10.1 General
This Section gives the recommendations for structural design aspect of reinforced load bearing and non-load bearing walls, constructed with solid or perforated burnt clay bricks, sand-lime bricks, stones, concrete blocks, lime based blocks or burnt clay hollow blocks in regard to the materials to be used, maximum permissible stresses and methods of design.
10.2 Terminology
For the purpose of 10, the definitions given below shall apply.
10.2.1 Cross-Sectional Area of Masonry Unit — Net cross-sectional area of a masonry unit shall be taken as the gross cross-sectional area minus the area of cellular space. Gross cross-sectional area of cored units shall be determined to the outside of the coring but cross-sectional area of grooves shall not be deducted from the gross cross-sectional area to obtain the net cross-sectional area
10.2.2 Grout — A mixture of cement, sand and water of pourable consistency for filling small voids.
10.2.3 Grouted Masonry
10.2.3.1 Grouted hollow-unit masonry — That form of grouted masonry construction in which certain designated cells of hollow units are continuously filled with grout.
10.2.3.2 Grouted multi-wythe masonry — That form of grouted masonry construction in which the space
between the wythes is solidly or periodically filled with grout.
10.2.4 Joint Reinforcement — A prefabricated reinforcement in the form of lattice truss which has been hot dip galvanized after fabrication and is to be laid in the mortar bed joint.
10.2.5 Pier — It is an isolated vertical member whose horizontal dimension measured at right angles to its thickness is not less than 4 times its thickness and whose height is less than 5 times its length.
10.2.6 Prism — An assemblage of masonry units bonded by mortar with or without grout used as a test specimen for determining properties of masonry.
10.2.7 Reinforced Masonry — Masonry which is reinforced to the minimum requirements of this Section and grouted so that the two materials act together in resisting forces.
10.2.8 Grouted Cavity Reinforced Masonry — Two parallel single leaf walls spaced at least 50 mm apart, effectively tied together with wall ties. The intervening cavity contains steel reinforcement and is filled with infill concrete so as to result in common action with masonry under load.
10.2.9 Pocket Type Reinforced Masonry — Masonry reinforced primarily to resist lateral loading where the main reinforcement is concentrated in vertical pockets formed in the tension face of the masonry and is surrounded by in situ concrete.
10.2.10 Quetta Bond Reinforced Masonry — Masonry at least one and half units thick in which vertical pockets containing reinforcement and mortar or concrete infill occur at intervals along its length.
10.2.11 Specified Compressive Strength of Masonry — Minimum Compressive strength, expressed as force per unit of net cross-section area, required of the masonry used in construction by the contract document, and upon the project design is based. Whenever the quantity is under the radical sign, the square root of numerical value only is intended and the result has units of MPa.
10.2.12 Wall Tie — A metal fastener which connects wythes of masonry to each other or to other materials.
10.2.13 Wythe — A continuous vertical tie of masonry one unit in thickness.
10.3 Materials
10.3.1 Masonry Units
10.3.1.1 Masonry units shall be bricks, blocks or stones conforming to relevant Indian Standards. Masonry units that have been previously used shall not be reused in brickwork or block work construction, unless they have
PART 6 STRUCTURAL DESIGN — SECTION 4 MASONRY
been thoroughly cleaned and conform to the code for similar new masonry units. The minimum compressive strength of masonry units used for reinforced masonry shall be 7 MPa.
10.3.1.2 The shape and dimension of masonry units, construction practices, including methods of positioning of reinforcement, placing and compacting of grout, as well as design and detailing should be such as to promote homogeneity of structural members, development of the bond of the grout to both reinforcement and masonry units and avoidance of corrosion of reinforcement.
10.3.2 Concrete
For reinforced masonry M20 grade of cement concrete (minimum cover 15 mm at top and bottom and 20 mm side cover) shall be used to ensure transfer of internal forces from steel reinforcement to masonry.
NOTE — In case cover is less or mortar is put in mortar bed, necessary precaution against corrosion shall be provided as per 10.5.10.2. High strength mortars (H1 and H2) shall be used in mortar bed.
10.3.3 Reinforcement
Steel reinforcement of grade Fe 415 or less only shall be used (see also Note under 10.5.2.1). Deformed bar shall be used.
10.3.4 Material Properties
10.3.4.1 General
Unless otherwise determined by test, the following modulus shall be used in determining the effects of elasticity.
10.3.4.2 Elastic modulus
For steel reinforcement, For clay masonry and concrete masonry, or the chord modulus of elasticity taken between 0.05 and 0.33 of the maximum compressive strength of each prism determined by test in accordance with Annex B.
10.4 Design Considerations
10.4.1 General
Design considerations shall be as per 4 along with the following provisions.
10.4.2 Structural Continuity
Intersecting structural elements intended to act as a unit shall be joined together to resist the design forces. Walls shall be joined together to all floors, roofs or other
elements which provide lateral support for the wall. Where floors or roofs are designed to transmit horizontal forces to walls, the anchorages to the walls shall be designed to resist the horizontal forces.
10.4.3 Effective Span
10.4.3.1 The effective span of simply supported/continuous members may be taken as the smaller of the following:
a) Distance between centres of supports.
b) Clear distance between supports plus an effective depth, .
10.4.3.2 Effective span of a cantilever shall be taken as,
a) distance between the end of cantilever and the centre of its support; and
b) distance between the end of cantilever and the face of support plus half its effective depth, whichever is greater.
10.4.4.1 Wall
Slenderness ratio (ratio of effective height to effective thickness ) should not exceed 27 for vertically loaded reinforced masonry walls in their plane.
10.5 Requirements Governing Reinforcement and Detailing
10.5.1 General
This section provides requirements for the working (allowable) stress design of masonry structure neglecting the contribution of tensile strength of masonry.
10.5.1.1 Members are designed for composite action, stresses shall be computed using transformed area concept of linear elastic analysis as follows: