Fracture Energy of Steel Fiber-Reinforced Concrete
Steel fiber-reinforced concrete (SFRC) is a cementitious material reinforced with discrete fibers. The energy absorption capacity is the main material property benefited by fiber reinforcement. Closed-loop servo-controlled equipment should be used to evaluate this property. The tests should be carried out using displacement control in order to obtain the postpeak force- displacement relationship (tensile strain-softening branch). To assess the fracture energy of SFRC, three-point bending tests were carried out using displacement control. Series of notched beams reinforced with 30, 60, and 90 kg/m3 of hooked-end steel fibers were tested. Besides the energy dissipated in fracturing the concrete, the energy determined from the force-displacement relationship can also include the energy absorbed during nonlinear behavior of concrete in compression. Ductile materials, such as concrete reinforced with a high content of fibers, develop large deflections before exhausting their energy absorption capacity. In these cases, the "fixed" points of the bar supporting the displacement transducer may not remain fixed, adding an extra deflection into the control displacement transducer and thus leading to incorrect evaluation of the fracture energy. These factors are analyzed in the present work in order to assess the suitability of the specimen dimensions and the test procedures for evaluating the fracture energy of SFRC.
Toughness Characterization of Steel‐Fiber Reinforced Concrete
The paper describes an experimental program in which four deformed commercial fibers with widely different geometries were investigated in steel‐fiber reinforced concrete. Three matrices with compressive strengths of 42, 52, and 85 MPa were reinforced with fibers at a dosage rate of 40 kg/m3. Compressive and flexural strengths were measured along with the elastic moduli. The focus of the study, however, was to measure and characterize the toughness improvements in the basic matrices due to the addition of various fibers. To this end, flexural load‐deflection curves were analyzed in accordance with the ASTM and Japan Society of Civil Engineers (JSCE) standard methods and also using a proposed‐analysis scheme. The paper points out the limitations of the current techniques of toughness characterization and identifies this as an area with immediate research needs. For the fibers and the matrices investigated, a strong influence of both fiber geometry and matrix strength on the toughness characteristics of fib...
A survey of aquaculture production economics and management
Abstract The literature on production economics and management of fish culture has grown as aquaculture has matured as a commercial industry. Salmon, catfish, shrimp and trout are the focus of this literature survey as a reflection of the volume of research that has been completed on these species and their importance in US production and world trade. In addition, a discussion of low resource production systems is included that is dominated by tilapia and carp culture systems. A brief overview of the principles of aquaculture production economics and management is presented followed by a review of economic studies.