Base Plate Analysis
Base Plate Analysis
(OP)
I am currently studying to take the Struct 1 and Struct 2 exams. I bought a practice exam for each from the NCEES and on the struct 2 exam there is a question that leads to designing a baseplate and the anchor bolts for a vertical load and an applied moment. From a couple of different books I have (and the way I have done it in practice) provide for analyzing the loading on the baseplate as the capacity of the concrete stress block for the allowable bearing of concrete (a uniform load over a small portion of the end of the baseplate). The NCEES solution assumes that the load is triangular in nature with the centroid of the load occuring at the exact location of the flange of the steel column. I can understand both methods, but they give very different solutions. The stress block method gives you a thicker baseplate, but a smaller tension force in the anchor bolts. With the NCEES method (for lack of better term) you get a much thinner baseplate and larger tensile forces. Are these both accepted methods? Is one of them preferred? Are they both right? Any advice?
akastud
akastud






RE: Base Plate Analysis
There have been several other threads on this site during the last year with similar topics and may be worth trying to find.
Regards,
-Mike
RE: Base Plate Analysis
Thanks for your response, I have also used Blodgett's equation (but I can guarantee you that I will not attempt it on the exam), but all of the design materials I have assume a uniform stress block that is not at all similar to the two methods you describe. I have searched the other topics, but I have not seen one that talks about the uniform stress block.
akastud
RE: Base Plate Analysis
Yes, I believe both methods are acceptable. I suppose if you do get a base plate problem on the exam, you should do it the way it is shown in the Solutions Manual.
DaveAtkins
RE: Base Plate Analysis
I didn't notice in your post the part about uniform load. I have not seen that method myself but I stay in the ASD world almost completely.
-Mike
RE: Base Plate Analysis
The stress block method is much like a concrete beam where you assume you get a uniform compression load (assumed to ease calculation) over a portion of the compression zone. In the baseplate analysis it is similar in that a small uniform compression area occurs over some distance at the dge of the plate for the full width. Thank you both for your responses.
akastud
RE: Base Plate Analysis
RE: Base Plate Analysis
"Design in Structural Steel" by John E. Lothers
Chapter 6 (p 241): Moment-Resisting Base Plates and Footings
RE: Base Plate Analysis
Have you checked out the design guide for column base plates by the AISC, Design Guide 1? It has some good information, but again its all back to assumptions. The AISC method is not fool-proof either. Your best bet might be to "play the game" and use what the NCEES recommends for your test, and your own judgment in practice.
RE: Base Plate Analysis