Response Spectrum Method for the Earthquake Check According to
ÖNORM B 4015
The soil acceleration and the calculation coefficients as
defined according to ÖNORM B 4015 based on the earthquake zone,
the foundation, the damping and the ductility of the structure.
For the check the reactions of the structure corresponding to
the resonant frequencies are calculated according to the
response spectrum method and superposed based on the SRSS or CQC
method.
The resulting internal forces are available for further
superposition with the static load cases and subsequent design
(for instance, according to ÖNORM B 4700). |
 |
To allow for the evaluation of the relevant
modes of vibration, the program outputs the applied as well as the
effective modal masses:
Sum of the applied masses (global)
Mx [t]
My [t] Mz [t]
-----------------------------------------------
Dead
weights: 1500.000 1500.000
0.000
Point masses: 0.000
0.000 0.000
-----------------------------------------------
Sum:
1500.000 1500.000
0.000
Effective modal masses
(global)
Eigenmode
Mx eff [t] My eff [t]
Mz eff [t]
------------------------------------------------
1
935.135
0.000
0.000
2
0.000
935.135
0.000
3
0.000
287.137
0.000
4
287.137
0.000
0.000
5
98.544
0.168
0.000
6
0.168
98.548
0.000
7
47.342
3.197
0.000
8
3.201
47.258
0.000
------------------------------------------------
Sum:
1371.526
1371.443
0.000
In this context, the ratio of the sums of the masses (effective
modal masses/total mass) is of interest.
Example: 3D reinforced concrete frame
 1st
eigenmode |
Corresponding internal forces My from the response spectrum
|
| 
Superposed internal forces My according to CQC method |
|
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