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Eurocode 8 Elastic acceleration and displacement response spectra (for design of structures in the elastic range and calculation of displacements)

Description:
Calculation of the elastic response spectrum in terms of spectral acceleration and spectral displacement representing the seismic action in the horizontal or vertical direction. Applicable for the design of structures that remain in the elastic range, seismic isolation systems, and calculation of seismic displacements.
According to:
EN 1998-1:2004 Sections 3.2.2.2, 3.2.2.3
Supported National Annexes:
In addition to countries that adopt the CEN recommended values for NDPs, the following National Annexes are also supported automatically: Belgium, Czech Republic, Greece, Norway, Portugal, Slovenia
All Calculations
Input

Hint: Select custom for Spectrum Type in order to manually specify the spectral parameters S, TB, TC, TD and the spectral amplification factor

Type 1 spectra correspond to typical high seismicity hazard. Low seismicity Type 2 spectra are recommended when the earthquakes that contribute most to the seismic hazard have a surface-wave magnitude, Ms, not greater than 5.5. For more details see EN1998-1 §3.2.2.2(2)P and the National Annex. Select custom to manually specify the parameters of the spectrum.
g
In accordance with EN1998-1 §3.2.1(2) and the seismic zones defined in the National Annex
In accordance with EN1998-1 §3.2.1(3), §2.1.4 and the corresponding importance factors is given in the relevant Parts of EN1998. An importance factor of γ = 1.0 corresponds to typical structures of average importance.
%
Typically equal to 5% for concrete structures in the elastic range. If for special cases a viscous damping ratio different from 5% is to be used, this is given in the relevant Part of EN1998.
Ground types A, B, C, D, and described by the stratigraphic profiles and parameters given in EN1998-1 Table 3.1, partially reproduced below. Select 'custom' ground type to manually specify the spectral parameters S, TB, TC, TD etc.
Ground types according to EN1998-1 Tables 3.1, 3.2
TypeParameters for Type 1 (high seismicity)Description
AS = 1.00, TB = 0.15 s, TB = 0.40 sRock or other rock-like geological formation, including at most 5 m of weaker material at the surface (vs,30>800m/s)
BS = 1.20, TB = 0.15 s, TB = 0.50 sDeposits of very dense sand, gravel, or very stiff clay, at least several tens of meters in thickness, characterized by a gradual increase of mechanical properties with depth (360m/s≤vs,30<800m/s, NSPT>50, cu>250kPa)
CS = 1.15, TB = 0.20 s, TB = 0.60 sDeep deposits of dense or medium dense sand, gravel or stiff clay with thickness from several tens to many hundreds of meters (180m/s≤vs,30<360m/s, 15≤NSPT<50, 70kPa≤cu<250kPa)
DS = 1.35, TB = 0.20 s, TB = 0.80 sDeposits of loose-to-medium cohesionless soil (with or without some soft cohesive layers), or of predominantly soft-to-firm cohesive soil (vs,30<180m/s, NSPT<15, cu<70kPa)
ES = 1.40, TB = 0.15 s, TB = 0.50 sA soil profile consisting of a surface alluvium layer with vs values of type C or D and thickness varying between about 5 m and 20 m, underlain by stiffer material with vs > 800 m/s
In accordance with EN1998-1 §3.2.2.3(1)P and the National Annex.
It is the acceration ratio of the constant acceration branch to the peak ground acceleration. According to EN1998-1 §3.2.2 the spectral amplification factor F is equal to 2.5 for the elastic spectrum in the horizontal direction, 3.0 for the elastic spectrum in the vertical direction, and 2.5 for the design spectrum in both horizontal and vertical directions.
In accordance with EN1998-1 §3.2.2.2(3) and the National Annex. A value of S = 1 is applicable for rock by definition. For more flexible soils S > 1.
s
In accordance with EN1998-1 §3.2.2.2(2)P and the National Annex
s
In accordance with EN1998-1 §3.2.2.2(2)P and the National Annex
s
In accordance with EN1998-1 §3.2.2.2(2)P and the National Annex. It is noted that for seismic isolation systems with long periods the displacement demands are directly proportional to TD. For bridges a larger value of TD = 2.5 s is recommended in EN1998-2 §7.4.1(1)P