V. S. Gopalaratnam

Bio: V. S. Gopalaratnam is an academic researcher from University of Missouri. The author has contributed to research in topics: Fiber-reinforced concrete & Fracture mechanics. The author has an hindex of 14, co-authored 28 publications receiving 2131 citations. Previous affiliations of V. S. Gopalaratnam include American Concrete Institute & University of Illinois at Chicago.

RILEM TC 162-TDF: Test and design methods for steel fibre reinforced concrete' - sigma-epsilon-design method - Final Recommendation

Abstract: General information Publication status: Published Organisations: Section for Structural Engineering, Department of Civil Engineering Contributors: Vandewalle, L., Nemegeer, D., Balazs, L., Barr, B., Barros, J., Bartos, P., Banthia, N., Criswell, M., Denarie, E., Di Prisco, M., Falkner, H., Gettu, R., Gopalaratnam, V., Groth, P., Hausler, V., Kooiman, A., Kovler, K., Massicotte, B., Mindess, S., Reinhardt, H., Rossi, P., Schaerlaekens, S., Schumacher, P., Schnutgen, B., Shah, S., Skarendahl, A., Stang, H., Stroeven, P., Swamy, R., Tatnall, P., Teutsch, M., Walraven, J. Pages: 560-567 Publication date: 2003 Peer-reviewed: Yes

On the characterization of flexural toughness in fiber reinforced concretes

Abstract: The article comprises two parts. The first part presents a summary of the available methods of characterizing the flexural toughness of fiber reinforced concretes (FRC), with a review of most of the toughness standards and guidelines from standards institutions and other professional agencies in North America, Europe and Japan. Also reviewed are other significant proposals available in the published literature. The second part of the article includes a discussion of the merits and drawbacks of these measures. Other related issues discussed include: the fundamental significance, problems with regard to experimental measurements and the potential for practical design implementation of a toughness measure.

Tensile Failure of Steel Fiber‐Reinforced Mortar

Abstract: Results are discussed from experimental and theoretical studies on the tensile failure of short, steel fiber-reinforced mortar/concrete SFRC composites. A displacement-controlled test method for conducting stable fracture tests on tension-weak brittle materials developed in an earlier study has been used for conducting uniaxial tension tests. Several concrete, mortar, paste, and SFRC mixes were tested. Fracture of SFRC in tension is observed to be influenced largely by the matrix softening behavior, the fiber-matrix interfacial response, and its composition parameters. The theoretical model proposed for the idealized SFRC composite takes into account these two primary nonlinear aspects of the failure mechanism in such composites, i.e., (1) the inelastic behavior of the fiber-matrix interface, and (2) the softening characteristics of the matrix. The model, in addition, is realistically sensitive to the reinforcement parameters like fiber volume content, aspect ratio, and the elastic properties of the fiber.

Plastic-Damage Model for Cyclic Loading of Concrete Structures

Abstract: A new plastic-damage model for concrete subjected to cyclic loading is developed using the concepts of fracture-energy-based damage and stiffness degradation in continuum damage mechanics. Two damage variables, one for tensile damage and the other for compressive damage, and a yield function with multiple-hardening variables are introduced to account for different damage states. The uniaxial strength functions are factored into two parts, corresponding to the effective stress and the degradation of elastic stiffness. The constitutive relations for elastoplastic responses are decoupled from the degradation damage response, which provides advantages in the numerical implementation. In the present model, the strength function for the effective stress is used to control the evolution of the yield surface, so that calibration with experimental results is convenient. A simple and thermodynamically consistent scalar degradation model is introduced to simulate the effect of damage on elastic stiffness and its recovery during crack opening and closing. The performance of the plastic-damage model is demonstrated with several numerical examples of simulating monotonically and cyclically loaded concrete specimens.

Two Parameter Fracture Model for Concrete

Abstract: Attempts to apply linear elastic fracture mechanics (LEFM) to concrete have been made for several years. Several investigators have reported that when fracture toughness, Klc, is evaluated from notched specimens using conventional LEFM (measured peak load and initial notch length) a significant size effect is observed. This size effect has been attributed to nonlinear slow crack growth occurring prior to the peak load. A two parameter fracture model is proposed to include this nonlinear slow crack growth. Critical stress intensity factor, KIcS, is calculated at the tip of the effective crack. The critical effective crack extension is dictated by the elastic critical crack tip opening displacement, CTODc. Tests on notched beam specimens showed that the proposed fracture criteria to be size independent. The proposed model can be used to calculate the maximum load (for Mode I failure) of a structure of an arbitrary geometry. The validity of the model is demonstrated by an accurate simulation of the experimen...

Fiber-reinforced concrete: An overview after 30 years of development

Abstract: This paper presents a rhetorical discussion on the subject of fiber-reinforced concrete, FRC. It is intended as an overview of the types of commercially available FRCs and how they work. It discusses commonly applied terminology and models of mechanical behavior that form a basis for understanding material performance without presenting mathematical details. Historical review is intended to help build a background for what is currently understood about FRC rather than as historical reporting. References from both early and contemporary authors are included as a means of tying the subject together along a time line.

Properties of strain hardening ultra high performance fiber reinforced concrete (UHP-FRC) under direct tensile loading

Abstract: Enhanced matrix packing density and tailored fiber-to-matrix interface bond properties have led to the recent development of ultra-high performance fiber reinforced concrete (UHP-FRC) with improved material tensile performance in terms of strength, ductility and energy absorption capacity. The objective of this research is to experimentally investigate and analyze the uniaxial tensile behavior of the new material. The paper reviews and categorizes a variety of tensile test setups used by other researchers and presents a revised tensile set up tailored to obtain reliable results with minimal preparation effort. The experimental investigation considers three types of steel fibers, each in three different volume fractions. Elastic, strain hardening and softening tensile parameters, such as first cracking stress and strain, elastic and strain hardening modulus, composite strength and energy dissipation capacity, of the UHP-FRCs are characterized, analyzed and linked to the crack pattern observed by microscopic analysis. Models are proposed for representing the tensile stress–strain response of the material.