Elements resisting lateral loads in masonry

In a masonry building, lateral forces from wind or earthquake are picked up by the floors and roof and passed to the walls that run parallel to the force; these walls then carry the force to the foundation. The main resisting elements are:

1. Shear walls (load-bearing masonry walls) in the direction of the force: resist the lateral force by in-plane shear and flexure. The shear capacity of a wall depends on its length, thickness, vertical load and mortar bond. These are the principal elements.
2. Floor and roof diaphragms: RCC slabs or rigid roofs act as horizontal deep beams that transmit the inertia load to the shear walls; flexible diaphragms (timber, GI sheet roofs) distribute the load poorly and need bracing.
3. Cross walls and piers or buttresses (transverse walls): stiffen the walls against out-of-plane forces by acting as vertical supports; the connection at the corners must be strong.
4. Bands (ring beams) and tie columns: RCC or timber horizontal bands at plinth, lintel, floor and roof levels tie the walls together and give box action; vertical reinforcement is placed at corners and jambs.
5. Foundation: transmits the load into the ground; a rigid, continuous plinth band is preferred.

 Load path
 Earthquake force -> Roof diaphragm -> Shear walls (in-plane)
                          |                |
                          v                v
                   Cross walls       Foundation -> ground
                   (out-of-plane support)

For good behaviour, all these elements must form a box with a continuous load path: roofs must be tied to the walls, walls tied to each other at the corners, and openings kept small.