Corrosion of steel bridge Girder anchor bolts
MetadataShow full item record
The research objectives for this project were to explicitly define the anchor bolt corrosion problem in the state of Georgia and recommend action to the Georgia Department of Transportation. The bearing assembly of concern is the plate bearing assembly, in which carbon steel and/or bronze plates are anchored by either carbon steel or stainless steel anchor bolts. Inspection report data revealed that anchor bolt corrosion was ubiquitous for all environments in Georgia; the problem was reported for 27% of the steel girder bridges throughout the state. Based on a synthesis of the field investigations, bolt failure analyses, laboratory experimental testing, and review of GDOT inspection report surveys, the corrosion of carbon steel anchor bolts is caused universally by concentration cell corrosion. Other corrosion mechanisms of concern are galvanic and crevice corrosion, which are both enhanced by the current bearing design. Corrosion protection provided through zinc galvanization cannot sufficiently protect the carbon steel bolt for its entire service life. Corrosion potential and cyclic polarization data confirmed that ASTM Type 304, Type 316, Type 2101, and Type 2205 were protected from concentration cell and localized corrosion in the simulated bearing environment. Therefore, it is recommended that the stainless steel anchor bolts of these types be use in future designs and that the bolts should be electrically separated from all dissimilar metals using a Nylon or Teflon washer to prevent preferential corrosion of carbon steel. It is further recommended that the bronze lube plate should be eliminated entirely and that the bearing type should be a reinforced elastomeric bearing. Maintenance of existing sliding plate bearings should include regular cleaning by brushing away debris from the bearing surfaces, and bridges with carbon steel anchor bolts should be retrofitted to provide additional lateral restraint according to current maintenance procedures.