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Development of UHPC Connection of Precast Bridge Elements (PBES) for Accelerate Bridge Construction Projects.

Description:

State DOTs operate under great expectations to minimize impact to the traveling public and commerce that result from construction activities. Given the operational needs of DOTs, project timelines have become more compressed and prescriptive in terms of when and how long they occur. In response to the need to minimize construction windows, DOTs have developed several accelerated bridge construction (ABC) tools that are focused at reducing construction duration and disruption to traffic operations. One aspect of the construction is the time required to erect bridge substructures. In recent years, several DOTs have developed Precast Bridge Elements and Systems (PBES) that are modular concrete elements. These elements are typically fabricated away from the construction site, brought to the site, and erected quickly. These precast concrete elements are generally of high quality and with precise details that can be attained in a controlled fabrication shop. However, the connection details often depend on grouted couplers that are mated with field placed reinforcement bars requiring a high degree of precision to successfully align and attach the precast elements.

The use of grouted couplers and associated tight tolerances add to the complexity, risk, and cost of using these elements in an accelerated construction environment. These adverse aspects of the grouted coupler connections may discourage DOTs from specifying PBES and may discourage contractors from electing them as a tool in managing construction schedules and delivering projects.

As an alternative, connections of PBES (piers and abutments) could be accomplished with the use of short conventional reinforcement and Ultra High-Performance Concrete (UHPC). This type of connection incorporates shorter reinforcement development lengths as resulting laps. If a practical connection could be developed that assured the DOTs and contractors that the tight tolerances and complexity of a grouted coupler joint could be avoided, there would be more desire and willingness by DOTs and contractors to incorporate the PBES in projects.

There would be several likely benefits with a simplified UHPC connection of PBES piers and abutments. They would include lower project risk of erecting misalignment, opportunity for the contractor to fabricate the elements with their own staff as opposed to purchase from a fabricator, shorter construction windows by inclusion of PBES, and increased safety to contractor staff and traveling public through reduced interaction of contractors and traffic operations. Use of UHPC connections will make precast elements more efficient and more desirable by industry. This could lead to wider acceptability and more frequent use of PBES for substructure design and construction.

Objective:

The objective of this research is to develop and test the details for the connection of precast pier elements using UHPC. Connections typically made with mechanical or grouted couplers will be detailed with UHPC connections that meet strength and fatigue requirements of the PBES elements. This research could also provide code guidance on development lengths of reinforcement, shear strength of connection region to be incorporated into the AASHTO LRFD Bridge Design Specifications. The intent of this research is not to develop connection details that are resistant to significant or extreme seismic loading.

Benefits:

This work will help simplify and remove construction risk associated with using PBES. This will lead to greater acceptability by DOT owners and construction contractors. This will ultimately lead to contractor buy-in on the use of PBES to deliver projects in shorter time frames with details that do not represent risk in erecting.

Related Research:

  • NCHRP 12-102 [Completed] AASHTO Guide Specification for ABC Design and Construction
Tasks:

  1. Study the existing inventory of State DOT ABC Projects that utilize PBES Precast Bridge Elements to document details used by DOTs to connect PBES. The FHWA National ABC Project Exchange should be utilized in developing and assessing the current inventory of ABC projects.

  2. Identify a subset of pier and abutment connection geometries representative of what has been utilized by DOTs in recent years.

  3. Develop example connection details that utilize UHPCs and model with appropriate analytical methods and software to determine the structural behavior.

  4. Develop and conduct laboratory tests that examine and validate analytic model results relating to strength and serviceability of UHPC connections for precast elements (piers and abutments).

  5. Produce design and construction guidance of connection details that are reflective of typical substructure geometries used by DOTs

  6. Develop AASHTO LRFD Bridge Design Specification guidance.

Implementation:

This research will give bridge designers and contractors tools to implement UHPC connection details in substructure elements. The use of PBES will become more desirable by Owners, Designers, and Contractors by simplifying the connection detail, removing the risks associated with alignment of grouted couplers, and reducing the overall project risks to schedule and cost.

Relevance:

Increased frequency of inclusion of PBES piers and abutments in construction projects at lower costs. More frequent occurrence of contractors viewing PBES as lower risk and doing the fabrication of PBES in their own yards or on job sites with their own staff.

Sponsoring Committee:AFH40, Construction of Bridges and Structures
Research Period:24 - 36 months
Research Priority:High
RNS Developer:William L. Oliva
Source Info:William L. Oliva
Chief of Structures Development Section
Wisconsin Department of Transportation
(608) 266-0075
William.oliva@dot.wi.gov
Date Posted:01/06/2019
Date Modified:01/11/2019
Index Terms:Ultra high performance concrete, Concrete bridges, Precast concrete, Structural connection, Bridge construction, Bridge members,
Cosponsoring Committees: 
Subjects    
Highways
Construction
Design
Materials
Bridges and other structures

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