Lateral Support & Bracing of a Bridge

Single Truss

The following is an example of how to provide adequate lateral support(support in the Z direction) for your model. Lateral support is required to prevent the top of the truss from falling over due to lateral loads caused by wind or earthquake.

To prevent collapse in the Z direction, you will need to provide some sort of bracing system. The classic structural sub-system used for this is a portal frame.

Portal Frame

The portal will probably require bracing to limit drift and add strength to the portal.

Braced Portal Frame

The portal above has bracing to limit drift. Remember, the brace must go in the top of the portal because traffic is driving through the bottom portion of the portal.

Example Portal Frames

Above are some typical examples of ways to brace a portal frame.

Portal Frame Brace

Don't forget to brace the top of the portal if you have placed a connection there.

Add longitudinal bracing in the horizontal plane to brace the portal.

Sloping Portal Frame

The above sketch shows the final structural sub-system required in the bridge superstructure. Use the diagonal braces at the entrance of the bridge as a laterally braced portal.

Also see "Extra for Experts" (2d) and "Extra for Experts" (3d).

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