Partial Depth Precast Panels: State-of-the-Practice
Presented By: Andrew Foden
Affiliation: HNTB
Description: Partial-depth precast concrete deck panels (PDDPs) are widely used in bridge construction to accelerate project delivery and enhance quality control. These relatively thin, prestressed precast elements span between girders and act compositely with a cast-in-place (CIP) concrete topping to form the full structural deck thickness. PDDPs offer notable benefits, including improved safety, simplified design, and reduced construction duration. This presentation summarizes the state-of-the-practice for PDDP design and construction, drawing on standard methodologies from six states with extensive experience in their use. Key topics include design criteria, fabrication techniques, and installation procedures, providing a practical overview for engineers, contractors, and transportation agencies seeking to implement or refine PDDP strategies in accelerated bridge construction programs.
End Zone Reinforcement for Precast/Prestressed Concrete Bridge Girders
Presented By: Yail Jimmy Kim
Affiliation: University of Colorado Denver
Description: This presentation examines the performance of different reinforcement arrangements in the end zones of prestressed concrete bulb-tee girders. A standard girder from a local transportation agency, featuring C-bars and spirals designed to mitigate cracking, is analyzed using three-dimensional finite element modeling. The models are employed to assess the end-zone width, strain behavior, crack patterns, damage levels, and splitting forces according to the specific reinforcement configuration. The quantity of C-bars does not significantly affect the development of strand stress along the girder. Maximum principal stresses surpass the conventional h/4 limit (with h representing girder depth); however, the 3h/4 threshold effectively captures the stress distribution, especially within the web. Concrete tensile strain varies with girder elevation, inclined strands induce local compression in the C-bars, and spiral strain remains largely unaffected by the number of bars.
Precast Concrete Elements for Transportation Projects
Presented By: Nestor Rubiano
Affiliation: Decon LLC
Description: The design, detailing, and construction of Precast Concrete Elements for transportation projects is presented using several cases studies including bent caps, prestressed girders, retaining and sound walls, etc. These cases illustrate the process from the conceptual stage, structural design, and reinforcement detailing to the construction phase and operation.
Innovative Precast Truss Beam Design for Bridges Using 3D Concrete Printing and Shape Memory Bars
Presented By: Bassem Andrawes
Affiliation: Univ of Illinois at Urbana-Champaign
Description: Standard precast concrete bridge girders typically have consistent cross-sections along their entire length. While this design simplifies construction, it also reduces material efficiency. This study proposes the use of geometrically optimized girders that have improved strength-to-weight ratios, leading to decreased material usage. The concept is initially explored through finite-element analysis of a topology-optimized concrete girder reinforced with locally prestressed shape memory alloy (SMA) bars. This innovative type of reinforcement can apply thermally triggered prestressing forces without the need for mechanical jacking. The analysis indicates that this optimized girder uses less material than conventional designs while still meeting the AASHTO limit states. A second design is developed by modifying an AASHTO Type-II girder so that its web functions as a Howe truss. This design balances the advantages of optimized geometry while maintaining ease of construction. Three large-scale prototype truss specimens are constructed and tested under three-point bending. One specimen is precast using traditional forms, while the other two are additively manufactured using a large-scale 3D concrete printer. To mitigate tensile cracking in all three specimens, SMA bars are employed to induce internal prestressing forces in the tensile members of the truss. The approach of using 3D concrete printing to combine optimization with constructability proves effective. The use of SMA bars in the tensile members of the truss effectively prestresses these members, preventing tensile cracks under service conditions.
Resolving Challenges Involving Precast Bridge Elements in the Southeast
Presented By: Samuel Keske
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: This presentation will review the author’s review and resolution of challenges working with various precast concrete bridge products, particularly within the southeastern United States. Topics will cover potential concerns regarding the effects of fabrication, erection, and construction detailing on ease of construction and long-term durability. Reviewed elements are anticipated to include precast substructures, girders, and girder-deck systems.