Single Plate Shear Connection vs extended Plate Shear Connection

[mrpid]

This is a question of curiosity more than anything, as any design I would perform would be in accordance with AISC.

In short AISC Table 10-9a provides allowable loads for Single Plate Shear connections, which is simply followed and covers all the modes of failure for this connection type with the exception of a coped beam which needs to be checked as well. Within the description of the table the max "a" dimension is 3".

Now looking at an extended plate connection, the bolt groups needs to be considered with eccentricity equal to "a". The req'd coefficient is covered in Table 7-7. What I find interesting is that with an e=3" has a coefficient less than 1.0 (for a 2-bolt connection).

The question I have when comparing this application with e=3", why is C not equal to 2.0 (for a 2 bolt connection). In this application it seems the extended plate connection is overly conservative.

Any shared knowledge would be appreciated.

 

[connectegr]

Several years ago research was done at UNC (if I recall), on the performance of the typical single plate connection, or shear tab with bolt eccentricity less than 3.5". These capacities are represented in the tables provided in the 13th Edition Manual. The design of these connections have changed in nearly every edition of the manual, including the 14th Edition. This research found that very small beam end rotations occured in these connection and therefore the force applied to the bolts were simply put, straight shear. However, this research was not applied to larger eccentricities. Therefore the design of extended shear connections with eccentricty greater than 3.5" remains similar to the design principle used for many years. The change in the 14th edition is that bolt shear strengths have increased. This change was not considered in the previous research. As with other bolt strength increases, other limit states may now need consideration. Therefore the tables in the 14th Edition match the 13th Edition capacities. And the design procedure has been changed to provide a reduced bolt strength.

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