Theoretical and Experimental Study on the Local Flexibility of Tubular Joints and its Effect on the Structural Analysis of Offshore Platforms

2004 ◽  
pp. 558-559
Keyword(s):  
Experimental Study ◽  
Structural Analysis ◽  
Offshore Platforms ◽  
Tubular Joints ◽  
Local Flexibility

Nonlinear Analysis of Offshore Platforms Subjected to Earthquake Loading Considering the Effects of Joint Flexibility

2009 ◽  
Author(s):  
S. Samadani ◽  
A. A. Aghakouchak ◽  
J. Mirzadeh Niasar
Keyword(s):  
Structural Analysis ◽  
Nonlinear Analysis ◽  
Offshore Structures ◽  
Offshore Platforms ◽  
Joint Flexibility ◽  
Modeling And Analysis ◽  
Shell Elements ◽  
Tubular Joints ◽  
Two Samples ◽  
Non Linear

In a conventional method of structural analysis, for modeling and analysis of jacket type offshore platforms, member connections are assumed to be rigid. In this method, members are rigidly connected which means there is no axial or rotational deformation at the end of brace member relative to chord axis. However in reality local deformations occur at chord surface due to applied loads from braces, which mean tubular joints are considerably flexible especially in non linear range of deformations. Therefore results of analysis based on rigid connections assumption differ from real behavior of the structure. Various research works have been carried out in the past on tubular joints and different methods have been presented in order to include the effect of joint flexibility in structural analysis. Most of these methods are just valid in elastic range but some non-linear methods have also been developed for simple tubular joints. In order to carry out a nonlinear analysis on a 3-D model of an offshore platform with multi-brace / multi-planar tubular joints, none of these simplified methods is applicable. In this case a complete model of tubular joints by non-linear shell elements is the most accurate one which is not only valid for non-linear analyses but also covers all type of tubular joints. In this paper two samples of offshore platforms are studied. These platforms are modeled using the following approaches: 1. No modeling of joints as structural elements (rigid connections). 2. Modeling of joint can with nonlinear shell elements (flexible connection). Different types of static non-linear analysis (Push over) are carried out and results are compared. In order to evaluate the results and compare this type of modeling with simplified methods included in professional software for the analysis of offshore structures, aforementioned platforms are also analyzed using the Fessler and MSL models to include effects of joint flexibility. The results of these types of modeling are also compared with the previous ones.

An experimental study on stainless steel hybrid tubular joints with square braces and circular chord

2020 ◽  
Vol 155 ◽  
pp. 106919 ◽  
Author(s):  
Ran Feng ◽  
Chaoqun Wu ◽  
Zhenming Chen ◽  
Krishanu Roy ◽  
Boshan Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Stainless Steel ◽  
Tubular Joints

scholarly journals Effect of RBD mutation (Y453F) in spike glycoprotein of SARS-CoV-2 on neutralizing antibody affinity

2020 ◽  
Author(s):  
Takuma Hayashi ◽  
Nobuo Yaegashi ◽  
Ikuo Konishi
Keyword(s):  
Experimental Study ◽  
Monoclonal Antibodies ◽  
Natural Selection ◽  
Structural Analysis ◽  
Growth Process ◽  
Three Dimensional ◽  
Neutralizing Antibody ◽  
Antibody Affinity ◽  
Protein Structural Analysis

AbstractNatural selection “adaptation” in the coronavirus can occur during coronavirus amplification in vivo in farmed minks. Natural selection in such viruses is observed by introduction of mutations in SARS- CoV-2 that are not observed during the growth process in humans. Infection with a mutant (Y453F) of SARS-CoV-2 from farmed minks is known to widely spread among humans. We investigated the virological characteristics of this SARS-CoV-2 mutant (Y453F) using three-dimensional protein structural analysis. Our experimental study suggests that virus variants with the Y453F mutation partially escaped detection by four neutralizing monoclonal antibodies. The spread of SARS-CoV-2 variants mediated by millions of infected farmed minks is uncontrolled; consequently, raising a concern that infection of SARS-CoV-2 mutants that cause serious symptoms in humans may spread globally.

Bayesian Estimation of Occurrence Probability of Cracks in Offshore Platforms

2006 ◽  
Author(s):  
D. Q. Li
Keyword(s):  
Ultrasonic Inspection ◽  
Crack Size ◽  
Bayesian Estimator ◽  
Accurate Estimation ◽  
Offshore Platforms ◽  
Occurrence Probability ◽  
Tubular Joints ◽  
Available Information ◽  
Non Destructive

To ensure safety of offshore platforms, non-destructive inspections are often conducted after the installation of offshore platforms. It is often impractical to inspect 100 percent of tubular joints of offshore platforms due to high costs and possible delays. Accordingly, the presence of cracks may not be fully detected as only a limited number of tubular joints can be inspected. This paper proposes a procedure to predict the occurrence probability of crack in tubular joints of offshore platforms based on ultrasonic inspections supplemented with engineers’ experiences. This procedure is developed in the Bayesian framework. To conduct the updating and estimating of the occurrence probability of cracks, formulae for calculating the updated probability distribution and Bayesian estimator of occurrence probability are derived. Then, the occurrence probability of crack is updated based on results from ultrasonic inspections. Results from numerical examples indicate that a reasonable estimation of the occurrence probability of crack can be obtained using the proposed procedure. Both the inspection results from the ultrasonic inspection and the crack size have a significant influence on the estimated occurrence probability of crack. The use of the available information from engineers’ experiences or similar projects can lead to a more accurate estimation of the occurrence probability of crack. The quality of offshore platforms will be overestimated if the uncertainty in crack size is not accounted for.

An Experimental Study of Bi-Directional Structure Vibration Suppression Using LPC Impact Dampers

2016 ◽  
Author(s):  
Mohamed Gharib ◽  
Mansour Karkoub
Keyword(s):  
Experimental Study ◽  
Free Vibration ◽  
Vibration Suppression ◽  
Free Vibrations ◽  
Offshore Platforms ◽  
3D Structures ◽  
High Rise ◽  
Particle Chain ◽  
Large Structures ◽  
Free Vibration Response

Vibration control of large structures has been the focus of a lot of research in recent years. Some of these structures include high rise buildings, offshore platforms, and bridges. In this article, we present the results of an experimental investigation of the usage of linear impact dampers in the control of the elasto-dynamic vibrations of 3D structures. Linear Particle Chain Impact Dampers (LPCIDs) are the off-spring of the commonly used conventional (single unit) impact damper. The free vibration response of a 3D symmetric frame subjected to a bidirectional initial condition is measured and analyzed. The objective is to examine the efficacy of the LPCID in attenuating the free vibrations of 3D frame structures. The settling times and amplitudes of vibration of the structure, with and without the LPCIDs, under free vibration conditions are measured and analyzed to study the efficacy of the dampers. The experimental study showed that the LPCID can be more effective in reducing the structure’s vibration when placed in specific orientations on the structure. Therefore, it can by concluded from the experiments’ outcomes that LPCIDs may be used to effectively attenuate the free vibrations of 3D structures.

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