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.
The portal will probably require bracing to
limit drift and add strength to the portal.
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.
Above are some typical examples of ways to
brace a portal frame.
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.
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
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