The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Hyun Kyoung Shin - One of the best experts on this subject based on the ideXlab platform.
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repeated lateral impacts on steel Grillage structures at room and sub zero temperatures
International Journal of Impact Engineering, 2018Co-Authors: Dac Dung Truong, Hyun Kyoung ShinAbstract:Abstract This paper presents experimental and numerical investigation results for the plastic response of steel Grillages, represented by one longitudinal stiffener and two transverse stiffeners of stiffened plates, used on ships or offshore structures under repeated mass impacts. The repeated mass impact scenario adopted in this paper could represent the repetition of impacted loads on marine structures due to contact with ice floes and floating objects during service. Repeated impact tests on Grillage models at room and sub-zero temperatures (−50 °C) were conducted by releasing a knife-edge striker using a drop testing machine. The ends of the Grillage models were firmly fixed onto a strong bed with support fixtures. To evaluate the repeated impact performance of the tested models, permanent deflections were measured after each impact test. Additionally, numerical simulations were performed using the commercial software package ABAQUS/Explicit to predict the extent of damage to the tested models caused by repeated impacts. In the calculations, the material properties of tested models were used to determine the strain hardening and strain rate hardening model using the equations recently proposed by the authors. Also, a simple analytical approach has been proposed to predict the damage evolution of the Grillage subjected to repeated mass impacts. Reasonable agreement was achieved between the predictions and test results. The results showed that when the structure was repeatedly impacted, permanent deflections of the Grillage significantly increased with increasing impact force. The permanent deflections tended to have certain values when the number of impacts increased. Based on the numerical results (which were substantiated with the experimental results), further calculations were then carried out to examine impact responses in greater detail and assess the effects of variations in boundary conditions and strain rate definitions on the response of Grillages to repeated mass impacts.
Tayfun Dede - One of the best experts on this subject based on the ideXlab platform.
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jaya algorithm to solve single objective size optimization problem for steel Grillage structures
Steel and Composite Structures, 2018Co-Authors: Tayfun DedeAbstract:The purpose of this paper is to present a new and efficient optimization algorithm called Jaya for optimum design of steel Grillage structure. Constrained size optimization of this type of structure based on the LRFD-AISC is carried out with integer design variables by using cross-sectional area of W-shapes. The objective function of the problem is to find minimum weight of the Grillage structure. The maximum stress ratio and the maximum displacement in the inner point of steel Grillage structure are taken as the constraint for this optimization problem. To calculate the moment and shear force of the each member and calculate the joint displacement, the finite elements analysis is used. The developed computer program for the analysis and design of Grillage structure and the optimization algorithm for Jaya are coded in MATLAB. The results obtained from this study are compared with the previous works for Grillage structure. The results show that the Jaya algorithm presented in this study can be effectively used in the optimal design of Grillage structures.
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Optimum design of Grillage structures to LRFD-AISC with teaching-learning based optimization
Structural and Multidisciplinary Optimization, 2013Co-Authors: Tayfun DedeAbstract:In this paper, a new efficient optimization algorithm called Teaching–Learning-Based Optimization (TLBO) is used for the optimum design of Grillage systems based on the LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Construction). Cross sectional area of W-shapes are considered as discrete design variables. Various Grillage structures are designed to show the efficiency of the TLBO algorithm. The results obtained from this study are compared with those reported in the literature. It is concluded that the TLBO algorithm presented in this study can be effectively used in the optimal design of Grillage structures.
Dac Dung Truong - One of the best experts on this subject based on the ideXlab platform.
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repeated lateral impacts on steel Grillage structures at room and sub zero temperatures
International Journal of Impact Engineering, 2018Co-Authors: Dac Dung Truong, Hyun Kyoung ShinAbstract:Abstract This paper presents experimental and numerical investigation results for the plastic response of steel Grillages, represented by one longitudinal stiffener and two transverse stiffeners of stiffened plates, used on ships or offshore structures under repeated mass impacts. The repeated mass impact scenario adopted in this paper could represent the repetition of impacted loads on marine structures due to contact with ice floes and floating objects during service. Repeated impact tests on Grillage models at room and sub-zero temperatures (−50 °C) were conducted by releasing a knife-edge striker using a drop testing machine. The ends of the Grillage models were firmly fixed onto a strong bed with support fixtures. To evaluate the repeated impact performance of the tested models, permanent deflections were measured after each impact test. Additionally, numerical simulations were performed using the commercial software package ABAQUS/Explicit to predict the extent of damage to the tested models caused by repeated impacts. In the calculations, the material properties of tested models were used to determine the strain hardening and strain rate hardening model using the equations recently proposed by the authors. Also, a simple analytical approach has been proposed to predict the damage evolution of the Grillage subjected to repeated mass impacts. Reasonable agreement was achieved between the predictions and test results. The results showed that when the structure was repeatedly impacted, permanent deflections of the Grillage significantly increased with increasing impact force. The permanent deflections tended to have certain values when the number of impacts increased. Based on the numerical results (which were substantiated with the experimental results), further calculations were then carried out to examine impact responses in greater detail and assess the effects of variations in boundary conditions and strain rate definitions on the response of Grillages to repeated mass impacts.
Norman Jones - One of the best experts on this subject based on the ideXlab platform.
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dynamic response of a Grillage under mass impact
International Journal of Impact Engineering, 1993Co-Authors: Norman JonesAbstract:Abstract An approximate theoretical analysis is presented in this paper for the dynamic plastic response of a clamped beam Grillage when struck transversely by a mass at the centre which produces large transverse displacements. The theoretical rigid-plastic predictions are compared with some recent experimental results on Grillages struck by large masses and the predictions of a quasi-static method of analysis. The influence of inertia is explored for the behaviour of a Grillage when struck by a small striker travelling with a high velocity.
Claude Daley - One of the best experts on this subject based on the ideXlab platform.
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evaluation of large structural Grillages subjected to ice loads in experimental and numerical analysis
Marine Structures, 2018Co-Authors: Claude DaleyAbstract:Abstract Laboratory-grown cone-shaped ice specimens (1 m diameter) were utilized to load large structural Grillages into a plastic response domain. The scantlings of the Grillages were typical of a transversely framed mid-body ice belt arrangement of a 10,000 ton Ice Class PC6 vessel. The maximum loads reached levels well beyond the elastic limit of the material and any acceptable plastic design point. The tests allowed for an evaluation of highly non-linear structural behavior and overload capacity considering the simultaneous failure of ice. Two separate large structural Grillage tests were carried out with ice specimens loaded at a quasi-static loading rate (0.5 mm/s). The first set of tests were performed in two loading steps at identical loading positions at the mid-span of the central stiffener. The second set of tests were carried out in three loading steps at different loading positions along the span of the central stiffener of the Grillage as a sequence of right-off, center, and left-off center. The experiments led to unique insight into the overload response and load carrying capacity of a large structural Grillage as well as the effect of prior plastic damage on the structural behavior. Load-deflection curves and deformed shapes measured by MicroScribe® were compared with the results of nonlinear finite element (FE) analysis. The FE analysis results show a strong agreement with the physical experiments, which confirms that the nonlinear FE analysis is a suitable tool for the analysis of ice-strengthened ship structures subjected to extreme ice loading.
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controlled plastic deformation of a Grillage using artificial freshwater ice at a large scale
22nd International Conference on Port and Ocean Engineering under Arctic Conditions (POAC'13)Federation of Finnish Learned SocietiesABSEspoo City of F, 2013Co-Authors: Mike Manuel, Claude Daley, Phani Suresh Reddy Gudimelta, Bruce ColbourneAbstract:This paper discusses the elastic and plastic stress and strain experienced by steel Grillage structures during large-scale ice indentation tests undertaken in a laboratory setting. The work is part of the STePS2 (Sustainable Technology for Polar Ships and Structures) project, a 5-year engineering research project at Memorial University. The present work builds on previous experiments and is a part of a multi-stage project to investigate high-energy ice-structure collisions. The current experiments involve artificial glacial (freshwater) ice blocks loaded into a Grillage representative of full-scale ship structure. The ice block is quasi-statically crushed against the Grillage, and load and response data is recorded. Raw data is acquired through a network of strain gauges, and other instruments. The experiments are also recorded through several high-speed cameras. The work is unique in the scale of the tests, using realistic Grillages and ice blocks at forces and pressure loads representative of a real-world ship-ice interaction. During loading, the structural Grillage undergoes extensive plastic deformation but displays tremendous overload capacity, much more than the material’s yield point, while demonstrating significant remaining reserve strength.
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realistic moving ice loads and ship structural response
The Twenty-second International Offshore and Polar Engineering Conference, 2012Co-Authors: Bruce W T Quinton, Claude Daley, Robert E GagnonAbstract:Prior work by the authors has shown that moving ice loads incite a significantly different structural response in steel Grillage structures than do stationary ice loads. The work was based on a validated explicit numerical model of a steel Grillage. The main drawback was that the ice load model was largely unrealistic in terms of the distributed pressure and ice motions. The present work employs two realistic ice load models: a dynamic 4D pressure model, and a validated "crushable foam" ice model. Results using these realistic ice load models lend credence to previous findings and enable more realistic modeling of the whole ice-ship impact scenario.
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response of iacs uri ship structures to real time full scale operational ice loads
SNAME Transactions Volume 120, 2012Co-Authors: Bruce W T Quinton, Claude Daley, Robert E GagnonAbstract:Moving ice loads can incite significantly different structural responses in a steel Grillage structure than can stationary ice loads. This is significant because the accepted standard for the design and analysis of ice-classed ship structures is to assume a stationary ice load (LACS URI 12.3.1). The following work utilizes the 4D Pressure Method ((Quinton, Daley, and Gagnon 2012)) to apply thirty-five of the most significant ice loads recorded during the USCGC Polar Sea trials (1982-86), to fourteen IACS URI PCI-7 classed Grillages; using explicit finite element analyses. Two Grillage variations for each of the seven PC classes were examined: Grillages with "built T" framing and Grillages with "flatbar" framing. In short, the following simulations directly employ real-time/real-space measured full-scale ice loads, and thus provide insight into the structural capabilities of the various IACS URI polar classes when subject to actual (moving) ice loads.
