Roof and Floor loading without the Roof or the Floor

 

 Roof and Floor loading without the Roof or the Floor  

In STAAD.Pro, there are many ways to properly account for loading to be distributed across the structural framing of roof and floor members. We will discuss some of the practical options for accurately assigning uniform pressure loads to roof and
floor members without modeling the slab or deck that distributes the loading to the structural members.

 

 

For this discussion we will focus on vertical loads due to gravity for Dead Load, Live Load, and Snow Load. There are a few considerations that we want to think about
before we begin the process of creating our roof and floor loads. The following are a few questions we can pose to help decide which STAAD.Pro loading tools which best suit the structural framing:


 
Do we have openings in sections of the floor or roof? Are portions of the framing system sloped? How is the uniform loading on the framing changing within each load case and also between separate load cases? What is the complexity of the structural member layout? Is the layout a simple rectangular bay system or are there curved members and variable member spacing?

The reason these questions are important for applying loading to the model is that the answers to these questions will help determine the most useful tools within STAAD.Pro to address the calculation, application, and automation of load distribution to our structural framing. Tools like floor beam groups and configurable floor loading make it possible to quickly calculate, apply, and adjust distributed loading to floor and roof systems.

Using floor beam groups will allow us to assign distributed loads to a set group of members without having to apply the load to the entire floor system. This tool works well in cases where loading varies across different portions of the floor or in a situation where the framing is sloped.


STAAD will automatically calculate the tributary area for the floor or roof member group
and apply the calculated uniform load as a one way or two load distribution based on your selection. Using the floor load command, you are able to apply a pressure load such as dead load due to a slab, or an assumed live load for roofs and floors, or a snow load to a group of members on a designated area of
the structural framing. For example this method works well for dead load due to
a slab, where the slab thickness and weight will be the same on multiple floors
however the framing layout or spacing will vary from floor to floor. Rather than manually calculating the tributary area for each member and assigning a uniform load on members one by one, the floor load can be designated to several floors at once and the uniform load for each member will be calculated automatically by STAAD.Pro based on the member tributary area.

 


It is necessary to fore warn you that not all floor configurations will allow STAAD.pro to automatically calculate the uniform load based on the member tributary area. Therefore, in complex structural framing situations it may be necessary to use multiple floor member groups or possibly even manually assign the uniform loads to members in order to accurately generate loads on the structure.

 

 

 

 

 

 


For single sloped roofs one floor group may be all that is required to assign the pressure loads to the structural framing. However for gable or hip roofs one floor member group will be required for each portion of the roof with an individual slope.

 

 

 

 

 

For additional information on floor loading in STAAD.Pro refer to the technical reference manual pages 5.32.4.3 Floor Load Specification. I hope that this information has been useful. Please feel free to email me with additional questions.

Thanks

Karimu.Rashad@Bentley.com