New Access Hatches in Existing Curved Box Girder Bridges: A Study Based onPractical and Structural Considerations

摘要

Steel box girders are inspected periodically by maintenance crews who walk orcrawl through the inside of the girders searching for signs of corrosion or damage. The interior of the box, which can be dangerous because of unusual temperatures and poor ventilation, is reached through access hatches that are usually provided in the bottom flange immediately before or after an expansion joint. These locations are chosen because (1) bending moments are small close to the expansion joint and (2) the pier over which the expansion joint is located facilitates access; inspection crews need only a ladder to reach the access hole. Nevertheless, the spans covered by box girders are often long, and the girders are constructed as continuous segments over three or more supports. Hence the distance between access hatches frequently exceeds the limit that rescue crews can reach in the event of an emergency. This situation has concerned safety officials and has prompted the Florida Department of Transportation safety office to request the construction of additional access holes in all existing box girder bridges. This study looks into finding locations where additional access holes can be placed in order to decrease the distance between access hatches in existing bridges.