What is a Load Table
 
Bar grating load tables list a grating’s bearing bar sizes and associated load and deflection characteristics. Deflection, or bending of the bar grating, should not be more than 1/4 inch. If the deflection exceeds 1/4 inch, the grating may have excessive bounce, making it uncomfortable to walk on.
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Purpose: Finding the Best Grating
 
Load tables help you to match a specific bar grating with your load requirement. As a grating’s bearing bar size (height and/or width) increases, the strength of the grating increases and the deflection under a given load is reduced, but cost increases. Your best value is a grating with a bearing bar size that results in a deflection closest to 1/4 inch for the load that applies to your application.
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Information Required
 
In order to use the bar grating load tables, you will need to know the:
  • Grating type and/or series designation
  • Material of the grating: plain steel, aluminum, etc.
  • Clear Span of you application (unsupported span)
  • Type of load the grating will carry
  • Maximum load expected
You then select the appropriate load table for the grating type and use it to determine the optimum bearing bar size.
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Load Types
 
There are two common types of loads: Uniform and Concentrated.

Use uniform load when your application?s load is applied equally across the full width and span of the grating. Examples include:
  • Pedestrian traffic
  • Multiple containers stacked across the span
Use concentrated load when the load for your application is applied at a point on the grating. Examples include:
  • Equipment with legs
  • A single stack of containers
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Uniform Load
 
Uniform Load, U, (measured in pounds per square foot) is a load that is applied equally across the the full width and span of the grating. This causes stress along the sides of the grating, resulting in deflection (D in the illustration to the right) of the bearing bars. Specific uniform loads and their resulting deflections for a given span are listed in the load tables.

A section from the McNichols? GCM-1 series (aluminum Close Mesh rectangular bar grating) load table is provided below. Spans are listed horizontally (along the top) and bearing bar sizes are listed vertically (along the left side). The engineering format of load tables may vary. For the GCM series, each bearing bar size has four rows giving load and deflection information. Uniform loads for each span are provided in the first row (U) of each bearing bar size. Deflections resulting from the uniform load are listed in the second row, (D).
 
 
Section from GCM-1 Series Load Table
Bearing Bar Size   Span
Height
(Inches)
Thickness
(Inches)
 
2’-0"
2’-6"
3’-0"
3’-6"
4’-0"
4’-6"
5’-0"
1 1/8 U 640 410 284 208 Right Arrow 1 1
D 0.192 0.300 0.430 0.585 Right Arrow 1 1
C 640 510 427 365 1 1 1
D 0.153 0.239 0.345 0.469 1 1 1
1 3/16 U 959 613 427 313 Right Arrow 1 1
D 0.191 0.299 0.432 0.588 Right Arrow 1 1
C 959 767 640 548 1 1 1
D 0.153 0.239 0.345 0.470 1 1 1
 
The last two rows for each bearing bar size contain the concentrated load (C) and the deflection (D) resulting from that concentrated load.

Shaded Areas (applies to pedestrian traffic only)

Gray shaded areas () in the a bar grating load table contain span and load combinations that result in a deflection of 1/4 inch or less under a uniform load of 100 pounds/square foot. This is a standard uniform load and as a general rule, is acceptable for pedestrian traffic.

The shaded areas are used to find the optimum bearing bar size as follows: Find the span that applies to your application and move vertically down the column until you reach the first uniform load value contained within the shaded area. The bearing bar size to the left of the first uniform load value in the shaded area is the minimum bar grating size that will meet the deflection criteria.

Note: Not all load tables contain shaded areas representing span and load combinations that result in a deflection of 1/4 inch or less under a uniform load of 100 pounds/square foot. In these tables, you must determine the maximum uniform or concentrated weight. Then, you find the first deflection value within the column for the application’s span that meets both the weight requirements and the 1/4 inch or less deflection value.
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Concentrated Load
 
Concentrated Load (measured in pounds per foot) is applied to the full width of the grating at mid-span but not across the full length of the span. This concentrated load is assumed to be carried equally by all bearing bars in one lineal foot and results in the deflection (D).

Concentrated loads (C) are listed in the third row of each bearing bar size. The deflections in inches (D) resulting from the specific concentrated load are listed in the fourth row.
 
 
Section from GW & GW-2 Series Load Table
Bearing Bar Size   Span (1?3/16 inches Center to Center Bar Spacing)
Height
(Inches)
Thickness
(Inches)
 
2’-0"
2’-6"
3’-0"
3’-6"
4’-0"
4’-6"
5’-0"
3/4 1/8 U 355 227 158   89 70 1
D 0.099 0.155 0.223 0.304 0.397 0.503 1
C 355 284 237 203 178 158 Right Arrow1
D 0.079 0.124 0.179 0.243 0.318 0.402 Right Arrow1
3/4 3/16 U 533 341 237 174 133 105 1
D 0.099 0.155 0.223 0.304 0.397 0.503 1
C N/A 426 355 305 266 237 Right Arrow1
D 0.079 0.124 0.179 0.243 0.318 0.402 Right Arrow1
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Wheel Traffic
 
Wheel traffic includes on- or off- road vehicles, forklifts, or other heavy wheeled equipment. Bikers or skaters are considered pedestrain traffic. The load tables available at this site are not appropriate for wheel traffic. If you have a wheel traffic application, please let us know when you request a quote.
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