A box beam is constructed of four wood boards as shown in the figure part (a). The webs are 8 in. x 1 in. and the flanges are 6 in. x 1 in. boards (actual dimensions), joined by screws for which the allowable load in shear is F = 250 lb per screw.
(a) Calculate the maximum permissible longitudinal spacing smax of the screws if the shear force is 1200lb.
(b) Repeat (a) if the flanges are attached to the webs using a horizontal arrangement of screws as shown in the figure part (b).

Transcribed Image Text:

yFlange Flange l in. Web in Web 0 8 in in l in in, I in 1 in 6 in l in. 1 in.