Steel Structure Bridge Truss

The layout and connection of steel structure bridge trusses are key links in bridge design and construction, which are related to the stability, safety, service life, and economy of the bridge. The following are the main considerations and design methods for the layout and connection of steel structure bridge trusses:

(1) Span and load analysis

Span calculation: The layout of bridge trusses should first be determined based on the span of the bridge, and the span size is the key to design. Conduct structural analysis based on traffic flow, bridge deck width, and loads (such as vehicle loads, pedestrian loads, wind loads, etc.) to ensure that the truss can effectively share these loads.

Load distribution: Bridge truss design needs to consider how different types of loads (such as live loads, dead loads, temperature loads, etc.) are distributed on the truss, and calculate appropriate structural dimensions and node positions through structural analysis.

(2) Geometric shape and arrangement of truss

The relationship between bridge span and depth: Large span bridge trusses are often arranged in geometric shapes such as triangles, rectangles, or inverted triangles. Common types of trusses include planar trusses and spatial trusses.

The design of trusses should meet practical needs: for longer bridges, multiple truss systems are usually required for support; For wider bridges, it may be necessary to add secondary trusses or strengthen the design of the main truss.

Support position selection: The support of the truss is usually set at both ends or in the middle of the bridge (if it is a multi span bridge) to ensure uniform structural stress. The support form can be fixed bearings, hinged bearings, etc.

(3) The combination of truss and bridge deck structure

The truss is usually the main load-bearing part of the upper structure of the bridge, and its combination with the bridge deck requires a reasonable arrangement of support points and connection methods to ensure that the load of the bridge deck can be effectively transmitted to the truss, and then transmitted to the supports of the bridge through various nodes of the truss.

(4) Height and depth of bridge truss

The height and depth of the truss are related to the bearing capacity and stiffness of the bridge. Reasonable truss height helps bridges maintain good stability under load. The height of the truss is generally adapted to the span, load, and design requirements of the bridge.

(1) Node connection method

Welding connection: Welding is a commonly used connection method in steel structure bridge trusses, especially at node connections. Welding can provide high-strength and dense connections, suitable for parts that bear large loads, and is usually used for complex triangular or other irregularly shaped truss nodes.

Bolt connection: Bolt connection is a common connection method, suitable for various parts of bridge trusses, especially when nodes need to be disassembled or maintained. High strength bolts can provide strong connection force and are easy to construct. Bolt connections are commonly used for vertical and horizontal branch nodes of bridges.

Rivet connection: Rivet connection is still used in some old steel structure bridges. Riveted connections are not as flexible as welding and bolted connections, but they are still effective for some old-fashioned truss structures.

(2) Node design

Simple supported nodes: Simple supported nodes are commonly used in bridges that require bearing unidirectional loads, typically at both ends of the bridge truss. Simple supported nodes are connected to other parts of the bridge through supporting bearings, facilitating the transfer of loads.

Fixed nodes: For parts that bear large bending moments, bridge truss nodes may be designed as fixed nodes. Fixed nodes can increase the stability of the structure and are suitable for the main truss part of bridges.

Articulated nodes: In designs that require allowing for truss rotation or significant deformation, articulated nodes can be used. Articulated connections can reduce the stiffness of the structure, allowing it to adapt to deformations caused by factors such as temperature and load changes.

(3) Connection between truss and support

The support of the truss is an important connecting part of the bridge truss. The design of support connections should ensure the stability of the bridge under load. The forms of bearings can be divided into fixed bearings, hinged bearings, and rolling bearings. The selection of bearings should take into account the type of load the bridge is subjected to, geological conditions, and design requirements of the bridge.

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