Design of Rafter

Spacing of truss = 1.8 mSpan of truss = 9.7 mSpacing of Purlins = 0.5 m

15 deg.Tributary area = 37.4 m2 Rate of reduction = 40 percentDead LoadPurlin's selfweight = 0.4 + 0.04L = 0.0312 kPaTruss selfweight = 0.4+0.04L = 1.67264 psf L = 31.816 ft

(C.E Fowler formula) = 0.08 kPaCorr. G.I. Sheet = 0.075 kPaMecanical duct allownce = 0.2 kPaInsulation = 0.0108 kPaceiling = 0.036 kPaLoad of top chord = 0.117 say kPaLoad of bottom chord = 0.236 say kPa

Roof Live LoadRoof slope: Flat or rise less than 4 units vertical in 12 units horizontal (33.3 slope)

Liveload 0.6 kPa

Wind Load (NSCP 2010)

Classification Summary:

The structure is rigidThe Wind force resisting element is Component and CladdingThe Building is enclosedThe building hass a Gable type roofingMean roof height h= 7.6 mHorizontal dimension parallel to wind L= 7.125 mHorizontal dimension normal to wind B= 24.2 m

Roof angle 15 deg.

Design procedure Method 2

Basic wind speed (sect. 207.5.4) Zone 2 V = 200 kphWind directionaly factor (table 207-2) Kd = 0.85Importance factor (sect. 207.5.5) Iw = 1Exposure category (sect 207.5.6.3) Exposure CVelocity pressure (sect. 207.5.6.6) kh = 0.7Topograhic factor (sect. 207.5.7) Kzt = 1

Slope of Roofing (θ) =

θ=

Gust effect factor (sect. 207.5.8) G = 0.85Enclosure classification (sect. 207.5.9) The Building is enclosedInternal pressure coeff. (sect. 207.5.11.1) GCpi = 0.18

-0.18External pressure coeff. (sect. 207.5.11.2) GCpVelocity Pressure (sect 207.5.10) qh= 0.0000473 (Kz)(Kzt)(Kd)(V^2)(Iw)

qh= 1125.74 N/m^2

Wind presure, p= qh ((GCp)-(Gcpi))Windward Leeward

Zone Area (m^2) GCp (+) GCp (-) with (+ GCpi) with (- GCpi) with (+ Gcpi) with (- Gcpi)1 12.023 0.3 -0.8 -135.0888 540.3552 -1103.2252 -697.95882 4.01 0.38 -1.4 -225.148 630.4144 -1778.6692 -1373.40283 0.49 0.6 -2.25 -472.8108 878.0772 -2735.5482 -2330.2818

Hence:Max. design wind pressure, p = -2735.548 N/m^2

Minimum design wind pressure = 500 N/m^2 < 2735.548 OK

Normal Load/linear meter, Wn0.017386662 kN/m

0.2897777 kN/mWLn = p*purlinspacing = -1.367774 N/m

Tangential load/linear meter, Wt0.0046587530.077645891

Trial sectionC50x75x1.2 mm purlins

A = 238.6 mm2w= 0.019 kN/mbf = 50 mmd = 75 mmtf = 1.2 mmtw = 75 mmSx = 6093.2 mm3Sy = 2892.7 mm3Ix = 228494 mm4Iy = 88295.1 mm4E = 200 GPaFy = 248 MPa

DLn = DL*purlinspacing*cosθ =LLn = LL*purlinspacing*cosθ =

DLt = DL*purlinspacing*sinθ =LLt = LL*purlinspacing*sinθ =

Load Moments (kN/m)Load Case Wn(kN/m) Wt(kN/m) Mn =WnL2/8 Mt =WtL2/8

1.4D 0.024341 0.024341327 0.00985824 0.0098582371.2D+1.6LL+0.8WL -0.609711 0.12982393 -0.2469329 0.0525786921.2D+1.6WL+0.5LL -2.022686 0.04441345 -0.8191876 0.017987447

Check on flexural strengthLoad Case fbx (MPa) fby (MPa) Fbx (MPa) Fby (MPa) fbx/Fbx + fby/Fby Remarks

1.4D 1.61791 6.815942 148.8 148.8 0.056679098 < 1 OK1.2D+1.6LL+0.8WL -40.526 36.35268 148.8 148.8 -0.028046412 < 1 OK1.2D+1.6WL+0.5LL -134.443 12.43644 148.8 148.8 0.987092538 < 1 OK

Check on deflectionϒn (mm) ϒt (mm) ϒr (mm) ϒ allowable Remarks

1.4D 0.07281 0.072806 0.102963489 < 10 OK1.2D+1.6LL+0.8WL 1.82368 0.38831 1.864559752 < 10 OK1.2D+1.6WL+0.5LL 6.04996 0.132843 6.05141653 < 10 OK

Therefore adoptC50x75x1.2 mm purlins

with 0.5 meter O.C.

2735.548