EN 1998-1 Horizontal Design Spectrum (UK, Europe, Singapore NA)
EN 1998-1 code spectra (UK, Singapore and Europe)
| Limits | Equation | Segment | Ref |
|---|---|---|---|
| 0 ≤ T ≤ TB | ag x S x [ 2/3 + T/TB x ( 2.5 / q - 2/3 )] | Start point/linear | 3.13 |
| TB ≤ T ≤ TC | ag x S x 2.5 / q | Constant | 3.14 |
| TC ≤ T ≤ TD | ag x S x TC/T x 2.5 / q | Constant/T | 3.15 |
| TD ≤ T ≤ 4s | ag x S x 2.5 / q x (TC x TD) / T2 | Constant/T2 | 3.16 |
EN 1998-1 site specific spectra - user defined (UK, Singapore and Europe)
Parameters
The following input parameters as
shown in the above figure are required:
- Suser(0)/ag
- Suser(TBuser) /ag
- TBuser
- TCuser
- TDuser
- TEuser
See the curve equation tables below for more details.
Input limits
- Suser(0) > 0
- Suser(TBuser) > 0
- 0s ≤ TBuser < TCuser < TDuser ≤ TEuser
Elastic Response Spectrum Curve Equations
Elastic Response Spectrum curves for Se/agare defined by:
| Line | Limits | Equation |
|---|---|---|
| (1) – straight line | 0 ≤ T ≤ TBuser | Se/ag(T) = Suser(0) + ((Suser(TBuser) x η – Suser(0)) x T / TBuser) |
| (2) – straight line | TBuser ≤ T ≤ TCuser | Se/ag(T) = Suser(TBuser) x η |
| (3) – curve | TCuser ≤ T ≤ TDuser | Se/ag(T) = Suser(TBuser) x η x TCuser/ T |
| (4) – curve | TDuser ≤ T ≤ TEuser | Se/ag(T) = Suser (TBuser) x η x TCuser x TDuser/ T2 |
| (5) – straight line continued from (4) |
Notes:
- The same curve applies for both Dir1 and Dir2
- Se/ag(T) is the elastic response spectrum to design ground acceleration ratio
- η is the damping correction factor
- See EC8 Clause 3.2.2.2 for more details
Design Spectrum Curve Equations
Design Spectrum for Elastic Analysis curves for Se/ag are defined by:
| Line | Limits | Equation |
|---|---|---|
| (1) – straight line | 0 ≤ T ≤ TBuser | Sd/ag(T) = [ 2/3 x Suser(0) + ((Suser(TBuser) / q – 2/3 x Suser(0)) x T / TBuser)] |
| (2) – straight line | TBuser ≤ T ≤ TCuser | Sd/ag(T) = Suser(TBuser) / q |
| (3) – curve | TCuser ≤ T ≤ TDuser | Sd/ag(T) = Suser(TBuser) x TCuser/ T / q |
| (4) – curve | TDuser ≤ T ≤ TEuser | Sd/ag(T) = Suser (TBuser) x TCuser x TDuser/ T2/ q |
| (5) – straight line continued from (4) |
Notes:
-
The same curve applies for both Dir1 and Dir2
-
Sd/ag(T) is the design spectrum to design ground acceleration ratio
-
If TBuser = 0, then no line (1) exists
-
If TDuser = TEuser then no line (4) exists