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RE: Old bridges and rivets (again)

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Title: RE: Old bridges and rivets (again)

I have a "dead" rivet collection from the "El" in Chicago sitting on my shelf. It's now over a hundred years old and the rivets I've found have all been purposefully removed in the course of maintenance. But I digress....

A few thoughts about your questions:

I'll hazard a guess that the rivets that are missing are near deep pockets of corrosion between plies. Long-term corrosion can easily pop rivets out if unaddressed. If it's not corrosion, you'll need to determine why the rivets are missing.

I'm not sure why you doubt the rivets that are still in place. Exception: pay attention to those that are near pockets of corrosion between plies for the reasons stated above. To rehab this structure, you'll have to get all that rust pack outta there and that will probably mean rivet removal and replacement (they use A325 bolts in maintaining the El)

Welding to this old steel is probably possible, but may not be practical, depending upon the chemistry of what you've got. If you want to weld to it, you can investigate that further. A good reference for this is "Field Welding to Existing Structures" by David T. Ricker. This was published in the AISC Engineering Journal.

As far as the pony truss stability assessment, look at Joe Yura and Todd Helwig's AISC/SSRC bracing lecture notes. That specific example is discussed at length because it is such a notable example of torsional bracing. If you need to get a copy, call Bob Lorenz at AISC (312/670-5406).

Charlie