Base Plate NCEES Example 526/versus SERM

[Hromis1]

Ladies and Gents, I just came across an interesting problem in the NCEES structural I example book. Problem 526, a simple base plate design. I could not believe I got the answer wrong. However on further review..the answer given in the NCEES book is "correct".

The SERM book pages 4-23 to 4-24 gives the traditional base plate design the way I have always done it. However, the "correct" solution follows the examples given in the CD given with the 13th ED. Essentially the plate thickness is reduced as the column is not fully loaded.

I don't really like this "Minimalist" engineering approach used in the NCEES sample question book, but it is the correct solution on paper. No spare capacity where all the serious corrosion occurs.

Sometimes I don't think the guys who wrote this stuff ever got out of the lab.

 

[Casey]

Designs that utilise more than 80% capacity scare the crap out of me!

 

[Hromis1]

Yep, specially when you feel that few people bother to check for durability/corrosion/fatigue. Looks good on paper, but fails quickly in the field. This is the kind of crud I see on micro-designed, pre-engineered buldings. Or sometimes on commercial buildings where the everything is "encased".

I am sitting right now trying to model a steel structure that has 30%+ section loss and some connections completely gone. Yet the structure is still standing do to alternate load paths and reserve capacity in other members. Mainly the original engineer was darn conservative on his loading.

This "Minimalist" design approach is not something that would last in an industrial application, or other weather exposed use. I also strongly recommend watching the concrete designs as covered in the exam as well. I have the same issue with them. Some of the problems play games with calculations when it is easier, cheaper just to throw in one extra rebar.

This stuff may get you the a PE/SE, but this design approach would not pass muster in our office.

But we all have to play the game to pass the exam.

 

[Casey]

I work in Oil & Gas up here in Alberta and pretty much everyone here designs to about 80% capacity. The main reason being is that the oil companies will eventually add upgrades which will put on additional loads to the structures. This is a given, even if the client tells you "not to design for future upgrades". Plus, as you mentioned, those structures take a lot of abuse.

And I totally agree, it usually doesn't cost that much to use a larger beam size or add another bar to your concrete...