Ultra-High Performance Steel Tube Concrete Bridge Structure Design Research

Literature Overview

This 2024 paper published in the Journal of Highway and Transportation Research by Gong Yunxia, Liu Yongjian, Jiang Lei, Li Ruosong, and Deng Shufei from Chang'an University, Chongqing University, and Yunnan Provincial Design Institute Group Co., Ltd. presents a comprehensive design study on medium-span deck-type ultra-high performance steel tube concrete (UHPC-SRC) bridges. The research was supported by the National Natural Science Foundation of China (Grant No. 52008026), the China Postdoctoral Science Foundation (Grant No. 2021M692746), and a central university high-tech research cultivation project (Grant No. 300102213207). The study is based on an actual project on the Hu-Wu Expressway and aims to promote the application of UHPC-SRC composite structures for bridge lightweighting and prefabrication.

Bridge Scheme Proposals

The authors proposed three bridge type schemes where the main structural members are primarily subjected to axial forces: composite truss girder bridge, tied-arch bridge, and cable-stayed plate bridge. Innovative features include the use of carbon fiber reinforced polymer (CFRP) hanger rods, CFRP prestressing tendons, and cold-formed roll-edge U-shaped cross beams combined with UHPC bridge deck panels.

Three Bridge Scheme Comparison

Scheme	Vertical Stiffness	Lateral Stability	Material Utilization	Construction Performance	Aesthetic Value
Simply supported composite truss girder	Moderate	Moderate	Moderate	Excellent	Moderate
Continuous composite truss girder	Relatively low	Moderate	Relatively high	Good	Moderate
Tied-arch bridge	Relatively large	Relatively poor	Moderate	Moderate	Excellent
Cable-stayed plate bridge	Relatively large	Relatively good	Moderate	Moderate	Excellent

Technical and Economic Analysis

Finite element models were established for each proposed bridge scheme to analyze strength, stiffness, stability, and dynamic characteristics. All verification results met the requirements of relevant specifications. The technical-economic analysis revealed the following material cost ratios under identical conditions:

Material Cost Ratio Analysis

Bridge Type	Relative Cost Ratio	Economic Assessment
Simply supported truss girder	1.00	Baseline
Tied-arch bridge	1.02	Slightly higher cost
Continuous truss girder	0.97	Most economical
Cable-stayed plate bridge	1.83	Significantly higher cost

The continuous composite truss girder offers the best economic performance, while the cable-stayed plate bridge has the highest material cost. However, the tied-arch bridge and cable-stayed plate bridge provide more prominent aesthetic effects, which may be preferred for landmark projects or urban expressway overpasses where visual impact is important.

Engineering Practice and Material Considerations

From a steel pipe manufacturing perspective, the use of UHPC-SRC composite structures in bridges introduces several important considerations. The rectangular steel tubes used in the composite truss girders and other structural members must be manufactured with high dimensional accuracy and surface quality to ensure proper bond with the UHPC infill. The steel tube material should have adequate strength and ductility to work in composite action with the UHPC.

Steel Tube Requirements for UHPC-SRC Bridge Structures

Parameter	Recommended Specification	Rationale
Steel grade	Q355 or Q420 per GB/T 1591	Adequate strength for composite action
Tube thickness	6-12 mm depending on span	Prevent local buckling under UHPC pressure
Surface treatment	Shot blasting to Sa 2.5	Ensure mechanical interlock with UHPC
Welding process	Submerged arc welding or gas metal arc welding	Ensure full penetration and weld quality
Dimensional tolerance	±1.0 mm for cross-sectional dimensions	Ensure proper UHPC infill and assembly

The CFRP hanger rods and prestressing tendons introduce additional complexity to the construction process. The anchorage systems for CFRP tendons require specialized design to ensure reliable load transfer and long-term durability. The cold-formed roll-edge U-shaped cross beams combined with UHPC deck panels represent an innovative approach to bridge deck construction that reduces dead weight and improves construction efficiency.

Study Insights and Reflections

This research demonstrates the feasibility and advantages of UHPC-SRC composite structures for medium-span bridge applications. The combination of UHPC and steel tubes provides high bearing capacity, high durability, construction convenience, and high prefabrication degree, meeting the current development needs for bridge lightweighting and thin-walled design. The study provides a valuable reference for the design of medium-span overpass bridges and the application of new materials such as UHPC and CFRP. The economic analysis clearly identifies the continuous composite truss girder as the most cost-effective option, while the aesthetic considerations may justify the higher cost of arch or cable-stayed schemes for specific projects. Future research should focus on long-term durability testing of UHPC-SRC composite members under fatigue and environmental exposure conditions.