Diamond Plate Deflection Requirement?

[BadgerPE]

Is anyone aware of any code mandated defelection restrictions for diamond plate (raised pattern floor)? AISC Table 3-18a limits deflection to L/100 which results in an extremly low allowable load. I am analyzing a few existing industrial mezzanines to determine an appropriate load rating them. I am working in the US and governed by IBC and ASCE 7.

 

[BadgerPE]

One thing I should add is that these mezzanines are for storage/equipment purposes only and are not accesible without a ladder or lift so comfort servicability (ie L/360) is not a major concern.

 

[jdgengineer]

L/100 is a fairly low deflection limit. When I have analyzed these in the past I have made sure to meet both the deflection requirements (using serviceability load combos) and strength requirements using factored load combos.

For access platforms you may be able to use a lower deflection limit than L/100, but that in my opinion is already fairly low.

 

[dik]

L/180 or L/240... depending on the day...

Dik

 

[MiketheEngineer]

Those numbers (L/d) are recommended by code. They can be exceeded. Bit L/100 will be quite noticeable to anyone who stands on or below the deck.

Stick closely to the code numbers,,

 

[jdgengineer]

To clarify my post since AISC uses L/100 for their deflection allowables for diamond plated floors, I'd use this as the absolute minimum. I wouldn't personally go below that deflection limit.

 

[jdgengineer]

Personally, I'd only apply that limit to the diamond plated floor itself. For the supporting structure, I'd use a higher deflection limit. The deflection limits of IBC may not apply since it's a maintenance platform. AISC is vague in its deflection requirements stating only that "deflection should not impair the serviceability of the structure".

Personally, I'd use something more strict than the L/100 for the supporting members, probably a minimum of L/120 for D + L and L/180 for L, and maybe considering using L/180 and L/240...

 

[BadgerPE]

Deflection of the supporting structure is a non-issue. Currently, I have 1/8" DP spanning 2.67'. Using the allowable stress of 16 ksi provided in AISC 3-18 I determine w_all=64.7 psf. However, under that load the deflection is 1.28" or L/25. If I adhere to the L/100 w_all=15.9 psf. If I subtract the self weight of the plate that leaves an allowable load=9.75psf which seems a little too low to justify. I am thinking of limiting total deflection to 1/2" for an allowable load of 24.85-6.15=18.7 psf. Thoughts?

 

[jdgengineer]

In the end its up to your judgement to some degree. Personally, I wouldn't exceed the AISC limits -- I'd retrofit the floor.

 

[ToadJones]

Cracker-

How is the deck plate supported?

How are you determining deflections?

Simple beam approach is super conservative

 

[JLNJ]

I don't like to walk on springy floor plate - even if I designed it and I know the stress is just fine.

 

[hokie66]

I've never seen 1/8" floor plate. Sounds cheap and springy to me.

 

[BadgerPE]

The worst case mezz has the deck supported on W-sections 3' apart. There is nothing in the long span for 19'. So I assumed the distance between the flanges for bending. These mezzanines are already in place and the just need to be load rated for insurance purposes. Due to the configuration, nobody can really access them. Mostly, they are used for very light storage. I wouldn't have picked 1/8" DP for flooring but that is what was used. Thanks all for the help!

 

[dicksewerrat]

Once they start storing stuff, the weights gho up as time goes by. No one remembers what the enginner told the first guy. According to some people paper is light. "Until it gets 8 feet high', and any one can put in a s set of steps to the storage area.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[hokie66]

In most types of storage, the load itself will distribute to the supporting members at these spans. So the deflection is really a concern only for moving loads like foot traffic.