Dynamic Analysis of Offshore Platforms By Frequency Dependent Stiffness Matrix Approach

1972 ◽  
Author(s):  
Bulet Ovunc
Keyword(s):  
Dynamic Analysis ◽  
Stiffness Matrix ◽  
Offshore Platforms ◽  
Matrix Approach ◽  
Frequency Dependent

Inversion of differences in frequency components of azimuthal seismic data for indicators of oil-bearing fractured reservoirs based on an attenuative cracked model

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. R163-R175
Author(s):  
Huaizhen Chen ◽  
Junxiao Li ◽  
Kristopher A. Innanen
Keyword(s):  
Reflection Coefficient ◽  
Stiffness Matrix ◽  
Fractured Reservoirs ◽  
P Wave ◽  
Parameter Estimates ◽  
Fluid Viscosity ◽  
Mathematical Form ◽  
Data Set ◽  
Frequency Dependent ◽  
Frequency Components

Based on a model of attenuative cracked rock, we have derived a simplified and frequency-dependent stiffness matrix associated with (1) a rock volume containing aligned and partially saturated cracks and (2) a new indicator of oil-bearing fractured reservoirs, which is related to pressure relaxation in cracked rocks and influenced by fluid viscosity and saturation. Starting from the mathematical form of a perturbation in this stiffness matrix across a reflecting interface separating two attenuative cracked media, we set up a linearized P-wave to P-wave reflection coefficient as an azimuthally and frequency-dependent function of dry rock elastic properties, dry fracture weaknesses, and the new indicator. By varying this reflection coefficient with azimuthal angle, we derive a further expression referred to as the quasidifference in elastic impedance, or [Formula: see text], which is primarily affected by the dry fracture weaknesses and the new indicator. An inversion approach is established to use differences in frequency components of seismic amplitudes to estimate these weaknesses and the indicator based on the derived [Formula: see text]. In synthetic inversion tests, we determine that the approach produces interpretable parameter estimates in the presence of data with a moderate signal-to-noise ratio (S/N). Testing on a real data set suggests that reliable fracture weakness and indicator are generated by the approach; fractured and oil-bearing reservoirs are identified through a combination of the dry fracture weakness and the new indicator.

Vibration Problem of Visco-Elastically Damped Structures

1983 ◽  
Vol 7 (2) ◽  
pp. 103-105
Author(s):  
Marc Van Overmeire
Keyword(s):  
Stiffness Matrix ◽  
Viscoelastic Damping ◽  
Frequency Dependent ◽  
Vibration Problem ◽  
Modal Superposition ◽  
Straightforward Method ◽  
Sequence Method ◽  
Superposition Technique

For the solution of vibrational problems, involving viscoelastic damping layers, the application of a modal superposition technique requires the solution of the eigenproblem, ([K(ω)] - ω2[M]) (u)=0, with frequency dependent stiffness matrix [K(ω)]. This paper presents a straightforward method, namely a slightly modified Sturm Sequence Method, for the solution of this eigenproblem.

scholarly journals An application of the transfer matrix approach for a dynamic analysis of complex spatial pipelines

2019 ◽  
Vol 349 ◽  
pp. 174-182 ◽  
Author(s):  
Anatolii Batura ◽  
Andrii Novikov ◽  
Andrii Pashchenko ◽  
Yaroslav Dubyk
Keyword(s):  
Dynamic Analysis ◽  
Transfer Matrix ◽  
Matrix Approach ◽  
Transfer Matrix Approach

Static and dynamic analysis of circular beams using explicit stiffness matrix

2016 ◽  
Vol 60 (1) ◽  
pp. 111-130 ◽  
Author(s):  
Mohammad Rezaiee-Pajand ◽  
Niloofar Rajabzadeh-Safaei
Keyword(s):  
Dynamic Analysis ◽  
Stiffness Matrix ◽  
Static And Dynamic Analysis

DYNAMIC ANALYSIS OF FRAMES WITH MATERIAL AND GEOMETRIC NONLINEARITIES BASED ON THE SEMIRIGID TECHNIQUE

2008 ◽  
Vol 08 (03) ◽  
pp. 415-438 ◽  
Author(s):  
F. T. K. AU ◽  
Z. H. YAN
Keyword(s):  
Dynamic Analysis ◽  
Stiffness Matrix ◽  
Plastic Hinge ◽  
Nonlinear Dynamic Analysis ◽  
Yield Condition ◽  
Computationally Efficient ◽  
Time Step ◽  
Geometric Nonlinearities ◽  
Frame Element ◽  
Sum Of Products

This paper presents a method for nonlinear dynamic analysis of frames with material and geometric nonlinearities which is based on the semirigid technique. The plastic hinge that accounts for the material nonlinearity is modeled as a pseudo-semirigid connection with nonlinear hysteretic moment-curvature characteristics at the element ends. The stiffness matrix of a frame element with material and geometric nonlinearities is expressed as the sum of products of the standard stiffness matrix and the geometric stiffness matrix of the element, with their corresponding correction matrices based on the plasticity factors developed from the section flexural stiffness at the plastic hinge locations. The combined stress yield condition is used for the force state determination of plastic hinges, and force equilibrium iterations and geometry updating for frames are carried out in every time step. When the key parameters of a structure are updated in a time step, the time step is split up into substeps to ensure accuracy while keeping the computations to a reasonable amount. The plastic rotation history can be calculated directly or in an approximate indirect way. The method is computationally efficient and it needs no additional connection elements, which makes it convenient for incorporation into existing linear dynamic analysis programs. Besides, the method can handle accurately and efficiently the dynamic analysis of nonlinear frames using relatively large time steps in conjunction with time step subdivision to cope with key parameter changes. A portal frame is used to verify the correctness of the proposed method. A more complicated five-story frame is used to illustrate the applicability and performance of the proposed method.

Incremental Dynamic Analysis Considering Pile-Soil-Structure Interaction for the Jacket Type Offshore Platforms

2008 ◽  
Author(s):  
Behrouz Asgarian ◽  
Alireza Fiouz ◽  
Ali Shakeri Talarposhti
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Response ◽  
Limit State ◽  
Nonlinear Behavior ◽  
Incremental Dynamic Analysis ◽  
Layered Soil ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Structure Interaction ◽  
Soil Deposits

Nonlinear response of piles is the most important source of potentially nonlinear behavior of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviors of the piles. Incremental dynamic analysis is an analysis method that has recently emerged as a promising tool for thoroughly evaluating the seismic performance of structures. It involves subjecting a structural model to a suite of ground motion records, each scaled to several intensities and recording the responses at each level to form IDA curves of response versus intensity. In this paper, jacket and soil-pile system is modeled and the effects of Soil-Pile-Structure Interaction (SPSI) are considered, and the Incremental Dynamic Analysis (IDA) is used to investigate nonlinear behavior of offshore platforms. An attempt is made to introduce a practical BNWF (Beam on Nonlinear Winkler Foundation) model for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. This model was incorporated into a Finite Element program (OpenSees). All the analyses are performed in two directions and the results are compared with each others. A computer program for Nonlinear Earthquake site Response Analyses of layered soil deposits (NERA) is used for analysis nonlinear response of soil layers. Limit state of the jacket is calculated from incremental dynamic analysis of the jacket using fiber elements for the nonlinear modeling of the system.

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