Question

The relation between the strength of brick masonry f_w, the strength of bricks f_b, and the strength of mortar f_m is given by (where K_w 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. \({f_w} = {K_w}\sqrt {{f_b}{f_m}} \)

Answer 1

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