• Structural Engineering and Mechanics
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• v.3 no.3
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• pp.289-297
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• 1995

A finite element algorithm for consideration of contact constraints is presented. It is characterized by introducing the geometric constraints, resulting from contact conditions, directly into the algebraic system of equations for the incremental displacements of an incremental iterative solution procedure. The usefulness of the proposed algorithm for efficient solutions of contact problems involving large displacements and large strains is demonstrated in the numerical investigation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.33-39
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• 1991

This Paper presents a geometrically nonlinear behaviors of shell problems by using the three-dimensional curved shell element, which includs large displacements and large rotations. The standard formulation of the geometrically nonlinearity is restricted to the assumption of infinitesmal rotation increments. This standard formulation for the displacement function is numerically improved by considering the second order expansions of Tayler series. The nonlinear behaviors of the single and double curved shells are compared wi th the other results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.788-791
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• 2005

Nodal displacements are referred to the Initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian formulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid fer structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacements and traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One closed loop structure undergoing large deformations is analyzed to demonstrate the efficiency and validity of the proposed method.

• Smart Structures and Systems
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• v.30 no.4
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• pp.411-420
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• 2022

Monitoring large structures is a significant issue involving public health on which new studies are constantly carried out. Although the Global Navigation Satellite System (GNSS) is the most preferable method for measuring structural displacements, total stations, one of the classical geodetic instruments, are the first devices that come to mind in cases that require complementary usage and auxiliary measurement methods. In this study, the relative displacements of the structural movements of a tower were determined using robotic total stations (RTS) and GNSS. Two GNSS receivers and two RTS observations were carried out simultaneously for 10 hours under normal weather conditions. The spectral analysis of the GNSS data was performed using fast Fourier transform (FFT), and while the dominant modal frequencies were determined, the total station data were balanced with the least-squares technique, and the position and position errors were calculated for each measurement epoch. It has been observed that low-frequency structural movements can be determined by both methods. This result shows that total station measurements are a helpful alternative method for monitoring large structures in situations where measurements are not possible due to the basic handicaps of GNSS or where it is necessary to determine displacements with short observations.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.275-282
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• 2021

Failure mechanism which can affect geotechnical infrastructures (shallow foundations, retaining walls, and piles) constitutes one of the most encountered problems during the design process. In this respect, the shear behavior of interfaces between grained soils and solid building materials, as well as those between cohesive soils should be investigated. Therefore, a range of ring shear tests with different cohesive soils and stainless-steel interfaces have been carried out through the Bromhead apparatus that allows simulating large displacements along a failure surface. The effects of steel rings roughness and soil type on the residual friction coefficient and the shear zone features (structure, thickness, and texture orientation angle) have been investigated using the Scanning Electron Microscopy. The obtained results indicate that the residual friction coefficient and the structural characteristics of the shear zone vary according to the surface roughness and the soil type. Scanning electron microscopy reveals that the particles inside the shear zone tend to be re-oriented. Also, the shear failure mechanism can be identified along with the interface, within the soil, or simultaneously at the interface and within the soil specimen.

• Journal of Korean Association for Spatial Structures
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• v.16 no.1
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• pp.65-72
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• 2016

Aerodynamic performance of solar wing system has been evaluated through wind tunnel test. The test model has 12 panels, each supported by 2 cables. The panels were installed horizontally flat, and gaps between panels were set constant. Sag ratios of 2% and 5%, and wind directions between $0^{\circ}$ and $90^{\circ}$ were considered. Mass of test model was determined considering the mass of full scale model, and Froude number and Elastic parameter were satisfied by adjusting the mean wind speed. From the wind tunnel test, it was found that the aerodynamic performance of the solar wing system is very dependent on the wind directions and sag ratios. When the sag was 2%, the fluctuating displacements between the wind directions of $0^{\circ}$ and $30^{\circ}$ increase proportionally to the square of the mean wind speed, implying buffeting-like vibration and a sudden increase in fluctuating displacement was found at large mean wind speed for the wind directions larger than $40^{\circ}$. When the wind direction was larger than $60^{\circ}$, a sudden increase was found both at low and large mean wind speed. When the sag ratio is 5%, distribution of mean displacements is different from that of sag ratio of 2%, and the fluctuating displacements show very different trend from that of sag ratio of 2%.

• Structural Engineering and Mechanics
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• v.71 no.6
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• pp.683-697
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• 2019

The reinforced concrete (RC) structures usually suffer large residual displacements under strong motions. The large residual displacements may substantially reduce the anti-seismic capacity of structures during the aftershock and increase the difficulty and cost of structural repair after an earthquake. To reduce the adverse residual displacement, several self-centering energy dissipation braces (SCEBs) have been proposed to be installed to the RC structures. To investigate the seismic responses of the RC structures with SCEBs under the earthquake excitation, an extended Bouc-Wen model with degradation and self-centering effects is developed in this study. The extended model realized by MATLAB/Simulink program is able to capture the hysteretic characteristics of the RC structures with SCEBs, such as the energy dissipation and the degradation, especially the self-centering effect. The predicted hysteretic behavior of the RC structures with SCEBs based on the extended model, which used the unscented Kalman filter (UKF) for parameter identification, is compared with the experimental results. Comparison results show that the predicted hysteretic curves can be in good agreement with the experimental results. The nonlinear dynamic analyses using the extended model are then carried out to explore the seismic performance of the RC structures with SCEBs. The analysis results demonstrate that the SCEB can effectively reduce the residual displacements of the RC structures, but slightly increase the acceleration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.534-539
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• 2005

Nodal displacements are referred to the initial configuration in the total Lagrangian formulation and to the last converged configuration in the updated Lagrangian furmulation. This research proposes a relative nodal displacement method to represent the position and orientation for a node in truss structures. Since the proposed method measures the relative nodal displacements relative to its adjacent nodal reference frame, they are still small for a truss structure undergoing large deformations for the small size elements. As a consequence, element formulations developed under the small deformation assumption are still valid for structures undergoing large deformations, which significantly simplifies the equations of equilibrium. A structural system is represented by a graph to systematically develop the governing equations of equilibrium for general systems. A node and an element are represented by a node and an edge in graph representation, respectively. Closed loops are opened to form a spanning tree by cutting edges. Two computational sequences are defined in the graph representation. One is the forward path sequence that is used to recover the Cartesian nodal displacements from relative nodal displacement sand traverses a graph from the base node towards the terminal nodes. The other is the backward path sequence that is used to recover the nodal forces in the relative coordinate system from the known nodal forces in the absolute coordinate system and traverses from the terminal nodes towards the base node. One open loop and one closed loop structure undergoing large deformations are analyzed to demonstrate the efficiency and validity of the proposed method.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.1
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• pp.69-76
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• 2017

Seismic analyses of a pile under a large rigid basement foundation embedded in the homogeneous soil layer were performed practically by a response displacement method assuming a sinusoidal wave form. However, it is hard to take into account the characteristics of a large mat foundation and a heterogeneous soil layer with the response displacement method. The response displacement method is relevant to the 2D problems for longitudinal structures such as tunnel, underground cave structure, etc., but might not be relevant with isolated foundations for building structures. In this study, seismic pile analysis by a pseudo 3D finite element method was carried out to compare numerical results with results of the response displacement method considering 3D characteristics of a foundation-soil system which is important for the building foundation analyses. Study results show that seismic analyses results of a response displacement method are similar to those of a pseudo 3D numerical method for stiff and dense soil layers, but they are too conservative for a soft soil layer inducing large soil pressures on the foundation wall and large pile displacements due to ignored foundation rigidity and resistance.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.495-502
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• 2016

In this paper, time and frequency domain characteristics of Gyeong-ju earthquakes were investigated, and nonlinear time history analyses were conducted for bi-linear hysteretic structures excited by short-duration ground accelerations. Previous studies showed that larger inelastic displacements than the peak displacement of the corresponding elastic system were observed especially for the structures with structural period shorter than 0.3s, and the similar results could be obtained when long-duration ground accelerations were used as excitation loads. For the short-duration earthquakes, however, the inelastic displacements were not so large and almost identical to the peak elastic displacements.