What do bridge builders to avoid torsion?

To avoid torsion in bridges, bridge builders use various design strategies and construction techniques. Here are a few common methods employed to minimize torsion:

Symmetrical Design: Bridges are often designed with a symmetrical layout to distribute loads evenly and minimize the potential for torsion. This means that the bridge's structural elements, such as piers, beams, and cables, are arranged in a symmetrical manner on both sides of the central axis.

Truss Structures: Truss bridges are commonly used to withstand torsional forces. Truss bridges consist of a series of interconnected triangular elements that form a rigid framework. The triangular shape of the trusses helps to distribute loads efficiently and reduce the effects of torsion.

Box Girders: Box girders are hollow structures used in bridge construction. They consist of two parallel webs connected by top and bottom flanges. Box girders provide high torsional stiffness due to their closed shape and the efficient distribution of material within the cross-section.

Diaphragms and Cross-Bracing: Diaphragms and cross-bracing are structural elements installed within the bridge to enhance its torsional resistance. Diaphragms are transverse members that connect the main girders or trusses, while cross-bracing refers to diagonal members that provide additional support against lateral forces and torsion.

Continuous Bridges: Continuous bridges, also known as multi-span bridges, have their spans connected at the piers. This type of bridge design creates a continuous structural system that can better resist torsional forces compared to simply supported bridges, where the spans are not connected.

Moment-Resisting Connections: Bridge builders use moment-resisting connections to ensure adequate torsional resistance at the joints between different structural components. These connections allow for the transfer of bending moments and torques between the elements, preventing unwanted twisting.

Stiffening Girders: Stiffening girders are horizontal beams installed at regular intervals along the bridge deck. They help to distribute loads more evenly across the bridge and reduce the potential for torsional deformation.

Wind Baffles: Wind baffles are vertical structures placed on bridges to minimize the impact of wind forces. They disrupt the airflow around the bridge, reducing the generation of torsional forces due to wind.

By employing these strategies and techniques, bridge builders can effectively minimize torsion and ensure the structural integrity and safety of their bridges under various loading conditions.