G. G. Portnov

FRP Reinforcing bars — designs and methods of manufacture (Review of Patents)

It is been suggested to devide all FRP reinforcing bars into three groups in accordance with the method used for establishing a bond between the core of the bars and concrete. Patents related to each group are cited and briefly described. At the end of the paper, ideas proposed in the patents are discussed. Problems connected with a practical implementation of FRP reinforcing bars will be considered in the next paper.

Grips for the transmission of tensile loads to a FRP strip

Designs of grips for flat strips made of fiber-reinforced polymers (FRPs) are put forward. They can be used for tests in tension, prestretching, and long-term loading. In order to prevent the rise of stress concentrations, special profiled grips with a varying surface curvature allowing the transmission of tensile loads to the strip by means of gradually increasing shear stresses (without peaks) have been elaborated. The results of a mathematical analysis of the stress state in the strip, an example of calculation, and experimental data obtained from testing a carbon-fiber-reinforced polymer strip in profiled model grips specially constructed for this purpose are presented.

Application of the theory of naturally curved and twisted bars to designing gorlov's helical turbine 1. System of governing equations

The method of designing a new type of turbine used in flows of various kinds is discussed. Static, kinematic, and constitutive equations for transversely isotropic naturally curved and twisted bars are given, and the hypotheses used are discussed. The statement of the problem is linear and corresponds to small displacements. A method for solving the statically indeterminate problem is proposed. The objectives of numerical calculations, which will comprise the content of the second part of the investigation, are formulated.

Fastening of a High-Strength Composite rod with a Splitted and Wedged end in a Potted Anchor 1. Experimental Investigation

The effectiveness of fastening of high-strength unidirectional CFRP/epoxy rods in potted anchors was investigated experimentally. The rods had splitted ends, in which duralumin wedges were glued. The experiments, performed for three types of contact between the composite rods and the potted material, showed that the most effective were full adhesion and adhesion–friction contacts, when the maximum load-carrying capacity of CFRP rods under tension could be reached. The full friction contact was ineffective because of the shear failure of CFRP rods inside the anchorage zone.

Rotation Stability of Anisotropic Disks

The critical state caused by the loss of stability of coils in rotating anisotropic disks is investigated by a numerical method. The investigation is performed for different ratios between the circumferential and radial elastic moduli and different relative thicknesses of the disks, Poisson ratios, and the ratios of radial and shear moduli. It is shown that, if a disk is made of materials compliant in the radial direction, the coils can lose their stability and shift according to the first harmonic (with displacement of the center of mass of the disk) or the second and third harmonics of vibrations (without displacement of the center of mass) within the range of its rotational velocities. These vibrations can be real for some materials, e.g., for unidirectional composites with a compliant (polyurethane) binder, and can precede the failure of disks from the action of circumferential stresses.

Fastening of a High-Strength Composite Rod with a Splitted and Wedged End in a Potted Anchor 2. Finite-Element Analysis

A finite element analysis is carried out to determine the stress-strain state of anchors for round rods made of a high- modulus, high-strength unidirectional carbon-fiber reinforced plastic. The rods have splitted ends in which Duralumin wedges are glued. Three types of contact between the composite rods and a potted epoxy compound are considered: adhesion, adhesion-friction, and friction ones. The corresponding three-dimensional problems in the elastic statement are solved by the finite-element method (FEM) with account of nonlinear Coulomb friction. An analysis of stresses on the surface of the composite rod revealed the locations of high concentrations of operating stresses. The results of FEM calculations agree with experimental data.