scholarly journals Evaluation of Nonlinear Material Behavior for Offshore Structures Subjected to Accidental Actions

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Martin Storheim ◽  
Hagbart S. Alsos ◽  
Jørgen Amdahl
Keyword(s):  
Structural Response ◽  
Offshore Structures ◽  
The Body ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Strain Rate Effects ◽  
Nonlinear Structural ◽  
Rate Effects ◽  
High Degree ◽  
Nonlinear Structural Response

Evaluation of the nonlinear structural response of any structure is a challenging task; a range of input parameters are needed, most of which have significant statistical variability and the evaluations require a high degree of craftsmanship. Hence, high demands are set forth both to the analyst and the body in charge of verification of the results. Recent efforts by DNVGL attempt to mitigate this with the second edition of the DNVGL-RP-C208 for the determination of nonlinear structural response, in which guidance or requirements are given on many of the challenging aspects. This paper discusses the various challenges and the direction to which the RP-C208 points compared to published research. Parameters affecting the plastic hardening, strain-rate effects, and ductile fracture are discussed separately. Then, the combined effect of the range of assumptions is evaluated to assess the resulting level of safety.

scholarly journals Evaluation of Nonlinear Material Behavior for Offshore Structures Subjected to Accidental Actions

2017 ◽  
Author(s):  
Martin Storheim ◽  
Hagbart S. Alsos ◽  
Jørgen Amdahl
Keyword(s):  
Structural Response ◽  
Offshore Structures ◽  
The Body ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Strain Rate Effects ◽  
Nonlinear Structural ◽  
Rate Effects ◽  
High Degree ◽  
Nonlinear Structural Response

Evaluation of the nonlinear structural response of any structure is a challenging task; a range of input parameters are needed, most of which has significant statistical variability and the evaluations require a high degree of craftsmanship. Hence, high demands are set forth both to the analyst and the body in charge of verification of the results. Recent efforts by DNVGL attempts to mitigate this with the second edition of the DNVGL-RP-C208 for determination of nonlinear structural response, in which guidance or requirements are given on many of the challenging aspects. This paper discuss the various challenges and the direction to which the RP-C208 points compared to published research. Parameters affecting the plastic hardening, strain-rate effects and ductile fracture are discussed separately. Then, the combined effect of the range of assumptions is evaluated to assess the resulting level of safety.

Nonlinear Structural Consequence Analysis of FPSO Topsides Under Fire

2012 ◽  
Author(s):  
Jeong Hwan Kim ◽  
Du Chan Kim ◽  
Cheol Kwan Kim ◽  
Md. Shafiqul Islam ◽  
Jeom Kee Paik
Keyword(s):  
Structural Response ◽  
Fire Risk ◽  
Offshore Structures ◽  
Nonlinear Material ◽  
Response Analysis ◽  
Element Analysis ◽  
Practical Procedure ◽  
Consequence Analysis ◽  
Nonlinear Structural ◽  
Structural Consequence

This study aims to develop a practical procedure for the nonlinear structural consequence analysis of structures under fire. The thermal and structural response analysis have been performed in this study using a commercial nonlinear Finite Element Analysis (FEA) code. The results of the structural response analysis are then compared to the experimental results. This study concludes by presenting methods for fire load applications and nonlinear material modeling. The insights offered by the modeling techniques and analysis procedures presented in this study should be very useful and practical in the fire risk assessment of offshore structures.

Structural Response and Remaining Life of Damaged Composites

2015 ◽  
Vol 813-814 ◽  
pp. 106-110
Author(s):  
Dalbir Singh ◽  
C. Ganesan ◽  
A. Rajaraman
Keyword(s):  
Hybrid Approach ◽  
Experimental Studies ◽  
Structural Response ◽  
Material Behavior ◽  
Experimental Results ◽  
Life Assessment ◽  
Nonlinear Material ◽  
Remaining Life ◽  
Design Effectiveness ◽  
Remaining Life Assessment

Composites are being used in variety of applications ranging from defense and aircraft structures, where usage is profuse, to vehicle structures and even for repair and rehabilitation. Most of these composites are made of different laminates glued together with matrix for binding and now-a-days fibers of different types are embedded in a composite matrix. The characterizations of material properties of composites are mostly experimental with analytical modeling used to simulate the system behavior. But many times, the composites develop damage or distress in the form of cracking while they are in service and this adds a different dimension as one has to evaluate the response with the damage so that its performance during its remaining life is satisfactory. This is the objective of the present study where a hybrid approach using experimental results on damaged specimens and then analytical finite element are used to evaluate response. This will considerably help in remaining life assessment-RLA- for composites with damage so that design effectiveness with damage could be assessed. This investigation has been carried out on a typical composite with carbon fiber reinforcements, manufactured by IPCL Baroda (India) with trade name INDCARF-30. Experimental studies were conducted on undamaged and damaged specimens to simulate normal continuous loading and discontinuous loading-and-unloading states in actual systems. Based on the experimental results, material characterization inputs are taken and analytical studies were carried out using ANSYS to assess the response under linear and nonlinear material behavior to find the stiffness decay. Using stiffness decay RLA was computed and curves are given to bring the influence of type of damage and load at which damage had occurred.

An Assessment of Load and Response for Horizontal Slamming Loads From Model Scale Experiments

2018 ◽  
Author(s):  
Martin Storheim ◽  
Gunnar Lian
Keyword(s):  
Structural Response ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Load Level ◽  
Material Behavior ◽  
Wave Impact ◽  
Large Variability ◽  
Slamming Load ◽  
Reasonable Approach ◽  
Wave Slamming

Steep breaking waves can result in high impact loads on offshore structures, and several model test campaigns have been conducted to assess the effect of horizontal wave slamming. High loads have been measured, and they can be challenging to withstand without significant deformation. For wave slamming problems it is common to estimate the characteristic slamming load and assume that this will give an equivalent characteristic response. One challenge related to the slamming load is that it has a large variability in load level, the duration of the load and the shape of the overall load pulse. This variability can have a large impact on the estimated response to the characteristic load, causing a similar or larger variability in response. Due to the sensitivity to the structural response, it may be difficult to interpret large amounts of such data to arrive at a relevant design load without making overly conservative assumptions. This paper investigates the sensitivity of the structural response to assumptions made in the material modelling and how the short term variability is affected if we instead of load use response indicators such as plastic strain and max deformation to arrive at a characteristic load. For this purpose, a simplified dynamic response model is created, and the recorded wave impact events can then be evaluated based on the predicted structural response from the simplified model. It was found that the structural response is sensitive to the structural configuration. The assumed material behavior and hydro-elastoplastic effects were identified to greatly affect the structural response. A reasonable approach to arrive at the q-annual response seems to be to first estimate the q-annual extreme slamming load, and then run the structural analysis on several of the measured slamming time series with the estimated q-annual extreme pressure.

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