LoadConst

[mehdi12345]

hello dear Silvia
I have a problem by understandig of LoadConst command, I have read opensees help but it confused me more.
I modeled a bulding and apply gravity loads on dummy columns once with this command and once without, when i use it and apply dynamic analysis, collapse is at 4 times higher PGAs than when i do not use this command, as i model collapse i can not put any reasonable diffrence to decide the correct answer,
Plz explain this command to me and explain when it has to be used.

[fmk]

the loadConst -time 0.0 command tels every load pattern that exists that the load factor being appled to the loads and constraints inside the load pattern is not to change no matter what happens to the pseudo time in the domain, i.e. a sname impllies the loads are now to be held constatnt.

the -time 0.0 resets the time in the domain to be 0.0.

[mehdi12345]

Hi Dr. Mckenna
thanx for your answer , as i understood I have to use LoadConst whenever I have a constant load during whole analysis like gravity loads and whenever I have a load like seismic loads that change in every step of loading, this command shouldn't be used.Is it OK?
my second question is What is pusedo time ?
and if I do not use LoadConst for a load pattern , how does it change?

[mehdi12345]

Hi
If i do not use Load Const for a pattern , how does it change in the analysis process.
Thanx for your answers.

[fmk]

if the time series associated with the load patterns is not constant, the load patterns will keep modifying the loads that are applied.

when you issue the loadConst command, it informs all existing load patterns that the timeseries is not to change anymore. all load patterns that are added after the comand will vary the loads as dictated by the time series.

[ucesjce]

Hello,

I am running ananalysis that consists of three phases: 1) gravity 2) lateral load control 3) lateral response control.
I am using the loadConst command after the gravity analysis and that is working well, I would like to know if I can call the LoadConst command a second time after adding lateral loads in the load control phase? i.e. holding the new loads constant on top of the original loads fixed gravity loads. I'm not sure how this would interact with the loads from the first time the LoadConst command is called?

Thank you in advance for your response

[fmk]

yes. it just sets aflag in the LoadPattern that tells it to keep the load multiplier the same from here on out.