Innovative structural and aesthetic design of a large-span all-steel footbridge

With the continuous development of the urban process, more and more street crossing facilities are shifting from the construction of underground passages back to the erection of above-ground steel footbridges. The direct reason for this shift is that steel footbridges have the advantages of light weight, strong spanning ability, low impact of construction on environment and traffic, recyclable later and adaptable to architects’ diversified shapes.

Structural and aesthetic design of footbridges

The main bridge has a clear height of 5 m and the main girder is a single span structure with a span of 43.6 m. The main girder adopts a variable cross-section double-lower flange welded H-girder with a section height of 0.75 m transitioning from the mid-span of 1.3 m to the root of the support, and the 4 bays of the main girder are connected to the whole by the welded box shaped steel pipe crossbeams with a spacing of 3 m and a height of 0.7 m, which are supported on double-bay inwardly inclined steel columns, and the columns adopt welded box shaped rectangular steel pipes with a maximum cross sectional size of 0.9 m×0.6 m. The maximum cross sectional size of the columns is 0.9 m×0.6 m. The steel columns are made of welded rectangular steel tubes with a maximum cross-section size of 0.9 m×0.6 m. Meanwhile, in order to meet the needs of architectural space modeling, the roof of the bridge is made of hot-rolled seamless steel tubes welded to the side girders, thus forming a space structure. Except for the foundation, which is made of concrete, all the other components of the bridge are made of steel, and the steel material is Q345B.

The architects pursued simplicity as much as possible in the form of the building, and for this reason, the structure was selected from a number of options, including straight columns, curved arch supports, and two-bay inwardly inclined steel folded columns, finally settling on two-bay inwardly inclined columns that support the staircase as well as the main girders. In order to enhance the aesthetic effect of the superstructure, cross-layered spiral steel pipes were installed above the sidewalk bridge deck.

After determining the main vertical load bearing members as steel folded columns, in order to maximize the structural material to give full play to its load bearing potential, the horizontal main girder is made of double lower flange welded H-steel, and the cross-section height is transitioned from 1.3 m in the middle of the span to 0.75 m at the root of the support with the load bearing state. This structural aesthetics not only saves the structural material, but also meets the requirement of the architect for the structure to be as light as possible. This structural aesthetic design not only saves structural material, but also meets the architect’s requirement of making the structure as light as possible.