Size effect of parallel-joint spacing on uniaxial compressive strength of rock

The existence of parallel joints has an impact on the size effect of the uniaxial compressive strength of rock, but the relationship is yet to be obtained. In this paper, the influence of parallel-joint spacing on the size effect and characteristic size of rock uniaxial compressive strength is studied by establishing five types of parallel-joint-spacing simulation schemes. The influence of parallel-joint spacing on the size effect of rock uniaxial compressive strength is explored by analyzing the stress–strain curves of rocks with different parallel-joint spacings and rock sizes. The relationship between the uniaxial compressive strength and the size of the rock with parallel joints and its special mathematical model are obtained, and the particular form of the compressive-strength characteristic size and parallel-joint spacing is obtained.

INFLUENCE OF STIFFNESS RELATED TO THE C40 STRENGTH CLASS OF THE HARDWOOD GROUP ESTABLISHED BY THE BRAZILIAN STANDARD IN THE DESIGN OF TIMBER STRUCTURES

The Brazilian standard ABNT 7190 (1997) establishes the strength classes C20, C30, C40 and C60 for the proper framework of the different wood types in the group of hardwoods. Associated with the strength class, which is based on the compressive strength characteristic value parallel to the fibers (fc0,k), the standard stipulates the respective values representing the stiffness (Ec0), with 19500 MPa being the reference value for the class C40, essential variables in structural design. For being the C40 class is the one with the greatest amplitude (20 MPa), it is possible that the value 19500 MPa is not the best representation of stiffness. This work aimed to verify the representativeness the stiffness value established by the Brazilian standard for C40 wood. The result obtained from the average confidence interval indicates the value of 14110 MPa as being the most representative, which may imply structures that are supposedly more rigid than they really are.

The Effect Of Special Exercises Using Assistive Devices To Build A Movement Program According To Some Biokinetic Variables In Teaching The Performance Of The Shooting Skill From The Angle, Opposite The Throwing Arm In Handball For Junior

Objectives of the study: Preparing special exercises using auxiliary means according to the values of some biomechanical variables to teach the performance of the shooting skill from the angle, unlike the preferred side of the junior handball. Knowing the effect of special exercises using auxiliary means on the values of some Biokinetic variables in teaching the skill of shooting from the corner, unlike the preferred side of the junior handball. Conclusions: The results showed the effectiveness of using special exercises according to the mechanical foundations of the angle shooting skill, unlike the preferred side of the hand ball for emerging players through the high level of shooting accuracy as a result of the development in the level of the series of biomechanical variables in the pre and post tests and in favor of the post test.The special exercises contributed directly to the development of the variables and characteristics of the strength characteristic, which showed in the development of values (the lowest strength in the absorption stage, the time of the lowest strength in the absorption stage, the maximum strength in the rise stage, and the area under the curve). Recommendations: The necessity to focus on the biomechanical laws that basically control every stage of performance, the skill of correcting from the angle, through what these values achieved in terms of moral differences that have effectively contributed to the high level of performance and with less effort.