Project location: New Caledonia (baseline), with applicability review for Philippines, Indonesia, Tonga, and Chile.

 

Parameter	Value
Building length	25.0 m
Single clear span	26.75 m
Eave height	9.0 m
Side columns	H750×250×6×10 (welded built-up)
Gable (wind) columns	H450×250×6×10
Roof beam (haunched segment)	H750–500×250×6×10 (tapered)
Roof beam (prismatic segment)	H500×250×6×10
Mezzanine (one side)	25 m × 3 m, three-storey
Mezzanine columns	H300×200×6×8
Mezzanine beams	H300×150×6×8

 

2.1 Load Evaluation

Dead Load (DL): Main frame self-weight 0.40–0.55 kN/m²; mezzanine floor 4.0 kN/m² (125 mm RC composite slab).
Live Load (LL): Hangar 5.0 kN/m²; Mezzanine 3.0 kN/m²; Roof 0.4 kN/m² (EN 1991-1-1).
Wind Load (WL): Basic wind velocity v_b,0 = 36 m/s (EN 1991-1-4), peak velocity pressure q_p(z) ≈ 1.25–1.45 kN/m².
Seismic Load (EQ): Zone 4, a_gR = 1.6 m/s² (French seismic zoning). The three-storey mezzanine introduces torsional eccentricity.

2.2 Critical Load Combinations (EN 1990 – ULS)

Combination	Formula	Governing Component
LC1	1.35 DL + 1.5 LL	Column axial, mezzanine beams
LC2	1.35 DL + 1.5 WL (pressure)	Column bending, foundation uplift
LC3	1.0 DL + 1.5 WL (suction)	Roof beam reversal, purlin anchorage
LC4	1.0 DL + 1.0 LL ± 1.0 EQ	Mezzanine lateral drift, ductility

Wind load (LC2/LC3) typically governs the main frame for this 26.75 m span.

2.3 Member Force Assessment

Side Column H750×250×6×10 (9.0 m high): Web slenderness h_w/t_w = 730/6 = 121.7 → Class 4 (slender). Effective section must be used, reducing flexural capacity by ~15–20%.

Wind Column H450×250×6×10: Lateral deflection ≈ h/150–h/200; acceptable for gable end but marginal.

Roof Beam (haunched + prismatic): H500×250×6×10 elastic moment capacity ~648 kN·m (S355), ample for mid-span moment of ~197 kN·m.

Mezzanine: Columns and beams are significantly over-designed for gravity loads (column demand ~79 kN vs. capacity ~15,800 kN). Lateral stability in transverse direction requires dedicated bracing due to single-sided attachment.

2.4 Deflection & Drift Summary

Component	Estimated Drift/Deflection	Limit	Status
Side column top (wind)	h/200–h/164	h/150	Acceptable
Roof beam mid-span (DL+LL)	L/760–L/595	L/250	Ample
Mezzanine inter-storey (EQ)	h/375–h/250	h/300	Borderline
Gable column top	h/164–h/138	h/200	Marginal

3.1 Unit Weights of Built-Up Sections

Section	tw (mm)	h (mm)	tf (mm)	b (mm)	Area (mm²)	Weight (kg/m)
H750×250×6×10	6	750	10	250	9,380	73.6
H450×250×6×10	6	450	10	250	7,580	59.5
H750–500 average	6	-	10	250	8,480	66.6
H300×200×6×8	6	300	8	200	4,904	38.5
H300×150×6×8	6	300	8	150	4,104	32.2

3.2 Quantities and Total Tonnage

Main Hangar Frame (Single Portal)

Member	Section	Length (m)	Qty	Total (m)	kg/m	Weight (kg)
Side column	H750×250×6×10	9.0	2	18.0	73.6	1,325
Wind column	H450×250×6×10	9.0	4	36.0	59.5	2,142
Roof beam (haunched)	H750–500 avg	13.4	2	26.8	66.6	1,785
Roof beam (prismatic)	H500×250×6×10	13.4	2	26.8	59.5	1,595
Subtotal per portal frame						6,847

6 frames at 5.0 m spacing: 6 × 6,847 = 41,082 kg

Other Components	Weight (kg)
Roof purlins (C/Z, 1.2 m spacing)	4,675
Wall girts (side + gable)	3,881
Bracing (roof + wall)	2,500
Subtotal Main Hangar	52,138

Three-Storey Mezzanine (25 m × 3 m)

Member	Section	Length (m)	Qty	Total (m)	kg/m	Weight (kg)
Columns	H300×200×6×8	9.0	6	54.0	38.5	2,079
Longitudinal beams	H300×150×6×8	5.0	18	90.0	32.2	2,898
Transverse beams	H300×150×6×8	3.0	15	45.0	32.2	1,449
Floor decking (steel)	-	-	225 m²	-	12 kg/m²	2,700
Stairs + bracing (allowance)	-	-	-	-	-	1,500
Subtotal Mezzanine						10,626

3.3 Total Steel Tonnage

Category	Weight (kg)	Tonnes
Main hangar structure	52,138	52.1
Three-storey mezzanine	10,626	10.6
+10% connections, base plates, misc.	6,276	6.3
Grand Total	69,040	~69.0

Estimated material cost (fabricated steel): please inquiry CBC for cost estimation.

4.1 New Caledonia (Baseline) – Good suitability

Wind 36 m/s, seismic zone 4 – design appropriate. Corrosion protection to C4–C5 marine environment essential.

4.2 Philippines – Marginal – requires redesign

Typhoon wind speeds 200–250 kph (3-s gust → ~40–50 m/s 10-min mean) exceed New Caledonia. High seismicity (PGA up to 1.0g). Columns likely need upsizing; mezzanine eccentricity critical. Recommend member upsizing + seismic bracing.

4.3 Indonesia – Acceptable with seismic retrofit

Wind moderate but seismicity very high (base shear 0.15g–0.35g). Mezzanine must be structurally separated or provided with ductile detailing. Add roof-level bracing and RBS connections.

4.4 Tonga – Conditionally suitable after wind upgrade

Cyclone region (Region C, AS/NZS 1170.2), wind 60–70 m/s gust. Upsize portal members (columns H800–900, rafters deeper). Cyclone-rated connections and cladding required.

4.5 Chile – Not suitable without full seismic redesign

Extreme seismicity (NCh 433, base shear up to 0.40g). Highly irregular mass distribution (single-sided mezzanine) would fail torsional checks. Mandatory: separate mezzanine, add braced frames, use toughness-rated steel (Charpy ≥27J at 0°C).

4.6 Comparative Summary

Country	Wind Critical?	Seismic Critical?	Current Design Adequate?	Primary Modification
New Caledonia	Yes (moderate)	Moderate	Yes	Corrosion protection
Philippines	Yes (typhoon)	Yes (high)	No	Upsize for wind + seismic bracing
Indonesia	Moderate	Yes (very high)	Partially	Mezzanine separation + ductile detailing
Tonga	Yes (cyclone)	Moderate	No	Upsize for cyclone wind
Chile	Low-Moderate	Yes (extreme)	No	Full seismic redesign

5.1 Column Web Classification

H750 web slenderness 121.7 → Class 4. Increase web to 8 mm (H750×250×8×10) to achieve Class 3 and full effectiveness.

5.2 Mezzanine Member Downsizing

Option	Column	Beam	Saving in mezzanine
Conservative	H250×150×6×8	H250×125×6×8	~25%
Optimized	H200×150×5×7	H200×100×5×7	~45%

Potential saving: 3–5 tonnes.

5.3 Portal Frame Spacing

Increase spacing to 6.25 m (5 frames over 25 m) → eliminates one frame, saves ~5.5–6.0 tonnes. (Suitable for New Caledonia; retain closer spacing for cyclone regions.)

5.4 Haunch Geometry

Shorten haunch to 8–10 m based on moment envelope; could save 600–800 kg per frame.

5.5 Corrosion Protection Optimization

Duplex system (HDG + polysiloxane) extends maintenance intervals to 30–40 years in C5 environments.

5.6 Optimization Summary

Strategy	Steel Saving (tonnes)	% of Total
Mezzanine downsizing	3–5	4–7%
Frame spacing increase (5 frames)	5.5–6.0	8–9%
Haunch length reduction	3.5–4.8	5–7%
Web thickness optimisation	–2.5 (increase)	–4%
Net Potential Saving	9.5–13.3	14–19%

Optimized tonnage: 55–60 tonnes.

 

Structural capacity: Main frame adequately sized; column web is Class 4 – increase to 8 mm or perform effective section analysis.

Total steel weight: Approximately 69 tonnes (52 t hangar + 11 t mezzanine + 10% allowances).

Transferability: Directly applicable only in New Caledonia. Indonesia requires seismic ductility; Philippines/Tonga need wind upgrades; Chile requires complete seismic redesign.

Optimization potential: 14–19% weight reduction achievable through wider frame spacing, mezzanine downsizing, and haunch shortening.