Facade Structural Analysis: Loads and Profile Selection (TS 498, EN 1991-1-4, EN 13830)

Facade structural analysis analyzes the safe and serviceable behavior of curtain wall systems under wind, glass weight, snow, and maintenance loads. This article outlines the calculation steps for vertical and horizontal profiles (mullions and transoms) based on TS 498, EN 1991-1-4, and EN 13830:2015+A1:2020 standards, providing a practical guide for profile selection and deflection control in facade systems.

1) Key Loads in Facade Structural Analysis

The primary loads in curtain wall systems include:

• Wind loads: Calculated per TS 498 and EN 1991-1-4, depending on building height and terrain roughness.
• Dead loads: Weight of glass, panels, and aluminum profiles.
• Snow loads: Considered per TS 498 for roof or skylight interactions.
• Maintenance/service loads: Applied as needed, e.g., for cleaning platforms.

2) Vertical Profile (Mullion) Calculation: Wind Load (SLS)

Wind load is a primary factor in designing vertical profiles. The calculation steps are:

1. Determine wind load: Wind velocity pressure (q, kN/m²) is selected based on building height, terrain roughness, and facade zone per TS 498 or EN 1991-1-4. The aerodynamic coefficient (Cp) is chosen based on facade geometry. Linear load: w = |q| × B (B: module/axis width, cm).
2. Deflection limit: Per EN 13830:2015+A1:2020, deflection limits are:
   • L ≤ 3000 mm → f_limit = L / 200
   • 3000 mm < L < 7500 mm → f_limit = 5 mm + L / 300
   • L ≥ 7500 mm → f_limit = L / 250
3. Required moment of inertia (I_req): For a simply supported, single-span beam:

   I_x,required ≈ [ (5 · w · L⁴) / (384 · E · f_limit) ]

   • w: linear wind load (kN/m)
   • L: span length (cm)
   • E: modulus of elasticity (≈ 70 GPa for aluminum)
   • f_limit: allowable deflection (cm)
4. Reactions and moments:
   • Reaction (SLS): R = w · L / 2 (kN)
   • Maximum moment (SLS): M = w · L² / 8 (kN·m)
   • ULS check: Stress is verified using yield strength and safety factor (γ_M1 = 1.1 for aluminum): σ_d = M_d / W ≤ f_y / γ_M1

3) Horizontal Profile (Transom) Calculation: Glass Load (SLS)

Horizontal profiles typically carry glass weight. The calculation steps are:

1. Calculate glass load: Glass specific weight is ~25 kN/m³. Total glass load:

   W_glass = 0.025 · t_total · L · G (kN)

   • t_total: glass thickness (mm)
   • L: span length (cm)
   • G: glass height (cm)
   Point load (each end): P = W_glass / 2 (kN).
2. Deflection limit: Per EN 13830 Clause 5.6: f_limit = L / 500.
3. Required moment of inertia (I_req): For symmetric double point loads:

   I_req = P · a · (3L² − 4a²) / (24 · E · f_limit)

   • P: point load (kN)
   • a: distance from support to load (cm)
   • L: span length (cm)
   • E: modulus of elasticity (GPa)
   • f_limit: allowable deflection (cm)
4. Reactions and moments:
   • Maximum moment: M_max = P · a (kN·m)
   • Deflection: Δ_max = P · a · (3L² − 4a²) / (24 · E · I) (m)
   • ULS check: Rd = P · γ (γ = 1.5 for ULS), σ_d = M_d / W ≤ f_y / γ_M1

4) Cp Coefficients and Wind Loads

For wind load calculations, the aerodynamic coefficient (Cp) is selected based on facade zones:

• Flat facade: Typical Cp values for pressure or suction (refer to TS 498 or EN 1991-1-4 tables).
• Corner zones: Higher suction coefficients, using increased absolute values.
• Side facade: Predominantly suction-driven.

5) Deflection Criteria and Profile Selection

Profile selection considers serviceability limit states (SLS) with deflection limits (L/200, L/250, or L/500) and compatibility with glass/gaskets. The selected profile’s moment of inertia (I) must exceed the calculated I_req. Ultimate limit state (ULS) stress checks are also required.

6) Quick Application Workflow

1. Determine q based on building height and terrain roughness (TS 498 or EN 1991-1-4).
2. Select Cp based on facade zone and geometry.
3. Calculate linear load: w = |q| × B (vertical profiles) or glass load: P = W_glass / 2.
4. Calculate required I_req based on deflection limits, ensuring consistent units.
5. Verify the selected profile’s I, W, and connection details for ULS/SLS compliance.

7) Frequently Asked Questions

Should I use Zone A or Zone D?

This depends on the element’s location and facade zone. Corner zones (Zone D) have higher suction coefficients. Refer to project specifications and EN 1991-1-4 tables/figures.

Can TS 498 and EN 1991-1-4 be used together?

In Turkey, TS 498 is primary, but EN 1991-1-4 can be used for international alignment. Final criteria are set by project specifications and local regulations.

What are EN 13830’s deflection limits?

For wind loads: L ≤ 3000 mm → L/200; 3000 mm < L < 7500 mm → 5 mm + L/300; L ≥ 7500 mm → L/250. For glass loads: L/500.

Need assistance with your project? Contact us for facade structural analysis calculations, anchor, bolt, welded connection checks, or continuous beam analyses.