Purlins Design

Design of Galvanised hi-Tensile C-Purlins to BS5950 : Part 5, 1987 : Cl 5.2 Job Job Titl Title e: Date :

Purl Purlin in Desi Design gn 9/11/2014

Purlin on sloping roof (simply supported) 1) Dimens Dimension ionss The span of the purlins Spacing of purlins (on slope) Rafter slope

L = s = β =

2) Loadin Loadings gs Roofing self-weight (on slope) Self weight of purlins Insulation, tie rods, & accessories Total dead loads Imposed load, (on plan) Unfactored loads Design loads

3.6 m 1.2 m 15 °

= = = DL = LL =

3.11 2.21 0.5 0.56 0.25

DL + LL = Wx = 1.4DL + 1.6LL = Use W =

For simply supported span, Design maximum bending moment 3) Purlin dimension dimensionss Try Purlin Type: D =

0.2618 rad

kg kg/m² kg/m² kN/m kN/m kN/m²

0.85 kN kN/m 1.24 kkN N/m 1.24 kN/m

= =

0.035 kN kN/m 0.02 kN/m

=

0.29 kN/m

to design

Mx = WL²/8 = 2.01 kN/m

C7516 75 mm

Mass

=

2.21 kg/m 6

4

3

3

B

=

45 mm

Ix

=

0.231 x10  mm

L t

= =

12 mm 1.6 mm

Zx E

= =

6.16 x10  mm 205000 N/mm²

Y (min. yield stress) Py (Design strength)

= =

450 N/ N /mm² 450 N/mm²

4) Bending Bending stress stress calculation calculation Design Moment, Bending Stress at x-x

Mx = Mx/Zx =

For BS5950, Part 5 Cl. 5.2.2.2 Max. allowable bending stress, P 0

=

= span / 200 dl = 18 mm

For 3.6 meters, simply supported Deflection, D

2.013 kNm 326.75 N/ N /mm²

4

= 5/384 WL /EIx = 57.3811 mm

(MPa)

= [1.13-0.00 [1.13-0.0019(D 19(D/t) /t) (Ys/280 (Ys/280)^1/ )^1/2] 2] P y = 457.6917 N/mm² (MPa)

Factor of safety on bending stress, P 0 / (Mx/Zx) 5) Deflection Deflection Check Check Ratio of Deflection limits Deflection limits,

(BS 5950: Part 5 Cl. 3.3.2) (High tensile galvanised steel)

1.401

PASS