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Elastic Response Spectrum - EN 1998-1

The EN 1998-1 standard considers the elastic response spectrum as the basic representation of the seismic load. The spectrum is defined with the help of several basic parameters ag, TB, TC, TD, S and ξ. The design acceleration ag can be acquired from the maps of seismic regions. The proportional damping ratio ξ determines the damping of seismic waves in the soil/rock layers. Its value is typically assumed to be equal to 5%. The values of the remaining four parameters are specified according to the type of subsoil (types A - F) and the type of the required spectrum (1 and 2).

The values of parameters describing the horizontal elastic response spectrum of type 1 according to EN 1998-1

Ground type:

S

TB [s]

TC [s]

TD [s]

A

1.00

0.15

0.40

2.00

B

1.20

0.15

0.50

2.00

C

1.15

0.20

0.60

2.00

D

1.35

0.20

0.80

2.00

E

1.40

0.15

0.50

2.00

The values of parameters describing the horizontal elastic response spectrum of type 2 according to EN 1998-1

Ground type:

S

TB [s]

TC [s]

TD [s]

A

1.00

0.05

0.25

1.20

B

1.35

0.05

0.25

1.20

C

1.50

0.10

0.25

1.20

D

1.80

0.10

0.30

1.20

E

1.60

0.05

0.25

1.20

The values of parameters describing the vertical elastic response spectrum to EN 1998-1

Spectrum

avg/ag

TB [s]

TC [s]

TD [s]

Type 1

0.90

0.05

0.15

1.00

Type 2

0.45

0.05

0.15

1.00

Literature:

EN 1998-1: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings, (2006).

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