• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.1
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• pp.91-96
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• 1997

In order to ensure the safety of a structure, it is essential to put in practice all sorts of measurement from the plan and execution to the management by stages. These measurements make it possible to verify a propriety of a plan and forecast an accident or a collapse caused by long lapse of time, making use of accumulated data. Close-Range Photogrammetry is a method to meet improvement and development of surveting technique. which offered data for maintenance and management of a structure. Dus to applying this way. reliance on measuring a variation of structure. Besides, data of variation will be utilized for maintenance and management of a structure.

• Wind and Structures
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• v.19 no.3
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• pp.233-247
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• 2014

Vortex-induced oscillation is a type of aeroelastic phenomenon, to which extended structures such as long-span bridges are most susceptible. The vortex-induced vibration (VIV) behaviors of a concerned bridge were investigated conventionally in virtue of wind tunnel tests on string-mounted sectional models. This necessitates the building of a linkage between the response of the sectional model and that of the prototype structure. Although many released literatures have related to this issue and provided suggestions, there is a lack of consistency among them. In this study, some theoretical models describing the vortex-induced structural motion, including the linear empirical model, the nonlinear empirical model and the modified (or generalized) nonlinear empirical model, are firstly reviewed. Then, the concept of equivalent mass density is introduced based on the principle that an equal input of energy should result in identical structural amplitudes. Based on these, the theoretical linkages between the amplitude of a section model and that corresponding to the prototype bridge are discussed with different analytical models. Theoretical derivation indicates that such connections are dependent mainly on two factors, one is the presupposed shape of deformation, and the other is the theoretical VIV model employed. The theoretical analysis in this study shows that, in comparison to the nonlinear empirical models, the linear one can result in obvious larger estimations of the full bridges' responses, especially in cases of cable-stayed bridges.

• Smart Structures and Systems
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• v.3 no.3
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• pp.385-403
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• 2007

The effectiveness of the newly developed smart passive control system employing a magnetorheological (MR) damper and an electromagnetic induction (EMI) part for seismic protection of base isolated structures is numerically investigated. An EMI part in the system consists of a permanent magnet and a coil, which changes the kinetic energy of the deformation of an MR damper into the electric energy (i.e. the induced current) according to the Faraday's law of electromagnetic induction. In the smart passive control system, the damping characteristics of an MR damper are varied with the current input generated from an EMI part. Hence, it does not need any control system consisting of sensors, a controller and an external power source. This makes the system much simpler as well as more economic. To verify the efficacy of the smart passive control system, a series of numerical simulations are carried out by considering the benchmark base isolated structure control problems. The numerical simulation results show that the smart passive control system has the comparable control performance to the conventional MR damper-based semiactive control system. Therefore, the smart passive control system could be considered as one of the promising control devices for seismic protection of seismically excited base isolated structures.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.54-59
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• 2012

Deformation of Lead plate blast pressure meter were measured after they were exposed to surface blasting. Blasting pressure was determined by comparing the data with calibration graph which was drawn from the laboratory experiments with gas gun of Hopkinson bar tester. The results were compared with calculated values from the equations of CONWEP (Conventional Weapons Effects Program) and DDESB (Department of Defence Explosives Safety Board). Measured values were lower than calculated values in near field. Gradual decaying tendency of the pressure was observed. It means that estimated blasting pressure of very near field with theoretical equations can be uncertain.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.24-34
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• 2007

Closed-loop active twist control of integral helicopter rotor blades is investigated in this paper for reducing hub vibration induced in forward flight. A four-bladed fully articulated integral twist-actuated rotor system has been designed and tested successfully in wind tunnel in open-loop actuation. The integral twist deformation of the blades is generated using active fiber composite actuators embedded in the composite blade construction. An analytical framework is developed to examine integrally twisted helicopter blades and their aeroelastic behavior during different flight conditions. This aeroelastic model stems from a three-dimensional electroelastic beam formulation with geometrical-exactness, and is coupled with finite-state dynamic inflow aerodynamics. A system identification methodology that assumes a linear periodic system is adopted to estimate the harmonic transfer function of the rotor system. A vibration minimizing controller is designed based on this result, which implements a classical disturbance rejection algorithm with some modifications. Using the established analytical framework, the closed-loop controller is numerically simulated and the hub vibratory load reduction capability is demonstrated.

• International Journal of Ocean System Engineering
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• v.1 no.2
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• pp.110-119
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• 2011

Numerical and experimental studies were performed to investigate the aerodynamic performance of a thin wing in close vicinity to the ground. The vortex lattice method (VLM) was utilized to simulate the wing in ground (WIG) effect, which included freely deforming wake elements. The numerical results acquired through the VLM were compared to the experimental results. The experiment entailed varying the ground clearance using the DHMTU (Department of Hydromechanics of the Marine Technical University of Saint Petersburg) wing and the WIG craft model in the wind tunnel. The aero-dynamic influence of the design parameters, such as angles of attack, aspect ratios, taper ratios, and sweep angles were studied and compared between the numerical and experimental results associated with the WIG craft. Both numerical and experimental results suggested that the endplate augments the WIG effect for a small ground clearance. In addition, the vortex lattice method simulated the wake deformation following the wing in the influence of the ground effect.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.387-394
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• 2000

This is study investigates the changes of subsidence and hydraulic conductivity by underground mining Coupling between post-mining induced strains and strain-dependent hydraulic conductivities is obtained by idealizing a jointed rock mass as an equivalent porous medium in which the hydraulic conductivity of a single joint is defined through parallel plate description. Results indicate that post-mining hydraulic conductivities are directly related to the strain field occurred by subsidence induced deformation. Maximum subsidence and hydraulic conductivity values increase as a panel width does widen. Joint spacing has an effect on the intensity of the changes in hydraulic conductivity.

• Wind and Structures
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• v.16 no.3
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• pp.279-300
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• 2013

This paper presents a new analysis framework for predicting the internal buffeting forces in bridge components under skew wind. A linear regressive model between the internal buffeting force and deformation under normal wind is derived based on mathematical statistical theory. Applying this regression model under normal wind and the time history of buffeting displacement under skew wind with different yaw angles in wind tunnel tests, internal buffeting forces in bridge components can be obtained directly, without using the complex theory of buffeting analysis under skew wind. A self-anchored suspension bridge with a main span of 260 m and a steel arch bridge with a main span of 450 m are selected as case studies to illustrate the application of this linear regressive framework. The results show that the regressive model between internal buffeting force and displacement may be of high significance and can also be applied in the skew wind case with proper regressands, and the most unfavorable internal buffeting forces often occur under yaw wind.

• Structural Engineering and Mechanics
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• v.46 no.5
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• pp.735-753
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• 2013

The wind load is always the dominant load of cooling tower due to its large size, complex geometry and thin-wall structure. At present, when computing the wind-induced response of the large-scale cooling tower, the wind pressure distribution is obtained based on code regulations, wind tunnel test or computational fluid dynamic (CFD) analysis, and then is imposed on the tower structure. However, such method fails to consider the change of the wind load with the deformation of cooling tower, which may result in error of the wind load. In this paper, the analysis of the large cooling tower based on the iterative method for wind pressure is studied, in which the advantages of CFD and finite element method (FEM) are combined in order to improve the accuracy. The comparative study of the results obtained from the code regulations and iterative method is conducted. The results show that with the increase of the mean wind speed, the difference between the methods becomes bigger. On the other hand, based on the design of experiment (DOE), an approximate model is built for the optimal design of the large-scale cooling tower by a two-level optimization strategy, which makes use of code-based design method and the proposed iterative method. The results of the numerical example demonstrate the feasibility and efficiency of the proposed method.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.2
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• pp.11-17
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• 2009

Terrestrial LiDAR can measure high capacity 3D-topography coordinates and try to apply to various public works such as tunnel surveying, facility deformation surveying. This experiment is about how to calculate ground cutting volume because the stage of the earth work spend lots of money and time among civil engineering works. Surveying cutting area using Terrestrial LiDAR and then calculating cutting area in planned area comparing sectional plan before construction and planned section and LiDAR data. Also, the values of the calculating ground cutting volume by three different resolution LiDAR has are compared and analyzed.