Live Load Testing and Load Rating of Five Reinforced Concrete Bridges
Five cast-in-place concrete T-beam bridges – Eustis #5341, Whitefield #3831, Cambridge #3291, Eddington #5107, and Albion #2832 – were live load tested. Revised load ratings were computed either using test data or detailed analysis when possible. In four of the five bridges, increases in rating factors were made through analysis alone. The Cambridge bridge was shown to have HL-93 operating rating factors greater than 1.0 for both shear and moment without testing. Additionally, gains are presented for two of the five bridges (Eustis and Whitefield) where test data were used to compute an adjustment factor K for midspan bending, where the revised rating factor equals K x RF. Adjustment factors were found to be 1.61 and 1.24 for Eustis and Whitefield, increasing their flexural rating factors to 1.14 and 1.06 if accepted by the Maine Department of Transportation (DOT). Similarly, the authors’ analyses indicate that Eustis has a rating capacity greater than 1.0 for shear. While Whitefield has a rating factor greater than 1.0 for shear at the supports, the rating factor for shear near the termination of the bent-up reinforcing is 0.48 based on the authors’ analyses. Low loads used in the live load tests of both Albion and Eddington, where only one truck was provided on site, preclude the development of revised rating factors based on the test data. However, both of these structures did exhibit better-than-expected live load distribution. Further, analysis of the Albion bridge indicates that the consultant-provided load ratings for this structure can likely be increased significantly. Use of these revised load ratings, live load test data, and extrapolation of these results to other structures is at the sole discretion of the bridge owner. The objective of this study, to implement an effective live load testing bridge program, was fulfilled.