• Steel and Composite Structures
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• 제37권4호
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• pp.463-479
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• 2020

Currently, there are many lateral resisting systems utilized in resisting lateral loads being produced in an earthquake. Such systems can significantly reduce the roof's displacement when placed at an optimum location. Since in the design of tall buildings, the minimum distance between adjacent buildings is important. In this paper, the critical excitation method is used to determine the best location of the belt truss system while calculating the minimum required distance between two adjacent buildings. For this purpose, the belt truss system is placed at a specific story. Then the critical earthquakes are computed so that the considered constraints are satisfied, and the value of roof displacement is maximized. This procedure is repeated for all stories; i.e., for each, a critical acceleration is computed. From this set of computed roof displacement values, the story with the least displacement is selected as the best location for the belt truss system. Numerical studies demonstrate that absolute roof displacements induced through critical accelerations range between 5.36 to 1.95 times of the San Fernando earthquake for the first example and 7.67 to 1.22 times of the San Fernando earthquake for the second example. This method can also be used to determine the minimum required distance between two adjacent buildings to eliminate the pounding effects. For this purpose, this value is computed based on different standard codes and compared with the results of the critical excitation method to show the ability of the proposed method.

• Steel and Composite Structures
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• 제37권4호
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• pp.391-404
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• 2020

Human-induced vibration could present a serious serviceability problem for large-span and/or lightweight floors using the high-strength material. This paper presents the results of heel-drop, jumping, and walking tests on a large-span composite steel rebar truss-reinforced concrete (CSBTRC) floor. The effects of human activities on the floor vibration behavior were investigated considering the parameters of peak acceleration, root-mean-square acceleration, maximum transient vibration value (MTVV), fundamental frequency, and damping ratio. The measured field test data were validated with the finite element and theoretical analysis results. A comprehensive comparison between the test results and current design codes was carried out. Based on the classical plate theory, a rational and simplified formula for determining the fundamental frequency for the CSBTRC floor is derived. Secondly, appropriate coefficients (β_rp) correlating the MTVV with peak acceleration are suggested for heel-drop, jumping, and walking excitations. Lastly, the linear oscillator model (LOM) is adopted to establish the governing equations for the human-structure interaction (HSI). The dynamic characteristics of the LOM (sprung mass, equivalent stiffness, and equivalent damping ratio) are determined by comparing the theoretical and experimental acceleration responses. The HSI effect will increase the acceleration response.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.548-553
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• 2001

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and protects the system from the external impact loads. Various space grids have been proposed and new designs are also being created. In this research, a new spacer grid is designed by the axiomatic approach. The Independence Axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1623-1630
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• 2002

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water, and maintains a coolable geometry from the external impact loads. In this research, a new shape of the spacer grid is designed by the axiomatic approach. The Independence axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• Steel and Composite Structures
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• 제23권3호
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• pp.331-338
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• 2017

Cold-formed lipped channel columns (CFLCCs) have been widely used in light gauge steel constructions. The distortional buckling is one of the important buckling modes for CFLCCs and the distortional buckling critical load depends significantly on the rotational restrain stiffness generated by the web to the lipped flange. First, a simplified explicit expression for the rotational restraint stiffness of the lipped flange has been derived. Using the expression, the characteristics of the rotational restraint stiffness of the lipped flange have been investigated. The results show that there is a linear coupling relationship between the applied forces and the rotational restraint stiffness of the lipped flange. Based on the explicit expression of the rotational restraint stiffness of the lipped flange, a simplified analytical formula has been derived which can determine the elastic distortional buckling critical stress of the CFLCCs subjected to axial compression. The simplified analytical formula developed in this study has been shown to be accurate through the comparisons with results from the distortional buckling analyses using the ANSYS finite element software. The developed analytical formula is easy to apply, and can be used directly in practical design and incorporated into future design codes and guidelines.

• 전자공학회논문지
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• 제50권7호
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• pp.175-180
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• 2013

본 논문에서는 멀티미디어 콘텐츠의 부정자를 추적하기 위하여, 공모된 핑거프린팅 코드를 해밍거리를 이용하여 XOR 공모공격을 분류하는 알고리즘을 제안한다. 기존의 공모된 핑거프린팅 코드는 상관관계수를 이용하여 부정자를 판정하였지만 제안된 방법은 해밍거리를 이용하였다. 그 결과 상관관계 계수에 의한 XOR 공모공격은 XOR의 심각한 선형문제 때문에 50% 정도의 공모자 수에서 불가능 했던 부정자 추적이 해밍거리를 이용하여 최소한 1명의 부정자를 추적할 수 있는 추적도의 성능을 향상시켰으므로, 제안된 부정자 추적의 기능동작은 Probabilistic Scheme에 부합하였다.

• 전산구조공학
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• 제8권4호
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• pp.137-148
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• 1995

이차원 선형탄성파괴역학 문제에서 인장모우드 상태의 응력확대계수를 명료하게 산정할 수 있는 독립적 적분경로에 근거를 둔 새로운 J-적분 균열모델이 제안되었다. 이 방법은 p-수렴 개념에 기초를 두며 기존의 유한요소 컴퓨터코드에 쉽게 적용할 수 있다. 본 연구에서는 균열선단에서의 응력상태가 조사되었으며, 균열선단으로부터 떨어진 정규거리로 표현되는 서로 다른 적분경로에 따라 J-적분치가 유한요소해석시 Rice의 이론처럼 경로에 독립적인 해를 얻을 수 있는지 분석되었다. 세가지 수치예제인 중앙균열판, 일변균열판과 양변균열판과 양변균열판의 p-수렴 해석결과가 종래의 h-수렴법에 의한 해석결과와 비교되었으며, 또한 이 결과는 제안된 방법의 정확성과 수치적 안정성을 보여주고 있다.

• Interaction and multiscale mechanics
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• 제3권4호
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• pp.309-320
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• 2010

With taking the geometric nonlinearity of bridge structure into account, a framework is presented for predicting the dynamic responses of a long-span suspension bridge subjected to running train and turbulent wind. The nonlinear dynamic equations of the coupled train-bridge-wind system are established, and solved with the Newmark numerical integration and direct interactive method. The corresponding linear and nonlinear processes for solving the system equation are described, and the corresponding computer codes are written. The proposed framework is then applied to a schemed long-span suspension bridge with the main span of 1120 m. The whole histories of the train passing through the bridge under turbulent wind are simulated, and the dynamic responses of the bridge are obtained. The results demonstrate that the geometric nonlinearity does not influence the variation tendency of the bridge displacement histories, but the maximum responses will be changed obviously; the lateral displacement of bridge are more sensitive to the wind than the vertical ones; compared with wind velocity, train speed affects the vertical maximum responses a little more clearly.

• Journal of Communications and Networks
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• 제7권4호
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• pp.450-461
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• 2005

In this paper, we derive analytical expressions for the exact pairwise error probability (PEP) of a space-time coded system operating over spatially correlated fast (constant over the duration of a symbol) and slow (constant over the length of a code word) fad­ing channels using a moment-generating function-based approach. We discuss two analytical techniques that can be used to evaluate the exact-PEPs (and therefore, approximate the average bit error probability (BEP)) in closed form. These analytical expressions are more realistic than previously published PEP expressions as they fully account for antenna spacing, antenna geometries (uniform linear array, uniform grid array, uniform circular array, etc.) and scattering models (uniform, Gaussian, Laplacian, Von-mises, etc.). Inclusion of spatial information in these expressions provides valuable insights into the physical factors determining the performance of a space-time code. Using these new PEP expressions, we investigate the effect of antenna spacing, antenna geometries and azimuth power distribution parameters (angle of arrival/departure and angular spread) on the performance of a four-state QPSK space-time trellis code proposed by Tarokh et al. for two transmit antennas.

• Steel and Composite Structures
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• 제27권3호
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• pp.355-370
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• 2018

In steel-concrete composite beams, longitudinal shear forces are transferred across steel flange-concrete slab interface by means of shear connectors. The connector behavior is highly non-linear and involves several complex mechanisms. The design resistance and stiffness of composite beams depends on the shear connection behavior and the accuracy in the connector resistance prediction is essential. However determining the stud shear resistance is not an easy process: analytical methods do not give an adequate response to this problem and it is therefore necessary to use experimental methods. This paper present a summary of the main procedures to predict the resistance of the stud shear connectors embedded in solid slab, and stud shear connectors in composite slab using profiled steel sheeting with rib perpendicular to steel beam. A large number of experimental studies on the behavior of stud shear connectors and reported in the literature are also summarized. A comparison of the stud shear resistance prediction using six reference codes (AISC, AASHTO, Eurocode-4, GB50017, JSCE and AS2327.1) and other procedures reported in the literature against experimental results is presented. From this exercise, it is concluded that there are still inaccuracies in the prediction of stud shear resistance in all analysed procedures and that improvements are needed.