Structural Drafting

Assembly Clearance Dimensions

Clearance Dimensions for Beams Connecting to Beams

In order for members to assemble readily, clearances are required between beams and columns or beams and beams. The dimension values can be found in the Dimensions and Properties Tables of the AISC manual.

E D E

C B C

A

Clearance Dimensions for Beams Connecting to Beams

Dimension A: Is the given center to center distance from the main beams. This dimension is found on the framing plans.

Dimension B: Dimension from the backs of the connection angles(A - (C1 + C2))

E D E

C B C

A

Clearance Dimensions for Beams Connecting to Beams

Dimension C: Clearance dimensions for the connection angles. This dimension is also referred to as "Setback." Note that the C dimension is calculated using the beam that is being connected to. C = (tw / 2) + 1/16

Dimension D: Actual length of connection beam. This is the dimension that the fabricators need to cut the beam to proper length to fit in the assembly.(D = B - (E1 + E2)

E D E

C B C

A

Clearance Dimensions for Beams Connecting to Beams

Dimension E: Nominal Setback clearance for beam. This is generally 1/2".

E D E

C B C

A

Clearance Dimensions for Beams Connecting to Beams

For Example: Given a W12 x 35 is connected to two W18 x 60 beams, calculate the following dimensions:

A = 26'- 4" (given on the framing plan drawing)

C = (tw /2) + 1/16 = 1/4 + 1/16 (The (tw /2) value is taken from the W18 x 60 beam not the W12 x 35)

E = 1/2

B = (A - (C1 + C2)) = 26'-4" - (5/16 +5/16) = 26' - 3 3/8"

D = B - (E1 + E2) = (26'-3 3/8") - (1/2 + 1/2) = 26' - 2 3/8"

Cope Cuts

When the tops of beams are to be flushed, a notch must be cut into the connecting beam to prevent interference with the flange of the other beam. Such a notch is called a cope, block, or cut. It is the practice of the structural detailer to draw the depth dimension to scale so that the relation of the detail is correct and so the fabricator can interpret the relation of the holes to bolts or other holes more readily.

Q1 = k distance This is a minimum dimension. Q1 can never be smaller than the k-distance

Q2 = ((bf - tw)/ 2) + 1/2 The Q2 dimension is measured from the back of the connection angle

Note: Q1 and Q2 are rounded to the nearest 1/4"

Cope Cuts

The intersection of the horizontal and vertical cuts (re-entrant cut) is shaped to a smooth radius to provide a fillet at this point. Although most shops routinely provide these fillets, they should always be shown on shop details. An approximate minimum radius to which this corner must be shaped is 1/2 inch (13th Edition AISC manual, Part 9).

Q1 = k distance This is a minimum dimension. Q1 can never be smaller than the k-distance

Q2 = ((bf - tw)/ 2) + 1/2 The Q2 dimension is measured from the back of the connection angle

Note: Q1 and Q2 are rounded to the nearest 1/4"

Clearance Dimensions for Beams Connecting to Columns

Given the beam (W10 x 45) connected to column A and column B, the total length of the beam can be calculated as follows:

Center to Center distance of Column A and Column B 16' - 0"Column A: tw/2 + 1/16 0' - 0 5/16"Column B: tw/2 + 1/16 0' - 0 5/16"Setback at Column A 0' - 0 1/2"Setback at Column B 0' - 0 1/2"Total Length of Beam W10 x 45 15' x 10 3/8"

Clearance Dimensions for Beams Connecting to Columns

Given the beam (W10 x 45) connected to column A and column B, the total length of the beam can be calculated as follows:

Center to Center distance of Column A and Column B 20' - 0"Half the depth of Column A + 1/16 0' - 5 3/16"Half the depth of Column B + 1/16 0' - 5 3/16"Setback at Column A 0' - 0 1/2"Setback at Column B 0' - 0 1/2"Total Length of Beam W10 x 45 19' x 0 5/8"