ACI 123 Forum: The Great Shear Failure Debate: Is It Cracked?

Incredible American Concrete Institute 123 forum this year discussing all things shear related! Half laughs and half serious (becoming a trend). All the fun sponsored by: Nishant Garg (co-moderator), Evan Bentz, Remy Lequesne, Dimitrios Kalliontzis, Giorgio Proestos and Trevor Hrynyk!

SP-I Lab participation higlighted some of our work on UHPC shear and considerations to fiber alignment effects. Here is the abstract of our talk:

UHPC Shear and Fiber Alignment: Does it Matter? How to Measure it?

Presented By: Dimitrios Kalliontzis
Affiliation: University of Houston
Description:

Bio

Dimitrios Kalliontzis is an Assistant Professor at the University of Houston. He completed his postdoctoral research at UC San Diego, where he investigated the shear behavior of the prestressed concrete piles in the Coronado bridge. At UH, he is using the Universal Panel Tester to investigate the shear behavior of UHPC.

Abstract

Though it may appear simple to mechanistically approach UHPC as an extension of conventional, or other fiber-reinforced, concretes, the structural behavior of UHPC under shear loads is complex and characterized by significant uncertainty. Evidence shows that fiber-fluid interactions at casting can alter the UHPC shear stress-strain behavior by 39% or more. Neglecting these interactions, pouring method, and formwork wall boundary effects can compromise shear model predictions. A multi-physics based approach is thus needed to understand how fibers flow during UHPC casting and to predict their alignment in the direction of interest for shear. Research performed with the Universal Panel Tester at the University of Houston provides a roadmap on how we can characterize and incorporate fiber alignment effects in UHPC shear models for improved simulation results. Future work intends to correlate these findings to fiber alignment predictions from computational multi-physics fluid-structure-interaction models.