Seismic Design of Offshore Structures under Simplified Pulse-Like Earthquakes
2. Simplified Pulse-Type Ground Motions
3. Offshore Jacket Platforms
4. Selected Results
4.1. Linear Analysis
4.2. Nonlinear Analysis
4.3. Small- and Large-Displacement Formulation
4.4. The Effects of the Angle of Incident of Seismic Pulses on the Platforms’ Dynamic Response
- Although this investigation considers only simplified pulses, its importance seems to be noteworthy taking into account that near-fault ground motions are frequently characterized by simple waveforms.
- The consideration of rigid soil strongly affects the response in comparison to the case of deformable soil, and the dynamic inelastic pile-soil-platform interaction should be taken into account. More specifically, the flexibility of the soil elongates the whole set of eigenperiods of platforms and, in most of the cases, it leads to higher values of maximum deformations in comparison with the case of fixed-based platforms.
- Each type of pulse under consideration led to different results, even in the case where the circular frequency and the maximum peak ground acceleration was identical in any case.
- When executing incremental dynamic analysis, it was found that geometric nonlinearity should be taken into account since their ignorance leads to a fictitious higher seismic performance and strength of platforms. More specifically, both the geometric nonlinearity of the soil and the diagonal braces, which lost their out-of-plane stability, leads to buckling-prone structures.
- The incidence angle of seismic waves appears to be a crucial parameter where, for some critical angles, the maximum deformation can be increased significantly in comparison to the ones corresponding to other, less crucial angles.
- The aforementioned findings and conclusions can be generalized to other types of platforms and pulses than those examined, but more analyses and investigations will be required.
Conflicts of Interest
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|Members||Storey||Circular Cross-Sections-ext. Diameter × Thickness [mm]|
|Columns||0||110.0 × 5.0|
|1||110.0 × 5.0|
|2||100.0 × 4.5|
|3||90.0 × 4.0|
|4||90.0 × 4.0|
|Beams||0||75.0 × 4.5|
|1||75.0 × 4.5|
|2||80.0 × 4.2|
|3||75.0 × 4.0|
|4||50.0 × 2.5|
|Braces||0||55.0 × 2.5|
|1||55.0 × 2.5|
|2||60.0 × 2.2|
|3||50.0 × 2.6|
|4||50.0 × 2.2|
|Rigid-Soil Assumption||Soil-Pile-Structure System|
|Eigenvalue||Natural Frequency ωn|
|Natural Frequency ωn|
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Konstandakopoulou, F.; Papagiannopoulos, G.; Pnevmatikos, N.; Evangelinos, K.; Nikolaou, I.; Hatzigeorgiou, G. Seismic Design of Offshore Structures under Simplified Pulse-Like Earthquakes. CivilEng 2020, 1, 310-325. https://doi.org/10.3390/civileng1030020
Konstandakopoulou F, Papagiannopoulos G, Pnevmatikos N, Evangelinos K, Nikolaou I, Hatzigeorgiou G. Seismic Design of Offshore Structures under Simplified Pulse-Like Earthquakes. CivilEng. 2020; 1(3):310-325. https://doi.org/10.3390/civileng1030020Chicago/Turabian Style
Konstandakopoulou, Foteini, George Papagiannopoulos, Nikos Pnevmatikos, Konstantinos Evangelinos, Ioannis Nikolaou, and George Hatzigeorgiou. 2020. "Seismic Design of Offshore Structures under Simplified Pulse-Like Earthquakes" CivilEng 1, no. 3: 310-325. https://doi.org/10.3390/civileng1030020