Design codes
Structural design to the Korean Design Standards (KDS)
How Struxt3D applies the Korean Design Standards: KDS 41 load combinations, live loads, wind and the KDS 41 17 spectrum, with KDS 14 steel and concrete checks.
The Korean Design Standards (KDS) replaced the old KBC building code with a numbered set of standards. Building loads and seismic design live in the KDS 41 series, and the material design standards in KDS 14. When you choose KDS in Struxt3D, the app uses Korean load combinations, live loads, H-section sizes and steel and concrete grades, and checks the members with the KDS 14 equations. This tutorial shows exactly what is applied and how to check it.
Standards used
| Standard | Topic | Used for |
|---|---|---|
| KDS 41 10 15 (2019) | Basis of design: load combinations | Strength combinations |
| KDS 41 12 | Building loads | Live loads by use |
| KDS 41 12 (wind) | Wind loads | Pressure from the basic (mean) wind speed |
| KDS 41 17 00 | Seismic design of buildings | Design spectrum from SDS, SD1; R (Table 6.2-1) |
| KDS 14 31 10 (2022) | Steel structures, LRFD | Steel members and cables (4.1.1) |
| KDS 14 20 | Concrete structures | Beams, columns, slabs, walls, footings |
KDS 14 31 10 follows the same LRFD structure as AISC 360, and KDS 14 20 is close to ACI 318, so engineers who know the US codes will recognise the checks. Timber members use EN 1995-1-1 rules for every code.
Load combinations
| Combination | Purpose |
|---|---|
| 1.4D | Dead load alone |
| 1.2D + 1.6L | Gravity |
| 1.2D + 1.0L + 1.3W | Wind with live load |
| 0.9D + 1.3W | Uplift and overturning |
| 1.2D + 1.0L + 1.0E | Earthquake with live load |
| 0.9D + 1.0E | Earthquake, minimum gravity |
| D + L (service) | Deflections |
Note the wind factor of 1.3: KDS wind pressures are not at strength level, unlike ASCE 7-16 and later. Wind combinations repeat for +X, −X, +Y and −Y; seismic ones for ±(EX + 0.3EY) and ±(0.3EX + EY). The seismic mass includes 25 % of the live load.
Live loads
| Use | L (kN/m²) |
|---|---|
| Office | 2.5 |
| Residential | 2.0 |
| Retail | 4.0 |
| Storage | 6.0 |
| Roof | 1.0 |
| Footbridge deck | 5.0 |
Wind
KDS gives a basic wind speed as a 10-minute mean at 10 m (28 m/s by default; read your region's value from the KDS basic wind speed map, which is higher on the coasts and islands). Struxt3D uses the same mean-speed pressure as for the Eurocode:
The KDS importance factor, topographic factor and gust response factor are not applied separately. If your site is in exposure A or B, or on a hill, increase the wind speed to match the KDS design pressure.
Seismic
KDS 41 17 00 defines the spectrum by SDS and SD1, which you work out from the effective ground acceleration S and the site coefficients Fa, Fv:
Enter SDS and SD1 in Supports & loads › Earthquake. The spectrum has the same shape as ASCE 7 and is divided by R:
| Structural system | R |
|---|---|
| Ductile (special) moment frame | 8 |
| Ordinary moment frame | 3.5 |
| Braced frame | 6 |
| Walls or core | 5 |
| Elastic | 1 |
The importance factor IE (1.5 for special, 1.2 for class 1, 1.0 for class 2) is not applied: multiply SDS and SD1 by IE before you enter them.
Materials and sections
| Material | Grades offered (default first) |
|---|---|
| Steel | SM355, SS275, SHN355 (E = 210 GPa) |
| Concrete | fck 27, 24, 30 MPa; Ec = 8500 ∛fcm MPa, fcm = fck + 4 |
| Reinforcement | fy = 400 MPa (SD400) |
| Glulam | 10S-30B, 8S-24B |
Beams are KS rolled H-sections from H-250×125×6×9 upwards, columns from H-200×200×8×12, and tubes are pipes named P-D×t. Steel resistance uses φ = 0.9 with the AISC-form column curve; concrete uses the KDS strength reduction factors (0.85 flexure, 0.65 tied compression, 0.75 shear).
Worked example: a five-storey office
- Open the Multi-storey frame template and set five storeys in Size.
- In Materials, choose KDS. Steel switches to SM355, concrete to fck 27 MPa and the sections to H-shapes.
- In Supports & loads, pick Office, wind 28 m/s, and turn on Earthquake.
- Press F5 and F6. The Design table and the calculation report quote KDS 14 31 10 and KDS 14 20 clauses.
Check 1: factored floor load
Check 2: wind pressure at 10 m
Check 3: spectrum inputs
As an example, suppose the site coefficients for your site class are Fa = 1.4 and Fv = 1.5 (take the real values from KDS 41 17 00 for your site). With S = 0.22 g:
How KDS changes the design
The KDS gravity combination 1.2D + 1.6L is the same as the US one, so gravity-governed members come out close to an AISC / ACI design with similar grades. The difference is in the lateral loads: KDS wind is factored 1.3 instead of 1.0 because the pressure is not at strength level, and the mean-speed wind profile gives a different variation with height from the gust-based US one.
KDS 14 31 10 and KDS 14 20 follow AISC 360 and ACI 318 closely: the same kind of compactness limits, lateral-torsional buckling equations and interaction checks for steel, and strength reduction factors that depend on the steel strain for concrete. SD400 bars (400 MPa) are a little weaker than US Grade 60 (420 MPa), so beams need slightly more steel area. KS H-sections have different sizes from US W-shapes; auto-sizing picks the lightest H-section that passes.
For seismic design, R = 8 for a special moment frame assumes the detailing of KDS 41 17 00 and the special seismic provisions for concrete. If your frame is ordinary (R = 3.5), the seismic forces are more than twice as large; choose the system that matches the detailing you will use.
What you still need to check
- Importance factors for wind and seismic, and the site class coefficients Fa, Fv.
- Snow loads and roof live load reductions are not generated.
- Base shear scaling of the response spectrum to the equivalent static force, accidental torsion and storey drift limits.
- Seismic detailing of special moment frames and walls (KDS 41 17 00 and the special provisions of KDS 14 20 80).
- Wind exposure categories other than open country, topography and local pressures on cladding.
See accuracy and limitations for what the analysis itself assumes.