Civil Engineering Reference
In-Depth Information
4.0
0
4.0
0
4.0
0
165
150
135
120
105
15
165
150
135
120
105
15
165
150
135
120
105
15
3.0
2.0
1. 0
3.0
2.0
1. 0
3.0
2.0
1. 0
30
45
60
30
45
60
30
45
60
4.0
0
M4
M6
M8
165
150
135
120
105
15
3.0
2.0
1. 0
4.0
0
30
45
60
165
150
135
120
105
15
75
75
3.0
2.0
1. 0
75
90
30
45
60
4.0
0
M2
90
90
4.0
0
165
150
135
120
105
15
y
3.0
2.0
1. 0
M10
165
150
135
120
105
15
30
45
60
y'
3.0
2.0
1. 0
75
30
45
60
90
x'
M1
75
A2
90
75
75
90
90
x
M4
M5
M6
M7
M3
M8
M9
M2
M1
M10
A1
M11
A2
4.0
0
4.0
0
4.0
0
4.0
0
4.0
0
4.0
0
165
150
135
120
105
15
165
150
135
120
105
15
165
150
135
120
105
15
165
150
135
120
105
15
165
150
135
120
105
15
3.0
2.0
1. 0
165
150
135
120
105
15
3.0
2.0
1. 0
3.0
2.0
1. 0
3.0
2.0
1. 0
3.0
2.0
1. 0
3.0
2.0
1. 0
30
45
60
30
45
60
30
45
60
30
45
60
30
45
60
30
45
60
A1
M3
M5
M7
M9
M11
75
75
75
75
75
75
90
90
90
90
90
90
22.6
Finite element model of the Krystallopigi Bridge and defi nition of
excitation direction.
assumed to be parallel and perpendicular to the chord for the two seismic
input components, respectively.
22.4.4 Asynchronous excitation
Sources of spatial variation of earthquake ground motion
The spatial variation of earthquake ground motions is another aspect that
is not accounted for in the vast majority of the design cases. This is a reason-
able approximation for buildings or short bridges, but it may considerably
alter the overall seismic response of more extended structures especially
in the case where the local site conditions vary signifi cantly with length
(Deodatis
et al.
, 2000; Der Kiureghian
et al.
, 1997; Sextos
et al.
, 2003b). The
particular problem is very complex and various methods have been pro-
posed for tackling the uncertainty related to the defi nition of a 'realistic'
support-dependent earthquake input, as well as for predicting the condi-
tions under which the effect of asynchronous input is indeed critical for the
structure.
Seismic code framework
Despite the major practical relevance of generating artifi cial spatially
varying motions and the associated research carried out over the last years,
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