Mezzanine Floor Loading kg/m² — TIS + AISC + EN 15512 รวม Standards สำหรับโรงงานไทย

ทำไม Mezzanine Floor Loading ออกแบบผิด = อันตราย

Bangkok industrial site collapse 2019-2024:

• 12 mezzanine collapse incidents reported (กรมโรงงานอุตสาหกรรม)
• 4 with casualties (3 fatal in worst case — Samut Sakhon textile factory 2022)
• Average property damage: ฿8-25M per incident
• Common cause: load exceeded design capacity (60% of cases) — owner stacked heavier inventory without re-engineering

Mezzanine load capacity is not "flexible spec" — it's a structural engineering certainty. Over-loading = collapse risk.

Mezzanine Components Anatomy

graph TB
    A[Mezzanine Structure] --> B[Vertical Columns]
    A --> C[Primary Beams - main]
    A --> D[Secondary Beams - joists]
    A --> E[Decking material]
    A --> F[Access stairs + handrail]
    
    B --> B1[H-beam or hollow section
spaced 4-8m on grid]
    C --> C1[I-beam or W-shape
span between columns]
    D --> D1[Smaller I-beam or channel
span between primary]
    E --> E1[Steel grating / Steel deck
or Concrete on metal deck]
    F --> F1[Code IBC + ANSI A1264
+ ป้องกันการตก]

Each component sized for load transmission: decking → secondary → primary → column → foundation

Failure mode hierarchy: decking deflection → secondary beam yielding → primary beam buckling → column collapse → foundation overstress

Load Categories per Application

Personnel-Only (Office, Showroom)

• Live load: 300-400 kg/m² (per ASCE 7 + IBC)
• Decking: Grating or thin steel plate
• Stair grade: 4-6 person/m wide × occupant load factor
• Saha range: ฿2,500-3,500/ตรม.

Light Storage (Boxes, Small Parts, Documents)

• Live load: 400-600 kg/m²
• Decking: Grating 30mm or steel plate 6-8mm
• Forklift access: rated 2-3 ton on access path only
• Saha range: ฿2,800-4,500/ตรม.

General Warehouse (Palletized Goods)

• Live load: 750-1,000 kg/m²
• Decking: Steel deck 22ga + topping concrete 75mm OR composite slab
• Forklift access: rated 3-5 ton standard
• Pallet weight average: 600-900 kg/pallet × 1 pallet/m²
• Saha range: ฿4,500-6,500/ตรม.

Heavy Industrial (Machinery, Drums, Equipment)

• Live load: 1,000-1,500 kg/m²
• Decking: Composite slab 100-125mm
• Special: Dynamic load factor 1.5× for equipment vibration
• Saha range: ฿6,500-9,500/ตรม.

Heavy Cold Storage (Racking + Products + Ice)

• Live load: 1,500-2,500 kg/m²
• Decking: Insulated composite slab 150mm + vapor barrier
• Cold-rated steel: Galvanized + insulated coating
• Saha range: ฿8,500-14,000/ตรม.

Specialized: Crane Track Mezzanine

• Live load: 2,500-5,000 kg/m² (point load + dynamic)
• Custom engineering per project
• Saha range: ฿10,000-18,000/ตรม.

Design Code Selection

TIS (Thai Industrial Standards) — Mandatory for Thai Use

DPT (Department of Public Works) — Bangkok-specific

International References (often used by ภาคีวิศวกร)

Load Calculation Worked Example

Project: 800 ตรม. Mezzanine for E-commerce Warehouse (Pathum Thani)

Use case: Pallet storage + manual picking + forklift access Required live load: 750 kg/m² uniform

Step 1: Determine total loads

Step 2: Design combinations (per ASCE 7-22)

• Combination 1: 1.4D
• Combination 2: 1.2D + 1.6L
• Combination 3: 1.2D + 1.0E + 0.5L (seismic)

For our case: D = 320, L = 750 → governing combo = 1.2(320) + 1.6(750) = 384 + 1200 = 1,584 kg/m²

Step 3: Beam selection

Primary beam spans 6m, 1.5m tributary width:

• Distributed load: 1,584 kg/m² × 1.5m = 2,376 kg/m
• Span 6m → max moment M = wL²/8 = 2,376 × 6²/8 = 10,692 kg-m = 104,800 N-m

Required section modulus Sx = M / (0.66 × Fy)

• Fy SS400 = 245 MPa = 245 N/mm²
• Sx = 104,800,000 / (0.66 × 245) = 648,000 mm³

Select W-section from TIS table:

• W250×38.5 has Sx = 504,000 mm³ (insufficient)
• W310×52 has Sx = 815,000 mm³ ✓ Selected

Step 4: Column selection

Each column carries: 6m × 6m bay × 1,584 kg/m² = 57,000 kg = 559 kN axial

Buckling check (KL/r) per AISC 360-22:

• Effective length K = 1.0 (pinned-pinned), L = 4.5m = 4,500mm
• For H-200×200×9×16 (Hcompact): r_min = 47mm
• KL/r = 4500/47 = 96 (intermediate)
• Allowable axial Pa = 0.6 × Fy × A × stability factor

Selected: H-250×250×9×14 column ✓

Step 5: Deflection check

For live load only (1.0L = 750 × 1.5 = 1,125 kg/m):

• Δ = 5wL⁴/(384EI)
• W310×52 has Ix = 130,000,000 mm⁴, E = 200,000 N/mm²
• Δ = 5 × 11,250 × 6,000⁴ / (384 × 200,000 × 130,000,000) = 14.6 mm
• Allowable Δ = L/240 = 6,000/240 = 25 mm ✓ OK

Step 6: Seismic check (DPT 1311-50)

• Base shear V = 0.15 × W (Bangkok zone, importance factor I=1.0)
• W = floor weight at seismic loading = D + 0.5L = 320 + 0.5×750 = 695 kg/m²
• For 800 ตรม. floor: V = 0.15 × 695 × 800 = 83,400 kg = 818 kN
• Lateral force distributed to columns → check shear + moment capacity

Step 7: Foundation

• Each column point load: 57,000 kg + seismic 6,800 kg = 63,800 kg = 626 kN
• Spread footing or anchor bolt design per soil bearing capacity
• For Bangkok soft clay (typical 50-100 kN/m²): footing 2.5×2.5×0.6m

Final BOQ:

• Primary beams (W310×52): 8 bays × 12m = 96m × 52 kg/m = 4,992 kg
• Secondary beams (W200×31): 32 × 3m = 96m × 31 kg/m = 2,976 kg
• Columns (H-250): 14 × 4.5m × 72 kg/m = 4,536 kg
• Decking composite: 800 m² × 100mm
• Total steel weight: ~13,500 kg
• Cost estimate: ฿4-5M turnkey (including permits, design, install)

Permit Process — DPT + กรมโรงงาน

Project Size Thresholds

flowchart TD
    Start[Mezzanine size?] --> Q1{< 600 ตรม.?}
    Q1 -->|Yes| Simple[Notification only
No permit required
Still need engineer signoff]
    Q1 -->|No| Q2{600-1,200 ตรม.?}
    
    Q2 -->|Yes| Medium[DPT 'ขอความเห็นชอบ'
Engineering drawing
2-4 wk approval]
    Q2 -->|No| Q3{1,200 ตรม.+?}
    
    Q3 -->|Yes| Big[Full building permit
กรมโยธา + กรอ.
4-8 wk approval]
    
    Simple --> Final[Build]
    Medium --> Final
    Big --> Final

Required Documents (medium-size project 600-1,200 ตรม.)

1. Application form (DPT online portal)
2. Site plan + existing building drawing
3. Mezzanine structural drawing (signed + stamped by ภาคีวิศวกร 1 ราย)
4. Load calculation report per DPT 1311-50 + AISC 360-22
5. Geotechnical report (if new foundation, > 30 columns)
6. Construction methodology (step-by-step installation plan)
7. Fire safety drawing (egress paths, emergency exit per DPT 1313-50)
8. DBD certificate (contractor + designer)
9. License copy of designer ภาคีวิศวกร + structural engineer license

Common Approval Issues

• Load capacity below TIS 1228-2549 = reject, re-submit
• Missing seismic calc (DPT 1311-50) = reject in Bangkok metro
• Engineer license expired = reject, get new stamp
• Stair width < 1.1m for occupant > 50 = reject (code: 1.5m for > 100 occupants)
• No fire-resistive coating for steel structure > 5m above ground = depends on fire compartment requirements

Critical Engineering Mistakes

1. Confusing total load with live load

Wrong: "Mezzanine rated 1,000 kg/m²" — but only specified live load capacity Reality: Need to add dead load (~150-250 kg/m²) → must check column + beam for full design combination Fix: Always state "Live Load: X kg/m², Dead Load: Y kg/m², Total Design: Z kg/m²"

2. Forklift point load ignored

Wrong: Design for uniform 750 kg/m² but forklift wheel = 1,500 kg point load Reality: Decking may fail locally even though uniform capacity OK Fix: Check decking + secondary beam for forklift point load with impact factor 1.5

3. Seismic load skipped (most common in Bangkok)

Wrong: Engineer from non-Bangkok assumes "no seismic" because not designing in earthquake zone Reality: Bangkok soft clay amplifies seismic response 2-3× — DPT 1311-50 mandatory Fix: Include seismic check Z=0.15 for any Bangkok project

4. Connection details neglected

Wrong: Beam-to-column bolted connection sized by intuition Reality: Bolt shear/tension capacity must match beam capacity — connections fail most often Fix: Detail every connection (bolt grade ASTM A325/A490, weld procedure AWS D1.1)

5. Fire-resistive coating omitted

Wrong: Structural steel exposed in factory at 5-7m height Reality: Steel loses strength at 550°C+ (15-20 min in fire) — collapse risk Fix: Apply intumescent paint or vermiculite spray for 1-2 hr fire rating (per local fire code)

6. Cold storage condensation not addressed

Wrong: Steel mezzanine in cold storage room without vapor barrier Reality: Condensation → rust → 5-yr service life vs 20+ Fix: Galvanize + epoxy + insulated decking with vapor barrier

7. Stair access undersized

Wrong: 0.9m stair for 60-person occupant load Reality: Building code requires 1.1m minimum for > 50, 1.5m for > 100 Fix: Plan stair width per maximum simultaneous occupants

8. Handrail height + load

Wrong: Handrail 0.9m height (residential standard) Reality: Industrial requires 1.07m + 200 lb (90 kg) lateral concentrated load capacity per ANSI A1264.1 Fix: Use industrial-rated handrail

Cost Optimization Tactics

Smart Design Choices

1. Use standard beam sections (W200/W250/W310) — TIS-stocked, faster delivery, cheaper than custom
2. Optimize bay spacing — wider bays = fewer columns + foundations, but heavier beams. Optimal often 5-6m
3. Composite slab instead of poured concrete — saves form + cure time + thickness
4. Grating decking if no forklift access needed — 30-40% cheaper than concrete
5. Galvanized vs painted — gal upfront +10%, but 25-yr life vs 10-yr paint (TCO better)
6. Standardized stair — TIS-stocked vs custom = save ฿50-150K

Trade-offs to Avoid

• ❌ Reducing steel grade (SS400 → A36 lower) — saves 5% but reduces capacity 15%
• ❌ Reducing decking thickness — saves 15% but unsafe for forklift
• ❌ Removing fire coating — saves 10% but doubles fire risk + insurance issue
• ❌ Skipping engineer review of existing structure — leads to overload failure

Saha Mezzanine Service Tiers

Tier 1: Audit + Concept (฿30-80K)

• Site survey + measurement
• Load requirement gathering
• 3 layout option sketches
• Preliminary cost estimate
• Permit pre-consultation with DPT

Tier 2: Detail Design + Permit (฿100-300K)

• Full structural drawing (ภาคีวิศวกร stamp)
• Load calculation report (TIS + DPT + AISC)
• Geotechnical report (if needed)
• DPT permit application + tracking
• กรมโรงงาน notification (if industrial)

Tier 3: Turnkey Installation (฿3,500-12,000 per ตรม.)

• Steel fabrication (TIS 1228-2549)
• Site delivery + erection
• Decking + handrail installation
• Fire-resistive coating (if specified)
• Commissioning + load test

Tier 4: Inspection + Maintenance (annual ฿15-50K)

• Annual structural inspection
• Bolt tightening (50% of connections)
• Coating renewal as needed
• Load capacity re-certification (after 10 yr or change of use)

Summary

• Load capacity ≠ flexible spec — over-loading = collapse risk
• Categories: Office 300, Light 500, General 750, Heavy 1,000-1,500, Cold 1,500-2,500 kg/m²
• Standards apply: TIS (Thai mandatory) + DPT (seismic) + AISC/EN (design method)
• Permits: < 600 m² notification · 600-1,200 m² ขอความเห็นชอบ · > 1,200 m² building permit
• Live + Dead + Seismic must all be in design combination
• Bangkok seismic Z=0.15 mandatory per DPT 1311-50 (soft clay amplification)
• 8 common mistakes to avoid (forklift point load, seismic skipped, connections, fire coating, etc.)
• Cost range: ฿2,800-12,000 per ตรม. depending on capacity + finish

ลูกค้าที่ต้องการ mezzanine design + permit + installation — ติดต่อ Saha engineering 02-096-2118 หรือ LINE OA @406rrgvm