Checkered Plate Deflection 4

[dik]

I was just looking at Alex's FLRPLATE spreadsheet for checkered plate calculations and note there is a deflection requirement of Span/164. I usually use L/180 or L/240. Is the L/164 a standard of some kind? I've not seen that limitation before. Thanks...

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[FeSE]

Is the check done with strength level loads? Could it be L/164 is a way to check deflection at strength level. e.g. 240/1.6=150

 

[dik]

all based on working strength design... not limit states...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JStephen]

I was just checking one of the grating manufacturers, and their criteria is 1/4" deflection under 100 psf uniform live load. And pulling up a couple of floor plate manufacturers, I see them using that same criteria. I assume that is based on walking comfort/sensation.

 

[human909]

A span ratio is a very poor way of measuring the effects of deflection regarding walking comfort. The user feels the acceleration of the floor (aka the springyness). The actual deflection is a good proxy for this. The span ratio is not.

 

[dik]

Concur... but it's a bit of measurement that includes some stiffness. A deflection ratio of L/300 is less likely to be a problem as one with a deflection ratio of L/120. The deflection is less than 3/16". I was aware of the 1/4" criteria... In addition, the coverplate is secured with bolts... I've reduced them to 2 per side from 3 and 4 per side.

I generally like to keep the ratio above L/200, and with the support on 4 sides, this has worked well in past, and never a vibration issue. The problem at hand is a cover over a pit in a crawlspace tunnel with infrequent access... so I'm not too concerned. I was just wondering why a value of L/164 was chosen.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[HTURKAK]

Two references ;

- AISC asd manual (89) ;for floor plates ; 1/100 of the span ..

- Process Industry Practice ; Grating design guide PIP STE05530 ; (1/4” deflection under uniform load of 100 psf. Based on experience, this is the maximum deflection to afford pedestrian comfort )









Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[dik]

Thanks HTURKAK... I didn't know the AISC had a recommendation of L/100... I usually use the 1/4" max... but didn't know why...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

Is there a usual concentrated load stipulated, too?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[HTURKAK]

- Grating design guide PIP STE05530 adresses the PIP STC01015 for minimum loads and PIP STC01015 specify 1,000 lb (4.5 kN)
concentrated load for Stairs and Exitways, Operating, Access Platforms, and Walkways...

- Copy and paste of footnote of PIP STE05530 Table 1 – SAFE LOADS AND DEFLECTIONS – WELDED STEEL GRATING (TYPE W-19)
2. Uniform loads (U) and concentrated loads (C) with corresponding deflections (Du and Dc) shown in this table are based on a
maximum bending stress of 18,000 psi for simply supported spans computed using gross sections and nominal sizes of
bearing bars with bearing bars spaced at 1-3/16” OC and grating cross bars spaced at 4” OC. Uniform loads are in units of
psf. Concentrated loads are at mid-span in units of pounds per foot of grating width. Deflections are in units of inches.







Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[dik]

Thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik