Load Cases in Strand7

[Wardzy]

Hi all,

I'm working on a model of a bridge design at the moment and being new to Strand7, I'm a little unsure on how to apply Dead load and Live load cases to the model to make sure the analysis is correct.

In the Load and Freedom cases, I have applied the gravity inertia load (-9.806650 in the Y direction) and all elements, including the cables, have a material properties assigned (including density). Is this sufficient for the dead load calculations using the Non-Linear static solver? I don't quite understand how the load increments section of the solver works and if it is required for the analysis.

I have yet to calculate the Live Load that needs to be applied but any information on how to apply it in the program would be greatly appreciated.

If you need any more information on the project, let me know

Thanks in advance,
Chris

 

[IDS]

If you are using the non-linear static solver then:

1. Open the solver dialog
2. Click the Load increments ... button
3. Create as many increments as you need (i.e. one for each different load combination)
4. Make sure that the load cases you want to use are ticked in the "include" column.
5. Enter the load factors for each load case, for each increment.

Note that you will need to define at least one increment to do a non-linear run.

I often use the non-linear solver for linear analyses as well because I find the load combination more convenient than using the linear solver. Just unselect the two non-linear options on the main dialog box.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Wardzy]

Thanks Doug.

Just to be clear, if I have the gravity loads applied and increment 1 set at 1.0, it will analyse with the full self weight of the structure?

And if I want to analyse the live load with the dead load, I create a second increment with a value of 1.0 for both the live and dead load cases?

When applying the live load to the structure, I'm assuming I have to have the load case set to a separate load before applying the loads?
I'm not focusing on the construction phases at the moment, just the overall static and dynamics of the completed structure so I only need a separate live load and dead load cases.

The other issue I'm having is the cable free length in relation to pretension. I've calculated the exact lengths of the cables but I'm unsure how to set a pretension in the cables to see how it will affect the structure.

Thanks,
Chris

 

[IDS]

Just to be clear, if I have the gravity loads applied and increment 1 set at 1.0, it will analyse with the full self weight of the structure?

And if I want to analyse the live load with the dead load, I create a second increment with a value of 1.0 for both the live and dead load cases?

Yes correct. Also check your members have the correct density (in mass/volume units), and the cross section dimensions are correct.

When applying the live load to the structure, I'm assuming I have to have the load case set to a separate load before applying the loads?
I'm not focusing on the construction phases at the moment, just the overall static and dynamics of the completed structure so I only need a separate live load and dead load cases.

Yes, select the load case from the drop down list at top-left, then apply the loads for that case. You can also copy loads from one case to another from the Global - Load and freedom case dialog.

The other issue I'm having is the cable free length in relation to pretension. I've calculated the exact lengths of the cables but I'm unsure how to set a pretension in the cables to see how it will affect the structure.

I'm not very familiar with using the cable elements, but all beam/cable elements have a "preload" attribute, so that should do what you want.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Wardzy]

Thanks for all your help Doug. Its greatly appreciated.

I'll give these a try and I'm sure I'll figure something out for the cables.

Cheers,
Chris