Structural Design Of A 18m × 55m × 6m Steel Warehouse For Papua New Guinea With 5-Ton Overhead Crane

Structural Design of a 18m × 55m × 6m Steel Warehouse for Papua New Guinea with 5-Ton Overhead Crane, Roof Ventilators, and Skylights

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Location: Papua New Guinea (PNG)

Climate: Tropical; no snow, negligible seismic activity

Wind Speed: 120 km/h (≈33.3 m/s) → Basic wind pressure ≈ 0.7 kN/m² (per AS/NZS 1170.2 or local code equivalent)

Building Dimensions:

Width: 18 m

Length: 55 m

Eave Height: 6 m

Roof Pitch: 5° (standard for drainage; rise ≈ 0.8 m at mid-span)

Wall & Roof Cladding: 0.45 mm pre-painted corrugated steel sheets (single skin)

Internal Equipment: One 5-ton electric overhead traveling crane (EOT), span ≈ 16.5 m, runway beams supported by main columns

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Main Frames: Rigid portal frames spaced at 7.86 m intervals (7 bays over 55 m length → 8 frames total, option will be 9 bays in 6.11m each bay).

Frame Configuration:

Columns: CBC customized H sections (welded plate sections)

Rafters: Tapered built-up I-sections

Base: Pinned or fixed base (fixed preferred for crane loads) embedded into reinforced concrete footings

Crane Runway System:

Crane runway beams: HEA/UB 300–350 (depending on deflection criteria)

Bracket connections welded to column flanges at ~5.5 m height

Crane rail: Standard QU70 or similar

Bracing: Horizontal and vertical bracing between runway beams

 

 

Purlins: C-sections (C200×60×20×2.5 mm) @ 1.5 m spacing on roof

Girts: C-sections (C150×60×20×2.0 mm) @ 1.2 m vertical spacing on walls

Bracing System:

Roof: X-bracing in end bays + longitudinal bracing along ridge/eaves

Walls: Cross-bracing in gable ends and one side wall

All bracing: Ø12–16 mm steel rods or angle sections

 

 

Ventilators: Continuous ridge ventilator (polycarbonate or metal) – 55 m length

Skylights: Translucent FRP or polycarbonate panels integrated every 3rd purlin bay (~4.5 m spacing), covering ~10% of roof area → approx. 100 m²

 

 

Reinforced concrete pad footings under each column (size estimated at 2.0 m × 2.0 m × 0.8 m deep, depending on soil bearing capacity ≥100 kPa)

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Dead Load (DL):

Roof cladding + purlins: 0.12 kN/m²

Crane girder + rail: 0.5 kN/m (line load on columns)

Live Load (LL): Maintenance load = 0.25 kN/m² (non-accessible roof)

Wind Load (WL):

Basic velocity pressure q = 0.613 × V² (V in m/s) → q ≈ 0.68 kN/m²

External pressure coefficients (Cp):

Windward wall: +0.7

Leeward wall: –0.5

Roof (5° slope): –0.9 (suction)

Internal pressure: ±0.2 (assumed partially open building)

Net design pressure ≈ 1.0–1.2 kN/m² (critical suction on roof)

Crane Load:

Vertical: 50 kN (5 t) + impact factor (25%) → 62.5 kN per wheel

Lateral: 10% of lifted load → 5 kN per wheel

Longitudinal: 5% braking force

 

 

Portal Frame: Designed for combined gravity + wind + crane loads using second-order analysis (P-Δ effects considered)

Deflection Limits:

Roof: L/180 under wind

Crane runway: L/600 under vertical load

Local Buckling: Web stiffeners at crane bracket locations

Connections: Welded moment connections at rafter–column joints; bolted splices for transport

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Item	Description	Quantity	Unit Weight (kg/m)	Total Weight (kg)
Main Frames	Tapered I-sections (avg. 110 kg/m)	8 frames × (2×6 m col + 18.5 m rafter) = 236 m	110	25,960
Crane Runway Beams	UB 356×171×51 (51 kg/m)	2 × 55 m	51	5,610
Purlins	C200×2.5 mm	(55/1.5 +1) × 18 m ≈ 684 m	3.2	2,189
Wall Girts	C150×2.0 mm	2×(55+18)×(6/1.2) ≈ 730 m	2.3	1,679
Bracing	Ø16 rod / L50×5 angles	~400 m	1.5 avg	600
Roof/Wall Sheets	0.45 mm PPGL	Roof: 55×18.2 ≈ 1,001 m²; Walls: 2×(55+18)×6 = 876 m²	4.5 kg/m²	8,457
Fasteners, Rails, Accessories	-	-	-	~2,000
Total Steel Weight				≈46,495 kg

Note: Excludes foundation rebar and concrete.

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Wind Speed: Up to 250 km/h (e.g., Typhoon Haiyan) → q ≈ 3.0 kN/m²

Key Changes:

Increase main frame section sizes by 30–50%

Reduce portal frame spacing to 6 m (9 bays) for better load distribution

Use thicker cladding (0.55–0.60 mm) with enhanced fastening (closer screw spacing, storm clips)

Strengthen roof-to-frame connections (use cleats instead of straps)

Add more bracing (both transverse and longitudinal)

Higher safety factors in wind uplift design (especially at eaves and corners)

Consider double-skin insulated roof to reduce thermal stress and improve durability

 

 

Seismic Coefficient: Sa(T) ≈ 0.6–0.9g (depending on soil and period)

Key Changes:

Switch from rigid portal frames to braced frames or moment-resisting frames with ductile detailing

Use uniform (non-tapered) H-sections to ensure plastic hinge formation control

Base plates designed for full moment + shear + uplift from seismic overturning

Crane supports must be seismically restrained (snubbers or lateral stops)

Roof diaphragm must act as rigid horizontal truss → closer purlin spacing (1.2 m) and stronger sheet fastening

Ductility class requirements per AISC 341 or local Chilean code (e.g., use of low-yield-point steel not permitted)

Foundations designed for high uplift and sliding resistance

Avoid brittle elements (e.g., thin rods); use structural angles or tubes for bracing

Note: In seismic zones, the crane itself may require special anchoring and damping provisions, which are unnecessary in PNG.

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The proposed warehouse for Papua New Guinea is optimized for moderate wind loads and crane operation, using cost-effective tapered frames and light-gauge cladding. For typhoon-prone Philippines, robustness against extreme wind governs the design, while in seismic Chile, ductility, redundancy, and energy dissipation become paramount-leading to fundamentally different structural systems and material usage. Local building codes (NSCP for Philippines, NCh for Chile) must be strictly followed in each case.