Soham Mantra
 R.C.C  Design

List of I.S. Codes generally required to be reffered for Building Design

7.1 The important I.S. Codes (with their latest editions/ amendments) to be referred to for design of building are as follows :
(i) I.S. 456-1978 : Code of practice for plain and reinforced concrete .
(ii) I.S. 800-1962 : Code of practice for use of structural steel in general building constriction.
(iii) I.S. 875-1987 : Designs loads other than (part I toV) earthquake for building Design.

Part-I : Dead loads .
Part-II : Imposed loads .
Part-III : Wind loads .
Part IV : Snow loads .
Part V : Special loads and load combinations.

(iv) I.S. 1080-1965 : Code of practice for design and construction of shallow foundation in soils (other than Raft, Ring and shell )
(v) I.S:1642-1988 : Fire safety of Bldgs. (General) Detail 3 of construction.
(vi) I.S.: 1643-1988: Code of practice for Fire safety of Bldgs(General) Exposure Hazard.
(vii) I.S. 1644-1988 : Code of practice for Fire safety of Bldgs(General) Exit requirements and personal Hazards.
(viii) I.S. 1888-1972 : Methods of load test on soils.
(ix) I.S. :1893-1984 : Criteria for earthquake resistant design of structures.
(x) I.S : 1904-1986 : Code of practice for design & construction of pile foundation in soil structural safety of building foundation.
(xi) I.S. 2911-1990 : Code of practice for design and construction of pile (Part I to IV) foundation.
(xii) I.S. 2950-1981 : Code of practice for design and construction of raft foundation.
(xiii) I.S. 3370-1965 : Code of Practice for water retaining structures .
(xiv) I.S. 3414-1987 : Code of Practice for Design and Installation of joints in buildings.
(xv) I.S. 4326-1993 : Code of practice for earthquake resistant design of structure .
(xvi) I.S. 6403-1981: Code of practice for Determination of bearing pressure of shallow foundation .
(xvii) I.S. 13920-1993 : Code of practice for ductility detailing of reinforced concrete structures subjected to seismic forces .
I.S. Codes are also available for design of special types of structures like folded plate ,shell structures etc. Refer publication list of BIS for the same .
Similarly there are special publications of I.S. which are useful for design of buildings such as .

(i) SP-16 : Design Aids to I.S. : 456-1978
(ii) SP-22 : Explanation to I.S. : 1893 & I.S. :4326.
(iii) SP-23 : Concrete Mix .
(iv) SP-24 :Explanation of I.S. 456-1978.
(v) SP-25 : Cracks in buildings and their repairs .
(vi) SP- 34 : Detailing in R.C.C. structures .
(vii) SP-38 : Design of steel trusses .

Besides above mentioned I.S. Codes ,Hand Book for R.C. Member " (Limit State Design ) Vol .I and II by P.L. Bongirwar and U.S. Kalgutkar ,published by P.W.D. (Govt.of Maharashtra) is very useful .

For general instructions regarding carring out R.C.C. works in field refer to Design Circle’s Technical Note No . 7502 and 7503 are kept at page 46 and page 59. respectively .

For aspects which are not covered by any other I.S. codes available, relevant British Standard Codes may be referred to .

7.2 While designing R.C.C. structures, important provisions of I.S. codes must be borne in mind . Some of the important provisions of I.S. :456-1978 are as follows.

7.2.1 The code has been divided into 6 sections.

Section-I : General .
Section-II : Material, Workmanship, inspection and testing .
Section-III : General Design requirements for structural members and systems .
Section-IV : Special Design requirement for structural members and systems.
Section-V : Structural Design .(Limit State Method ).
Section-VI : Structural Design (Working Stress Method ).

7.2.2 General Provisions.

Clause No. 19 : Deals with stability of the structure against overturning and sliding.
Clause No. 25.2.1 : Development length of bars.
Clause No. 25.3.1 : Minimum distance between individual bars .
Clause No.25.3.2 : Maximum distance between bars in tension .
Clause No.25.4 : Cover to reinforcement .
Clause No.26 : Expansion joints .

7.2.3 Provision regarding slabs :

Clause No.21.2 : Effective span.
Clause No.21.4.1 : Arrangement of live load .
Clause No.21.5 : Moment and shear co-efficient for continuous beams .
Clause No.22.2 : Control of deflection.
Clause No.23.1 : Provisions regarding solid slabs .
Clause No. : Minimum reinforcement.
Clause No. : Maximum diameter.

7.2.4 Provisions regarding beams :

Clause No.21.2 : Effective span
Clause No.21.4.1 : Arrangement of live load .
Clause No. 21.5 : Moment and shear co-efficient for continuous beams.
Clause No. 22.2 : Control of deflection.
Clause No. 22.3 : Slenderness limits for beams.
Clause No. : Requirement of tensile reinforcement for beams .
Clause No. :Compression reinforcement.
Clause No. : Side face reinforcement.
Clause No. : Maximum spacing of shear reinforcement.
Clause No. : Minimum shear reinforcement.
Clause No. : Distribution of torsion reinforcement.

7.2.5 Provisions for columns;

Clause No.24.1.2 : Short and slender compression members .
Clause No.24.1.3 : Unsupported length .
Clause No.24.2 : Effective length of compression members.
Clause No.24.3 : Slenderness limits for columns .
Clause No.24.4 : Minimum eccentricity .
Clause No.25.5.3 : Longitudinal reinforcement.
Clause No. : Transverse reinforcement.
Clause No.42.2 : Cracking Consideration .

7.2.6 Provisions for footings :

Clause No. 33.1.2 : Thickness at the edge of footing .
Clause No.33.4 : Transfer of load at the base of column .

Other references /Literature generally referred to are

(i)           Reinforced Concrete Designer’s Hand Book by Reynolds & Steelman.
(ii) Limit State Theory & Design of Reinforced Concrete by Karve and shah .
(iii) Hand Book of Reinforced Concrete Design (I.S.:456-1978)by Karve .
(iv) Limit State Design of Reinforced Concrete by Vergis .





8. General practice followed in Design Circle :

(i) The loading to be considered for design of different parts pf the structure including wind loads shall be generally as per I.S. 875-1987 (Part I to IV) and I.S. 1893-1984 (seismic loads )with there latest amendments .

(ii) Live load for sanitary block shall be 200 kg/m2.

(iii) Lift machine room slab shall be designed for live load of 1000 kg/m2 .

(iv) Lift load shall be considered as per relevant I.S. codes as per capacity of lift and the same shall be increased by 100% for impact while designing .

(v) Loading due to electrical installation e.g. AC. ducting , exhaust fans etc.shall be got confirmed from the Executive Engineer, electrical wing of P.W. Department .

(vi) Seismic loads shall be as per I.S. 1883-1984 and I.S. 4326-1993. The method of analysis and values of various parameters shall be taken as per relevant provisions of codes .

(vii) Ductility provisions specified in I.S. 4326-1993 and I.S. 13920-1993 shall be adopted in design, if the value of (Alpha h) is greater than or is equal to 0.05.

(viii) Any other loads which may be required to be considered in the designs due to special type or nature of the structure shall be got approved in advance from the Superintending Engineer .

(ix) Deduction in dead loads for opening in walls need not be considered.

(x) Unless otherwise specified ,the weight of various materials shall be considered as given below .

(a) Brick masonry :1920kg/m3

(b) Reinforced cement concrete : 2500kg/m3

(c) Floor finish : 100kg/m3

(d) Brick Bat Coba of 112mm thickness

laid on terrace for water proofing treatment : 200kg/m2

(a) Brick Bat Coba in bath &W.C. depending on

thickness of water proofing treatment : 1920 kg/m3

(xi) The analysis shall be carried out separately for dead loads, live loads, seismic loads, wind loads . All the structural components shall be designed for the worst combination of the above loads as per relevant codal provisions.

(xii) In case of tall building, if required Model analysis shall be done for horizontal forces, as per I.S. : 1893 and I.S. 875 (Part III).

(xiii) Minimum reinforcement in all structural members shall be as per relevant clause I.S. 456-1978.

(xiv) The R.C.C. detailing in general shall be as per SP:34 .

(xv) High Yield Stress Deformed bars shall be used for main reinforcement .Mild Steel bars are used only as distribution steel .

(xvi) Diameter of bars in footings shall be not less than 10 mm .

(xvii) Spacing of stirrups in beams shall not exceed 30cm.

(xviii) Thickness of slab shall not be less than 10cm and in toilet blocks not less than 15cm.

(xix) Depth of beam shall not be less than 23cm .

(xx) Spacing of ties in columns shall not exceed 30cm.

(xxi) The longitudinal bars in columns shall not be less than 12mm in diameter


12. Guidelines for fixing the Slab Directions :

(I) Slab shall be designed as one way slab if ratio of Ly to Lx is more than 2 and two way slab, if the ratio is equal or less than 2.

Where Lx is shorter span and Ly is longer span of the slab.

(II) However as per Designs Circle practice slabs up to 2.5m spans may be designed as one way slabs .

(III) Canopy, Chajja, balcony slabs are generally provided as cantilever slabs.

(IV) W.C. slab is generally made sloping or sunk by about 50cm .below general floor level for Indian type water closet .Slabs for toilet block and Nahani slab are generally sunk by 20cm. below general floor level .

(V) Staircase waist slab shall be generally one way slab .

(VI) Loft slabs over toilets are generally supported on partition walls of toilet and W.C.Loft load should be considered while designing the beams supporting these walls