Introduction To Block Shear resistance.
Brief content of the video.
The first point of discussion is about the slenderness value for tension members. The value of L/r value for tension members whether it has a certain ratio, does the code make a provision for such ratio or not? For the L/r ratio, we are going to consider two points, the first point is the recommendations.
The second point regarding code provisions is the introduction to shear block, This video has a subtitle and closed caption in English.
This is the content of the lecture.
Slenderness ratio as recommended by Aisc.
The first part is about the recommendation of the slenderness ratio L/r from the code that is preferred to be =300 due to handling and controlling vibration effects.
Regarding very slender sections, there is a problem with the handling of these sections, the main requirement while handling is to make handling without inadvertent bending.
While lifting a slender section by crane, it might buckle or be distorted due to transportation and erection, experience has shown that if you limit the slenderness L/r to 300.
You are less likely to have problems handling the member with the experience if we deal with a slenderness ratio L/r at a value of 300.
The problems that will occur during handling can be minimized, there is not a strength limit state, the limit state is the same for both LRFD and ASD, L/r is not related to LRFD or ASD parameters
The recommendation in code is in chapter D. Design of Members for tension, specification 16.1- page 28, AISC 360 In chapter D1 for members designed on the basis of tension. The slenderness ratio L/r preferably should not exceed 300, This suggestion does not apply to rods or hangers in tension.
The Introduction to block shear resistance.
If we have two sections connected by bolts, these sections are acted upon by two equal and opposite tensile forces.
Upon Studying one section, we will find out that the tensile force can be resolved into two components, one component is perpendicular to part bc, refer to the picture, and the other component causes shear for part ab. There will be two possibilities of fracture either by yielding or by rupture for both tension and shear forces.
Deriving the equation for block shear for tension members.
Block shear Formula.
This is the nominal value Rn as given by the formula, for which there are two parts, one account for shear, and the other accounts for tension.
The difference between the upper limit and lower limit.
The difference between the upper limit of fracture, and the other limit of failure, will be considered as follows, the upper limit of fracture, has a combination of Tension failure by rupture and shear failure by yielding.
UBS values are varying based on the uniformity of distribution of stress for angles & guest plates. The UBS values are shown in the next slide image.
In the next slide is the reference in the specs for the chapter relating to the connections which are Chapter J.The provision of steel connections in the specification.
In the next slide, the equation for the block shear strength is J4.5.The block shear strength equation from Aisc specification.
This is the pdf file used in the illustration of this post.
There is a very useful external link-Block Shear Rupture–
The next post is a Solved problem 4-4, How to get Pult without block shear.