Lateral bracing of bridge girders

Structural Engineering general discussion Bridge Design
#1

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QUESTION
Can anybody give me guidence (or suggest any book) for design of lateral (wind) bracing of bridge girders.How we can incorporate/add wind load in to the load calculations during construction i.e before placement of concrete deck?

REPLIES

bridgebuster
You can design the bracing system as though it were a truss. I assume you checked AASHTO to see if bracing is needed.

If this is LRFD you have to perform the calculation for bracing the compression flange during construction. If you’re using the Standard Specs no check for construction conditions is required. However, there are methods you could use. For instance, check the girder about the weak axis assuming the diaphragms act as a support.

The old old US Steel bridge design manuals had an example.

#2

For calculating the wind loads on erected girders (before stay in place forms, etc. that block the wind from going around the girders), there’s also a recently released AASHTO guide spec for Wind Loads during construction (1st edition, 2017).

After stay-in-place forms are in place, the wind loading is the AASHTO bridge design spec would govern.

We generally provide diagonal bracing in one bay between girders which attaches to girders at the rows of cross frames or diaphragms, usually near the bottom flange. The presence of the cross frames provides lateral bracing to both flanges.