Force-based design
TBDY Chapter 4. Linear analysis by the equivalent lateral force or modal response spectrum method; seismic effects are reduced by the response modification factor (R) and the overstrength factor (D).
Home / New buildings
TBDY 2018 and current codes
New buildings designed for the seismic hazard of their site.
We design the structural systems of residential, commercial, public and industrial buildings to be economical, earthquake-resistant and coordinated with the architecture, in line with the Turkish Building Earthquake Code (TBDY 2018) and related standards.
Design inputs
Settled before the calculations start
Under TBDY 2018 the earthquake load no longer comes from a seismic zone map by province; it depends on the site coordinates and soil conditions.
- Seismic hazard · TBDY Chapter 2
Earthquake ground motion levels
Short-period (SS) and 1-second (S1) spectral acceleration coefficients are taken from the AFAD Turkish Earthquake Hazard Map for the site coordinates. The code defines four ground motion levels:
Level Probability of exceedance in 50 years Return period DD-1 2% 2475 years DD-2 (standard design earthquake) 10% 475 years DD-3 50% 72 years DD-4 (service earthquake) 68% 43 years 
Shape of the horizontal elastic design spectrum: SDS plateau and SD1/T descending branch (schematic) - Soil · local site class
Site classes ZA–ZF
The local site class from the geotechnical report directly shapes the design spectrum. Six classes range from rock (ZA) to soils needing site-specific study (ZF), for which a site response analysis is required.
- Use · TBDY Chapter 3
Building use class and importance factor
Class Typical use Importance factor (I) BKS-1 Buildings needed immediately after an earthquake (hospitals, schools, fire stations etc.) and buildings with hazardous contents 1.5 BKS-2 Buildings with short-term dense occupancy (shopping centres, sports halls, cinemas etc.) 1.2 BKS-3 Other buildings such as housing, offices and hotels 1.0 The seismic design class (DTS-1 to DTS-4a) follows from SDS and the use class; it sets the permitted analysis methods, structural systems and detailing rules. The building height class (BYS-1 to BYS-8) follows from the height and design class; BYS-1 covers tall buildings, which the code treats separately.
Design approach
An earthquake-resistant structural system
Deformation-based assessment and design
TBDY Chapter 5. Nonlinear analysis checks member deformation demands directly. Used for tall buildings, seismically isolated buildings and where needed for others.
Irregularity checks
Plan and vertical irregularities (TBDY Chapter 3) are checked at the start of design and, where possible, resolved together with the architecture.
Capacity design and limits
Strong columns and weak beams, shear capacity above flexural capacity, and storey drifts within code limits, so that the building behaves in a ductile rather than brittle way in a major earthquake.
Structure types
The rules for each type of structure
TBDY Chapter 7 · TS 500
Reinforced concrete buildings
Frame, wall and dual systems designed to seismic rules, with detailing of columns, beams, walls, slabs, confinement zones and beam-column joints.
TBDY Chapter 9 · Turkish Steel Code
Steel buildings
Industrial buildings, warehouses, roof structures and multi-storey steel buildings; members, connections and base plates.
Steel structures →
Geotechnical data · TBDY
Retaining structures
Cantilever and gravity retaining walls: sliding, overturning and bearing checks under static and seismic earth pressures, and section design.
Codes and standards
What our designs are based on
- Turkish Building Earthquake Code (TBDY 2018)Published in the Official Gazette on 18 March 2018, in force since 1 January 2019. Covers seismic design of new buildings and assessment and strengthening of existing ones (Chapter 15).
- AFAD Turkish Earthquake Hazard MapSpectral accelerations by site coordinates; in force together with TBDY 2018.
- TS 500Design and construction of reinforced concrete structures.
- TS 498Design loads: dead, live and snow loads.
- Turkish Steel Structures Design CodeDesign of steel members and connections, applied together with TBDY Chapter 9.
This page is for general information. The rules for each project depend on the current versions of the codes, their relevant provisions and the project's own conditions.