How are SOMD leveled if beams deflect? 1

[SeizeTheMoment]

This question mostly refers to slabs on 2nd story and higher, let's say using typical steel beams that are not cambered. If these beams are always subject to deflection, wouldn't the slab always have a slope and not be leveled? How is this addressed structurally, and in the field?

Don't bend to the stress, seize the moment!

 

[KootK]

I have the slabs cast level rather than to a constant thickness. This creates a ponding concern with the wet concrete as the volume of concrete increases as the slab deflects and create a pool for it to collect. See this related thread started by yours truly back in the Mesozoic: Link

 

[SeizeTheMoment]

Thank you KootK! Those are great references from the ancient thread.

My takeaway is that from the construction standpoint - they would have to at least estimate 10% more concrete volume if we cast the slab leveled (due to the ponding effect). From the design standpoint, additional calculations seem unnecessary as we expect increased moment capacities from the "ponding" concrete(?) Or have you also started increasing the design loads to account for this?

Don't bend to the stress, seize the moment!

 

[OldDawgNewTricks]

I have always increased the concrete dead load by about 10% to account for the extra concrete (both for the gravity design of the floor and also the seismic weight to the lateral system).

 

[lexpatrie]

Here's an Engineering Journal article on the subject.

https://www.aisc.org/globalassets/modern-steel/archives/2005/09/2005v09_ponding.pdf

Regards,
Brian