Web Hole Analysis

[cazkoop]

We are performing a load rating on a bridge that exhibits significant corrosion of the steel webs near the abutments. There are several holes in the webs near the bottom flanges, the largest of which is 2" high, 16" long. I am having trouble calculating the shear capacity. I am uncomfortable using the reduced web depth for calculating a conventional shear capacity (reduced d x tw x Fy), but I also believe I should not give a capacity of zero either. Is there any information out there for analyzing such a case?

Thanks for any information.

 

[Qshake]

There is sufficient redistribution for the load especially if it doesn't exhibit any distress in the web above the corroded area.

But many factors are at play here. It could be that the web has never experience a load that would yield the web or that the properties of the girder are greater than thought or the redistribution or others.

It is common practice to use the decreased depth to determine the load rating for shear. Again your going to determine what percentage of a HS20 vehicle may traverse the bridge. That percentage may not even be as low as to match with the typical traffic on the bridge.

The fix is relatively simple. Plate the old web and provide angles which attach the new web plates to the bottom flange.

Regards,
Qshake

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