Seismic Soil-Structure Interaction Design Considerations for Offshore Platforms

2016 ◽  
Author(s):  
Jiun-Yih Chen ◽  
Richard Litton ◽  
Albert Ku ◽  
Ramsay Fraser ◽  
Philippe Jeanjean
Keyword(s):  
Soil Structure ◽  
Ground Motions ◽  
Time History ◽  
Time History Analysis ◽  
Radiation Damping ◽  
Soil Structure Interaction ◽  
Offshore Platforms ◽  
Bending Moments ◽  
Structure Interaction ◽  
History Analysis

Offshore platforms for oil and gas production in seismic regions around the world are often required to be designed for seismic hazards according to International Standards (e.g., ISO 19901-2 [1] and ISO 19902 [2]). This paper discusses three important aspects of the nonlinear dynamic time history analysis commonly used to design for Abnormal Level Earthquakes (ALE) in light of findings from recent centrifuge modeling and numerical simulation of the response of offshore structures under earthquake excitations. First, greater-than-expected ground motion de-amplification has been observed in a recent seismic soil-structure interaction centrifuge program for typical “soft” marine clays with undrained shear strength up to 100 kPa per API RP 2GEO [3]. Second, the current industry practice of using uniform down-pile ground motions in the time history analysis tends to underestimate pile bending moments. Use of depth-varying ground motions is strongly recommended to better characterize pile bending moments. Alternatively, a simplified design approach is proposed to account for the higher bending moments from the use of more realistic depth-varying ground motions. This approach is illustrated with a design example. Lastly, hysteretic and radiation damping in soil-structure interaction is discussed. Modeling of hysteretic damping is achieved using nonlinear elasto-plastic soil springs with unload-reload behavior following Masing’s rule, whereas modeling of radiation damping is achieved using viscous dashpots in a parallel or series arrangement with the axial and lateral soil springs and with dashpot coefficients based on O’Rourke and Dobry [4]. The centrifuge data show that proper modeling of radiation damping is important to accurately predict pile load and settlement.

scholarly journals Soil-pile-structure interaction effects on high-rise building under seismic shaking

2019 ◽  
Vol 2 (1) ◽  
pp. 153-164
Author(s):  
Umesh Jung Thapa ◽  
Ramesh Karki
Keyword(s):  
Soil Structure ◽  
Seismic Analysis ◽  
Time History ◽  
Soil Structure Interaction ◽  
Base Shear ◽  
Structure Interaction ◽  
High Rise ◽  
High Rise Building ◽  
History Analysis ◽  
Fixed Base

In this paper, study of the response (base shear, time period, storey drift, storey displacement) of a structure is done for the tall building including basement with fixed base and with pile foundation considering Soil Structure Interaction (SSI). Finite element based program ETABS2016 v16.1.0 is used for the analysis of the superstructure. Seismic analysis is done to get the dynamic response of superstructure for two types of model,one model is with fixed baseand second is Model with Winkler spring for Chhaya Center, Thamel, a high rise building with 14 story including double basements. Itisobserved with the consideration of Soil Structure Interaction (SSI). The soil is replaced by spring and assigned at joints. El Centro earthquake (1940) is used for time history analysis. The response obtained due to SSI effect is compared with fixed based model. Results of analysis presented include the comparison of natural periods, base shears, displacements and overturning moment. It is observed that the natural periods increase and the base shears decrease as the base become more flexible.

scholarly journals Critical Analysis of Nonlinear Base-Isolated Building Considering Soil–Structure Interaction under Impulsive and Long-Duration Ground Motions

Geotechnics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 76-94
Author(s):  
Hiroki Akehashi ◽  
Izuru Takewaki
Keyword(s):  
Soil Structure ◽  
Base Isolation ◽  
Ground Motions ◽  
Time History ◽  
Sine Wave ◽  
Soil Structure Interaction ◽  
Input Energy ◽  
Structure Interaction ◽  
Long Duration ◽  
Critical Responses

Critical responses are investigated for nonlinear base-isolated buildings considering soil–structure interaction under near-fault ground motions and long-duration ground motions. A double impulse and a multi impulse are employed to simulate the nonlinear critical responses of the models under such ground motions. The base-isolation story is assumed to consist of lead rubber bearings and to have a bilinear force–deformation relation. Two types of critical timings for a MDOF building model supported by a swaying-rocking spring-dashpot system are derived: (1) the timing that maximizes the total input energy to the whole system and (2) the timing that maximizes the instantaneous input energy to the base-isolated building excluding the swaying-rocking system. These two types of critical timings are compared through numerical examples. Finally, time-history response analyses were conducted under the critical double impulse, the corresponding one-cycle sine wave, and the critical multi impulse. The effect of the soil–structure interaction on the maximum responses of the nonlinear base-isolated building is clarified.

Study on Seismic Response Characteristics of Step-Terrace Frame Structure on the Slope

2014 ◽  
Vol 580-583 ◽  
pp. 1718-1722
Author(s):  
Li Ping Liu ◽  
Ji Jin Liu ◽  
An Liang Li ◽  
Ming Zi Tan
Keyword(s):  
Seismic Response ◽  
Soil Structure ◽  
Time History ◽  
Frame Structure ◽  
Soil Structure Interaction ◽  
Soil Parameters ◽  
Structure Interaction ◽  
Response Characteristics ◽  
History Analysis ◽  
Dynamic Time

The seismic response of step-terrace frame structure is affected by the slope. Considered soil parameters of slope, the floor numbers and span numbers of layers below the scarp, 45 step-terrace frame example structures were designed, and three excitations at bedrock were selected to analyze the example structures response with dynamic time-history analysis method. The research indicates that when the other conditions are the same, the soil becomes softer, or structure's span numbers on the slope becomes larger or the slope becomes higher, the dynamic interaction between slope and step-terrace frame structure becomes more obvious. When the inputted ground motion at slope foot is adopted and the slope soil is soft, the seismic response of structure without soil-structure interaction is smaller than that of with soil-structure interaction.

scholarly journals Evaluation of Soil-Structure Interaction on the Seismic Response of Liquid Storage Tanks under Earthquake Ground Motions

2016 ◽  
Author(s):  
Mostafa Farajian ◽  
Mohammad Iman Khodakarami ◽  
Denise-Penelope N. Kontoni
Keyword(s):  
Seismic Response ◽  
Soil Structure ◽  
Ground Motions ◽  
Time History ◽  
Soil Structure Interaction ◽  
Storage Tanks ◽  
Structure Interaction ◽  
Earthquake Ground Motions ◽  
Liquid Storage ◽  
Matlab Programming

Soil-structure interaction (SSI) could affect the seismic response of structures. Since liquid storage tanks are vital structures and must continue their operation under severe earthquakes, their seismic behavior should be studied. Accordingly, the seismic response of liquid storage tanks founded on half space soil is scrutinized under different earthquake ground motions. To better comparison, the six considered ground motions are classified based on their pulse like characteristics, into two groups, named far and near fault ground motions. To model the liquid storage tanks, the simplified mass-spring model is used and the liquid is modeled as two lumped masses known as sloshing and impulsive, and the interaction of fluid and structure is considered using two coupled springs and dashpots. The SSI effect, also, is considered using a coupled spring and dashpot. Besides, four types of soils are used to consider wide variety of soil properties. To this end, after deriving the equations of motion, the MATLAB programming is employed to obtain the time history responses. Results show that although the SSI effect leads to decrease the impulsive displacement, overturning moment and normalized base shear, the sloshing (or convective) displacement is not affected by such effects due to its long period.

Soil-structure interaction at CDMG and USGS accelerograph stations

1989 ◽  
Vol 79 (1) ◽  
pp. 1-14
Author(s):  
C. B. Crouse ◽  
Behnam Hushmand
Keyword(s):  
Soil Structure ◽  
Transfer Functions ◽  
Ground Motions ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Imperial Valley ◽  
Structure Interaction ◽  
Fundamental Frequencies ◽  
Vibration Tests ◽  
40 Hz

Abstract Forced harmonic and impulse-response vibration tests were conducted at several California accelerograph stations operated by the California Division of Mines and Geology (CDMG) and U.S. Geological Survey (USGS) to determine the extent to which soil-structure interaction may be affecting the recorded ground motions. The results of the tests on the foundations comprising USGS Station 6 in the Imperial Valley and CDMG Cholame 1E and Fault Zone 3 stations in the Cholame Valley indicated the presence of highly damped fundamental frequencies between 20 and 40 Hz. However, at the much larger Differential Array station, a masonry-block structure approximately 6 km southwest of Station 6, a moderately damped fundamental frequency of 12 Hz was observed. Approximate transfer functions between earthquake motions recorded at the stations and the free-field motions were computed from the response data obtained from the forced harmonic vibration tests. For the three smaller stations, these functions showed peak amplification factors ranging from 1.25 to 1.4 at frequencies between 20 and 40 Hz. The amplification at smaller frequencies was insignificant. For the Differential Array station, the amplification factor was 1.5 at 12 Hz and was roughly 0.6 for frequencies between 14 and 25 Hz. These results suggest that soil-structure interaction will have little effect on ground motions recorded at the smaller stations provided that most of the energy in these motions is confined to frequencies less than approximately 20 Hz. However, at the Differential Array station, soil-structure interaction probably has had, and will continue to have, a significant influence on the motions recorded at this station.

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