |
| Steel tube fabrication | Tube cutting, bending, welding | Geometric accuracy, weld quality |
| Temporary support system | Falsework or cable-stayed erection | Load capacity, stability |
| Arch segment erection | Segment hoisting, alignment, splicing | Positional tolerance, connection integrity |
| Concrete infilling | Core concrete pumping, compaction | Concrete quality, void detection |
| Construction monitoring | Stress, displacement, temperature monitoring | Real-time feedback, deviation correction |
The installation of steel tube arches typically follows one of two primary methods: (1) falsework-supported erection, where the steel tube arch is assembled on temporary falsework spanning the full width, and (2) cable-stayed erection, where segments are erected from the piers using temporary cable stays. For a span of 3168 meters, the cable-stayed method is more practical and cost-effective, as constructing full-span falsework at this scale would be prohibitively expensive and logistically challenging.
Steel Tube Specifications and Welding Requirements
The steel tubes used in the arch ribs of this bridge would typically conform to GB/T 8163 for fluid transport steel pipes or GB/T 3077 for alloy structural steel tubes, depending on the grade and application. For large-span arch bridges, the steel tubes are often made from Q345 or Q390 grade steel with wall thicknesses proportional to the arch rib depth. The following table presents typical specifications:
| Parameter | Specification | Standard |
|---|---|---|
| Steel grade | Q345B / Q390B | GB/T 1591 |
| Tube diameter | 300-600 mm (typical) | GB/T 8163 |
| Wall thickness | 10-25 mm | GB/T 8163 |
| Longitudinal weld | SAW or ERW | GB/T 9711, API 5L |
| Circumferential weld | SAW or SMAW | GB/T 985, GB/T 986 |
| Weld NDT | UT + MT | GB/T 11345, GB/T 26951 |
The welding of steel tube segments during erection is a critical activity that directly affects the structural integrity of the arch. Butt welds between segments must be designed and executed to achieve full penetration and complete fusion. The welding procedure must be qualified per NB/T 47014 or ISO 15614, and the welders must be certified per NB/T 47015 or ISO 9606-1. Preheating requirements for thick-walled tubes in cold weather conditions must be carefully controlled to prevent cold cracking in the heat-affected zone.
Construction Control and Monitoring
Construction control for steel tube arch bridges involves the continuous monitoring of geometric shape, internal forces, and stress states during the erection process. The key monitoring parameters include:
| Monitoring Parameter | Measurement Method | Acceptance Criteria |
|---|---|---|
| Arch rib elevation | Total station, GPS | Within +/- 5 mm of design |
| Arch rib horizontal position | Total station, GPS | Within +/- 5 mm of design |
| Steel tube stress | Strain gauges, vibrating wire sensors | Below allowable stress per GB 50017 |
| Concrete infill level | Leveling survey | Uniform along arch length |
| Temperature | Thermocouples | Recorded for thermal correction |
The construction sequence for cable-stayed erection of steel tube arches typically begins from the piers and proceeds toward the crown. Temporary cable stays provide support during the erection of each segment, and the stays are gradually released as the arch achieves self-support. The sequence and timing of stay release are critical construction control activities that must be carefully planned to prevent excessive deformation or stress concentrations in the partially erected arch.
Reflections on Engineering Practice
This paper, though brief, captures the essence of steel tube arch bridge construction technology in the late 1990s in China. The Rainbow Bridge project in Tianjin was among the pioneering applications of steel tube-concrete arch technology in China, and the construction experience gained contributed significantly to the subsequent development of this structural system in the country. The installation methodology described, while based on the technological capabilities of the time, established principles and practices that continue to inform modern steel tube arch bridge construction.
The challenges of steel tube arch installation are primarily related to geometric accuracy, weld quality, and construction sequencing. Any deviation in the erected geometry from the design shape can lead to secondary bending moments that reduce the structural efficiency of the arch. The use of construction monitoring to detect and correct deviations in real time is therefore essential. Modern projects now employ advanced monitoring systems including fiber optic sensors, automated total stations, and real-time data processing systems that provide more comprehensive and timely feedback than was available in 1998.
Summary and Outlook
The Rainbow Bridge steel tube arch installation methodology documented in this paper represents an important milestone in Chinese steel tube-concrete arch bridge engineering. The construction technology described, including the cable-stayed erection method, segment splicing, concrete infilling, and construction monitoring, forms the foundation upon which subsequent projects have built more advanced and refined construction practices. Modern steel tube arch bridges now incorporate innovations such as automated welding systems, real-time construction control algorithms, and advanced sensor networks that significantly enhance construction quality and safety. The fundamental principles established in this early project remain valid and continue to guide the design and construction of steel tube-concrete arch bridges worldwide.