• Smart Structures and Systems
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• 제10권4_5호
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• pp.485-499
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• 2012

Mode shape expansion is useful in structural dynamic studies such as vibration based structural health monitoring; however most existing expansion methods can not consider the modelling errors in the finite element model and the measurement uncertainty in the modal properties identified from vibration data. This paper presents a reliable approach for expanding mode shapes with consideration of both the errors in analytical model and noise in measured modal data. The proposed approach takes the perturbed force as an unknown vector that contains the discrepancies in structural parameters between the analytical model and tested structure. A regularisation algorithm based on the Tikhonov solution incorporating the L-curve criterion is adopted to reduce the influence of measurement uncertainties and to produce smooth and optimised expansion estimates in the least squares sense. The Canton Tower benchmark problem established by the Hong Kong Polytechnic University is then utilised to demonstrate the applicability of the proposed expansion approach to the actual structure. The results from the benchmark problem studies show that the proposed approach can provide reliable predictions of mode shape expansion using only limited information on the operational modal data identified from the recorded ambient vibration measurements.

• 한국구조물진단유지관리공학회 논문집
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• 제22권6호
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• pp.1-8
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• 2018

본 연구의 목적은 해석적 방법을 통하여 내화 재료의 특성을 파악하고 섬유 강화 폴리머로 보강된 철근콘크리트의 보의 적절한 내화설계 방법을 제안하는 것이다. 이를 위해, 내화재료의 가열실험을 실시하고 유한요소해석을 통해 열전도율과 비열을 구하고 또한 고온에서 FRP로 보강된 철근콘크리트 보 실험체에 대한 유한요소 해석을 통해 실험결과와 해석결과를 비교하였다. 이 과정에서 실험과 해석적 접근의 신뢰성을 확인하였다. 최종적으로 FRP로 보강된 철근콘크리트 보의 열적특성을 제안된 해석 방법으로 분석하고 고온으로 감소된 휨내력을 계산하였다. 최종적으로 제안된 방법을 이용하여 FRP로 보강된 부재에서 고온 노출시 열특성을 반영한 부재의 열전도를 파악하고 이를 이용하여 내력을 산정할 수 있는 것으로 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.105-108
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• 2002

This paper analytical models of a centralized approach based on SNMP Protocol, distributed approach based on mobile agent, and mixed model which is tile existing mobile agent model in order to overcome large communication numbers of SNMP and accumulated data of mobile agent. And then, we compare and analyze these analytical models. Performance evaluation results show that performance of mobile agent and the mixed model is less sensitive to the network traffic and more profitable for complex network environment than that of SNMP.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.461-473
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• 2023

This study aims to solve for nonlinear cylindrical shell systems with a semi-analytical and numerical approach implementing the P-T method. The procedures and conditions for such a study are presented in practically solving and analyzing the cylindrical shell systems. An analytical model for a nonlinear thick cylindrical shell (TCS) is established on the basis of the stress function and Reddy's higher-order shear deformation theory (HSDT). According to Reddy's HSDT, Hooke's law in three dimensions, and the von-Kármán equation, the stress-strain relations are developed for the thick cylindrical shell systems, and the three coupled nonlinear governing equations are thus established and discretized as per the Galerkin method, for implementing the P-T method. The solution generated with the approach is continuous everywhere in the entire time domain considered. The approach proposed can also be used to numerically solve and analyze the nonlinear shell systems. The procedures and recurrence relations for numerical solutions of shell systems are presented. To demonstrate the application of the approach in numerically solving for nonlinear cylindrical shell systems, a specific nonlinear cylindrical shell system subjected to an external excitation is solved numerically. In numerically solving for the system, the present approach shows higher efficiency, accuracy, and reliability in comparison with that of the Runge-Kutta method. The approach with the P-T method presented is practically sound especially when continuous and high-quality numerical solutions for the shell systems are considered.

• Structural Engineering and Mechanics
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• 제73권3호
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• pp.331-337
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• 2020

This paper proposes a new approximate analytical solution for highly nonlinear vibration of mechanical systems called Hamiltonian Approach (HA) that can be widely use for structural health monitoring systems. The complete procedure of the HA approach is studied, and the precise application of the presented approach is surveyed by two familiar nonlinear partial differential problems. The nonlinear frequency of the considered systems is obtained. The results of the HA are verified with the numerical solution using Runge-Kutta's [RK] algorithm. It is established the only one iteration of the HA leads us to the high accurateness of the solution.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.239-246
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• 2020

In this paper, a novel analytical method, Max-Min Approach (MMA), has been presented and applied to consider the nonlinear vibration of dry cask storage systems. The nonlinear governing equation of the structure has been developed using the shell theory. The MMA results are compared with numerical solutions derived by Runge-Kutta's Method (RKM). The results indicate a satisfying agreement between MMA and numerical solutions. Parametric studies have been conducted on the nonlinear frequency of dry casks. The phase-plan of the problem is also presented and discussed. The proposed approach can potentially ca be extended to highly nonlinear problems.

• Steel and Composite Structures
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• 제48권6호
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• pp.641-648
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• 2023

In this article, we explore the issue concerning semiconductors half-space comprised of materials with varying thermal conductivity. The problem is within the framework of the generalized thermoelastic model under one thermal relaxation time. The half-boundary space's plane is considered to be traction free and is subjected to a thermal shock. The material is supposed to have a temperature-dependent thermal conductivity. The numerical solutions to the problem are achieved using the finite element approach. To find the analytical solution to the linear problem, the eigenvalue approach is used with the Laplace transform. Neglecting the new parameter allows for comparisons between numerical findings and analytical solutions. This facilitates an examination of the physical quantities in the numerical solutions, ensuring the accuracy of the proposed approach.

• Geomechanics and Engineering
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• 제11권4호
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• pp.457-469
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• 2016

Steep rock slope with water-filled tension crack will happen to overturn around the toe of the slope under seismic loading. This failure type is completely different from the common toppling failure occurring in anti-dipping layered rock mass slopes with steeply dipping discontinuities. This paper presents an analytical approach to determine the seismic factor of safety against overturning for an intact rock mass slope with water-filled tension crack considering horizontal and vertical seismic coefficients. This solution is a generalized explicit expression and is derived using the moment equilibrium approach. A numerical program based on discontinuous deformation analysis (DDA) is adopted to validate the analytical results. The parametric study is carried out to adequately investigate the effect of horizontal and vertical seismic coefficients on the overall stability against overturning for a saturated rock slope under two water pressure modes. The analytical results show that vertically upward seismic inertia force or/and second water pressure distribution mode will remarkably decrease the slope stability against overturning. Finally, several representative design charts of slopes also are presented for the practical application.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권6호
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• pp.46-57
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• 2011

In this study, analytical solution of multip-species transport equations coupled with a first-order reaction network under constant concentration boundary condition or total flux boundary condition is obtained using similarity transformation approach of Clement et al. (2000). The study shows the schematic process about how multi-species transport equations with first-order sequential reaction network is transformed through the similarity transformation approach into independent and uncoupled single species transport equations with first-order reaction. The analytical solution was verified through the comparison with popular commercial programs such as 2DFATMIC and RT3D. The analytical solution can be utilized in nuclear waste sites where radioactive contaminants and their daughter products occur and in industrial complex cities where chlorinated solvent such as PCE, TCE, and its biodegradation products produces. In addition, it can help the verification of the developed numerical code.

• Steel and Composite Structures
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• 제18권5호
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• pp.1259-1277
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• 2015

The present study is focused on the behavior and design of perforated steel storage rack columns under axial compression. These columns may exhibit different types of behavior and levels of strength owing to their peculiar features including their complex cross-section forms and perforations along the member. In the present codes of practice, the design of these columns is carried out using analytical formulas which are supported by experimental tests described in the relevant code document. Recently proposed analytical approaches are used to estimate the load carrying capacity of axially compressed steel storage rack columns. Experimental and numerical studies were carried out to verify the proposed approaches. The experimental study includes compression tests done on members of different lengths, but of the same cross-section. A comparison between the analytical and the experimental results is presented to identify the accuracy of the recently proposed analytical approaches. The proposed approach includes modifications in the Direct Strength Method to include the effects of perforations (the so-called reduced thickness approach). CUFSM and CUTWP software programs are used to calculate the elastic buckling parameters of the studied members. Results from experimental and analytical studies compared very well. This indicates the validity of the recently proposed approaches for predicting the ultimate strength of steel storage rack columns.