PMI/PCCM SEMINAR SERIES SPRING 2025: Barzin Mobasher, Arizona State University

Hosted by Reza Moini
Date
Feb 5, 2025, 12:25 pm – 1:30 pm
Location

Details

Event Description

Reinforcement Design in Structural Concrete using Multi-Scale Hybrid Applications

Abstract: More than 4 billion tons of Portland cement is used in concrete production once it is reinforced with more than 500 million tons of steel rebar every year. This single application contributes more than 10% of the carbon footprint of the developing world. The tools of design are based on a macroscopic perspective that assigns tensile loads to the steel while ignoring any potential contribution from the brittle concrete. Furthermore, the design approach has remained scientifically stagnant due to the straightforward and simplified building codes that rely on 100-year-old solution strategies as concrete under tension has all the weight and carbon footprint cost, but contributes nothing to the overall efficiency. In this talk I address the utilization of toughening mechanisms to improve the design efficiency in brittle matrix composites and address concrete reinforcement design from a microstructural point of view.
While fiber reinforcement in concrete has been used for more than 60+ years, the adoption of enhanced tensile properties using secondary reinforcement to focus on serviceability and efficiency are still under development. Our research activity focuses on closed loop control tension, flexure, high-speed, impact, fatigue, full-structural scale, and creep tests. Models based on non-linear fracture, strain energy dissipation using R-Curves, and plasticity- based moment-curvature section properties are then used to better understand alternative reinforcement strategies to develop Ultra-High-Performance Concrete (UHPC), Textile reinforced concrete (TRC), and hybrid applications. Design tools incorporated in the efficient design reduce the volume of the section and rebars while improving the durability.
Our research focuses on toughening mechanisms such as: strain softening and hardening, distributed cracking, tension stiffening, debonding and pullout, toughening by crack bridging, deflection, and blunting. Once activated, these mechanisms dissipate significant energy through fracture toughness of distributed damage, and lead to quasi-plastic behavior of matrix that prevents structural collapse. The analytical solutions represent the constitutive response using parametric piecewise linear segments which integrate stress distribution over the strain profile to satisfy the internal equilibrium. Generalized solutions in closed-form parametric terms are presented for any material model and applicable to tension, flexural, and compression members.
Highlighted applications conducted in the past five years showcase the cost savings of using FRC, TRC, and UHPC as breakthroughs of mechanical performance and enhanced durability compared to conventional concrete. By correlating the ductility, crack width, stiffness degradation, and fatigue response at service loads, material and structural design can be concurrently designed. Case studies are presented for beams, slabs, retaining walls, precast tunnel lining, light rail track slabs, bridge components, shotcrete canal lining, and buried structures. Other examples include corrosion prevention by replacement of steel rebars with steel fibers which provide significant construction savings.

 

Bio: Barzin Mobasher obtained his BS, MS, and PhD. in Civil Engineering from University of Wisconsin-Platteville, Northeastern University, and Northwestern University in 1983, 1985, and 1990 respectively. After a brief two-year career in Industry, he joined Arizona State University in 1991 as Assistant Professor of Structural Materials and has been a professor of engineering at the School of Sustainable Engineering and Built Environment at ASU since 2004. Dr. Mobasher has led programs involved with the design, analysis, materials testing, and full-scale structural testing of construction, structural, and aerospace materials. His publications include two books on fiber and textile reinforced concrete, five edited books, and more than 220 research papers in leading professional journals and conference proceedings. His fundamental contributions are in the analytical and experimental fields of fiber and textile reinforced concrete materials, their application areas, and mechanics of toughening in UHPC, textile composites, durability modeling, and experimental mechanics. He has served as the Chair of American Concrete Institute, ACI committee 544 on Fiber Reinforced Concrete, and Technical Activities Committees of both ACI and RILEM. He is a fellow of both ACI and RILEM.

All seminars are held on Wednesdays from 12:25 -1:30p.m. in the Bowen Hall Auditorium Room 222.   A light lunch is provided at 12:00p.m. in the Bowen Hall Atrium immediately prior to the seminar.