Key regulations for steel structure design in Turkey: TBDY 2018, the steel design regulation and EN 1090

The abbreviations in a steel quotation or technical specification can be confusing. This article summarises the core regulations that directly concern steel load-bearing systems in Turkey, and what each of them covers.

Turkish Building Earthquake Code (TBDY 2018)

In force since 1 January 2019, the code sets the design rules for all buildings under seismic action. For steel structures it defines the structural system types (moment-resisting frames, concentrically and eccentrically braced frames), ductility levels and special requirements for connections. The seismic hazard is taken from the Turkish Earthquake Hazard Map for the coordinates of the building.

Regulation on Design, Calculation and Construction Principles of Steel Structures

It governs how steel members and connections are sized: tension, compression, bending, shear, combined actions, bolted and welded connections, composite members. It offers the designer two methods: load and resistance factor design (LRFD) and allowable strength design (ASD). It is used together with TBDY.

Load standards

The loads acting on the structure come from separate standards: TS 498 for dead and live loads, TS EN 1991-1-3 for snow and TS EN 1991-1-4 for wind. For light steel roofs, snow and wind are often the governing loads.

Material: TS EN 10025

It defines the grades of structural steel. In the names S235, S275 and S355, the number is the yield strength of the steel (N/mm²). The grade to be used is stated in the structural design; material is received with a mill certificate (usually a 3.1 document to EN 10204).

Fabrication: TS EN 1090

It governs the fabrication and conformity assessment of structural steel components.

• EN 1090-1: conformity assessment required for structural components to carry the CE mark
• EN 1090-2: technical rules for the fabrication and erection of steel structures; execution classes (EXC1–EXC4) set the level of fabrication and inspection

In welded fabrication, welder and procedure qualification (e.g. EN ISO 9606, EN ISO 15614) and quality requirements (EN ISO 3834) are part of this framework.

Fire

Fire-resistance periods for load-bearing members are set by the Regulation on Fire Protection of Buildings, depending on the occupancy class and height of the building.

What is it good for in practice?

When assessing a quotation or contract, you can ask:

• Which regulations was the structural design prepared to?
• What is the steel grade, and will a material certificate be supplied?
• Which execution class will fabrication follow, and how will weld inspections be documented?
• Is fire protection included in the quotation?

This article is for general information and summarises the regulations as of its publication date. Refer to the Official Gazette and TSE publications for current texts; design decisions belong to the licensed engineer.