Thanks for the help.
Just to clarify:
1. then, you must always specify a dof for the arc-length method? if it is so, why there's the option hpcmode 0 ? what is that option for? and for which cases?
2. what exactly "donotfixload" does? in the manual, it is written that this prevents the load level to be reset, but here we have a single metastep.
3. what exactly happens when psi > 0 ? I cannot figure out how the solution is controlled. ("For nonzero values the load control applies together with displacement control (ALM)." says the manual). Anyway, I cannot figure out how to impose that the analysis arrive at least at 100% of the load - this is due to the autostepping I suppose.
4. I noticed you corrected the NodalLoad records, the intended function was no. 2 since load has to be applied with a ramp. This is different of what I would have done with direct control.
I'm trying to perform a pushover analysis on the steel frame. Springs have discontinuities (after failure, the strenght drops to a residual value).
IMHO the calm solver must be improved with some warning or errors - currently, it is difficult to set an NL analysis by reading the manual and the code. In my test, deltaLambda in calmls.c was always 0, and in "computeDeltaLambda" function there are many division by zero is the analysis is not preperly set (see here and here).
EDIT: anyway, I reverted the modifications I made to the code, since I'm not sure of them. Hence, returning to my nl model, I cannot get easily a convergence. Many iterations are perfomed with the same result - see below, same residuals every 2 iterations:
CALMLS: 224 1.251010e-001 6.207579e+000 1.276643e+000
CALMLS: 225 4.367693e-001 1.777724e+000 4.582599e+000
CALMLS: 226 1.251010e-001 6.207579e+000 1.279821e+000
CALMLS: 227 4.367693e-001 1.777724e+000 4.542186e+000
CALMLS: 228 1.251010e-001 6.207579e+000 1.283015e+000
CALMLS: 229 4.367693e-001 1.777724e+000 4.502479e+000
CALMLS: 230 1.251010e-001 6.207579e+000 1.286226e+000
CALMLS: 231 4.367693e-001 1.777724e+000 4.463461e+000
CALMLS: 232 1.251010e-001 6.207579e+000 1.289452e+000
CALMLS: 233 4.367693e-001 1.777724e+000 4.425113e+000
CALMLS: 234 1.251010e-001 6.207579e+000 1.292695e+000
CALMLS: 235 4.367693e-001 1.777724e+000 4.387419e+000