Why Do Earthquakes Affect Heavier Buildings More?
Earthquake physics is simple: F = m × a. Seismic force is directly proportional to the mass of the structure (m) and ground acceleration (a). You cannot change ground acceleration — but you can change the mass of the structure.
A reinforced concrete structure is 8 to 12 times heavier than a light steel structure of the same floor area. This difference means that the force transferred to the load-bearing system during an earthquake grows by the same proportion. In other words, a light steel structure has to carry far less seismic load, from foundation to roof.
| Structure Type | Average Weight (kg/m²) | Relative Seismic Force |
|---|---|---|
| Light steel (LGSF) | 30 – 45 | 1x (reference) |
| Timber frame | 50 – 80 | ~2x |
| Precast concrete panel | 200 – 280 | ~7x |
| Reinforced concrete frame | 300 – 420 | ~10x |
| Masonry brick | 500 – 700 | ~15x |
A 150 m² single-story structure: reinforced concrete weighs ~55 tons, light steel ~6 tons. In the same earthquake, the seismic force transferred to the light steel structure is roughly 9 times less than for the reinforced concrete one. This directly affects the load-bearing system, the foundation, and the connection elements.
Ductility: The Capacity to Absorb Seismic Energy
In earthquake engineering, it isn't just strength that matters — ductility is just as critical. Ductility measures how much a structure can deform before it collapses.
Reinforced concrete structures are ductile when reinforced correctly. However, reinforced concrete structures without sufficient stirrup spacing or with irregular geometry behave in a brittle manner — they can collapse suddenly and without warning.
In light steel structures, OSB-clad shear wall panels absorb seismic energy through the plastic deformation of screw connections. This mechanism provides high energy dissipation while preventing sudden collapse — large deformations occur first, giving occupants time to evacuate.
How Does the OSB Shear Wall System Work?
In light steel structures, the main element resisting lateral loads (earthquake, wind) is the shear wall panel. These panels consist of:
- A galvanized steel stud frame (C140/1.2 or similar profile)
- OSB-3 board screwed to both faces (minimum 11mm)
- Anchor connections at the corners (hold-down)
- Connection to the foundation via anchor bolts or cast-in fasteners
The OSB board distributes lateral force across the entire panel surface. When screw connections exceed the elastic limit, they exhibit plasticity — this is precisely the energy dissipation mechanism. The result: high lateral stiffness combined with controlled energy dissipation.
The unit lateral stiffness (Ga) of an OSB-clad shear wall panel is approximately 0.55 kN/mm/m (D1 system). With diagonal strap bracing, this value rises to 0.75 kN/mm/m. The seismic load reduction coefficient is taken as R = 4 (OSB cladding) and R = 3 (gypsum board cladding).
What Do TBDY 2018 and the 2026 Regulation Say?
Light steel structures are now fully defined within Turkey's legal framework.
- TBDY 2018: Light steel structures are evaluated under "steel structures with high ductility level." The R coefficient (seismic load reduction) is determined according to the cladding system per TBDY Article 10.2.6.1.
- 2026 Light Steel Building Regulation (Official Gazette No. 33256): Minimum profile thicknesses, stud dimensions, cladding requirements, and the seismic calculation method have been standardized in Turkish. As of January 1, 2027, a regulation-compliant report will be mandatory for permit applications.
Since the 2026 Regulation came into force, a building permit for a light steel structure can be obtained with a structural report signed by an authorized engineer. The claim that "light steel can't get a permit" is now false and outdated. MefSteel prepares this report in-house for every project.
Assessment by Earthquake Zone
According to AFAD's earthquake hazard map, Turkey is divided into zones based on the DD-2 design earthquake. Light steel structures can be applied in every earthquake zone — but the calculation becomes progressively more critical.
| Region / Example Province | Relative Seismic Risk | Light Steel Suitability | Critical Point |
|---|---|---|---|
| Tekirdağ, Edirne | Moderate | Suitable | Standard calculation is sufficient |
| Istanbul (European side) | High | Suitable | Soil class is critical |
| Izmir, Bursa | High | Suitable | Hold-down anchors mandatory |
| Kahramanmaraş, Hatay | Very High | Suitable (careful design) | Geotechnical survey required, extra measures on Z4 soils |
| Kırklareli, Çanakkale | Moderate–Low | Suitable | Standard calculation is sufficient |
Light Steel Performance in Real Earthquakes
In major earthquakes in the United States (Northridge 1994, Seattle 2001), Japan, and New Zealand (Canterbury 2011), light steel structures generally performed well. Key observations:
- Structural damage is minimal: In most cases the building remained usable, and repair costs came out lower than for reinforced concrete.
- No collapses occurred: No collapse has been recorded in light steel structures fitted with OSB shear wall systems during earthquakes within their design life.
- Connection points are critical: In damaged structures, the common cause was incorrect anchoring or insufficient hold-down connections. This is why structural calculation and build quality are decisive.
The seismic performance of light steel structures depends directly on the accuracy of the system design and the quality of execution. Profile manufacturing precision, assembly sequence, and screw torque — all of these are how the calculation translates to the job site. At MefSteel, we control every stage from factory production to assembly.
How Important Is Soil Class?
Soil class is decisive for both light steel and reinforced concrete. According to TBDY 2018 Table 2.1, five soil classes are defined, from ZA to ZE.
- ZA–ZB (hard, solid rock): Ideal for both systems. Foundation cost is low.
- ZC (medium stiff): Light steel has the advantage — its low mass keeps foundation size small.
- ZD (soft): Geotechnical survey mandatory. Piled foundation if needed. Light steel remains advantageous.
- ZE (very soft): Engineering solutions are essential for both systems. Soil improvement should be evaluated.
Thanks to the low weight of light steel structures, foundation costs on ZC and ZD soils drop significantly compared to reinforced concrete.
Frequently Asked Questions
How many stories can light steel structures have?
Under the 2026 Regulation, light steel structures are typically designed up to 3 stories (ground + 2). For taller buildings, heavy steel frame systems or hybrid solutions are preferred. Light steel is the ideal range for single- or two-story residential projects.
Is earthquake insurance (DASK) valid for light steel structures?
Yes. Every structure with a legal building permit and occupancy certificate is covered under DASK. Being a light steel structure does not negatively affect the DASK premium; the premium is calculated based on the structure's value and the region's risk coefficient.
Can a light steel addition be built onto an existing reinforced concrete structure?
Yes — and this is one of the most practical uses of light steel. It's the preferred choice for adding an extra floor, enclosing a terrace, or adding an independent extension to an existing reinforced concrete structure. Thanks to its low weight, it doesn't add excessive load to the existing load-bearing system; however, this must always be verified by a structural engineer.
Can a light steel building permit be obtained in Tekirdağ?
Yes. The Tekirdağ Metropolitan Municipality and district municipalities issue light steel building permits based on an engineering report prepared under the 2026 Regulation. MefSteel manages this process from start to finish.
Call 0553 543 02 12 for free information about your land's soil class and earthquake zone. We'll visit your site in Tekirdağ and surrounding provinces and determine the best structural system for your project together.