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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 1254 Abstracts search results
April 22, 2021
Marta Roig-Flores, Eduardo J. Mezquida-Alcaraz, Ariel A. Bretón-Rodríguez, Juan Navarro-Gregori and Pedro Serna
Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) is a type of concrete with superior mechanical and durability properties, which might be improved even further with the addition of nano-materials. This work studies the influence of adding nano-additions to two UHPFRCs with compressive strength around 150MPa (21755 psi), with and without crystalline admixtures. Two nano-materials were considered: cellulose nano-crystals (4-5 nm diameter, 50–500 nm length, 0.157-0.197 μin diameter, 1.97-19.7 μin length); in a dosage up to 0.15% by the cement weight; and aluminum oxide nanofibers (diameter 4-11nm, length 100-900nm, 0.157-0.433 μin diameter, 3.94-35.4 μin length) in a dosage of 0.25% by the cement weight. Water content of the mixes with nanomaterials was modified to maintain workability in a similar range aiming to maintain the self-compacting behavior. The following properties were analyzed: workability, compressive strength, modulus of elasticity and tensile properties calculated through a simplified inverse analysis after performing four-point bending tests. The study considered the effect of using three levels of mixing energy to ensure a proper dispersion of all the components, and its effect in the aforementioned properties. The results show a potential effect of these nanomaterials as nanoreinforcement,
with slightly better ultimate strength and strain values for the higher energy level.
March 1, 2021
Serhan Guner, Trevor D. Hrynyk, and Andac Lulec
Current computational modeling approaches used to evaluate the impact-resisting performance of
reinforced concrete infrastructure generally consist of high-fidelity modeling techniques which are expensive in terms
of both model preparation and computation cost; thus, their application to real-word structural engineering problems
remains limited. Further, modeling shear, erosion, and perforation effects presents as a significant challenge, even
when using expensive high-fidelity computational techniques. To address these challenges, a simplified nonlinear
modeling methodology has been developed. This paper focuses on this simplified methodology which employs a
smeared-crack continuum material model based on the constitutive formulations of the Disturbed Stress Field Model.
The smeared-crack model has the benefit of simplifying the modeling process and reducing the computational cost.
The total-load, secant-stiffness formulation provides well-converging and numerically stable solutions even in the
heavily damaged stages of the responses. The methodology uses an explicit time-step integration method and
incorporates the effects of high strain rates in the behavioral modeling of the constituent materials. Structural damping
is primarily incorporated by way of nonlinear concrete and reinforcement hysteresis models and significant secondorder
mechanisms are considered. The objective of this paper is to present a consistent reinforced concrete modeling
methodology within the context of four structural modeling procedures employing different element types (e.g., 2D
frames, 3D thick-shells, 3D solids, and 2D axisymmetric elements). The theoretical approach common to all
procedures and unique aspects and capabilities of each procedure are discussed. The application and verification of
each procedure for modeling different types of large-scale specimens, subjected to multiple impacts with contact
velocities ranging from 8 m/s (26.2 ft/s) to 144 m/s (472 ft/s), and impacting masses ranging from 35 kg (77.2 lb) to
600 kg (1323 lb), are presented to examine their accuracy, reliability, and practicality.
Thong M. Pham, Tin V. Do, and Hong Hao
This study experimentally and numerically investigated the impact responses of reinforced concrete (RC)
beams with a rectangular hollow section (HCB) in comparison with a rectangular solid section (SCB). Experimental
tests of the two types of RC beams were firstly conducted under the drop-weight impact of a 203.5-kg-solid-steel
projectile. Numerical models of the beams under impact loads were then developed in the commercial software namely
LS-DYNA and carefully verified against the experimental results. The numerical models were then used to investigate
the stress wave propagation in the two beams. The effect of the top flange depth, contact area, and impact velocity on
the impact responses of the beams was also investigated. The experimental and numerical results in this study showed
that although the two beams were designed with similar reinforcement ratio, their impact responses were considerably
different, especially when the shear failure dominated the structural response. The HCB exhibited a smaller peak
impact force but higher lateral displacement than the SCB when these beams were subjected to the same impact
condition. Besides, more shear cracks were observed on the HCB while that of SCB has more flexural cracks.
Furthermore, the decrease of the top flange depth of the hollow section and the increase of the impact velocity changed
the failure modes of the two beams from flexural failure to shear failure with concrete scabbing. The change of the
contact area also shifted the failure mode of the beam from global response to direct shear, inclined shear, punching
shear and concrete scabbing at the top flange of the section close to the impact location.
Andrew D. Sorensen, Robert J. Thomas, Ryan Langford and Abdullah Al-Sarfin
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.
Tarek Kewaisy, Ayman Elfouly, and Ahmed Khalil
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.
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