Chapter 6General Requirements

6.1 Methods of Construction

6.2 Minimum Thickness of Walls from Consideration other than Structural

Thickness of walls determined from consideration of strength and stability may not always be adequate in respect of other requirements, such as resistance to fire, thermal insulation, sound insulation and resistance to damp penetration for which reference may be made to the appropriate Parts/Sections of the Code, and thickness suitably increased, where found necessary.

6.3.1 General

Workmanship has considerable effect on strength of

masonry and bad workmanship may reduce the strength of brick masonry to as low as half the intended strength. The basic compressive stress values for masonry as given in Table 9 holds good for commercially obtainable standards of workmanship with reasonable degree of supervision.

6.4 Joints to Control Deformation and Cracking

Special provision shall be made to control or isolate thermal and other movements so that damage to the fabric of the building is avoided and its structural sufficiency preserved. Design and installation of joints shall be done according to the appropriate

recommendations in accordance with good practice [6-4(6)].

6.6.1 Where corbelling is required for the support of some structural element, maximum projection of masonry unit should not exceed one-half of the height of the unit or one-half of the built-in part of the unit and the maximum horizontal projection of the corbel should not exceed one-third of the wall thickness.

6.6.2 The load per unit length on a corbel shall not be greater than half of the load per unit length on the wall above the corbel. The load on the wall above the corbel, together with four times the load on the corbel, shall not cause the average stress in the supporting wall or leaf to exceed the permissible stresses given in 5.4.

6.6.3 It is preferable to adopt header courses in the corbelled portion of masonry from considerations of economy and stability.

7 REINFORCED BRICK AND REINFORCED BRICK CONCRETE FLOORS AND ROOFS

The construction and design of reinforced brick and reinforced brick concrete floors and roof shall be in accordance with good practices [6-4(7)].

8 SPECIAL CONSIDERATION FROM EARTHQUAKE POINT OF VIEW

8.0 Special features of design and construction for earthquake resistant masonry buildings are given in 8.2 to 8.8.2. However, special features of design and construction for improving earthquake resistance of low strength masonry buildings is covered in 9.

8.1 For the purpose of 8 and 9, the definitions given below shall apply in addition to those given in 2.

8.1.1 Separation Section — A gap of specified width

between adjacent buildings or parts of the same building either left uncovered or covered suitably to permit movement in order to avoid pounding due to earthquake.

8.1.1.1 Crumple section — The separation gap filled with appropriate material that crumples or factures in the event of an earthquake.

8.1.2 Centre of Rigidity — The point in a structure where application of lateral force produces equal deflections of its components at any level in any particular direction.

8.1.3 Shear Wall — A wall designed to resist lateral force in the own plane. Braced frames, subjected primarily to axial stresses, shall be considered as shear walls for the purpose of this definition.

8.1.4 Space Frame — A three-dimensional structural system comprised of interconnected members, without shear or bearing walls, so that to function as a complete self-contained unit with or without the aid of horizontal diaphragms or floor bracing systems.

8.1.4.1 Vertical load carrying frame — A space frame designed to carry all the vertical loads, the horizontal loads being resisted by shear walls.

8.1.4.2 Moment resistant frame — A space frame capable of carrying all vertical and horizontal loads, by developing bending moments in the members and at joints.

8.1.4.3 Moment resistant frame with shear walls — A space frame with moment resistant joints and strengthened by shear walls to assist in carrying horizontal loads.

8.1.5 Box System — A bearing wall structure without a space frame, the horizontal forces being resisted by the walls that act as shear walls.

8.1.6 Band — A reinforced concrete or reinforced brick runner provided in the walls to tie them together and to impart horizontal bending strength in them.

NOTE — For low strength masonry buildings, wooden runners may also be used as runner.

8.1.7 Seismic Zone and Seismic Coefficient — The Seismic Zones II to IV as classified in 5 of Part 6 'Structural Design, Section 1 Loads, Forces and Effects' of the Code and corresponding basic seismic coefficient $\alpha_{\mathrm{o}}$ as specified in 3.4 of good practice [6-4(8)].

8.1.8 Design Horizontal Seismic Coefficient — The value of horizontal seismic coefficient $A_{h}$ computed taking into account the soil-foundation system and the importance factor as specified in 6.4 of good practice [6-4(9)].

8.1.9 Concrete Grades — 28 day compressive strength

of concrete cubes of $150\mathrm{mm}$ size, in MPa; for example, for Grade M20 as per good practice[6-4(10)], the characteristic compressive strength equals to $20\mathrm{MPa}$.

8.1.10 Zone Factor (Z) — It is a factor to obtain the design spectrum depending on the perceived maximum seismic risk characterized by maximum considered earthquake (MCE) in the zone in which the structure is located.