The Beishan Touring Steel Pipe Structure in Xiaoshan City, Zhejiang Province, is a fully welded arched steel tube structure located on the Tonghui section of National Highway 4. Designed as a prominent landmark, it consists of several key components including the arch rib, top beam, billboard, truss, horizontal contact, bridge, and piers. The entire steel structure weighs approximately 850 tons. This paper presents a detailed structural analysis, focusing on static and dynamic behavior, stability, and finite element modeling.
The main arch rib is composed of steel pipes arranged in a square truss configuration with a clear span of 193 meters. It is made up of 40.81.15 segments, with the arch axis following a parabolic curve and a central angle of 91.674 degrees. The billboard, also a steel truss structure, measures 8.8 meters in length, 10.5 meters in width, and 16.1 meters in height, weighing around 132 tons. It is installed at a height of 54.21 meters above ground level, with a 3.0-meter-wide sidewalk beneath it. The billboard and arch rib form an integrated system that works together to provide structural support.
A reinforced concrete pedestrian bridge is situated on the bridge piers, spanning 75.1 meters in length. These piers are connected by a steel tube structure, forming a unified system. The total weight of the steel part is approximately 961 tons. The foundation rests on rock strata with a compressive strength ranging from 500 to 800 kPa. Static analysis was conducted using a spatial structure model, with beam elements representing the steel pipes. All connections were considered as rigid joints, and various simplifications were applied during the finite element modeling process.
The design of the structure ensures that the angles between branch and main pipes, diameter ratios, and wall thickness ratios meet code requirements. No eccentricity effects were considered in the node analysis. The connection between the arch foot and pier is fixed, while the arch top beam is hinged to the foundation. The model includes 646 nodes and 5,376 space beam elements, capturing the complexity of the structure.
In terms of loading, the primary static loads include self-weight, temperature, and wind. The temperature difference is considered as ±20°C, and the wind pressure at 10 meters height is 1.78 kN/m². Load combinations were analyzed to ensure safety under different conditions. The maximum vertical displacement of 125.85 mm was observed, which is about 1/500 of the net span, indicating sufficient stiffness. Most cross-sections showed stresses between 100–150 MPa, confirming adequate strength.
Dynamic analysis revealed that the fundamental frequency of the structure is significantly higher than typical rigid arches, indicating a more flexible system. The first mode is antisymmetric, and the second mode is symmetric, with the structure showing good stability against wind loads. However, the torsional modes suggest that the arch top beam plays a significant role in higher-order vibrations.
Seismic analysis was performed using the response spectrum method, with a damping ratio of 5%. The results showed that seismic displacements and internal forces were lower than those from design loads, meaning seismic action is not critical. Overall stability checks confirmed that the structure meets all required safety factors, both globally and locally.
In conclusion, the Beishan Touring Steel Pipe Structure demonstrates excellent performance in terms of stiffness, strength, and stability. Its unique design and advanced analysis methods ensure long-term safety and functionality. Future studies may focus on optimizing its dynamic response and enhancing wind resistance further.
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