Strength of Joints of Wall Cupboards

Wall cupboards, especially bathroom and kitchen cupboards, are attached to the walls with the use of furniture handles screwed to the body, top or simultaneously to the top and side wall using screws (Fig. 7.75). Embedded in the wood, they should be screwed into the properly drilled holes with a diameter 2 mm smaller than the diameter of the screw core. Drillings should be made on a section of about 80 % of the length of the screw. In structures made of particle boards, drillings are not used.

Because screws of handles of metal wall cabinets work on bending and shearing, the number t of single-sheared screws should be determined from the equations:

Fig. 7.75 Methods of mounting cupboards

where

t number of single-sheared screws, d screw diameter,

Vt volume of element,

Pi density of element material,

A, usable area of horizontal elements, qi surface load of horizontal elements, g 9.81 m/s2,

n number of horizontal elements and m number of vertical elements

The above relation applies when the depth of embedding the screw L amounts to

L > 8d. (7.258)

In other cases, i. e. when

4d < L < 8d, (7.259)

the calculated number of screws must be corrected by the coefficient k:

k = L/8d. (7.260)