Strand7 modelling
Strand7 modelling
(OP)
Hello friends,
I am using Strand7 for the first time, I need to model a 2 storey 2D structure with isolated footings, can anybody help me in modelling isolated footing.
I am using Strand7 for the first time, I need to model a 2 storey 2D structure with isolated footings, can anybody help me in modelling isolated footing.





RE: Strand7 modelling
Are you wanting to model the soil or just the structure?
Either way, which particular aspects are you wanting help with?
At the moment I'm not sure what problems are presented by the footings, different from the rest of the structure.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
RE: Strand7 modelling
ST7-1.10.20.13 Response Spectrum and Power Spectral Density
(You will need to be a current supported user to download)
Also have a browse of the other web-notes at the Strand7 site, there may well be something on modelling base isolation systems.
For a 2D model I would suggest plane strain plate elements for the soil and footings and beam elements for the structure. I do a lot of soil-structure interaction work, and usually use 8-noded plate elements. As noted by glass99, if you are doing a response-spectrum analysis you don't need to worry about non-linear material properties, but the stiffness does need to be appropriate to the strains you are getting.
I don't know whether or not a response spectrum analysis is appropriate for a base isolation system; a post in the seismology engineering section might be best on that question.
Any Strand7 specific questions I'll be glad to help.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
RE: Strand7 modelling
RE: Strand7 modelling
RE: Strand7 modelling
My guess is a pad footing, but whichever it is, the answer to the question of how to model it in Strand7 is the same way as any other finite element package:
!) Create the mesh
2) Define boundary and global freedom conditions
3) Define element properties
4) Apply loads
5) Run analysis
6) Extract results
7) Review to see if they make sense.
To give any more detailed advice, without writing a book, we need to know exactly what problems have been encountered in following that process.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
Regards,
http://files.engineering.com/getfile.aspx?folder=7...
RE: Strand7 modelling
I'm sure that's how many people still do it, but I really don't see the point of using springs (with the added complication of how to determine the spring stiffness), rather than just modelling the soil with plane strain plate elements.
divyeshrohit - if you tell us specifically what problems you are having we can probably help.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
RE: Strand7 modelling
glass99 - I don't follow your point. Using springs also requires engineering judgement to determine the properties of the soils at any given location, with the added level of engineering judgement required for allowing for scale effects etc. If you are happy to use a simplified rule of thumb to give you a spring stiffness, why are you not happy with the same approach to give you soil properties?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
FEMA formula is THE FORMULA for footing springs under seismic loads. As far as I know it's the only one used in USA. Lots of work has been done do develop this formula, it's commonly accepted outside of US as well. More refined will be Method 2 presented in the same FEMA document - modeling subgrade reaction by a series of vertical compression only springs. Using elastic soil FE for this purpose is very uncommon, hard to defend and to come up with justifiable assumptions.
RE: Strand7 modelling
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 modelling
RE: Strand7 modelling