Shear Behavior of Ultra-High Performance Concrete (UHPC)

As Ultra-High Performance Concrete (UHPC) is being applied in several structural systems and expanding into new applications in North America, understanding its shear behavior is critical to avoid failures that could be induced by diagonal cracks. Shear-dominated mechanisms in a number of applications can be affected by the tension and compression fields within the UHPC members. Assessing the vulnerability of UHPC members to combined shear and axial loads is important for the development of structural design guidance and key to UHPC’s wider acceptance in practice.

Furthermore, comparisons between theoretical and experimental data have shown that the shear behavior of UHPC girders may not be well understood and design equations could be overly conservative. This conservatism was attributed, in part, to member shape and size effects that were not incorporated in the design calculations (Tadros et al. 2021). These effects are well recognized to influence the shear capacity of concrete members (ACI 318-19). To safely expand the application range of PCI-UHPC in new building and bridge members, it is imperative to better quantify its shear behavior and improve accuracy of the design equations accordingly.

This project utilizes the unique capabilities of the Universal Panel Tester at University of Houston with the objective to understand the shear behavior of UHPC members under axial load and size effects and assist in the development of UHPC shear design equations. The Universal Panel Tester enables testing of full-scale panels that represent shear-resisting elements in UHPC members. The panels can be tested under any configuration of loading, including the combination targeted in this project with shear and axial loads. The experimental work is supplemented with a parametric computational study to investigate a broader set of design variables, including variations in the compression and tension loads, UHPC material properties and sizes, and transverse reinforcement ratios.

This research is expected to produce results that will facilitate the ongoing effort by ACI Subcommittee 239-C and PCI to develop a UHPC structural design guide.

Presentations:

1. American Concrete Institute Fall Convention (2023). “Experimental and Analytical Study on the Shear Behavior of UHPC Considering Axial Load Effects.”

2. American Concrete Institute Fall Convention (2022). “Experimental Investigation of Shear Behavior of UHPC Considering Axial Load Effects.” by Abdulrahman Salah, PhD student.

3. American Concrete Institute Fall Convention (2022). “Softened Membrane Model for UHPC.” by Noran Shahin, MSc student.

Publications:

1. Salah, A., Shahin, N., and Kalliontzis, D. (2023). “Experimental Study of Shear Behavior of UHPC Considering Axial Load Effects.” 3rd International Interactive Symposium on Ultra-High Performance Concrete, June 4-7, Wilmington, Delaware. https://doi.org/10.21838/uhpc.16637

2. Shahin, N. (2023). “A Softened Membrane Model for Ultra-High-Performance Concrete (SMM-UHPC).” MSc Thesis, Cullen College of Engineering, University of Houston, December 2023.

3. Kalliontzis, D., and Salah, A. (2024). “Material Characterization of Ultra-High-Performance Concrete (UHPC).” Database in DesignSafe-CI. https://doi.org/10.17603/ds2-7gar-ps40.

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