Experimental Evaluation and Field Monitoring of Prestressed Box Beams for SCC Demonstration Bridge

2007PDFTech ReportBurgue\uf1o, RigobertoBendert, David A.Michigan State University. Department of Civil and Environmental EngineeringMichigan. Dept. of TransportationMichigan. Dept. of Transportation. Construction and Technology DivisionMichiganUnited StatesBox beamsFlexural strengthPrestressed concreteSelf compacting concreteShear strengthShrinkageConcrete bridgesBridges and other structuresHighwaysI24: Design of Bridges and Retaining WallsRC-14892002-053211-09-04 to 12-31-06Self-consolidating concrete (SCC), with its ability to flow without vibration, minimize construction labor and achieve superior finish quality, is very attractive to the concrete industry. However, its acceptance in the U.S. has been slow. Particularly in bridge applications, where questions and concerns about design and construction issues perceived to influence the performance of members built with SCC have prevented Departments of Transportation (DOT) from accepting SCC. With support from the FHWA and the Michigan DOT, the demonstration project, summarized in this report, has permitted the evaluation of the aforesaid concerns. The M-50/US-127 Bridge over the Grand River, B02 of 38071 (Jackson, Michigan) features SCC prestressed box beams on half of its structure (3 beams). The demonstration project considered the evaluation of three different mix design approaches to SCC together with a reference normally consolidated concrete mix (NCC). Before the SCC beams were accepted for implementation, their performance was evaluated through full-scale (27\u201d x 36\u201d x 52\u2019) structural testing to ensure that their flexural and shear performance was equal to or better than that exhibited by the NCC beams. All of the SCC beams met the nominal flexure and shear design capacities and their performance with respect to the NCC beams was found to be essentially the same. The SCC beams were thus approved for use on the demonstration bridge and construction was completed in October 2005. To evaluate of long-term performance, a field monitoring system composed of thermocouples and strain gages was placed on the SCC beams and one of the NCC beams at different cross-sections along their lengths and one year of recorded data, from December 2005 to December 2006, has been studied. The data shows that while some variations exist in the initial strain levels of the girders (due to concrete variations such as shrinkage and elastic modulus), the variation of strain once the bridge was in service seems to be very similar for all girders. However, it is recognized that the monitoring process has been in place for slightly over a year. Evaluation of true long-term performance will require acquisition of data for several more years before more sound conclusions on the long-term behavior of SCC prestressed elements can be reached.95