Field and Laboratory Testing of Precast Concrete Channel Bridges

• Published in: Transportation research record 2006-01, Vol.1976 (1976), p.88-94
• Main Authors: Wipf, Terry, Klaiber, F., Ingersoll, J., Wood, Douglas
• Format: Article
• Language: English
• ISSN: 0361-1981
• DOI: 10.3141/1976-12

The precast channel bridge (PCB) was commonly constructed on Iowa's secondary roads approximately 40 years ago. Each PCB span consists of eight to 10 simply supported precast panels ranging in length from 19 to 36 ft. The panels resemble a steel channel in cross section; the web is orientated horizontally to form the roadway deck, and the vertical legs act as shallow beams. Bundled bars in each leg are used for flexural reinforcement. Many of the approximately 600 PCBs in Iowa show signs of significant deterioration. Typical deterioration consists of spalled concrete cover and corrosion of the bundled primary reinforcement. The objective of this research was to assess the structural sufficiency of the deteriorated PCBs through field and laboratory testing. Four deteriorated PCBs were instrumented with strain gauges to measure strains in both the concrete and the reinforcing steel and with transducers to measure vertical deflections. Responses from loaded trucks were recorded and analyzed. Test results revealed that all measured strains and corresponding stresses were well within acceptable limits. Likewise, measured deflections remain well below the maximum recommended AASHTO values. Laboratory testing consisted of loading 12 deteriorated panels to failure in a four-point bending arrangement as well as testing a fourpanel model bridge. Although all panels exhibited significant deflection before failure, the experimental capacity of 11 of the panels exceeded their theoretical capacity. Service tests and an ultimate strength test were performed on the laboratory bridge model to determine the effect of various keyway connection configurations.