Eng : DW

Chk : ZM

Date : 2015-09-10

Calculation Sheet Rev : 0

1 of 2

PURLIN DESIGN

Purlin design based on Code Abbreviation

CSA-S16-09 Limit States Design of Steel Structures CSA-S16-09

NBCC 2005 Division B 4.1.7 NBC05

NBCC 2005 Commentary I NBC05 Comment I

Assumptions

1. When purlin is subjected to dead & snow load, purlin top flange is fully supported by roof sheeting

2. When purlin is subjected to uplift wind force, purlin bottom flange is unsupported and unsupport length is full span

3. Gravity load is applied at purlin top flange. The component parallels to the roof will cause torsion to purlin.

Use only half of minor axis flexure resistance capacity in the design to account the torsional effect.

4. Sag rods act as transverse supports for minor axis (y-axis) bending

Input Code Reference

Building importance category Normal

Wind pressure q 1/50 q = 0.40 [kPa] NBC05 Comment I

Reference height h = 2.000 [m] Fig I-7 Note (5)

Ce = 0.90 For open terrain NBC05 4.1.7.1 (5)

Iw = 1.00 For importance category Normal building NBC05 Table 4.1.7.1

NBC05 Comment I

Building category - internal pressure Category 3 Page I-22 Para. 31

Internal pressure coefficient - Cpi = -0.70 + Cpi = 0.70

Internal gust factor Cgi = 2.0 NBC05 4.1.7.1 (6)(c.)

Roof slope = 4.8

Roof snow area load sn = 1.46 [kPa]

Roof cladding self-weight Arc = 0.20 [kPa]

Encrustation +M & E allowance Aad = 1.68 [kPa]

Purlin size C310x31

Purlin self-weight sw = 0.31 [kN/m]

Purlin span L = 7.620 [m]

No of sag rod in the span npln = 2

Purlin spacing (plan) Spln = 1.520 [m]

Purlin spacing (slope) s = 1.525 [m]

Conclusion

[The Purlin Section Is Adequate for Applied Force] ratio = 0.79

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Building Purlin C12X20.7 - 2 Tie Rod

Eng : DW

Chk : ZM

Date : 2015-09-10

Calculation Sheet Rev : 0Subject :

0

0

0

Project :

Job No :

Doc No :

Building Purlin C12X20.7 - 2 Tie Rod

2 of 2

Purlin Check - Dead & Snow Load Code Reference

Factored UDL w = 1.25xsw+1.25(Arc+Aad)xs +1.5xsnxs = 7.31 [kN/m]

wx = w x sin = 0.61 [kN/m]

wy = w x cos = 7.29 [kN/m]

Factored moment

Major axis Mfx = (wy x L2) / 8 = 52.9 [kNm]

Minor axis Mfy = (wx x L2) / 32 for 1 sag rod = 0.4 [kNm]

(wx x L2) / 90 for 2 sag rod

Unsupported length roof sheeting provides fully lateral support for top flange

Lx = = 0.000 [m]

Ly = L / (npln + 1) = 2.540 [m]

Purlin flexure C310x31 ratio = 0.79 OK

Purlin deflection (snow load only) ws = sn x s x cos = 2.22 [kN/m]

= (5 x ws x L4) / (384 x E x Ix ) = 9.1 [mm] CSA-S16-09

a = L / 180 = 42.3 [mm] Table D.1

ratio = 0.22 OK

Purlin Check - Wind Uplift

External Surface Pressure NBC05 Comment I

Tributary area A = L x Spln = 11.58 [m2]

External suction -CpCg = = -2.00 Fig I-9

Internal Surface Pressure

Internal pressure +CpiCgi = = 1.40 Page I-22 Para. 31

Most severe uplift case : external suction + internal pressure

Wind uplift pressure on roof panel p = Iw q Ce [ -CpCg - (+CpiCgi) ] = -1.22 [kPa]

Wind linear uplift load on purlin ww = p x s = 1.87 [kN/m]

Purlin and roof panel selfweight wd = sw + Arc x s = 0.62 [kN/m]

Factored linear uplift on purlin w = 1.4 x ww -1.25 x wd = 1.84 [kN/m]

Factored moment Mfx = w x L2 / 8 = 13.4 [kNm]

When purlin is subjected to uplift wind force, purlin bottom flange is unsupported and unsupport length is full span

Lu = = 7.6 [m]

Purlin flexure C310x31 ratio = 0.57 OK

Purlin deflection (wind only) ULS = (5 ww L4) / (384 E Ix ) = 7.7 [mm] NBC 05

SLS = ULS / Iw (ULS) x Iw (SLS) = 5.7 [mm] Table 4.1.7.1

a = L / 180 = 42.3 [mm]

ratio = 0.14 OK

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