Consider a steel W shape column framing the exterior of an i

Consider a steel W shape column framing the exterior of an industrial building The column is a W310 x 67, CSA G40.21 350W steel. The height of the column from the top of the baseplate to the center depth of the roof beams is 9.0 m. Recommend the spacing of bracing members, (positioned along the wall of the building), so that the member resistance is based on strong axis behaviour, (ie the resistance is not limited by the weak axis response.)

Solution

Consider the number of bracings to be one and just assume to be the1/3rd of height of the industrial column

so place a bracing at 3m height from both the intervals

Now calculate the design strength based on both major axis and minor axis

first consider major axis buckling

Fy=350 Mpa

Ixx=144x10⁶mm⁴

Iyy=20.7x10⁶mm⁴

Rx=131 mm

Ry=49.5mm

Area=8450 mm²

KLx/Rx=0.7x9000/131=48.09

KLy/Ry=0.7x3000/49.5=42.42

so the major value will take control of the design load

Now as it is an industrial building it will be having fixed ends on both the sides so take

K=0.7

Fcr=3.14x3.14xE/(KL/r)²

Fcr=3.14x3.14x2x10⁵/(0.7x9000/49.5)²

Fcr=121.71 Mpa

The load=FcrxAg=121.7x8450=1028.668 KN

If we apply a reduction factor of 0.9, then the load will be

0.9x1028.668=925 KN

so it is adequate to provide a bracing at 1/3rd height from top and bottom at 3m .