• Computers and Concrete
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• v.24 no.6
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• pp.561-570
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• 2019

Understanding the realistic behavior of concrete up to failure under different loading conditions within the framework of damage mechanics and plasticity would lead to an enhanced design of concrete structures. In the present investigation, QR (Quick Response) code based random speckle pattern is used as a non-contact sensor, which is an innovative approach in the field of digital image correlation (DIC). A four-point bending test was performed on RC beams of size 1800 mm × 150 mm × 200 mm. Image processing was done using an open source Ncorr algorithm for the results obtained using random speckle pattern and QR code based random speckle pattern. Load-deflection curves of RC beams were plotted for the results obtained using both contact and non-contact (DIC) sensors, and further, Moment (M)-Curvature (κ) relationship of RC beams was developed. The loading curves obtained were used as input data for material model parameters in finite element analysis. In finite element method (FEM) based software, concrete damage plasticity (CDP) constitutive model is used to predict the realistic nonlinear quasi-static flexural behavior of RC beams for monotonic loading condition. The results obtained using QR code based DIC are observed to be on par with conventional results and FEM results.

• Steel and Composite Structures
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• v.20 no.3
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• pp.501-512
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• 2016

High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.168-173
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• 2002

The durability test, along with the crashworthiness test, requires the most time and expense in the vehicle development process. The durability design using CAE tools reduces the time required for both the durability test and actual vehicle production. Existing dynamic stress analyses designed fir the analysis of vehicle fatigue mainly calculate the dynamic stress history and fatigue after performing dynamic analysis and stress analysis with relevant software applications and then superpositioning the dynamic load history and stress influence coefficient at each joint. This approach is a complex process, taking into account the flexibility of the parts. It is, however, incapable of giving accurate consideration to the contacts between components, the non-linearity of materials, and tire-road surface interactions. This approach also requires that the analysts have an expertise in software applications of various kinds or an expert in each area must perform the analysis. This requires as a great deal of manpower and time. In order to complement the existing approaches for dynamic stress analysis, this study aims at the following: (1) to suggest the simple and accurate analysis technique which is capable of producing all the possible necessary results; (2) to reduce dramatically the time and manpower needed to construct a model designed to analyze dynamics, quasi-static stress, and fatigue; and (3) to enable an accurate analysis of fatigue by improving the accuracy of dynamic stress. we verify the presented analysis method through durability evaluation of the knuckle of passenger car.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.195-203
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• 2008

This paper aims to evaluate the yield stress of SM570TMC concrete-filed H-shape steel columns subjected to axial force. These columns were evaluated and compared using quasi-static tests. The displacements and the axial loads column specimens were measured during the tests, and test results showed that the yield stress of concrete-filed H-shape steel columns subjected to axial load could be predicted using the previously proposed yield stress of steel columns.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.260-267
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• 2016

Considering the effect of dynamic response amplification, a reliability analysis of an offshore wind turbine support structure under an earthquake is presented. A reliability analysis based on the dynamic response requires a large amount of time when using not only a level 3 approach but also level 2 such as a first order reliability method (FORM). Moreover, if a limit state is defined by using the maximum stress at a structural joint where stress concentration occurs, a three-dimensional element should be used in the finite element analysis. This makes the computational load much heavier. To deal with this kind of problem, two techniques are suggested in this paper. One is the application of a quasi-static structural analysis that takes the dynamic amplification effect into account. The other is the use of a stress concentration factor to estimate the maximum local stress. The proposed reliability analysis is performed using a level 2 FORM and verified using a level 3 simulation approach.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.60
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• pp.37-46
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• 2000

A biomechanical model of lower extremity in seated postures was developed to assess muscular activities of lower extremity involved in a variety of foot pedal operations. The model incorporated four rigid body segments with the twenty-four muscles to represent lower extremity This study deals with quasi-static movement to investigate dynamic movement effect in seated foot operation. It is found that optimization method which has been used for modeling the articulated body segments does not predict the forces generated from biarticular muscles and antagonistic muscles reasonably. So, the revised nonlinear optimization scheme was employed to consider the synergistic effects of biarticular muscles and the antagonistic muscle effects from the stabilization of the joint. For the model validation, three male subjects performed the experiments in which EMG activities of the nine lower extremity muscles were measured. Predicted muscle forces were compared with the corresponding EMG amplitudes and it showed no statistical difference. For the selection of optimal seated posture, a physiological meaningful criterion was developed for muscular load sharing developed. For exertion levels, the transition point of type F motor unit of each muscle is inferred by analyzing the electromyogram at the seated postures. Also, for predetermined seated foot operations exertion levels, the recruitment pattern is identified in the continuous exertion, by analyzing the electromyogram changes due to the accumulated muscle fatigue.

• Earthquakes and Structures
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• v.16 no.1
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• pp.41-54
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• 2019

Reinforced Concrete (RC) shear walls are widely used in Nuclear power plants as effective lateral force resisting elements of the structure and these may experience nonlinear behavior for higher earthquake demand. Short shear walls of aspect ratio less than 1.5 generally experience combined shear flexure interaction. This paper presents the results of the displacement-controlled experiments performed on six RC short shear walls with varying aspect ratios (1, 1.25 and 1.5) for monotonic and reversed quasi-static cyclic loading. Simulation of the shear walls is then carried out by Finite element modeling and also by macro modeling considering the coupled shear and flexure behaviour. The shear response is estimated by softened truss theory using the concrete model given by Vecchio and Collins (1994) with a modification in softening part of the model and flexure response is estimated using moment curvature relationship. The accuracy of modeling is validated by comparing the simulated response with experimental one. Moreover, based on the experimental work a multi-linear hysteretic model is proposed for short shear walls. Finally ultimate load, drift, ductility, stiffness reduction and failure pattern of the shear walls are studied in details and hysteretic energy dissipation along with damage index are evaluated.

• Steel and Composite Structures
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• v.44 no.3
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• pp.423-436
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• 2022

This paper proposes an innovative thin-walled square concrete filled steel tubular (CFST) column with an octagonal/circular lining steel tube, in which the outer steel tube and the inner liner are fabricated independently of each other and connected by slot-weld or self-tapping screw connections. Twelve thin-walled square CFST columns were tested under quasi-static loading, considering the parameters of liner type, connection type between the square tube and liner, yield strength of steel tube, and the axial load ratio. The seismic performance of the thin-walled square CFST columns is effectively improved by the octagonal and circular liners, and all the liner-stiffened specimens showed an excellent ductile behavior with the ultimate draft ratios being much larger than 1/50 and the ductility coefficients being generally higher than 4.0. The energy dissipation abilities of the specimens with circular liners and self-tapping screw connections were superior to those with octagonal liner and slot-weld connections. Based on the test results, both the finite element (FE) and simplified theoretical models were established, considering the post-buckling strength of the thin-walled square steel tube and the confinement effect of the liners, and the proposed models well predicted the hysteretic behavior of the liner-stiffened specimens.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.501-519
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• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.

• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.347-368
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• 2023

In the first part of this study, a numerical simulation model was developed using the mechanical APDL software to validate the results of the 3D-elastisity theory on the laminated sandwich plate developed by Panago. The numerical simulation model showed a good agreement to the results of Pagano's theory in terms of deflection, normal stresses, and shear stresses. In the second part of this study, the developed numerical simulation model was used to define different plates dimensions and fibers layup orientations to examine the load response in terms of deflection and stresses. Further analysis was implemented on the natural frequencies of laminated xxx plates of the plates. The layup configurations include Unidirectional (UD), Cross-Ply (CP), Quasi-Isotropic (QI), the linear bio-inspired known as Linear-Helicoidal (LH), and the nonlinear bio-inspired known as Fibonacci-Helicoidal (FH). The following numerical simulation model can be used for the design and study of novel, sophisticated bio-inspired composite structures in a variety of configurations subjected to sinusoidal or constant loads.