Recent content by darkwing88

Notice the difference in the 3rd root condition for both tables. Interestingly, one shows lateral restraint for only the top flange while the other shows lateral and torsional restraint for only the bottom flange. The k values are identical except with the tip restaint being both top and...

Here's a reference for information on designing the cantilever beam and end bracing options: (http://www.modernsteel.com/steelinterchange_details.php?id=197). Consider top flange loading of the cantilever beam: using top and bottom flange bracing of the beam at the girder support, this...

RFreund, do you know the definition of unsupported lateral distance for a beam? Do you know the difference between relative and nodal bracing?

Bracing is inexpensive and gets you huge load capacity increases for members. Don't be shy about using bracing.

In addition to the x-bracing you have shown in your sketch, also put another line of x-bracing between the beams over the girder. No need for anchoring the x-bracing to side walls. Lateral support distances for the beams will be between end of beam and x-bracing, between x-bracing, and...

A proper free body diagram needs dimensions and boundary conditions also. From what you have provided, I would consider this tube fully braced.

I have been doing this stuff for 27 years. I suppose it is normal to get "code change fatique." Some people lap it up, but some like me just want to get the job done and go hunting or fishing. I am going to backtrack on what I said I was going to do about this structure and do it the old...

jones: how one figures out how much is Mnt and Pnt and how much is Mlt is Plt for a given load case is beyond me. It is probably just me, but who out there would actually use this method?

An aside: I think bueaucrats have infiltrated the AISC 360 committee. I'm trying to get a handle on that convoluted stability provision rat maze.

So here is what I plan to do. Am I missing anything? 1) reduce the stiffness for all beams and columns; 2) model the structure either with out-of-straightness built-in or notional loads; 3) use factored loads; 4) use the P-delta solver; 5)'05 LRFD specification for code checking; and finally...

jones: you just reduce the E value parameter to reduce the stiffness in selected members. So to answer the question, it can handle the reduced stiffnesses for the solver, however, the allowble stesses are based on these same stiffnesses. An unintended consequence.

It is a given that the DAM can not be done properly with '06 Staad. Possibly a conservative way might be to model the out-of-straightness displacements and set the elastic modulus to a reduced value. However, this method will result in Staad using the reduced modulus during the AISC checks.

eit: Staad '06 does not have DAM option to my knowledge. jones: I think your right about '89 and '05 not yielding too different results. However, I thought someone here may have researched the topic.

I am using ASD '89 and Staad '06. I have a braced frame structure to design. Is there a way to set-up the model parameters to get results nearly identical to the results using ASD '05?

Below is an excerpt from the NUCOR Product and Engineering Manual 3.0 Specification Guide. It says they use AISC 9th Edition. I don't see any design latitude mentioned (i.e. proprietary design methods using research papers, etc.) At this point, I don't know of a reason not to use the AISC 9th...