Anchor bolts corroded ....Repairs?

[moonwalker]

Anchor bolts(1 3/4" dia.) of a steel tower are corroded just above the base plates and reduced in section down to between 1" dia. and 1 1/2" dia. I am asking for advice or recommended specs for fixing this condition while the steel columns are in place. The base plates sit on reinforced concrete foundations that extend to about 21 ft below grade and with 10" projection above the surrounding asphalt concrete.

 

[VoyageofDiscovery]

Hi Moonwalker,

If the existing a/b are capable of shear capacity, I would drill into the concrete new a/b rotated 90 degrees, outside the base plate, to handle the design uplift (actually, more for future loading).

These a/b should then be tied together by rectangular bars subjected to shear only from the existing base plate during uplift. The ends of the bars will have a welded collar for the a/b.

In plan view, if your a/b pattern is square you will then have a square of bars with collars at the corners.

Regards,

VOD

 

[QSE]

You have an interesting problem, here is a suggestion

1-First priority is to stop further corrosion. Apply galvicon with paint brush with the nuts removed, assuming the nuts are not spot welded. (Of course, remove nut on one anchor at a time, and not on a windy day) Other suggestions are welcome

2-Do you have access to tower reactions and anchor bolt spec.? If so, check anchors for combined shear and uplift considering anchors with reduced section. Anchors are normally designed conservatively and if that is the case existing reduced anchors could be adequate. If you do not have access to tower reactions, then a structural analysis is required, you should know what you are dealing with.

3-Reinforcement, if necessary, can then be designed and implemented.