How to find Strain
How to find Strain
(OP)
Hi,
I'm interested to find out the strain change along length of a member due to the applied stress/load. Can SAP2K provide such graph like displacement or moment? I think I can find it indirectly but not sure what exactly I'm supposed to do. Any comment guys?
Peace
I'm interested to find out the strain change along length of a member due to the applied stress/load. Can SAP2K provide such graph like displacement or moment? I think I can find it indirectly but not sure what exactly I'm supposed to do. Any comment guys?
Peace





RE: How to find Strain
In the past I tried to do the same, No Luck :(. SAP doesn't report strain directly. You need to do post processing to arrive at that.
Step 1. Find Initial position of i and j nodes of sap - Arrive at Initial Length
Step 2. From the displacement + initial coordinates, calculate the displaced position. - Arrive at the deformed length
Step 3. Strain Calc
You can automate this using API or Excel (after exporting tables).
Thanks,
RE: How to find Strain
Thanks for your response. Sorry but I couldn't figure out your explanation. Let's say I have a S.S beam and run the analysis for point load @ center. From output tables, I export the joint coordinates and displacement (due to load) to the excel. Then what? Would you elaborate it for me possibly with an example?
Heaps of thanks
RE: How to find Strain
For SS beam, create a point near each support, SAP reports displacement at joints. If you restrain Joint, No displacement.
Step 1, i = (0,0,0), J= (5,0,0) length = 5'
Step 2: under load, i+di = (0.01,0,0) j +dj = (5.05,0,0), Note sap reported disp are based on initail co-ordinates
Step 3: Calc length = sqrt((5.05-0.1)^2 +(0)^2 + (0)^2) = 5.04'
Strain = .04/5
Cheers!
RE: How to find Strain
Thanks again.
How you got 5.05 while the displacement is 0.01?
Plus, I reckon in sqrt((5.05-0.1)^2 length due to external load needs to be deducted from 0.01 not 0.1, right?
lastly, in Strain = .04/5 you used the strain formula (change in length divided the original length).
Thanks mate
RE: How to find Strain
RE: How to find Strain