# The relation between the strength of brick masonry fw, the strength of bricks fb, and the strength of mortar fm is given by (where Kw is a coefficient

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The relation between the strength of brick masonry fw, the strength of bricks fb, and the strength of mortar fm is given by (where Kw is a coefficient based on the layout of the bricks and the joints)
1. ${f_w} = \sqrt {{K_w}\frac{{{f_b}}}{{{f_m}}}}$
2. ${f_w} = {K_w}\sqrt {\frac{{{f_b}}}{{{f_m}}}}$
3. ${f_w} = \sqrt {{K_w}{f_b}{f_m}}$
4. ${f_w} = {K_w}\sqrt {{f_b}{f_m}}$

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Correct Answer - Option 4 : ${f_w} = {K_w}\sqrt {{f_b}{f_m}}$

Concept:

The basic compressive stress of masonry depends upon the crushing strength of masonry units (bricks) and type of mortar used.

Basic compressive stress also depends upon surface characteristics, water absorption property of units, uniformity of shape and size of units, thickness of joints etc.

For a wall, the slenderness ratio shall be the effective height divided by the effective thickness and stiffening coefficient (Kn) or the effective length divided by the effective thickness, whichever is less.

Thus, $SR = \frac{h}{{t{K_n}}}$

The relation between the strength of brick masonry fw, the strength of bricks fb, and the strength of mortar fm is given by,

${f_w} = {K_w}\sqrt {{f_b}{f_m}}$

 No. of storeys Thickness of wall Maximum values of S.R Mortar containing cement Mortar not containing cement Not exceeding 2 Any 27 20 Exceeding 2 Walls of 90 mm thickness or more 27 13 Wall less than 90 mm thickness 20 13