Deck Overlays and Connections

UHPC Placement for Bridge Deck Replacement - Casting Sequencing and Staging

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Abstract

The purpose of this presentation is to demonstrate UHPC placement techniques for various types of precast bridge component connections ranging from longitudinal joints only to more complex systems which include a combination of longitudinal and transverse joints with beam haunches or shear pockets. The presentation will address the importance of appropriate staging for on-site mixing equipment as well as the sequence of placement for various types of applications. Mitigation of risk along larger projects will be addressed by the installation of strategic bulkheads to portion sections into manageable pour amounts. A typical layout of precast sections will be dissected as a simple scenario to examine and simplify UHPC placements into sections. Placement mechanisms for UHPC mixing and transportation from mixing station to placement will be addressed for various types and sizes of projects. The material placement and transition of open field joints to closed system joints will be addressed using the head pressure system along with commonly used practices to ensure projects are poured efficiently and effectively. The presentation will elaborate on placement techniques for structures with longitudinal joints only (e.g. Adjacent Box Beams, Deck Bulb Tees,Next Beams, Prefabricated Bridge Units,etc.) and more complex systems with longitudinal and transverse joints that all intersect(e.g.Full-Depth Deck Panels, Half-and/or Full-Width Panels, Beam Haunches, Shear Pockets, etc.). An example of a more complex system is illustrated below. This example is of atypical single-span bridge composed of precast deck panels with longitudinal and transverse UHPC joints and continuous beam haunches, all of which intersect. The UHPC placement for a system like this is typically partitioned into multiple pours using bulkheads in strategic locations. The blue tick marks in the illustration represent leave-in-place bulkheads located in the beam haunch areas and the redtick marks represent temporary bulkheads located in the deck-level connections. This partitioning is performed during UHPC placement to split up the pours into manageable volumes consistent with the mixers’ output capacity and the UHPC’s working time. Generally, the beam haunches and deck-level joints are completed in one monolithic pour between the bulkhead locations. The bulkheads also help to minimize the volume of UHPC lost should the formwork start to leak during placement. The sequencing of UHPC placement and the staging of equipment are critical factors that need to be considered prior to commencing UHPC placement on-site. Most specifications will require the Contractor to submit a UHPC Placement Plan outlining the proposed sequencing and staging for the UHPC placement. This presentation will highlight the key considerations for developing an appropriate Placement Plan on a typical bridge project with UHPC connections.

How to Cite:

Dlugosz, L. & Rebrovich, J., (2019) “UHPC Placement for Bridge Deck Replacement - Casting Sequencing and Staging”, International Interactive Symposium on Ultra-High Performance Concrete 2(1). doi: https://doi.org/10.21838/uhpc.9726