Here are the design steps to be followed for an unreinforced masonry wall.
- Estimate the self weight and imposed loads. See IS 875 part 1&2 on how to go about it.
- Estimate the eccentricity ratio taking moments about the centerline of the wall. You can use the equation stated below to calculate eccentricity ratio. WE=w1e1+w2e2 where W is the weight of the masonry wall and E is the eccentricity. Eccentricity ratio is E divided by thickness of the wall.
- Estimate the effective height, length and thickness of the wall.
- Calculate slenderness ratio as the lesser of the 2; effective height / effective thickness or effective length / effective thickness.
- With the eccentricity and slenderness ratios; estimate the stress reduction factor from the code . If necessary you can also estimate area reduction factor and shape modification factor.
- Calculate the compressive stress of the wall based on the wall load. Then divide by stress reduction factor, to arrive at the basic compressive stress required.
- Apply increase in basic compressive stress if eccentricity is significant. Increase of up to 25% is allowed by the code
- With the help of TABLE 8 of the IS code 1905,and using the basic compressive stress, chose the appropriate unit strength and mortar mix required.