Finite Element Analysis 1

[structural-eng]

I'm looking for recommendation regarding structural finite element analysis software for designing simple steel structures for an electrical substation. We have a client (an electrical engineer) that we have been designing substation structures and foundations for that is looking to bid on a new project and the spec for the project requires "Structural Finite Element Method (FEM) analysis should be used as a base method for design. Hand calculations of components may be used only under written approval." Our company has been around for 40+ years and we have never gotten into finite element design. The work that we do is not complicated enough to warrant it. These substations are very basic structures (cantilevered columns, pinned and simple fixed end connections, etc) and the member sizes used are driven by desired geometry and deflection limits and rarely by strength requirements. The only area where we believe we could likely reduce the structure size from our current designs is the base plates which have large holes for galvanizing and are on leveling nuts which requires very thick plates when using a traditional design approach. Any recommendations would be appreciated.

 

[r13]

Yes, for power and petrochemical projects, it has gradually became common place to require all disciplines work on/off a shared 3D model. But not the shop drawings as I am aware of.

 

[human909]

For many industrial construction applications it just makes sense to use a common 3D package. If you want your steel structure to line up millimetre perfect with your equipment it is more reliable to have it all modeled in 3d in the one model. Packages like Tekla can readily export to your common 3D format and then readily produce workshop drawings.

That is my experience anyway.

 

[mronlinetutor]

The industrial standard structural finite element software is Sap2000 and Etabs.

I use Midas Gen.

The purpose of using structural finite element software is to find out the resonance frequency of the structure so that it won't coincide with the natural vibration of wind and earthquake and the natural vibrational mode shape of the structure. And you cannot do it without a computer for a complex structure. This is the basic principle of design no matter whether you design a ship, a rocket, a car, or a building. For a simple structure such as a single cantilever arm, you probably can work out the resonance frequency by hand. But when you are dealing with a large structure, you need a computer. That where the structural finite elements program comes in. The solution to modal vibration is a matter of eigenvalues and eigenvectors. The stress of the structure is structural mechanics and solid mechanics. Finite elements have been around since the 18th century. Finite elements are actually a numerical solution to one partial differential equations or to a group of partial differential equations. In the early time, you can only work out a few nodes because the numerical solution is tedious. But now with modern computers, you can work out the natural frequency of a structure in a split second.

After you work out the resonance frequency of the structure, you can design the components of the building.

From

Stanley.

disclaimer: all calculations and comments must be checked by senior engineers before they are taken to be acceptable.

 

[ldeem]

retired13 and human909 - I am a big fan of 3D models myself but the requirement in this project was for 3D detailing model but it was not one of the deliverables. They also have very specific structural drawing deliverable requirements which are 2D only.

 

[dauwerda]

This is a typical requirement for the design of the manufactured tapered tube structures that are used for H-Frames, A-frames, Static masts, and transmission towers (i.e. line supporting structures). The design of these are typically governed by ASCE 48 which requires the use of 2nd order non linear analysis - this is typically done by using FEA software. PLS-Pole is the industry standard design software that is used. I would not be surprised if this requirement is being misapplied (whether through poor wording or poor understanding)to all substation structures rather than just structures that have their design governed by ASCE 48.