Code of practice for earthquake-resistant design and construction of buildings
1993 Edition

According to IS 4326, earthquake-resistant masonry walls should utilize materials such as well-fired bricks complying with IS 1077:1992 with a minimum compressive strength of 3.5 MPa, solid concrete blocks adhering to IS 2185 (Part 1):1979 also with at least 3.5 MPa crushing strength, and stone masonry units including squared stone, stone blocks, or hollow concrete blocks conforming to IS 1597 (Part 2):1992 with adequate strength. Design and workmanship must follow IS 1905:1987 and IS 2212:1991 to guarantee durability and seismic performance.

IS 4326 specifies that vertical reinforcement bars, typically high strength deformed bars, must be embedded within the plinth masonry and extend continuously through lintel bands, floor slabs, and roof bands to ensure effective load transfer and corrosion protection via concrete or mortar pockets. Horizontal reinforcement, such as reinforced concrete bands with minimum M15 grade concrete, should encompass lintel, floor, and roof levels with specified widths and cover. Welding or lapping of bars should conform to IS 2751 and IS 9417. The reinforcement sizes and placement vary depending on building category and number of storeys, ensuring adequate seismic resilience.

Per IS 4326, timber stud wall construction involves framing vertical studs and corner posts into sills, wall plates, and top plates, with horizontal noggings and diagonal braces to enhance lateral stiffness. Wall panels are typically covered with rigid materials such as EKRA or timber sheathing. Minimum member sizes should not be less than stud dimensions to maintain structural continuity. The frame and wall assembly must resist the total seismic lateral load, with the frame alone designed to carry at least 25% of this force. Connections use bolts and washers, with double studs reinforcing openings to ensure integrity during earthquakes.

IS 4326 addresses prefabricated floors and roofs in clauses dealing with small precast units such as channel/cored slabs, reinforced concrete planks and joists, brick panels with joists, and waffle units. It mandates that these components be designed to act as rigid diaphragms, transferring lateral seismic forces effectively to vertical resisting elements. For precast types not explicitly covered, the entire building must be analyzed for maximum seismic demands. Reinforcement detailing, including tie beams and dowel bars, is specified to ensure the structural system works integrally during seismic events.

IS 4326 requires the provision of separation gaps or crumple zones between adjoining structural parts to prevent collision and damage during seismic movement. Separation sections are intentional gaps allowing independent motion, while crumple sections are filled with deformable materials that absorb seismic energy by controlled crushing or fracturing. The width of these gaps must accommodate expected displacements, and their length should not exceed three times the building width. Alternative design approaches include aligning centers of rigidity and mass to minimize torsional effects, thereby sometimes avoiding the need for separation.