understanding influence lines to see if a spanner truss has too much weight on it.

[Jayme McColgan]

i need some guidance on understanding how the influence lines work. I'm trying to determine if the Center Point Loads on my spanner trusses are too much but the truss website gives me a lbs rating but Braceworks uses lbf-ft for everything. 

[jcogdell]

The first thing to do is to turn most of them off so only a single line is visible, this makes it far easier to see the data that the line is presenting.

Personally the Du (Deflection unified) is the first thing I tend to look at as this gives a very quick indicator of whther the truss is overloaded and can be compared with the manufacturers load charts

Another option is to use the Nx (or force normal) line as this will show the force acting on the truss at a given point
Its also a good idea to adjust the inflence line scaling in the braceworks settings to make it easier to see the lines.

 

Another option if you are using a hoist as a drop, is to look at its high hook weight equivalent field in the Hoist object properties, this will tell the load acting on the spreader truss at that point. This is a good option if the truss you are working with doesn't have a Braceworks cross section available in the database.

 

[Jayme McColgan]

On 5/16/2023 at 5:45 AM, jcogdell said:

The first thing to do is to turn most of them off so only a single line is visible, this makes it far easier to see the data that the line is presenting.

Personally the Du (Deflection unified) is the first thing I tend to look at as this gives a very quick indicator of whther the truss is overloaded and can be compared with the manufacturers load charts

Another option is to use the Nx (or force normal) line as this will show the force acting on the truss at a given point
Its also a good idea to adjust the inflence line scaling in the braceworks settings to make it easier to see the lines.

 

Another option if you are using a hoist as a drop, is to look at its high hook weight equivalent field in the Hoist object properties, this will tell the load acting on the spreader truss at that point. This is a good option if the truss you are working with doesn't have a Braceworks cross section available in the database.

 

 

because we mostly do shows in ballrooms, if we are doing spanner truss its probably connected directly to the truss below it and not using any drop down motors. i guess for the sake of running weights i could fake it and add a drop motor to get the weights and then put it back before sending it off for approval. 

[jcogdell]

An easier option is to use the truss cross label, once you do a calculation the truss cross will display the force being transmitted trough the connection point, using your document units

[Jayme McColgan]

sweet! using Newtons as the force should be fine for me. i can convert that to pounds pretty easly. thanks!