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I’m looking for any testing that has been done regarding the anchor bolts that are used to connect an AGT to the bridge concrete buttress. Our standard plan shows hex anchor bolts that go all the way through the buttress and use a nut and washer on the back side. We also have a detail for cast-in anchors, but I don’t know what kind of testing has been done on either of these anchorage methods.

We have a contractor that is wanting to attach guardrail to a bridge concrete buttress using wedge bolts, shown below. This would be for a temporary installation on the downstream end of a bridge, but it’d be for a full construction season on the interstate. The buttress is an old design that is over twice the thickness of a normal buttress and does not have any existing anchorage on the downstream end, so drilling all the way through it would not be easy. So I need to figure out what other options there might be.

The best option we have for that situation is to use Hilti HIS- N anchors with ¾” A325 bolts. These are post installed threaded inserts that can be epoxied in a barrier.

https://www.hilti.com/c/CLS_FASTENER_7135/CLS_ANCHOR_RODS_ELEMENTS_7135/r260?activeTab=preconfigured-kits-tabs

Anchorage for the end shoe is typically done with five, 7/8” diameter A307 bolts. The Hilti HIS-N anchors with ¾” A325 bolts provide similar capacity due to the higher bolt grade. The anchors also provide for consistent installation and sufficient capacity to develop the entire bolt strength.

For other transitions dealing with PCBs, we have used alternative anchorages. We have used five ¾” screw bolt mechanical anchors in those systems without any issues. While the wedge bolt anchors have 26.5% lower cross-sectional area, the have almost 2.5 times the yield strength and 1.5 times the ultimate strength. These would not be as robust as the HIS-N option above and they are not as consistent in terms of installation. However, they might be applicable in this more temporary application.

https://anchors.dewalt.com/anchors/products/mechanical-anchors/screw-anchors/screw-boltplus/screw-boltplus_hex_head.php

Use of a threaded rod that extends past the nut for the thrie beam connection causes some concern as the threaded rod poses an extended snag threat along the vehicle. As such we have not typically used them.

Thanks