built-up steel beam

7/28/2019 Built-up steel beam

1/4

Design wind load 0.16 kN/m^2

[As per IS 800- 2007]

Analysis:

DL = 0.05 kN/m2

WL thr = 0.16 kN/m2

-Thrust pressure (downwards)

1.2 m

4 m

Loading on main beam:

0.2 kN/m

0.64 kN/m

Load Combinations for design: (As per IS 800-2007)

1.40601 kN/m -Acting downwards

WLthr = 0.16 x 4 = -UDL on main beam due to Thrust pressure

1 DESIGN OF MAIN BEAM

Purlin spacing =

Main beam spacing=

DL = 0.05 x 4 = -UDL on main beam due to DL

*Considering the loads acting on main beam as UDL instead of point loads that are transferred from purlin tomain beam.

1.5 (DL+WLthr) =

1

1.2 m

8 m

Re Rf

1.2 m

7

-From the symmetry of the loading, the reaction force from beam support are;

Re = Rf= 5.62404 kN -For the load case 1.5 (DL+WLthr), downwards

Bending Moment:

Mmax = 11.248 kN-m -For the load case 1.5 (DL+WLthr), downwards

(Maxm. BM at section of the beam)

UDL

Loading on the main beam and support condition

Spacing of purlins =

No. of purlins =

1


2/4

Trial Section: bf= 80

tf= 4

BUILT UP SECTION (refer fig.)

Grade: E 350

fu= 490 MPa

fy= 350 MPa dw = 150 tw = 4

dw- clear depth of the web

bf- width of the flange

*All dimensions are in mm

Sectional properties:

A = 1240 mm2

m = 9.73 kg/m

H = 158

rz= 63.0 mm ry= 16.6 mm

tf, tw- thickness of flange & web

respectively

2

Zze= 62.3 x103

mm3 Zye= 8.6 x10

3mm

3

Iz= 4.92 x106

mm4 Iy= 0.3421 x10

6mm

4

Zzp= 71.780 x103

mm3 Zyp= 13.40 x10

3mm

3

Y_ver= 57.887 mm X_hori= 10.8065 mm

m- mass per unit length of the section

Classification of section

= 0.8452

For I-sections:

Plastic Compact

9.4 10.5

7.944 8.874

b/tf= 9.500

Zzp,Zyp- Plastic section modulus @ major & minor axes respectively

Zze,Zye- Elastic section modulus @ major & minor axes respectively

Iz,Iy- Second moment of area @ major & minor axes respectively

rz,ry- Radius of gyration @ major & minor axes respectively

D,t- Depth & thickness of the section respectively

Semi-compact[ As per Table 2 of IS 800- 2007]

15.7

13.269

b- outstand element of compression flange

tf- thickness of the flange

.'. Section is Semi-compact

=(250/_ )

2


3/4

b = 0.868

Moment carrying capacity of the section

= 72.243

h= 154.0 mm

tf= 4 mm

h/tf= 38.50

h/tLLT/r 35 38.5 40

70 485.5 478.85 476

72.243 455.4736

80 381.2 374.62 371.8

Md- moment carrying capacity of the section

zp- plastic section modulus for the given c/s

fbd- design bending compressive stress

Calculation of fbd:

h- c/c distace betwn. the flanges

fcr,b interpolation

_=_ _ _

_/

_

3

.'. fcr,b = 455.4736004

LT= 0.49

fy

.'. fcr,b 340 350 360500 200.9 203.55 206.2

455.4736 195.0455

450 191.6 194 196.4

.'. fbd = 195.045 MPa

.'. Md = 12.148 kN-m

Md > Mmax. SAFE Stress Ratio= 0.926

where, M max. is maxm. bending moment in the main beam for the all possible load cases.

Shear capacity of the section:

Vu,max = 5.62404 kN -For the load case 1.5 (DL+WL thr), downwards

-Maxm. SF at section of the beam

fyw - yield strength of web of the section

-Table 14 of IS 800- 2007

-For Builtup steel sections

fbd interpolation

-Table 13 (b) of IS 800- 2007

-Moment carrying capacity of the section

Vd - shear capacity of the section

mo - partial safety factor= 1.1

_=(__

)/(_3)

3


4/4

Av = 600 mm2

fyw= 350 MPa

.'. Vd= 110.221 kN

0.6 Vd= 66.13 kN

.'. 0.6 Vd > Vu,max

[As per Cl. 8.2.1.2 of IS 800- 2007]

Deflection:

Load Combinations for serviceability:

0.937 kN/m -Acting downwards

50.800 mm (occuring at the mid-point of the beam)

span/150 = 53.33 mm Hence OK

-Maxm. deflection at any point in the beam for

any possible load case

Av -Shear area of the section i.e web area for I-sectn.

-So, no reduction in moment carrying capacity is to bemade

Hence SAFE

1.0 (DL+WLthr) =

_

=

_=

_=(5_

^4)/384

44

built-up steel beam

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