An Efficient Technique for Derivation of the Kurtosis of Offshore Structural Response Due to Random Morison Wave Loading

2004 ◽  
Author(s):  
G. Najafian ◽  
R. Burrows ◽  
R. G. Tickell
Keyword(s):  
Structural Response ◽  
Computational Effort ◽  
Complex Structures ◽  
Structural Elements ◽  
Wave Loading ◽  
Structural Behaviour ◽  
Evaluation Procedures ◽  
Probabilistic Description ◽  
Non Gaussian

Nonlinear wave loading leads to non-Gaussian offshore structural response so that higher-order statistical moments, such as kurtosis, are often necessary for its probabilistic description. The existing models for determination of these moments are computationally very demanding. Consequently, the distributed wave loading on the structure is idealised by a relatively small number of nodal loads, requiring care and experience in the representation of the continuous loading on (complex) structures with many structural elements. These shortcomings are successfully overcome by an approximate approach, as described herein, offering a dramatic reduction in computational effort so that the distributed loading can be idealised more realistically by a large number of nodal loads. The effectiveness of the proposed procedures, which have arisen from a UK EPSRC-sponsored project, are demonstrated by applying them to a test structure under different environmental conditions. With these improved tools, designers can now consider incorporation of more robust and precise probabilistic analysis into their evaluation procedures for structural behaviour, without facing onerous computational effort.

Time Histories of Wave-in-Deck Loading on Jacket Decks

2006 ◽  
Author(s):  
Katrine van Raaij ◽  
Ove T. Gudmestad
Keyword(s):  
Time Variation ◽  
Structural Response ◽  
Engineering Practice ◽  
Offshore Platforms ◽  
Wave Loading ◽  
Extreme Wave ◽  
Incoming Wave ◽  
Time Histories ◽  
The Difference

Most researchers agree that wave-in-deck loading is of dynamic nature and that the dynamic effects on the structural response are important. However, there exists no engineering practice for the determination of load time histories for waves hitting the decks of fixed offshore platforms. This applies to both the time variation and the magnitude of the loading. This paper presents the main recommendations for wave-in-deck loading with reference to wave tank experiments of a model of the Statfjord A Condeep platform subjected to extreme wave loading. The recommendations for loading from these tests comprise time variation as well as magnitude. These recommendations are used as a basis to suggest a simplified method to estimate wave-in-deck loading on jacket platform decks, for which, to the difference from Condeep platforms, the wave height amplification due to the interaction between the incoming wave and the structure (Swan et al., 1997) is negligible. The resulting ‘recipe’ for wave-in-deck time histories on North Sea jacket platforms is compared to relevant results previously reported in the literature. The method is categorised as a ‘global’ approach, that is, one uses an effective deck area as opposed to a detailed deck model. The method is suggested to be applicable for analyses where a ‘rough but reasonable’ estimate for wave-in-deck loading is sufficient.

The Accuracy of the MFMNS and FMNS Models in Predicting Long-Term Distribution of the Extreme Values of Offshore Structural Response

2014 ◽  
Author(s):  
N. I. Mohd Zaki ◽  
M. K. Abu Husain ◽  
G. Najafian
Keyword(s):  
Probability Distribution ◽  
Extreme Values ◽  
Structural Response ◽  
Offshore Structures ◽  
Computational Effort ◽  
Random Wave ◽  
Wave Loading ◽  
Offshore Structure ◽  
Extreme Responses

Offshore structures are exposed to random wave loading in the ocean environment, and hence the probability distribution of the extreme values of their response to wave loading is of great value in the design of these structures. Due to nonlinearity of the drag component of Morison’s wave loading and also due to intermittency of wave loading on members in the splash zone, the response is often non-Gaussian; therefore, simple techniques for derivation of the probability distribution of extreme responses are not available. Monte Carlo time simulation technique can be used to derive the probabilistic properties of offshore structural response, but the procedure is computationally demanding. Finite-memory nonlinear system (FMNS) modeling of the response of an offshore structure exposed to Morison’s wave loading has been introduced to reduce the computational effort, but the predictions are not very good for low intensity sea states. To overcome this deficiency, a modified version of the FMNS technique (referred to as MFMNS modeling) was proposed which improves the accuracy, but is computationally less efficient than the FMNS modeling. In this study, the accuracy of the 100-year responses derived from the long-term probability distribution of extreme responses from FMNS and MFMNS methods is investigated.

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

scholarly journals Structural design principles for specific ultra-high affinity interactions between colicins/pyocins and immunity proteins

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Avital Shushan ◽  
Mickey Kosloff
Keyword(s):  
Protein Interactions ◽  
Structural Elements ◽  
Protein Protein Interactions ◽  
Immunity Protein ◽  
Rational Engineering ◽  
High Affinity ◽  
Comparative Structure ◽  
Polar Interactions ◽  
Exquisite Specificity

AbstractThe interactions of the antibiotic proteins colicins/pyocins with immunity proteins is a seminal model system for studying protein–protein interactions and specificity. Yet, a precise and quantitative determination of which structural elements and residues determine their binding affinity and specificity is still lacking. Here, we used comparative structure-based energy calculations to map residues that substantially contribute to interactions across native and engineered complexes of colicins/pyocins and immunity proteins. We show that the immunity protein α1–α2 motif is a unique structurally-dissimilar element that restricts interaction specificity towards all colicins/pyocins, in both engineered and native complexes. This motif combines with a diverse and extensive array of electrostatic/polar interactions that enable the exquisite specificity that characterizes these interactions while achieving ultra-high affinity. Surprisingly, the divergence of these contributing colicin residues is reciprocal to residue conservation in immunity proteins. The structurally-dissimilar immunity protein α1–α2 motif is recognized by divergent colicins similarly, while the conserved immunity protein α3 helix interacts with diverse colicin residues. Electrostatics thus plays a key role in setting interaction specificity across all colicins and immunity proteins. Our analysis and resulting residue-level maps illuminate the molecular basis for these protein–protein interactions, with implications for drug development and rational engineering of these interfaces.

Single-Degree-of-Freedom Based Pressure-Impulse Diagrams for Blast Damage Assessment

2014 ◽  
Vol 567 ◽  
pp. 499-504 ◽  
Author(s):  
Zubair Imam Syed ◽  
Mohd Shahir Liew ◽  
Muhammad Hasibul Hasan ◽  
Srikanth Venkatesan
Keyword(s):  
Damage Assessment ◽  
Structural Response ◽  
Blast Loading ◽  
Computational Effort ◽  
Degree Of Freedom ◽  
Negative Phase ◽  
Single Degree Of Freedom ◽  
Pressure Impulse ◽  
Single Degree ◽  
Structural Resistance

Pressure-impulse (P-I) diagrams, which relates damage with both impulse and pressure, are widely used in the design and damage assessment of structural elements under blast loading. Among many methods of deriving P-I diagrams, single degree of freedom (SDOF) models are widely used to develop P-I diagrams for damage assessment of structural members exposed to blast loading. The popularity of the SDOF method in structural response calculation in its simplicity and cost-effective approach that requires limited input data and less computational effort. The SDOF model gives reasonably good results if the response mode shape is representative of the real behaviour. Pressure-impulse diagrams based on SDOF models are derived based on idealised structural resistance functions and the effect of few of the parameters related to structural response and blast loading are ignored. Effects of idealisation of resistance function, inclusion of damping and load rise time on P-I diagrams constructed from SDOF models have been investigated in this study. In idealisation of load, the negative phase of the blast pressure pulse is ignored in SDOF analysis. The effect of this simplification has also been explored. Matrix Laboratory (MATLAB) codes were developed for response calculation of the SDOF system and for repeated analyses of the SDOF models to construct the P-I diagrams. Resistance functions were found to have significant effect on the P-I diagrams were observed. Inclusion of negative phase was found to have notable impact of the shape of P-I diagrams in the dynamic zone.

ChemInform Abstract: Determination of Complex Structures by Combined Neutron and Synchrotron X-Ray Powder Diffraction.

ChemInform ◽  
2010 ◽  
Vol 24 (2) ◽  
pp. no-no
Author(s):  
R. E. MORRIS ◽  
W. T. A. HARRISON ◽  
J. M. NICOL ◽  
A. P. WILKINSON ◽  
A. K. CHEETHAM
Keyword(s):  
Powder Diffraction ◽  
Complex Structures ◽  
X Ray

Study of the residual imperfections using methods of probability theory

2021 ◽  
Vol 87 (9) ◽  
pp. 44-49
Author(s):  
D. A. Kuzmin
Keyword(s):  
Probability Theory ◽  
Generalized Equation ◽  
Structural Elements ◽  
Non Destructive Testing ◽  
Operational Control ◽  
Destructive Testing ◽  
Control Procedures ◽  
Non Destructive ◽  
A Current

Discontinuities in the products that occur during manufacture, mounting or upon operation can be missed during non-destructive testing which do not provide their complete detectability at a current level of the technology. Therefore, it is necessary to take into account that certain structural elements may have discontinuities of significant dimensions. We present the results of using the methods of probability theory in studying the residual imperfections that remains in the structure after non-destructive control and repair of the previously identified defects. We used the results of operational control of units carried out by ultrasonic and radiographic methods. We present a method for determining a multifactorial coefficient that takes into account the detectability of defects, the number of control procedures and the errors in the instrumentation and methodological support, as well as a generalized equation for the probability distribution of detecting discontinuities. The developed approach provides assessing of the level of damage to the studied objects, their classification proceeding from the quantitative data and determination of the values of postulated discontinuities for deterministic calculations. The results obtained can be used to improve the methods of monitoring NPP facilities.

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