The geometric configuration and dimensional requirements for a structural steel weld access hole, commonly known as a rat hole, are established in the web of a structural member adjacent to the flange to allow continuous welding of moment connections. The height H is defined as the greater of 1.5 times the web thickness tw or 1 inch, but not greater than 2 inches. The width W is specified as the greater of 1.5 times the web thickness tw or 1 1/2 inches with a tolerance of plus or minus 1/4 inch. A minimum radius R of 3/8 inch is required at the internal notch, accompanied by a sloped transition between the web and flange to prevent stress concentrations.
SLOPE TO FORM A TRANSITION BETWEEN WEB AND FLANGE H W R W = GREATER OF 1.5tw OR 1 1/2" (TOLERANCE = +/- 1/4") H = GREATER OF 1.5tw OR 1" BUT NOT GREATER THAN 2". R = 3/8" RADIUS MINIMUM
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