Member deflection vs floor deflection
Member deflection vs floor deflection
(OP)
Typically floors (steel or composite beams with concrete on metal deck) are designed for deflection limits of TL/240 & LL/360 per IBC 1640.3. But I am wondering if these are deflection limits for individual members for the floor system? Please see attached for a graphical representation of my question. If I was design for TL/240, I could have a 2.5” deflection at some point in floor.
I thought that these deflection limits applied to the individual members but 2.5” worst case deflection for the grid such as the attached seems excessive.
I thought that these deflection limits applied to the individual members but 2.5” worst case deflection for the grid such as the attached seems excessive.






RE: Member deflection vs floor deflection
As a result, IMHO, your true deflection should factor in the deflection of the girder and added to the beam to figure out a bay's deflection.
I will post the paper once I find it.
RE: Member deflection vs floor deflection
RE: Member deflection vs floor deflection
http://www.concreteconstruction.net/Images/Control...
RE: Member deflection vs floor deflection
RE: Member deflection vs floor deflection
Of course this section begins with “1604.3 Serviceability. Structural systems and members thereof shall be designed to have adequate stiffness to limit deflections and lateral drift.” So the total structural system needs to have “ adequate stiffness to limit deflections” but these limits (except for special cases) are not well defined in the code, that I can find.
So we are left with applying our engineering judgment/experience, for the most part, in designing the structural system for adequate stiffness.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Member deflection vs floor deflection
Slick: Thanks the paper you linked. Looking at that I think the somewhat easier solution would be to camber the girders only. Not sure though, I gotta think about this.
RE: Member deflection vs floor deflection
Also a cursory check on vibration never hurt anything if the bay is large enough for concern.
RE: Member deflection vs floor deflection