Grate loading capacity

[DoctorRobert]

I recently got a submittal from a contractor for an inlet frame and grate. It appears to follow the Maryland State Highway standard detail but I cannot find any detail on how the frame and grate dimensions were derived. Is it safe to assume that a frame and grate designed for a traffic area can handle a specified load (H-20 or H-25)? The State Highway Detail is MD 374.02.

 

[msquared48]

"Is it safe to assume that a frame and grate designed for a traffic area can handle a specified load (H-20 or H-25)?"

No!!!!!!!!!!!!!!

I just ran into a similar situation where a grate manufacturer, in his HS tables, did not allow for the AASHTO required 22.5 kip concentrated load at the center of the span for the grate, which controlled. DO NOT believe every manufacturer's table you see.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BenJohnson]

Contractor's submittals must show a product that meets the requirements of the plans and specs. Never assume anything that is not written in the submittal. That's an axiomatic rule: never assume anything that you don't see written in black and white. If you have the slightest question in your mind, reject the submittal as failing to conform to specs.

 

[DoctorRobert]

Thanks for the responses. You confirmed my fears were accurate.

 

[bimr]

Most employers do not want to pay enough to hire experience staff, so many of the workers do not have much experience. For that reason, it is good practice not to assume anything. You've seen the joke about assume? Assuming makes ass/u/me.

 

[TerryScan]

On the other hand, this is a standard DOT grate. You can probably contact Maryland SHA and obtain the load rating of the grate.

 

[boo1]

Pepco has some dwg on line for reference:

http://www.pepco.com/business/services/new/res/#stand

 

[bridgebuster]

Usually a grate ( or a manhole cover) is designed for H-20, i.e. a single 16k wheel because the grate isn't very large ( 2'x4'). I've haven't come across anything designed for HS-25. I would call MDSHD and inquire, unless the drawing specifically states the loading.