13. All-bolted single-angle connection (beam-to-girder web).

EXAMPLE 10.13. All-bolted single-angle connection (beam-to-girder web).

SPECIAL CONSIDERATIONS FOR SIMPLE SHEAR CONNECTIONS 10–173

The angle of skew A appears in Figure 10-38a and represents the horizontal bevel to which

Rev.

the fittings must be bent or set, or the direction of gage lines on a seated connection.

When the skew angle is less than 5 ◦ (1-in-12 slope), a pair of double angles can be bent inward or outward to make the connection as shown in Figure 10-39. While bent angle sections are usually drawn as bending in a straight line from the heel, rolled angles will tend to bend about the root of the fillet (dimension k in Manual Part 1). This produces a significant jog in the leg alignment, which is magnified by the amount of bend. Above this angle of skew, it becomes impractical to bend rolled angles.

For skews approximately greater than 5 ◦ (1-in.-12 slope), a pair of bent plates, shown in Figure 10-40, may be a more practical solution. Bent plates are not subject to the deformation problem described for bent angles, but the radius and direction of the bend must be considered to avoid cracking during the cold-bending operation.

Bent plates exhibit better ductility when bent perpendicular to the rolling direction and are, therefore, less likely to crack. Whenever possible, bent connection plates should be billed with the width dimension parallel to the bend line. The length of the plate is measured on its mid-thickness, without regard to the radius of the bend. While this will provide a plate that is slightly longer than necessary, this will be corrected when the bend is laid out to the proper radius prior to fabrication.

Fig. 10–39. Skewed beam connections with bent double angles.

11–16 DESIGN OF FLEXIBLE MOMENT CONNECTIONS

Try a 5 / 16 -in. fillet weld. The minimum length of weld l min is:

min =

uf

1.392D 150 kips

1.392(5 sixteenths) = 21.6 in.

Use 8 in. of weld along each side and 6 1 / 4 in. of weld along the end of the flange plate.

Select tension flange plate dimensions To provide for an 8-in. weld length and an unwelded length of 1 1 / 2 times

the plate width, use PL 3 / 4 in.×6 1 / 4 in.×17 1 / 2 in. Determine required weld size for fillet welds to supporting column flange.

P uf

D min =

1.5 × 2 × 1.392 l 144 kips

= 5.52 → 6 sixteenths Use 3 / 8 -in. fillet welds.

Design the compression flange plate and connection The compression flange plate should have approximately the same area

as the tension flange plate (4.69 in. 2 ). Assume a shelf dimension of 5 / 8 in. The plate width, then, is 7.495 in. + 2( 5 / 8 in.) = 8.745 in. To approxi- mately balance the flange-plate areas, try a 5 / 8 in.×8 3 / 4 in. compression flange plate.

Check design compressive strength of flange plate Assuming K = 0.65 and l = 3 / 4 in. ( 1 / 2 -in. setback plus 1 / 4 -in. tolerance). Kl

0.65( 3 / 4 in.)

(8 3 / 4 in.)( 5 / 8 in.) 3 / 12 (8 3 / 4 in.)( 5 / 8 in.)

PART 11 REFERENCES 11–17

and the design compressive strength of the flange-plate is

φ R n =φ c F cr A = (30.59 ksi)(8 3 / 4 in.× 5 / 8 in.)

= 167 kips > 144 kips

o.k.

Determine required weld size and length for fillet welds to beam flange As before for the tension flange plate, with 5 / 16 -in. fillet welds, use 8 in.

along each side and 6 1 / 4 in. along the end of the compression flange plate. Select compression flange plate dimensions

Use PL 5 / 8 in.×8 3 / 4 in.×1 ′ -0.

Determine required weld size for fillet welds to supporting column flange

P uf

D min =

1.5 × 2×1.392 l 144 kips

= 3.94 → 4 sixteenths Use 1 / 4 -in. fillet welds.

Comment: The column section should be checked for stiffening requirements. A check of the applicable limit states from LRFD Specification Section K1 (refer to “Column Stiffening at Moment Connections in this Part) will show the W14×109 column in the above example is adequate without stiffening.