Load factors AS 5100

[Shz713]

Hi all,

Can someone explain to me what's the application of using load factors when safety increased or decreased. How we can determine if the dead load increases/decreases safety?
Besides, what 'site specific measurements' implies?
Cheers,

Shoot for the Moon, even if U miss, U still land among Stars!

 

[Retrograde]

If you have an uplift wind load, then a downwards dead load is increasing safety and should have a lower ULS factor for that particular load case.

 

[apsix]

Or for a cantilevered beam; dead load on the cantilever reduces safety while on the backspan it increases safety.

 

[Shz713]

Thanks for clarifications, so in case of moving load then it reduces safety.
Also does "site specific measurements" means that we've obtained the geometrical measurement from the site and did the DL calculation?



Shoot for the Moon, even if U miss, U still land among Stars!

 

[rapt]

No, it reduces safety at a point it it causes a moments of opposite sign to the moving load at that point.

 

[IDS]

Which version of AS 5100 is that table from? The load factors are in Tables 5.2 and 5.3 in the 2004 version, and Tables 6.2 and 6.3 in the current recently released version. They don't have the "site-specific measurement" columns.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Shz713]

Do you mean the +ve n -ve moment due to ML? Since the direction of ML is downward and also DL is in gravity direction, then it reduces safety; if I understand you correctly.


This is from AS 5100.7:2017 page 25 section 12.2

Shoot for the Moon, even if U miss, U still land among Stars!

 

[IDS]

Shz713 - AS 5100 Part 7 is for load rating of existing bridges. So if the estimated weights of the elements of the bridge are based on a survey of the actual bridge the load factors can be closer to 1, which seems reasonable.

The load factors for new bridges are given in Part 2.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/