Strand7 geometry
Strand7 geometry
(OP)
Need to clean geometry and plate free edges, I am not able to connect/attach plate free edges. I am attaching a pic of the model, "yellow" outlines are plate free edges. please help
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RE: Strand7 geometry
RE: Strand7 geometry
You know that plate elements can only join at an edge if they have the same corner nodes (and mid-side nodes, if they have them)? You can't join two or more short edges to a single edge of a bigger element.
Have you downloaded the new manual?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry
RE: Strand7 geometry
http://julianh72.blogspot.com
RE: Strand7 geometry
RE: Strand7 geometry
RE: Strand7 geometry
You need to do something to match the number of nodes across the incompatible junctions. E.g. use the "Grade Plates and Bricks" tool, and select a row of elements on the "coarse" side of the junction (see "Selected Elements"). This will subdivide the selected elements (according to which "Grade" tool you have chosen), to produce a compatible mesh similar to the attached "Graded Elements". It's not a pretty mesh, but at least it is node-compatible.
You could then try using the "Smooth Plates" tool to generate a smoother graded mesh (similar to "Smoothed Elements") - still not an ideal mesh, but it's heading in the right direction.
Hope this helps!
http://julianh72.blogspot.com
RE: Strand7 geometry
RE: Strand7 geometry
RE: Strand7 geometry
There are several options:
1 Rigid links; select Create-Link and choose rigid from the drop down box
2 Create a beam type with properties of concrete and appropriate cross section area, but zero mass so you don't double count the mass
3 Create a beam with "point contact" properties, which will transfer compressive normal forces and friction forces limited by the friction factor
I'd suggest trying 1 or 2 to get the model running. You might look at 3 if you get a large shear transfer across the base of the footings, but this will need a non-linear analysis which will make things much more difficult with a time history analysis (and there isn't much point unless you are using a non-linear model for the soil and concrete as well).
For appropriate damping refer to standard textbooks and try a range of values.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry
With respect, it sounds like you need a LOT of assistance / mentoring to get up to speed with the task that you have been assigned. (Is this a student posting?) What you are asking is a bit beyond the scope of a forum such as this to provide useful support.
You should read some FEA reference texts, and check out the Strand7 Reference Manual and Verification Manual (which should be installed on your C: drive in the program folder). Also, assuming you are a supported Strand7 user, check out the Web Notes on the Strand7 site http://www.strand7.com/webnotes/ - there are several downloadable articles with example models on damping, seismic analysis, etc.
http://julianh72.blogspot.com
RE: Strand7 geometry
RE: Strand7 geometry
See also Strand7 Web Note ST7-1.40.35.22 "AS 1170.4-2007 Earthquake Analysis in Strand7" which you can download form the website if you have an active maintenance account with Strand7: http://www.strand7.com/webnotes/request/?w=ST7-1.4...
Hope this helps!
http://julianh72.blogspot.com
RE: Strand7 geometry
RE: Strand7 geometry
RE: Strand7 geometry
If you have plate elements with plane strain properties, these need to be restrained in the X and Y directions along the base and X only up the sides. No other nodes should be restrained.
If you are doing a 2D analysis you also need to set up a global freedom case, which should be 2D Beam (since you are using beam elements). This allows translation in the X and Y directions, with rotation about the Z axis, with the other three freedoms fixed.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry
RE: Strand7 geometry
RE: Strand7 geometry
Restraints (in this case) are representing the body of soil outside the model. It follows that top nodes should not be restrained (other than the top corner at the sides of the model).
Side nodes are normally restrained in the horizontal direction only, but they should be far enough away from the structure that they don't have a significant effect. Three times the depth of foundation either side of the structure is a reasonable rule of thumb, so your model should be a good bit wider.
Also some aspects of the model look strange, but its hard to tell from a jpg, especially when you have the grid points displayed. If you want to upload an st7 file I'll have a (quick) look at it.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry
RE: Strand7 geometry
There is no benefit in having the footings so finely meshed. I suggest greatly simplifying the footings and the associated soil elements, but use 8 node elements rather than 4 node, since these can model bending behaviour much better.
The elements between the footings and the structure should be concrete rather than soil, I presume.
You have plane strain elements for the soil, which is appropriate for a 2D analysis, but remember you are analysing a unit width of soil, with a structure on top representing a much greater width, so you will need to modify properties accordingly.
You have restrained the nodes around each footing, but there are no restraints to the soil boundaries, so in effect you have a structure somehow suspended in space with a block of soil hanging off it. Remove the restraints to the footing, and add restraints to the soil boundaries that are in contact with more soil (not the top surface).
I'm not a seismic expert, but I don't think the node damping at the base is necessary. You can always add it later to see what effect it has.
Did you download the Strand7 web-note on seismic analysis; it looks like it should cover most of what you need.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Strand7 geometry