Characteristic load values per TS 498, ULS and SLS combinations per TSC 2018, seismic directional combination rules, and a worked example showing how to establish governing design demands for a typical residential building.
TS 498:1997 specifies characteristic values for dead loads and imposed loads to be used in Turkish structural design. These values are combined using TSC 2018 combination rules.
| Occupancy Category | qk (kN/m²) | ψ0 | ψ1 | ψ2 |
|---|---|---|---|---|
| Residential — bedrooms, living rooms | 2.0 | 0.7 | 0.5 | 0.3 |
| Residential — stairs, corridors, terraces | 3.0 | 0.7 | 0.5 | 0.3 |
| Office | 3.0 | 0.7 | 0.5 | 0.3 |
| Classroom, reading room | 3.0 | 0.7 | 0.6 | 0.6 |
| Assembly areas (assembly halls, theaters) | 5.0 | 0.7 | 0.7 | 0.6 |
| Shopping areas, markets | 5.0 | 0.7 | 0.7 | 0.6 |
| Storage — light | 5.0 | 1.0 | 0.9 | 0.8 |
| Storage — heavy | 7.5+ | 1.0 | 0.9 | 0.8 |
| Parking — passenger vehicles | 2.5 | 0.7 | 0.7 | 0.6 |
| Roof — accessible (flat) | 2.0 | — | — | — |
| Roof — maintenance only | 1.5 | — | — | — |
ψ factors are the combination coefficients: ψ0 = accompanying value in ULS combinations; ψ1 = frequent value (SLS); ψ2 = quasi-permanent value (long-term deflection, creep). These align with EN 1990 Annex A categories.
TS 498 does not define regional snow zones — engineers are directed to use TS EN 1991-1-3 with the Turkish National Annex for detailed snow load maps. In practice, a characteristic snow load of sk = 0.75 kN/m² is commonly adopted as the flat-roof value for most of western Turkey (Marmara, Aegean); interior Anatolia uses 1.0–2.0 kN/m² depending on altitude.
TS 498 §12 specifies a basic wind pressure based on a reference wind speed. For detailed wind analysis, TS EN 1991-1-4 is used. See Article 7 of this series for full wind load calculation procedures.
TSC 2018 §4.4.1 specifies the following Ultimate Limit State combinations for gravity loading (no earthquake), consistent with TS EN 1990:
Where G = dead load; Q = floor live load; Qr = roof live load; S = snow load; W = wind load. The governing combination must be identified for each member and each critical section.
When earthquake effects are included, TSC 2018 §4.4.2 specifies two seismic combinations that must both be checked:
Where Qm is the reduced (seismic) live load — not the full live load:
For a typical residential building (n = 0.70 for 6+ storeys; ψ2 = 0.3): Qm = 0.70 × 0.3 × Q = 0.21Q. This significantly reduces the seismic mass compared to the full imposed load, reflecting that not all floors are fully loaded during an earthquake.
Buildings must be designed for earthquake in both principal horizontal directions simultaneously. TSC 2018 §4.4.2.3 specifies the directional combination rule:
Both combinations must be considered with all sign permutations (four combinations each direction pair = 8 total), giving the worst-case loading for each structural element. For three-dimensional structures with significant torsional response, TSC §4.4.2.4 requires additional accidental eccentricity of 5% of the building dimension in each plan direction.
For DTS 1 and DTS 2 buildings taller than 60 m, and for specific elements such as cantilever slabs longer than 2 m, horizontal beams of transfer structures, and base-isolated systems, TSC §4.4.2.5 requires inclusion of the vertical earthquake component:
Where SDS is the short-period design spectral acceleration (see Article 6 on Seismic Design). For most buildings in Turkey under 60 m with regular plan and no cantilevers, Ez is not required.
Deflection and crack width checks use unfactored or reduced load combinations. TS 500 §13 and TS EN 1992 specify serviceability limits.
| Element | Limit (TS 500 §13) | Condition |
|---|---|---|
| Beams and slabs — total | L / 250 | Quasi-permanent combination |
| Beams and slabs — after finishes | L / 500 | To avoid damage to brittle partitions |
| Cantilever beams — total | Lc / 125 | Quasi-permanent |
| Roof structure | L / 300 | Including ponding risk |
| Inter-storey drift (seismic) | δmax / h ≤ 0.02 | TSC 2018 §4.9 (reduced seismic forces) |
| Exposure Class | wmax (mm) | Combination |
|---|---|---|
| XC1 — dry indoors | 0.4 | Quasi-permanent |
| XC2/3 — humid, outdoor | 0.3 | Quasi-permanent |
| XS1–3, XD1–3 — chloride | 0.2 | Frequent |
| Prestressed (bonded) | 0.1 | Frequent |
A simply-supported beam in an office building floor has the following characteristic loads per unit length:
For a 6 m span beam, the design moment is Md = 28.8 × 6² / 8 = 129.6 kN·m at ULS. The quasi-permanent moment for deflection calculation is Mqp = 14.7 × 6² / 8 = 66.2 kN·m, giving a reference deflection to check against L/250 = 24 mm.
| Combination Rule | TSC 2018 | ASCE 7-22 | EN 1990 |
|---|---|---|---|
| Gravity-only ULS (basic) | 1.4G | 1.4D | 1.35G |
| Gravity dominant | 1.2G + 1.6Q | 1.2D + 1.6L | 1.35G + 1.5Q |
| Seismic combination | 1.2G + Qm + E | 1.2D + f1L + Ev + Eh | G + ψ2Q + AEd |
| Uplift seismic | 0.9G ± E | 0.9D ± Eh ∓ Ev | Ginf + AEd |
| Directional combination | Ex ± 0.3Ey | Ex ± 0.3Ey (100-30 rule) | Ex ± 0.3Ey (EN 1998) |
| Seismic live load fraction | n·ψ2·Q (varies 0.21–0.30 for residential) | f1L = 0.5L (storage: 1.0L) | ψ2·Q (0.3 residential) |
| SLS deflection limit | L/250 (TS 500) | L/360 (live only) | L/250 (EN 1992) |