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UHPC is a relatively new material for precast, prestressed concrete bridge products. This material has been generally used for connections between adjacent precast members. Significant effort is underway in the precast industry to bring UHPC into the mainstream for precast bridge girder products.

UHPC features in this software are considered to be experimental. They are based on structural design guidance developed by PCI (1) and the draft AASHTO LRFD Guide Specifications for Structural Design with Ultra-High-Performance Concrete (2). The design guidance is based on research, international guidelines and testing. UHPC features are subject to change and may be removed at any time. They may be incomplete, inaccurate, and incompatable with guides, specifications and research reports that have been published or may be published in the future.

Features based on design guidance in (1) are noted as PCI UHPC and based on (2) are noted as UHPC.

Through 2022, the AASHTO Committee on Bridges and Structures, Technical Committee 10 (T-10) has been reviewing proposed structural design guidance and have been developing a draft guide specification for balloting in 2023. The guide specification is closely aligned with the design guidance developed by FHWA. This software conforms withthe AASHTO guide specifications prior to balloting by the AASHTO Committee on Bridges and my not reflect the final design guidelines.

The AASHTO LRFD Bridge Design Specifications are applicable for bridges with specified concrete strength up to 15 ksi. UHPC is a high strength material with specified concrete strength in the range of 18-22 ksi. The equations, procedures, recommendations, and other related information from the AASHTO LRFD Bridge Design Specifications are applied to UHPC concrete members. The applicability of the AASHTO LRFD Bridge Design Specifications to UHPC concrete members has not been verified or validated.

There are many potential benefits of UHPC precast, pretensioned concrete bridge components. UHPC can lead to smaller, lighter, and more efficient girders. Experimental girders made from UHPC have thinner webs and flanges, greatly reducing weight. Web and flange buckling are typically not a concern for traditional precast girders. Web and flange buckling, and other behavior related to thin members, are not evaluated by this software. Additional analysis beyond the scope of this software may be required.

Because of fibers in UHPC, some tension capacity can be relied upon for shear strength. In some cases, UHPC girders can be constructed without shear stirrups. This translates to significant savings in labor and materials during girder fabrication.

‍Implementation of UHPC structural design guidance developed by PCI or AASHTO should not be construed as an endorsement of the methodology by the Washington State and Texas Departments of Transportation. The UHPC features in this software are developed by the Washington State DOT and are a service to and indended to support the bridge engineering community at large as UHPC class materials evolve into common use. WSDOTs intentions are to implement other structural design guidance currently under consideration and ultimately provide implementation for a single, unified, approach to UHPC design based on any AASHTO guide specifications that may be published in the future.

References

Tadros, et. al., "Implementation of Ultra-High Performance Concrete in Long-Span Precast Pretensioned Elements for Concrete Buildings and Bridges, Phase II Report", PCI, September 2021
"Proposed Draft Version of AASHTO LRFD GUIDE SPECIFICATIONS FOR STRUCTURAL DESIGN WITH ULTRA-HIGH-PERFORMANCE CONCRETE", submitted for balloting to AASHTO Committee on Bridges, February 2023.

‍USE THESE EXPERIMENTAL FEATURES WITH EXTREME CAUTION