A sign of weight W is supported at its base by four bolts anchored in a concrete footing. Wind pressure p acts normal to the surface of the sign; the resultant of the uniform wind pressure is force F...

A sign of weight W is supported at its base by four bolts anchored in a concrete footing. Wind pressure p acts normal to the surface of the sign; the resultant of the uniform wind pressure is force F at the center of pressure (C.P.). The wind force is assumed to create equal shear forces F/4 in the y direction at each bolt (see figure parts a and c). The overturning effect of the wind force also causes an uplift force R at bolts A and C and a downward force (-R) at bolts B and D

(see figure part b). The resulting effects of the wind and the associated ultimate stresses for each stress condition are normal stress in each bolt (s_u
=410 MPa); shear through the base plate (t
_u
= 115 MPa); horizontal shear and bearing on each bolt (
_bu
=170 t MPa and

_bu
= 520 MPa); and bearing on the bottom washer at B (or D) (
_bw
= 340MPa).

Find the maximum wind pressure p
_max
(Pa) that can be carried by the bolted support system for the sign if a safety factor of 2.5 is desired with respect to the ultimate wind load that can be carried.

Use the following numerical data: bolt d_b
= 19 mm; washer d_w
= 38 mm; base plate t_bp
= 25 mm; base plate dimensions: h = 350 mm and b = 300 mm; W = 2.25 kN ; H = 5.2 m; sign dimensions: L
_v= 3
 L_h
= 3.7 m; pipe column diameter: d = 150 mm; and pipe column thickness: t = 10 mm.