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Showing 1-5 of 15 Abstracts search results

Document: 

SP347

Date: 

March 15, 2021

Publication:

Symposium Papers

Volume:

347

Abstract:

Sponsors: Sponsored by ACI 370 Committee Editors: Eric Jacques and Mi G. Chorzepa This Symposium Volume reports on the latest developments in the field of high strain rate mechanics and behavior of concrete subject to impact loads. This effort supports the mission of ACI Committee 370 “Blast and Impact Load Effects” to develop and disseminate information on the design of concrete structures subjected to impact, as well as blast and other short-duration dynamic loads. Concrete structures can potentially be exposed to accidental and malicious impact loads during their lifetimes, including those caused by ballistic projectiles, vehicular collision, impact of debris set in motion after an explosion, falling objects during construction and floating objects during tsunamis and storm surges. Assessing the performance of concrete structures to implement cost-effective and structurally-efficient protective measures against these extreme impacting loads necessitates a fundamental understanding of the high strain rate behavior of the constituent materials and of the characteristics of the local response modes activated during the event. This volume presents fourteen papers which provide the reader with deep insight into the state-of-the-art experimental research and cutting-edge computational approaches for concrete materials and structures subject to impact loading. Invited contributions were received from international experts from Australia, Canada, China, Czech Republic, Germany, South Korea, Switzerland, and the United States. The technical papers cover a range of cementitious materials, including high strength and ultra-high strength materials, reactive powder concrete, fiber-reinforced concrete, and externally bonded cementitious layers and other coatings. The papers were to be presented during two technical sessions scheduled for the ACI Spring 2020 Convention in Rosemont, Illinois, but the worldwide COVID-19 pandemic disrupted those plans. The editors thank the authors for their outstanding efforts to showcase their most current research work with the concrete community, and for their assistance, cooperation, and valuable contributions throughout the entire publication process. The editors also thank the members of ACI Committee 370, the reviewers, and the ACI staff for their generous support and encouragement throughout the preparation of this volume.


Document: 

SP-347_04

Date: 

March 1, 2021

Author(s):

Tarek Kewaisy, Ayman Elfouly, and Ahmed Khalil

Publication:

Symposium Papers

Volume:

347

Abstract:

For protective construction applications involving high-velocity projectile impacts, design engineers rely on properly designed reinforced concrete barriers to provide the necessary resistance to penetration. Typically dynamic testing, analytical, semi-empirical and/or computational approaches are called upon to properly handle this highly complex physical problem. The presented research evaluates the use of Applied Element Method (AEM), implemented in Extreme Loading for Structures (ELS) software, to predict the localized damage and penetration of concrete slabs due to high-velocity normal impacts of rigid projectiles. Two validation cases were considered involving different concrete and reinforcing rebar material properties and projectile impact velocities. The applicability of AEM simulations was validated by comparing predicted damage and projectile penetrations to corresponding observations and measurements obtained during impact testing. A limited parametric study including seven analytical cases was performed to investigate the effects of varying concrete strengths, reinforcement arrangements and concrete thickness on the penetration resistance of concrete targets. To achieve this, three concrete classes; Normal Strength Concrete (NSC), Medium Strength Concrete (MSC) and High Strength Concrete (HSC), three reinforcement configurations (unreinforced, single-layer/ larger bar, double-layers) and larger thickness were considered. The application of the engineering-oriented AEM/ ELS software was found to provide impact response predictions that are in good agreement with physical test results. The results of the parametric study confirmed the advantages of using higher concrete strengths and higher reinforcement ratios in improving the penetration resistance and reducing the scabbing damage of reinforced concrete barriers.


Document: 

SP-347_07

Date: 

March 1, 2021

Author(s):

Andrew D. Sorensen, Robert J. Thomas, Ryan Langford and Abdullah Al-Sarfin

Publication:

Symposium Papers

Volume:

347

Abstract:

The impact resistance of concrete is becoming an increasingly important component of insuring the durability and resilience of critical civil engineering infrastructure. Design engineers are not currently able to use impact resistance as a performance-based specification in concrete due to a lack of a reliable standardized impact test for concrete. An improved method of the ACI standard, ACI 544.2R-89 Measurement of Properties of Fiber Reinforced Concrete, is developed that provides a resistance curve as a function of impact energy and number of blows (N) to failure. The curve provides information about the life cycle (N) under repeated sub-critical impact events and an estimate of the critical impact energy (where N=1), whereas the previous method provided only a relative value. The generated impact-fatigue curve provides useful information about damage accumulation under repeated impact events and the effectiveness of the fiber-reinforcement. In this paper, the improved method is demonstrated for three fiber types: steel, copolymer polypropylene, and a monofilament polypropylene. Additionally, the analytical solution for the specimen geometry is given as well as the theoretical considerations behind the development of the impact-life curve. The use of a specimen geometry provides a path to generalize the test results to full-scale structures.


Document: 

SP-347_01

Date: 

March 1, 2021

Author(s):

Iurie Curosu, Viktor Mechtcherine, Daniele Forni, Simone Hempel and Ezio Cadoni

Publication:

Symposium Papers

Volume:

347

Abstract:

Synopsis: Strain-hardening cement-based composites (SHCC) represent a special type of fiber reinforced concretes, whose post-elastic tensile behavior is characterized by the formation of multiple, fine cracks under increasing loading up to failure localization. The high inelastic deformability in the strain-hardening phase together with the high damage tolerance and energy dissipation capacity make SHCC promising for applications involving dynamic loading scenarios, such as earthquake, impact or blast.

However, the main constitutive phases of SHCC, i.e. matrix, fibers and interphase between them, are highly rate sensitive. Depending on the SHCC composition, the increase in loading rates can negatively alter the balanced micromechanical interactions, leading to a pronounced reduction in strain capacity. Thus, there is need for a detailed investigation of the strain rate sensitivity of SHCC at different levels of observation for enabling a targeted material design with respect to high loading rates.

The crack opening behavior is an essential material parameter for SHCC, since it defines to a large extent the tensile properties of the composite. In the paper at hand, the rate effects on the crack opening and fracture behavior of SHCC are analyzed based on quasi-static and impact tensile tests on notched specimens made of three different types of SHCC. Two SHCC consisted of a normal-strength cementitious matrix and were reinforced with polyvinyl-alcohol (PVA) and ultra-high molecular weight polyethylene (UHMWPE) fibers, respectively. The third type consisted of a high-strength cementitious matrix and UHMWPE fibers. The dynamic tests were performed in a split Hopkinson tension bar and enabled an accurate description of the crack opening behavior in terms of force-displacement relationships at displacement rates of up to 6 m/s (19.7 ft/s).


Document: 

SP-347_11

Date: 

March 1, 2021

Author(s):

Victor Lopez, Mi G. Chorzepa, and Stephan A. Durham

Publication:

Symposium Papers

Volume:

347

Abstract:

This paper presents the drop-weight impact performance of recycled tire chip and fiber-reinforced cementitious composites. Emphasis is placed on maximizing the energy dissipation capacity of rubberized fiber reinforced concrete (FRC) mixtures subjected to impact forces for the purpose of improving the impact resilience of concrete elements such as concrete traffic barriers and other applications. The first part of this study involved smallscale testing of preliminary mixtures to optimize compressive strength, modulus of rupture, and impact resilience using a fixed percentage of tire chip replacement of the coarse aggregate and varying volume fractions of steel, polypropylene, and polyvinyl alcohol fibers. Rubberized FRC beams were then tested under static loads to maximize the static energy dissipation potential of steel fiber inclusion at varying tensile steel reinforcement ratios. The final part of this study involved performing scaled drop-weight impact tests on reinforced concrete beam. Results confirmed that rubberized and/or fiber reinforced cementitious composite members exhibit significantly improved energy dissipation capacity and impact resilience, particularly with 1.0% steel fiber addition and 20% tire chip replacement. It was observed that more energy was dissipated through the steel fiber addition alone than FRC mixtures with the tire chips.


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