A sign of weight W is supported at its base by four bolts anchored in a...

 

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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. 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 (o, = 75 ksi); shear through the base plate (tu = 38 ksi); horizontal shear and bearing on each bolt (Thu = 40 ksi and Gbu = 80 ksi); and bearing on the bottom washer at B (or D) (Obw = 60 ksi). Find the maximum wind pressure pmax (psf) that can be carried by the bolted support system for the sign if a safety factor of 3 is desired with respect to the ultimate wind load that can be carried. Use the following numerical data: bolt d, = 1 in.; washer d, = 1.25 in.; base plate thp = 1.5 in.; base plate dimensions h = 30 in. and b = 30 in.; W = 1200 lb; H = 32 ft; sign dimensions (L, = 12 ft. x LA = 16 ft.); pipe column diameter d = 18 in., and pipe column thickness t= 3/4 in. Explain all your answers and check if the numerical data complies with the design or you have to make changes to the numerical data. Sign (L, X Lp) Pipe column W FH Rh Resultant L One half of over - turning moment about x axis acts of wind C.P. pressure dp on each bolt pair dw. Base plate (Ip) Pipe F14 Footing column D Overturning Compression Tension R H C moment B about x axis (b) FH FH FH at each 4 bolt W at each 4 bolt in. (a) W R+ F 4 W 4. F 4 4 (c) 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. 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 (o, = 75 ksi); shear through the base plate (tu = 38 ksi); horizontal shear and bearing on each bolt (Thu = 40 ksi and Gbu = 80 ksi); and bearing on the bottom washer at B (or D) (Obw = 60 ksi). Find the maximum wind pressure pmax (psf) that can be carried by the bolted support system for the sign if a safety factor of 3 is desired with respect to the ultimate wind load that can be carried. Use the following numerical data: bolt d, = 1 in.; washer d, = 1.25 in.; base plate thp = 1.5 in.; base plate dimensions h = 30 in. and b = 30 in.; W = 1200 lb; H = 32 ft; sign dimensions (L, = 12 ft. x LA = 16 ft.); pipe column diameter d = 18 in., and pipe column thickness t= 3/4 in. Explain all your answers and check if the numerical data complies with the design or you have to make changes to the numerical data. Sign (L, X Lp) Pipe column W FH Rh Resultant L One half of over - turning moment about x axis acts of wind C.P. pressure dp on each bolt pair dw. Base plate (Ip) Pipe F14 Footing column D Overturning Compression Tension R H C moment B about x axis (b) FH FH FH at each 4 bolt W at each 4 bolt in. (a) W R+ F 4 W 4. F 4 4 (c)