Minimum bearing length and AISC Table 10-5

[TehMightyEngineer]

Ran into an interesting conundrum. AISC Table 10-5 for unstiffened seated connections has you enter the table with a required bearing length, Nreq. Let's say you calculate a very small required bearing length for the loads you're taking with the connection. However, per AISC 360 J10.2 the minimum bearing length lb = not less than k for end beam reactions. So, if we have a large beam which has a large k value per Table 1-1 what do we enter Table 10-5 with? The minimum bearing length of k or the calculated minimum bearing length?

My thought was to use the calculated bearing length but wasn't sure if this would be 100% conservative.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[Hokie93]

I would enter Table 10-5 with k_des since l_b,req cannot be less than k_des. I am assuming that, in this case, the required bearing length based on loads, N, is less than k_des. With a very small N value, local web yielding or local web crippling may control over flexural and shear yielding of the outstanding leg and would have to be manually checked per Chapter J10 since Table 10-5 assumes l_b,req is never less than k_des.

 

[TehMightyEngineer]

I couldn't find a reference that showed Table 10-5 assumes l_b,req is never less than k_des. Do you have a source for that? This questions is for someone else so I need to find something that I can point to.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[TehMightyEngineer]

Oh, nevermind, found an example in the AISC example PDF. EXAMPLE II.A-12 if anyone is wondering. Thanks Hokie.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[Hokie93]

The requirement for the minimum bearing length (k_des) is discussed in the text immediately prior to Table 10-5 of the 14th edition AISC Steel Construction Manual. The requirement was part of an errata (#4, I think) for the 13th edition AISC Steel Construction Manual.

 

[TehMightyEngineer]

Excellent, thanks. I thought I had all the errata noted in my 2005 manual but I'll definitely check again.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com