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SINGLE DEGREE OF FREEDOM STRUCTURES
Other factors involved in designing offshore structures for earthquake résistance not included in this simplified approach are inelastic structural behavior,
ground-structural interactions, and the interactions of vertical and horizontal
motions. Key référencés on these effects are included in the brief discussions of
Gould and Abu-Sitta (1980) and in the more extensive analyses of Clough and
Penzien (1993). There is some evidence, however, that the simplified approach
just presented is conservative in that it often overpredicts the motion of the
Figure 5.8 Pseudovelocity response of a single degree of freedom structure to the El
Centro earthquake, south eastern component, May 18, 1940.
Example Problem 5.1. For the jackup rig shown in Figure 2.17, estimate the
cntical responses to the horizontal motion of the 1940 El Centro earthquake for
which vg is given in Figure 2.14. The structural data needed for this calculation
are given m Example Problems 2.8 and 5.3 as: h0 = 3180 in., a?0 = 1.36 rad/sec,
and Aq = 6.82 x 104 Ib/in. The structural period is To = 4.61 sec.
From Figure 5.8, the values of Sv for ( = 0 and 0.1 are about 12 and 8 in./sec,
respective y. From équations (5.78)-(5.80), the corresponding upper and lower
SINGLE DEGREE OF FREEDOM STRUCTURES
Other factors involved in designing offshore structures for earthquake résistance not included in this simplified approach are inelastic structural behavior,
ground-structural interactions, and the interactions of vertical and horizontal
motions. Key référencés on these effects are included in the brief discussions of
Gould and Abu-Sitta (1980) and in the more extensive analyses of Clough and
Penzien (1993). There is some evidence, however, that the simplified approach
just presented is conservative in that it often overpredicts the motion of the
Figure 5.8 Pseudovelocity response of a single degree of freedom structure to the El
Centro earthquake, south eastern component, May 18, 1940.
Example Problem 5.1. For the jackup rig shown in Figure 2.17, estimate the
cntical responses to the horizontal motion of the 1940 El Centro earthquake for
which vg is given in Figure 2.14. The structural data needed for this calculation
are given m Example Problems 2.8 and 5.3 as: h0 = 3180 in., a?0 = 1.36 rad/sec,
and Aq = 6.82 x 104 Ib/in. The structural period is To = 4.61 sec.
From Figure 5.8, the values of Sv for ( = 0 and 0.1 are about 12 and 8 in./sec,
respective y. From équations (5.78)-(5.80), the corresponding upper and lower