Annex A[Clause 3.3.2.1(b)] Illustrative Example Showing Reduction of Uniformly Distributed Imposed Floor Loads in Multi-storeyed Buildings for Design of Columns

NBC 2016 (SP 7:2016) Volume 1

2016 · PDF page 520

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A-1 The total imposed loads from different floor levels (including the roof) coming on the central column of a multi-storeyed building (with mixed occupancy) is shown in Fig. 21. Calculate the reduced imposed load for the design of column members at different floor levels

using 3.3.2.1. Floor loads do not exceed $5.0\mathrm{kN / m^2}$ .

A-1.1 Applying reduction coefficients in accordance with 3.3.2.1, total reduced floor loads on the column at different levels is indicated along with Fig. 21.

FLOOR NO.FROM TOPINCLUDINGROOF	IMPOSEDFLOOR LOADSON COLUMNSAT DIFFERENTFLOORS, kN		DISCOUNTED IMPOSED LOADING ON COLUMNS, kN
1	30	ROOF	DISCOUNTED IMPOSED LOADING ON COLUMNS, kN
2	40		30
3	50		(30 + 40) (1 - 0.1) = 63
4	50		(30 + 40 + 50) (1 - 0.2) = 96
5	40		(30 + 40 + 50 + 50) (1 - 0.3) = 119
6	45		(30 + 40 + 50 + 50 + 40) (1 - 0.4) = 126
7	50		(30 + 40 + 50 + 50 + 40 + 45) (1 - 0.4) = 153
8	50		(30 + 40 + 50 + 50 + 40 + 45 + 50) (1 - 0.4) = 183
9	40		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50) (1 - 0.4)= 213
10	40		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40)(1 - 0.4) = 237
11	40		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40)(1 - 0.4) = 261
12	55		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40+ 40) (1 - 0.5) = 237.5 < 261adopt 261 for design
13	55		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40+ 40 + 55) (1 - 0.5) = 265
14	70		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40+ 40 + 55 + 55) (1 - 0.5) = 292.5
15	80		(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40+ 40 + 55 + 55 + 70) (1 - 0.5) = 327.5
			(30 + 40 + 50 + 50 + 40 + 45 + 50 + 50 + 40 + 40+ 40 + 55 + 55 + 70 + 80) (1 - 0.5) = 367.5

FIG. 21 LOADING DETAILS

PART 6 STRUCTURAL DESIGN — SECTION 1 LOADS, FORCES AND EFFECTS

$H_{\mathrm{s}} =$ Height factor for resonant response
$H =$ Height above mean ground level on the topography feature
$I =$ Turbulence intensity
$I_{\mathrm{h,i}} =$ Turbulence intensity at height in terrain category

h,i

=

h

i

I_{\mathrm{z,i}} =

Turbulence intensity at height

z

in terrain category

i

IF =

Interference factor

k =

Mode shape power exponent

k_1, k_2, k_3, k_4 =

Wind speed modification factors

\overline{k}_{2,i} =

Hourly mean wind speed factor

K =

Force coefficient multiplication factor for individual members of finite length

K_{\mathrm{a}} =

Area averaging factor

K_{\mathrm{c}} =

Combination factor

K_{\mathrm{d}} =

Wind directionality factor

l =

Length of the member or larger horizontal dimension of a building

L =

Actual length of upwind slope

L_{\mathrm{e}} =

Effective length of upwind slope

L_{\mathrm{h}} =

Integral turbulence length scale at the height,

h

m_0 =

Average mass per unit height of the structure

M_{\mathrm{a}} =

Design peak along wind base bending moment

M_{\mathrm{c}} =

Design peak across wind base bending moment

N =

Effective reduced frequency

p_{\mathrm{d}} =

Design wind pressure

p_{\mathrm{z}} =

Design wind pressure at height

z

\overline{p}_{\mathrm{d}} =

Design hourly mean wind pressure corresponding to

\overline{V}_{\mathrm{z,d}}

p_{\mathrm{e}} =

External pressure

p_{\mathrm{i}} =

Internal pressure

r =

Roughness factor which is twice the longitudinal turbulence intensity at height

h, I_{\mathrm{h,i}}

R_{\mathrm{e}} =

Reynolds number

s =

Level on a building/structure for the evaluation of along wind load effects

S_{\mathrm{o}} =

Factor, which depends on

H

and

X

, used for the evaluation of

k_3

factor

S_{\mathrm{t}} =

Strouhal number

S =

Size reduction factor

V_{\mathrm{b}} =

Regional basic wind speed

V_{\mathrm{z}} =

Design wind speed at height

z

NATIONAL BUILDING CODE OF INDIA 2016