Lateral Load (manual and software)

[torogiak]

Why is that in solving lateral loads by using structural software and using say portal method, their computed moments are different? Is it because of the presence of diaphragm in using software?

 

[KootK]

It`s not the diaphragms. Old school hand calculation methods like the portal method and the spurr method are approximations. They are, in general, inexact. As an example, the portal method assumes that all of your columns have inflection points at mid-height. In reality, that`s almost never true. At the same time, it`s often pretty darn close to true.

So long as you`ve nailed your input, FEM software will always give more exact answers. The portal and spurr methods are invaluable for both preliminary design and FEM output checking however.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[paddingtongreen]

Another factor in this is that even if you use Moment Distribution or other method for statically indeterminate structures, you cover only the primary load paths, with FEM you include all of them.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[Archie264]

KootK,

I've never heard of the Spurr method and I couldn't find anything about it through a search. Do you have a link you could refer me to or a quick description of it? Thanks.

 

[paddingtongreen]

Archie, I wondered that myself, I found this

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[Archie264]

Excellent! Thank you.

 

[KootK]

I managed to get my hands on a tattered, yellowed edition of the 1920's book that Spurr presented his method in. Book synopsis: it's windy in New York, maybe we should should brace our sky scrapers. It's frickin' awesome.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[torogiak]

Thanks KootK, can you suggest FEM softwares that i may use for computing lateral load?

 

[KootK]

Sure. SAP, Risa, IES, RAM.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.