Pattern loading in 3-D Model 2

[ali07]

Lot of engineers use 3-D Modelling for buildings etc for design or analysis purposr. Just need to know how you consider pattern loading or it is not needed.

 

[271828]

You mean for lateral models? I don't know anybody who would use pattern loading for that, even though it's technically required in some codes.

For example, what pattern would give the highest base plate anchor rod shear at a given column? It's a practical impossibility to come up with pattern loads for every limit state in an entire structure. Talking tens of thousands (or more) combos required to theoretically do that.

 

[ali07]

I am talking about concrete structures as normally for flat slab structure it is more critical than for pin ended steel structure. I just want to know the general trend.

 

[271828]

I think SAFE pattern loads for that. I think the RAM system does too. No clue about ETABS or SAP.

 

[patswfc]

I was at a presentation in the UK regarding the design of concrete structures, about two years ago. Several software companies where there to demonstrate their products (RAM, CADS, ROBOT MILLINIUM, INTEGER, ETC). I asked them all about pattern loading. EG If I put an imposed load over an entire floor plate can the software implement a routine so that this load can be analysed with different bays loaded (pattern loading) to determine the worst forces in the structure. All of the companies said that their programme was not able to do this and that they didn't intend to include such a feature. They said that too difficult to implement such a routine, especially for irregular geometry frames. Thus the user should apply the load to the floor in a series of loadcases and create combinations to account for the worst forces due to pattern loading. This would take a bit of time, but is the approach that i would use if i had to design a concrete framed building. Luckily/Unluckily I havent had to design any concrete frames in the 4 years since I have finished Uni.
If SAFE has such a feature then it is possible that other software companies have now included this feature.

 

[stressed]

SAP will not automatically do pattern loading with all the load generation and combos which would be required, but SAP does offer something call a "pattern live load factor" under Options>Preferences, which as I recall, was a kinda sorta approximation for pattern loading. CSI tech support explained it to me at the time, but I can't remember now.