Summer 2019

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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ASPIRE Summer 2019 | 39 C O N C R E T E B R I D G E T E C H N O L O G Y by Dr. Ayman M. Okeil and Marco Canales, Louisiana State University; Dr. Mohsen Shahawy, SDR Engineering; and Jenny Fu, Louisiana Department of Transportation and Development Ouachita River Bridge /RXLVLDQD·V7HVW%HGIRU/LQN6ODEV This article describes a research project to evaluate a simplified continuity detail that is now adopted in the recently released revision 8 of the Louisiana Department of Transportation's LaDOTD Bridge Design and Evaluation Manual (BDEM). 1 The new detail calls for a continuous deck slab over the joint between the ends of simply supported prestressed concrete girders, 2 which is different from the previous standard detail in which girder ends from adjacent spans were embedded in a continuity diaphragm after a bond breaker was applied to allow for relative movement. The simplified detail discussed here i s a l s o di f f er e n t f ro m t h e d e t a il recommended in National Cooperative Highway Research Program Report 519, 3 in which full continuity is achieved by extending positive moment reinforcement into continuity diaphragms. The latter detail was employed on another LaDOTD project. 4 Several states have adopted similar simplified details, which may be referred to as "link slabs"; however, there is no consensus on a rational design for this type of detail, and its behavior in service is not yet fully understood. LaDOTD used the Ouachita River Bridge as a test project to evaluate the performance of several variations of the link-slab detail and the older continuity-diaphragm detail. Ouachita River Bridge Project The new Ouachita River Bridge carries Louisiana Highway 8 over the Ouachita River at Harrisonburg, La. It has a clear roadway width of 44 ft and consists of 20 spans with a total length of 3275 ft. All spans, except for the three-span main unit crossing the river, have a typical cross section consisting of American Association of State Highway and Transportation Officials (AASHTO) bulb- tee (BT-72) prestressed concrete girders supporting an 8.5-in.-thick slab. There are three types of units: the typical unit has two 135 ft continuous spans (270 ft); one unit has four continuous 135 ft spans (540 ft); and there is a single 135 ft simply supported span. Design variations, such as continuity details, numbers of spans per unit, link-slab reinforcement materials (stainless steel versus mild steel bars), and crack control details, were used at different locations. Two diaphragm details were used at interior supports of continuous units: Detail I for "floating" units, which are not fixed to bents, and Detail II for "anchored" units, which, when required, are tied to a bent by reinforcement extending into the full- depth diaphragm. A 1 3 6 - s e n s o r s t r u c t u r a l h e a l t h - monitoring sys tem was ins talled to assess performance of the different details. Strains, displacement, rotations, and ambient environmental conditions Configuration of approach spans for the new Ouachita River Bridge. Note: E = expansion bearing, F = fixed bearing. The type of link-slab detail (I or II) used at each interior bent is also indicated. Figure: Dr. Ayman Okeil.

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