Structural Evaluation of Precast Concrete Channel Beams in Bridge Superstructures

During the period from the mid-1950s through the mid-1970s a large number of bridges were constructed throughout Arkansas using a 5.79-m (19-ft) long, precast, non-prestressed, concrete channel beam that was then standard. A survey of highway departments has identified 12 states that have used a similar bridge element in the past. It has been determined that nearly 400 of these bridges remain in use in Arkansas alone. Recently, the Arkansas State Highway and Transportation Department discovered that a number of these sections are exhibiting potentially serious deterioration. The deterioration appears to have been initiated by corrosion of the flexural reinforcement in the beam stems. An additional issue is that these beams were fabricated without any shear reinforcement. Moreover, some sections are showing signs of concrete degradation. The need to determine the in-place load capacity, serviceability, and durability of these sections has reached a critical level. To date, 20 beams have been removed from existing structures and tested for their flexural load capacity and the material properties of the concrete and longitudinal reinforcement. Results have varied depending on the extent of deterioration. However, in nearly every case shear failure has controlled the load capacity of a section. Based on this research, a draft field guide, intended for use by inspection crews, is being prepared. This guide will aid inspectors in prioritizing sections for repair, rehabilitation, and removal.