Annex H(Clause 37.1)

NBC 2016 (SP 7:2016) Volume 1

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Moments of Resistance for Rectangular and T-sections

H-0 The moments of resistance of rectangular and T-sections based on the assumption of 37.1 are given in this annex.

H-1 Rectangular Sections

H-1.1 Sections Without Compression Reinforcement

The moment of resistance of rectangular sections without compression reinforcement should be obtained as follows:

a) Determine the depth of neutral axis from the following equation:

\frac {x _ {\mathrm{u}}}{d} = \frac {0 . 8 7 f _ {\mathrm{y}} A _ {\mathrm{st}}}{0 . 3 6 f _ {\mathrm{ck}} b . d}

b) If the value of $x_{u}/d$ is less than the limiting value (see Note below 37.1), calculate the moment of resistance by the following expression:

M _ {\mathrm{u}} = 0. 8 7 f _ {\mathrm{y}} A _ {\mathrm{st}} d \left[ 1 - \frac {A _ {\mathrm{st}} f _ {\mathrm{y}}}{b d f _ {\mathrm{ck}}} \right]

c) If the value of $x_{u}/d$ is equal to the limiting value, the moment of resistance of the section is given by the following expression:

M _ {\mathrm{u}, \lim} = 0. 3 6 \frac {x _ {\mathrm{u} , \max}}{d} \left[ 1 - 0. 4 2 \frac {x _ {\mathrm{u} , \max}}{d} \right] b d ^ {2} f _ {\mathrm{ck}}

d) If $x_{\mathrm{u}} / d$ is greater than the limiting value, the section should be redesigned.

In the above equations,

x _ {\mathrm{u}} = \text { depth of neutral axis },

d = \text {effective depth},

\left| \begin{array}{c} f _ {\mathrm{y}} = \text {characteristic} \quad \text {strength} \quad \text {of} \\ \text {reinforcement,} \end{array} \right|

A _ {\mathrm{st}} = \text {area of tension reinforcement}

$f_{ck}$ = characteristic compressive strength of concrete,

$b =$ width of the compression face,

$M_{u,\lim} = \text{limiting moment of resistance of a section without compression reinforcement, and}$

$x_{\mathrm{u,max}} =$ limiting value of $x_{\mathrm{u}}$ from 37.1.

H-1.2 Section with Compression Reinforcement

Where the ultimate moment of resistance of section exceeds the limiting value, $M_{\mathrm{u,lim}}$ compression

reinforcement may be obtained from the following equation:

M _ {\mathrm{u}} - M _ {\mathrm{u,lim}} = f _ {\mathrm{sc}} A _ {\mathrm{sc}} (d - d ^ {\prime})

where

M _ {\mathrm{u}}, M _ {\mathrm{u,lim}}, d \text {are same as in H - 1.1}

\begin{array}{r l} f _ {\mathrm{sc}} = & \text {design stress in compression reinforcement} \\ & \text {corresponding to a strain of} \end{array}

0. 0 0 3 5 \frac {\left(x _ {\mathrm{u,max}} - d ^ {\prime}\right)}{x _ {\mathrm{u,max}}}

x _ {\mathrm{u}, \max} = \text {the limiting value of} x _ {\mathrm{u}} \text {from 37.1.}

A _ {\mathrm{sc}} = \text { area of compression reinforcement, and }

$d' = \text{depth of compression reinforcement from compression face.}$

The total area of tension reinforcement shall be obtained from the following equation:

A _ {\mathrm{st}} = A _ {\mathrm{st1}} + A _ {\mathrm{st2}}

where

$A_{\mathrm{st}} =$ area of the total tensile reinforcement,

$A_{st1}$ = area of the tensile reinforcement for a singly reinforced section for $M_{u,lim}$ , and

\mathrm{A} _ {\mathrm{st2}} = A _ {\mathrm{sc}} f _ {\mathrm{sc}} / 0. 8 7 f _ {\mathrm{y}}

H-2 Flanged Section

H-2.1 For $x_{\mathrm{u}} < D_{\mathrm{f}}$ , the moment of resistance may be calculated from the equation given in H-1.1.

H-2.2 The limiting value of the moment of resistance of the section may be obtained by the following equation when the ratio $D_{\mathrm{f}} / \mathrm{d}$ does not exceed 0.2:

\begin{array}{c} M _ {\mathrm{u}} = 0. 3 6 \frac {x _ {\mathrm{u,max}}}{D} \left[ 1 - 0. 4 2 \frac {x _ {\mathrm{u,max}}}{D} \right] f _ {\mathrm{ck}} b _ {\mathrm{w}} d ^ {2} + \\ 0. 4 5 f _ {\mathrm{ck}} \left(b _ {\mathrm{f}} - b _ {\mathrm{w}}\right) D _ {\mathrm{f}} \left[ d - \frac {D _ {\mathrm{f}}}{2} \right] \end{array}

where

$M_{\mathrm{u}}, x_{\mathrm{u,max}}, d$ and $f_{\mathrm{ck}}$ are same as in H-1.1,

$b_{\mathrm{f}} =$ breadth of the compression face/flange,

$b_{\mathrm{w}} =$ breadth of the web,

$D_{\mathrm{f}} =$ thickness of the flange.

H-2.2.1 When the ratio $D_{\mathrm{f}} / d$ exceeds 0.2, the moment of resistance of the section may be calculated by the following equation:

PART 6 STRUCTURAL DESIGN — SECTION 5 CONCRETE: 5A PLAIN AND REINFORCED CONCRETE

\begin{array}{r l} M _ {\mathrm{u}} = & 0. 3 6 \frac {x _ {\mathrm{u,max}}}{D} \Bigg [ 1 - 0. 4 2 \frac {x _ {\mathrm{u,max}}}{D} \Bigg ] f _ {\mathrm{ck}} b _ {\mathrm{w}} d ^ {2} + \\ & 0. 4 5 f _ {\mathrm{ck}} \left(b _ {\mathrm{f}} - b _ {\mathrm{w}}\right) y _ {\mathrm{f}} \Bigg [ d - \frac {y _ {\mathrm{f}}}{2} \Bigg ] \end{array}

where $y_{\mathrm{f}} = (0.15x_{\mathrm{u}} + 0.65D_{\mathrm{f}})$ , but not greater than $D_{\mathrm{f}}$ and the other symbols are same as in H-1.1 and H-2.2.

H-2.3 For $x_{\mathrm{u,max}} > x_{\mathrm{u}} > D_{\mathrm{f}}$ , the moment of resistance may be calculated by the equations given in H-2.2 when $D_{\mathrm{f}} / x_{\mathrm{u}}$ does not exceed 0.43 and H-2.2.1 when $D_{\mathrm{f}} / x_{\mathrm{u}}$ exceeds 0.43; in both cases substituting $x_{\mathrm{u,max}}$ by $x_{\mathrm{u}}$ .

The following list records those standards which are acceptable as ‘good practice’ and ‘accepted standards’ in the fulfillment of the requirements of the Code. The latest version of a standard shall be adopted at the time of enforcement of the Code. The standards listed may be used by the Authority for conformance with the requirements of the referred clauses in the Code.

In the following list, the number appearing in the first column within parentheses indicates the number of the reference in this Subsection.

IS No. Title

(1) 3370 Concrete structures for the storage of liquids — Code of practice

(Part 1): 2009 General requirements (first revision)

(Part 2): 2009 Reinforced concrete structures (first revision)

2210 : 1988 Criteria for design of reinforced concrete shell structures and folded plates (first revision)

3201 : 1988 Criteria for design and construction of precast-trusses and purlins (first revision)

4090 : 1967 Criteria for design of reinforced concrete arches

4991 : 1968 Criteria for blast resistant design of structures for explosions above ground 4995 Criteria for design of reinforced concrete bins for storage of granular and powdery materials

(Part 1): 1974 General requirements and bin loads

(Part 2): 1974 Design criteria

4998 : 2015 Criteria for design of reinforced concrete chimneys (third revision)

6922 : 1973 Criteria for safety and design of structures subject to underground blasts

IS No. Title

(2) 4845 : 1968 Definitions and terminology relating to hydraulic cement 6461 Glossary of terms relating to cement: (Part 1) : 1972 Concrete aggregates (Part 2) : 1972 Materials (Part 3) : 1972 Concrete reinforcement (Part 4) : 1972 Types of concrete (Part 5) : 1972 Formwork for concrete (Part 6) : 1972 Equipment, tool and plant (Part 7) : 1973 Mixing, laying, compaction, curing and other construction aspect (Part 8) : 1973 Properties of concrete (Part 9) : 1973 Structural aspects (Part 10) : 1973 Tests and testing apparatus (Part 11) : 1973 Prestressed concrete (Part 12) : 1973 Miscellaneous

(3) 269 : 2015 Ordinary Portland cement — Specification (sixth revision) 8041 : 1990 Specification for rapid hardening Portland cement (second revision) 455 : 2015 Specification for Portland slag cement (fifth revision) 1489 Specification for Portland pozzolana cement: (Part 1) : 2015 Fly ash based (fourth revision)

(Part 2): 2015 Calcined clay based (fourth revision)

8043 : 1991 Specification for hydrophobic Portland cement (second revision)

12600 : 1989 Specification for low heat Portland cement

12330 : 1988 Specification for sulphate resisting Portland cement

(4) 12600 : 1989 Specification for low heat Portland cement

IS No.	Title	IS No.	Title
(5) 6452 : 1989	Specification for high alumina cement for structural use (first revision)	(17) 4082 : 1996	Recommendations on stacking and storage of construction materials and components at site (second revision)
(6) 6909 : 1990	Specification for supersulphated cement (first revision)	(18) 516 : 1959	Method of test for strength of concrete
(7) 3812	Pulverized fuel ash — Specification: Part 1 For use as pozzolana in cement, cement mortar and concrete (third revision)	5816 : 1999	Method of test for splitting tensile strength of concrete (first revision)
(8) 15388 : 2013	Specification for silica fume	(19) 1343 : 2012	Prestressed concrete — Code of practice (second revision)
(9) 16353 : 2015	Specification for Metakaolin	(20) 1199	Methods of sampling and analysis of concrete : Part 6 Tests on fresh self compacting concrete (under preparation)
(10) 12089 : 1987	Specification for granulated slag for manufacture of Portland slag cement	(Part 6)
(11) 9103 : 1999	Specification for admixtures for concrete (first revision)	(21) 455 : 2015	Specification for Portland slag cement (fifth revision)
(12) 383 : 2016	Specification for coarse and fine aggregates for concrete (third revision)	(22) 1489	Specification for Portland pozzolana cement : Part 1 Fly ash based (fourth revision)
(13) 3025	Methods of sampling and test (physical and chemical) for water and waste water:	(Part 1) : 2015	Specification for concrete batching and mixing plant (first revision)
(Part 22) : 1986	Acidity (first revision)	(23) 4925 : 2004	Code of practice for ready-mixed concrete (second revision)
(Part 23) : 1986	Alkalinity (first revision)	(24) 4926 : 2003	Methods of test for aggregates for concrete: Part 3 Specific gravity, density, voids, absorption and bulking
(Part 18) : 1984	Volatile and fixed residue (total filterable and non-filterable) (first revision)	(25) 2386	Specification for batch type concrete mixers (second revision)
(Part 24) : 1986	Sulphates (first revision)	(Part 3) : 1963	General requirements for pan mixers for concrete
(Part 32) : 1988	Chloride (first revision)	(26) 1791 : 1985	Methods for testing performance of batch-type concrete mixers (first revision)
(Part 17) : 1984	Non-filterable residue (total suspended solids) (first revision)	12119 : 1987	Guidelines for falsework for concrete structure
(14) 516 : 1959	Method of test for strength of concrete	(27) 4634 : 1991	Code of practice for bending and fixing of bars for concrete reinforcement
(15) 4031	Methods of physical tests for hydraulic cement: Part 5	(28) 14687 : 1999	Recommended practice for welding of mild steel plain and deformed bars for reinforced construction (first revision)
(Part 5) : 1988	Methods of physical tests for hydraulic cement: Part 5	(Determination of initial and final setting times (first revision)	Recommendations for welding cold worked bars for reinforced concrete construction (first revision)
(16) 432	Specification for mild steel and medium tensile steel bars and hard-drawn steel wire for concrete reinforcement: Part 1	(30) 2751 : 1979	Concrete vibrators – Immersion type – General requirements
(Part 1) : 1982		(Mild steel and medium tensile steel bars (third revision)	General requirements for screed board concrete vibrators (first revision)
1786 : 2008	High strength deformed steel bars and wires for concrete reinforcement — Specification (fourth revision)	9417 : 1989	Specification for concrete vibrating tables
1566 : 1982	Specification for hard-drawn steel wire fabric for concrete reinforcement (second revision)	(31) 2505 : 1992	Concrete vibrators – Immersion type – General requirements
2062 : 2011	Hot rolled medium and high tensile structural steel — Specification (seventh revision)	2506 : 1985	General requirements for screed board concrete vibrators (first revision)

PART 6 STRUCTURAL DESIGN — SECTION 5 CONCRETE: 5A PLAIN AND REINFORCED CONCRETE

IS No.	Title	IS No.	Title
(32) 7861	Code of practice for extreme weather concreting		concrete reinforcement — Specification
(Part 1): 1975	Recommended practice for hot weather concreting	(39) 3414: 1968	Code of practice for design and installation of joints in buildings
(Part 2): 1981	Recommended practice for cold weather concreting	(40) 3951 (Part 1): 2009	Hollow clay tiles for floors and roofs —Specification: Part 1
(33) 9013: 1978	Method of making, curing and determining compressive strength of accelerated cured concrete test specimens	(41) 6061 (Part 1): 1971	Filler type (second revision)Code of practice for construction of floor and roof with joists and filler blocks: Part 1 With hollow concrete filler blocks
(34) 13311	Methods of non-destructive testing of concrete	6061	Code of practice for construction of floor and roof with joists and filler blocks: Part 2 With hollow clay filler blocks (first revision)
(Part 1): 1992	Ultrasonic pulse velocity	(Part 2): 1981
(Part 2): 1992	Rebound hammer
(35) 10262: 2009	Guidelines for concrete mix design proportioning	(42) 432 (Part 1): 1982	Specification for mild steel and medium tensile steel bars and hard-drawn steel wire for concrete reinforcement: Part 1 Mild steel and medium tensile steel bars (third revision)
(36) 1786: 2008	High strength deformed steel bars and wires for concrete reinforcement — Specification (fourth revision)
(37) 13620: 1993	Fusion bonded epoxy coated reinforcing bars — Specification	(43) 1566: 1982	Specification for hard-drawn steel wire fabric for concrete reinforcement (second revision)
(38) 16172: 2014	Reinforcement couplers for mechanical splices of bars for

PART 6 STRUCTURAL DESIGN

Section 5 Concrete: 5B Prestressed Concrete

BUREAU OF INDIAN STANDARDS

Section 5B (a) General

SCOPE
TERMINOLOGY
SYMBOLS

Section 5B (B) Materials, Workmanship, Inspection and Testing

4 MATERIALS ... 6
5 CONCRETE ... 8
6 WORKABILITY OF CONCRETE ... 11
7 DURABILITY OF CONCRETE ... 11
8 CONCRETE MIX PROPORTIONING ... 15
9 PRODUCTION OF CONCRETE ... 15
10 FORMWORK ... 17
11 ASSEMBLY OF PRESTRESSING AND REINFORCING STEEL ... 17
12 PRESTRESSING ... 19
13 TRANSPORTING, PLACING, COMPACTING AND CURING ... 25
14 CONCRETING UNDER SPECIAL CONDITIONS ... 25
15 SAMPLING AND STRENGTH TEST OF DESIGN CONCRETE MIX ... 25
16 ACCEPTANCE CRITERIA ... 25
17 INSPECTION AND TESTING OF STRUCTURES ... 25

Section 5B (C) General Design Requirements

18 GENERAL DESIGN REQUIREMENTS ... 26