• Title, Summary, Keyword: mechanics performance

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Mechanics feasibility of using CFRP cables in super long-span cable-stayed bridges

  • Zhang, Xin-Jun
    • Structural Engineering and Mechanics
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    • v.29 no.5
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    • pp.567-579
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    • 2008
  • To gain understanding of the applicability of CFRP cables in super long-span cable-stayed bridges, by taking a 1400 m cable-stayed bridge as example, mechanics performance including the static behavior under service load, dynamic behavior, wind stability and seismic behavior of the bridge using either steel or CFRP cables are investigated numerically and compared. The results show that viewed from the aspect of mechanics performance, the use of CFRP cables in super long-span cable-stayed bridges is feasible, and the cross-sectional areas of CFRP cables should be determined by the principle of equivalent axial stiffness.

On the fatigue performance of Aluminum alloy 2024 scarfed lap joints

  • Yan, W.Z.;Gao, H.S.;Yuan, X.;Wang, F.S.;Yue, Z.F.
    • Structural Engineering and Mechanics
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    • v.44 no.1
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    • pp.35-49
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    • 2012
  • A series of fatigue test were carried out on scarfed lap joints (SLJ) using in airfoil siding to explore the effect of structural details, such as rows of rivets, lap angles, on its fatigue performance. Finite element (FE) analysis was employed to explore the effect of lap angle on load transfer and the stress evolution around the rivet hole. At last, the fatigue lives were predicted by nominal stress approach and critical plane approach. Both of the test results and predicted results showed that fatigue life of SLJ was remarkably increased after introducing lap angle into the faying surface. Specimen with the lap angle of $1.68^{\circ}$ exhibits the best fatigue performance in the present study.

Performance of Dual Polarized MIMO System using Six-Port Receiver for Cognitive Radio

  • Lee Sang-Yub;Yang Wan-Cheol;Lee Jeong-Suk;Kim Hak-Sun
    • Broadcasting and Media Magazine
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    • v.11 no.1
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    • pp.78-85
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    • 2006
  • Cognitive radio is a paradigm for wireless communication in which either network of wireless node itself changes particular transmission or reception parameters to execute its tasks efficiently without interfering with the licensed users. This paper represents a performance of the cognitive radio technology on dual polarized MIMO system using six-port receiver. Six-port technology is well known direct conversion receiver. In this paper, a six-port phase discriminator based polarization signal separation is shown. That is, the SER(Symbol Error Rate) performance is improved using polarization separator and simple receiver architecture is proposed applying six-port receiver. The six-port technology has priority to adapt changeable frequency system and variable environments for cognitive radio. In general, dual polarized MIMO system has good capacity and quality using polarization separator [1].

Development of an Ultra-Slim System in Package (SiP)

  • Gao, Shan;Hong, Ju-Pyo;Kim, Jin-Su;Yoo, Do-Jae;Jeong, Tae-Sung;Choi, Seog-Moon;Yi, Sung
    • Journal of the Microelectronics and Packaging Society
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    • v.15 no.1
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    • pp.7-18
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    • 2008
  • This paper reviews the current development of an ultra-slim SiP for Radio Frequency (RF) application, in which three flip chips, additional passive components and Surface Acoustic Wave (SAW) filters are integrated side-by-side. A systematic investigation is carried out for the design optimization, process and reliability improvement of the package, which comprises several aspects: a design study based on the 3D thermo-mechanical finite element analysis of the packaging, the determination of stress, warpage distribution, critical failure zones, and the figuration of the effects of material properties, process conditions on the reliability of package. The optimized material sets for manufacturing process were determined which can reduce the number of testing samples from 75 to 2. In addition the molded underfilling (MUF) process is proposed which not only saves one manufacturing process, but also improves the thermo-mechanical performance of the package compared with conventional epoxy underfilling process. In the end, JEDEC's moisture sensitivity test, thermal cycle test and pressure cooker tests have also been carried out for reliability evaluation. The test results show that the optimized ultra-slim SiP has a good reliability performance.

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Monolayer Rotating Ball Electronic Paper Display

  • Lee, Hwan-Su;Cha, Hye-Yeon;Lee, Chung-Hui;Lee, Sang-Mun;Gwak, Jeong-Bok;Kim, Sang-Jin;Lee, Yeong-U;Park, Jeong-Min;O, Yong-Su
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.20.1-20.1
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    • 2010
  • 'Electronic paper (EP)' provides desirable viewing characteristics of paper with being thin, lightweight, flexible, and recordable with minimal power consumption. Currently, a number of different technologies to realize the EP are actively competing. Here we demonstrate a newly developed monolayer rotating ball (MRB) electronic paper display where optically anisotropic rotating balls were disposed in a monolayer, and controllably closely packed with respect to one another. The close packed monolayer configuration provides high brightness and improved contrast with better electrical and optical features in comparison with the typical (Gyrion) rotating ball display. In this talk, we present characteristics of the MRB display in terms of performance, with particular emphasis on the response time as a function of the electric field.

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Investigation on the seismic performance of T-shaped column joints

  • Chen, Changhong;Gong, He;Yao, Yao;Huang, Ying;Keer, Leon M.
    • Computers and Concrete
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    • v.21 no.3
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    • pp.335-344
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    • 2018
  • More and more special-shaped structural systems have been widely used in various industrial and civil buildings in order to satisfy the new structural system and the increasing demand for architectural beauty. With the popularity of the special-shaped structure system, its seismic performance and damage form have also attracted extensive attention. In the current research, an experimental analysis of six groups of (2/3 scale) T-shaped column joints was conducted to investigate the seismic performance of T-shaped column joints. Effects of the beam cross section, transverse stirrup ratio and axial compression ratio on bearing capacity and energy dissipation capacity of column joints were obtained. The crack pattern of T-shaped column joints under low cyclic load was presented and showed a reversed "K" mode. According to the crack configurations, a tensile-shear failure model to determine the shear bearing capacity and crack propagation mechanisms is developed.

Investigation on mechanics performance of cable-stayed-suspension hybrid bridges

  • Zhang, Xin-Jun
    • Wind and Structures
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    • v.10 no.6
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    • pp.533-542
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    • 2007
  • The cable-stayed-suspension hybrid bridge is a cooperative system of the cable-stayed bridge and suspension bridge, and takes some advantages and also makes up some deficiencies of both the two bridge systems, and therefore becomes strong in spanning. By taking the cable-stayed-suspension hybrid bridge, suspension bridge and cable-stayed bridge with main span of 1400 m as examples, the mechanics performance including the static and dynamic characteristics, the aerostatic and aerodynamic stability etc is investigated by 3D nonlinear analysis. The results show that as compared to the suspension bridge and cable-stayed bridge, the cable-stayed-suspension hybrid bridge has greater structural stiffness, less internal forces and better wind stability, and is favorable to be used in super long-span bridges.

Study on the local damage of SFRC with different fraction under contact blast loading

  • Zhang, Yongliang;Zhao, Kai;Li, Yongchi;Gu, Jincai;Ye, Zhongbao;Ma, Jian
    • Computers and Concrete
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    • v.22 no.1
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    • pp.63-70
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    • 2018
  • The steel fiber reinforced concrete (SFRC) shows better performance under dynamic loading than conventional concrete in virtue of its good ductility. In this paper, a series of quasi-static experiments were carried out on the SFRC with volume fractions from 0 to 6%. The compressive strength increases by 38% while the tension strength increases by 106% when the fraction is 6.0%. The contact explosion tests were also performed on the ${\Phi}40{\times}6cm$ circular SFRC slabs of different volume fractions with 20 g RDX charges placed on their surfaces. The volume of spalling pit decreases rapidly with the increase of steel fiber fraction with a decline of 80% when the fraction is 6%, which is same as the crack density. Based on the experimental results, the fitting formulae are given, which can be used to predict individually the change tendencies of the blast crater volume, the spalling pit volume and the crack density in slabs with the increase of the steel fiber fraction. The new formulae of the thickness of damage region are established, whose predictions agree well with our test results and others. This is of great practical significance for experimental investigations and engineering applications.

Damage mechanics approach and modeling nonuniform cracking within finite elements for safety evaluation of concrete dams in 3D space

  • Mirzabozorg, H.;Kianoush, R.;Jalalzadeh, B.
    • Structural Engineering and Mechanics
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    • v.33 no.1
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    • pp.31-46
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    • 2009
  • An anisotropic damage mechanics approach is introduced which models the static and dynamic behavior of mass concrete in 3D space. The introduced numerical approach is able to model non-uniform cracking within the cracked element due to cracking in Gaussian points of elements. The validity of the proposed model is considered using available experimental and theoretical results under the static and dynamic loads. No instability and stress locking is observed in the conducted analyses. The Morrow Point dam is analyzed including dam-reservoir interaction effects to consider the nonlinear seismic behavior of the dam. It is found that the resulting crack profiles are in good agreement with those obtained from the smeared crack approach. It is concluded that the proposed model can be used in nonlinear static and dynamic analysis of concrete dams in 3D space and enables engineers to define the damage level of these infrastructures. The performance level of the considered system is used to assess the static and seismic safety using the defined performance based criteria.

Capabilities of stochastic response surface method and response surface method in reliability analysis

  • Jiang, Shui-Hua;Li, Dian-Qing;Zhou, Chuang-Bing;Zhang, Li-Min
    • Structural Engineering and Mechanics
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    • v.49 no.1
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    • pp.111-128
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    • 2014
  • The stochastic response surface method (SRSM) and the response surface method (RSM) are often used for structural reliability analysis, especially for reliability problems with implicit performance functions. This paper aims to compare these two methods in terms of fitting the performance function, accuracy and efficiency in estimating probability of failure as well as statistical moments of system output response. The computational procedures of two response surface methods are briefly introduced first. Then their capabilities are demonstrated and compared in detail through two examples. The results indicate that the probability of failure mainly reflects the accuracy of the response surface function (RSF) fitting the performance function in the vicinity of the design point, while the statistical moments of system output response reflect the accuracy of the RSF fitting the performance function in the entire space. In addition, the performance function can be well fitted by the SRSM with an optimal order polynomial chaos expansion both in the entire physical and in the independent standard normal spaces. However, it can be only well fitted by the RSM in the vicinity of the design point. For reliability problems involving random variables with approximate normal distributions, such as normal, lognormal, and Gumbel Max distributions, both the probability of failure and statistical moments of system output response can be accurately estimated by the SRSM, whereas the RSM can only produce the probability of failure with a reasonable accuracy.