Masonry structures gain stability from support offered by cross walls, floors and roof. Load-bearing walls are structurally sound as long as the load is applied axially without any eccentricity.
Lateral support for load-bearing walls or columns limit the slenderness of the structure. Further the lateral supports reduce the possibility of buckling of member due to vertical loads and to resist horizontal forces. Thus in total the lateral support ensures stability against sliding and overturning.
It is mandatory that an RCC floor or roof slab, irrespective of the direction of space, has to bear on a wall or cross wall for a minimum length of 90 mm.
Stability of a wall or column subject to vertical and lateral loads should be ensured. The lateral support provided for a wall or column should be capable of resisting simple static reactions at the point of lateral support to all the lateral loads, plus 2.5% of total vertical load.
In case of load-bearing buildings up to four storeys, stability requirements are ensured when the height-to-width ratio of building does not exceed two.
Cross walls used as stiffening walls continuously from outer wall to outer wall or outer wall to load-bearing wall shall have the spacing and thickness as given in Table 17.1.
Table 17.1 Thickness and spacing of stiffness walls
Halls exceeding 8 m span have to be adequately laterally supported.
For basement walls the following stability requirements are needed:
- 1. Bricks should have a minimum crushing strength of 5 N/mm2.
- 2. Mortar used in masonry should be of grade M1 or better.
- 3. Clear height of ceiling in basement should not exceed 2.6 m.
- 4. Adequate cross walls.
- 5. Thickness of basement should be 300–400 m for spans up to 1.75 m and 2.5 m, respectively.
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