Solver Error when using the Direct Analysis Method
Solver Error when using the Direct Analysis Method
(OP)
As anyone getting errors similar to this when using DAM?
***ERROR - AT JOINT 11 DIRECTION = MY
PROBABLE CAUSE NEGATIVE L-DIAGONAL
K-MATRIX DIAG= 6.5431013E+03 L-MATRIX DIAG= -1.9110223E+01 EQN NO 17
If I run using PERFORM ANALYSIS instead of PERFORM DIRECT ANALYSIS it works. Also I found that if I decrease the offending load below a certain level it elimates the error. I've already submitted this to Bentley but I'm just curious if anybody else has come across this because they always make me feel like I'm the only person in the entire world that ever has a problem.
Oh, and to save some of you time. Yes, I'm sure I've got the boundary conditions correct. Yes, I'm sure I didn't get my units fouled up. Yes, I'm sure I'm holding my mouth right. Actually, these problems were brought to me by other people in the company so I've already asked them these things.
BTW, what's an L-matrix?
***ERROR - AT JOINT 11 DIRECTION = MY
PROBABLE CAUSE NEGATIVE L-DIAGONAL
K-MATRIX DIAG= 6.5431013E+03 L-MATRIX DIAG= -1.9110223E+01 EQN NO 17
If I run using PERFORM ANALYSIS instead of PERFORM DIRECT ANALYSIS it works. Also I found that if I decrease the offending load below a certain level it elimates the error. I've already submitted this to Bentley but I'm just curious if anybody else has come across this because they always make me feel like I'm the only person in the entire world that ever has a problem.
Oh, and to save some of you time. Yes, I'm sure I've got the boundary conditions correct. Yes, I'm sure I didn't get my units fouled up. Yes, I'm sure I'm holding my mouth right. Actually, these problems were brought to me by other people in the company so I've already asked them these things.
BTW, what's an L-matrix?





RE: Solver Error when using the Direct Analysis Method
My guess is that Tau_b is approaching zero or has become negative. That's what's causing the "negative L diagonal" message. If you have a value that is zero (or less than zero) in the main diagonal of the stiffness matrix, then that would probably be bad.
The above is really just a guess based on what I know about the direct analysis method and the description you gave. I'm not really a STAAD expert.... I usually use another analysis package.
RE: Solver Error when using the Direct Analysis Method
RE: Solver Error when using the Direct Analysis Method
Are you using 2007 build 5?
RE: Solver Error when using the Direct Analysis Method
Unfortunately, we don't have the advanced analysis engine. I've used it before and its pretty nice, though I feel it's a bit shady on their part to say, "Oh, by the way, if you want a quality solver, you have to pay us another $3k".
Anyway, good question about build 5. Yes, that's what I'm using. Build 4 (and I assume 3, though we skipped that one) has known problems.
RE: Solver Error when using the Direct Analysis Method
If you have an enterprise license, they're offering the advanced solver free now. See the notice here: http://feeds.rapidfeeds.com/8131/
Supposedly build 6 is coming out soon, so maybe that will fix it.
Good luck
RE: Solver Error when using the Direct Analysis Method
Also, be sure to run your Direct Analysis on REPEAT LOADs that represent realistic loading conditions. Try to avoid running it on individual load cases that don't represent realistic loading conditions in and of themselves.
RE: Solver Error when using the Direct Analysis Method