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H=Hyatt Regency Dallas; U=Union Station

UHPC – New Insights, Part 2 of 3

Sunday, October 23, 2022  1:00 PM - 3:00 PM, H-Reunion E

Ultra-high-performance concrete (UHPC) continues to attract more researchers, engineers, architects, students, and experts across disciplines due to its fascinating material properties.
Over the last decades novelties have been shared in material design, mixing technology, material characterization and application, structural performance and design. While more innovations and novelties have been shared and exciting application examples are being presented, more knowledge gaps, research needs and questions have been raised.

This session will invite national and international research groups, material suppliers and contractors to share new insights in UHPC technology, structural design and applications.

Learning Objectives:
(1) Describe the shear behavior of UHPC;
(2) Recognize its potential of interface shear;
(3) Evaluate new insights in material based dynamic impact factors;
(4) Appraise the potential of the softened membrane model for UHPC.


Experimental Investigation of Shear Behavior of Ultra-High Performance Concrete Considering Axial Load Effects

Presented By: Abdulrahman Salah
Affiliation: University of Houston
Description: 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. This research study utilized the unique capabilities of the Universal Panel Tester at the University of Houston to better understand the pure shear and combined axial-shear load behavior using UHPC panels representing full-scale elements in structural members. The Universal Panel Tester servo-control system’s ability to capture the entire pre-peak and post-peak response of bi-axially loaded elements allowed for a comprehensive understanding of the shear behavior of UHPC at different stages of loading. Experimental results will be used in the development of UHPC shear design formulas.


Shear Behavior of UHPC

Presented By: Amr Soliman
Affiliation: SUNY University of Buffalo
Description: It is well known that Ultra-High-Performance Concrete (UHPC), and Fiber-Reinforced Composites (FRC) in general, can achieve significantly higher shear strength compared to conventional concrete due to the contribution of the fibers. However, in the design standards/recommendations, the shear strength is estimated based on the compressive strength only, disregarding the effect of the fibers, leading to inefficient utilization of the UHPC. In this study, direct shear push-off tests are performed on six different UHPC and FRC composites to determine their direct shear strength. The parameters governing the shear strength are determined based on the cracking strength of the matrix and the post-cracking contribution of the fibers. A predictive model is developed to estimate the shear strength of different composites based on the matrix and fibers properties.


Softened Membrane Model for Ultra-High Performance Concrete

Presented By: Noran Shahin
Affiliation: University of Houston Central
Description: Understanding the shear behavior of UHPC members is crucial to avoid brittle responses that could be induced by diagonal shear cracks. This motivates the development of computational modeling methods that can capture the shear responses of UHPC members with good accuracy. However, most available modeling methods for UHPC members focus on simulating their flexure-dominant behavior, giving less or no consideration to shear-dominated effects. This research study utilizes the Softened Membrane model (SMM) to simulate the shear responses of UHPC panels that were tested in the Universal Panel Tester at University of Houston. To achieve good accuracy, a parametric study was conducted in order to calibrate a number of modeling parameters involved in the SMM. With the proposed modifications, the resulting SMM, named UHPC-SMM enables reliable calculations for the shear resistance of UHPC members. The intent of the research team is to incorporate UHPC-SMM in existing finite element frameworks and derive simplified analysis equations for use in practice.


Material Based Dynamic Increase Factor Models for UHP-FRC Under Compression and Tension

Presented By: Kay Wille
Affiliation: University of Connecticut
Description: Ultra-high performance fiber reinforced concretes (UHP-FRC) exhibit strain rate sensitivity when subjected to dynamic loadings. In recent years, concerns have been raised among researchers that structural effects, such as lateral inertial confinement and frictional confinement at the specimen’s face, could contribute to the strain rate sensitivity under high strain-rate testing using a split Hopkinson pressure bar (SHPB) besides material inherent property. The enhanced material strength by structural effect is often misinterpreted as material strain rate effect, and hence overestimating the material’s dynamic increase factor (DIF). If the overestimated DIF is used in numerical simulations, and some constitutive models have already adopted such overestimated DIF, the structural effects will be double-counted and misinterpreted as material property, leading to overestimated material resistance. To the best knowledge of the authors, there exists (1) no empirical equations for the nominal DIF models of UHP-FRC, which is directly obtained from experimental tests with structural effect; (2) no material based DIF models of UHP-FRC, which consider isolating structural effects. In this paper, based on the authors’ previous research on isolation of structural effects of UHP-FRC subjected to dynamic loadings, material based DIF models of UHP-FRC under compression and tension are proposed.

Upper Level Sponsors

Ash Grove
Baker
Conseal
Controls Group
Euclid Chemical
GCP
Master Builders
PoreShield
PS=0
ACI Northeast Texas Chapter

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