AISC Design Guide 1

[btomcik]

I'm using AISC Design Guide 1 - in my situation I have a horizontal cantilever tube imparting the moment on the plate. There is no axial force P, plate dimensions N=11", B=11". Following the examples, I used e=M/P which goes to infinity, so e>e-crit so I have a large moment case.

Going through the numbers I get a plate thickness of 1.5". I thought it was high, so I then checked my answer using Tedds, which puts the eccentricity e = N = 11", which totally changes the required plate thickness to 5/8".

It's been a long day reading the Design Guide over and over, and I can't find a clue as to why Tedds would put e = N. I must be missing something with the statics - obviously M can't = P*e, because P = 0, M would be 0, which is not the case.

Any insight would be appreciated. Thanks.

Thanks.

 

[Hokie93]

For your scenario, the tension force in the anchor rods should be based on a simple force couple concept with M=Fd, where 'd' is the distance from the anchor rod to the far edge of the base plate. Assuming your anchor rods are located 1.5" from the edge of the base plate, d would equal 9.5" for your case. The thickness of the base plate would follow based on AISC Design Guide 1. I created a test case in TEDDS and got the same e=N that you did but when I checked the anchor rod force (and associated base plate thickness), it was based on M=Fd. So I think TEDDS is behaving correctly but I cannot explain the e=N output and it is not clear to me that e=N is being used elsewhere.

 

[btomcik]

Thanks. My gut was saying M=Td too.

 

[DST148]

@btomcik>>> Assuming d is the distance from the centre of anchor rod to edge of base plate,
tension "T" in the anchor rod is approx. given by T = M / [(5/6) * d]
The term 5/6 is to account for the lever arm between c.g. of tension and compression.