Browsing by Subject "Restraint moment"

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    Full-Depth Precast Concrete Bridge Deck System: Phase II
    (Minnesota Department of Transportation, 2012-10) Halverson, Max; French, Catherine; Shield, Carol
    The Minnesota Department of Transportation (MnDOT) has developed a design for a precast composite slab-span system (PCSSS) to be used in accelerated bridge construction. The system consists of shallow inverted-tee precast beams placed between supports with cast-in-place (CIP) concrete placed on top, forming a composite slab-span system. Suitable for spans between 20 and 60 ft., the MnDOT PCSSS is useful for replacing a large number of aging conventional slab-span bridges throughout the United States highway system. The PCSSS has particular durability, constructability, and economical concerns that affect its value as a viable bridge design. To address these concerns, the performance of existing PCSSS bridges was evaluated and a review of a number of PCSSS design details was conducted. The field inspections demonstrated that design changes made to the PCSSS over its development have improved performance. A parametric design study was also conducted to investigate the effects of continuity design on the economy of the PCSSS. It was recommended that the PCSSS be designed as simply supported rather than as a continuous system.
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    Monitoring and Analysis of Mn/DOT Precast Composite Slab Span System (PCSSS)
    (Minnesota Department of Transportation, 2008-09) Smith, Matthew; Eriksson, Whitney; Shield, Carol; French, Catherine
    The Mn/DOT Precast Composite Slab Span System (PCSSS) was initially designed by Mn/DOT with input from the University of Minnesota researchers and local fabricators. The bridge system consisted of a series of precast prestressed concrete inverted tee bridge elements that also served as stay-in-place formwork for the cast-in-place (CIP) portion of the deck placed in the field. One of the Mn/DOT implementations, located in Center City, MN, was instrumented, and subsequently, monitored for 24 months to investigate reflective cracking and continuity over the piers since the deck was cast. The data obtained from the field study indicated that cracking had initiated in the bridge at the locations of some of the transverse gages in the CIP just above the longitudinal flange joint at midspan and some of the longitudinal gages near the support. The cracking was determined to be the result restrained shrinkage and environmental effects rather than due to vehicular loads. Transverse load distribution was evaluated with a static truck test. In addition, a two-span laboratory specimen was constructed and load tested to investigate effects of variations in flange thickness, bursting reinforcement, horizontal shear reinforcement, and flange surface treatment. The positive restraint moment that developed at the pier was also monitored for the first 250 days after continuity was made. The data from the laboratory and field tests were analyzed with respect to reflective cracking, transverse load distribution, pier continuity, bursting, and restraint moment, and design recommendations were made.