• Title/Summary/Keyword: Structural energy

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Investigation of stiffening scheme effectiveness towards buckling stability enhancement in tubular steel wind turbine towers

  • Stavridou, Nafsika;Efthymiou, Evangelos;Gerasimidis, Simos;Baniotopoulos, Charalampos C.
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1115-1144
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    • 2015
  • Current climate conditions along with advances in technology make further design and verification methods for structural strength and reliability of wind turbine towers imperative. Along with the growing interest for "green" energy, the wind energy sector has been developed tremendously the past decades. To this end, the improvement of wind turbine towers in terms of structural detailing and performance result in more efficient, durable and robust structures that facilitate their wider application, thus leading to energy harvesting increase. The wind tower industry is set to expand to greater heights than before and tapered steel towers with a circular cross-section are widely used as more capable of carrying heavier loads. The present study focuses on the improvement of the structural response of steel wind turbine towers, by means of internal stiffening. A thorough investigation of the contribution of stiffening rings to the overall structural behavior of the tower is being carried out. These stiffening rings are placed along the tower height to reduce local buckling phenomena, thus increasing the buckling strength of steel wind energy towers and leading the structure to a behavior closer to the one provided by the beam theory. Additionally to ring stiffeners, vertical stiffening schemes are studied to eliminate the presence of short wavelength buckles due to bending. For the purposes of this research, finite element analysis is applied in order to describe and predict in an accurate way the structural response of a model tower stiffened by internal stiffeners. Moreover, a parametric study is being performed in order to investigate the effect of the stiffeners' number to the functionality of the aforementioned stiffening systems and the improved structural behavior of the overall wind converter.

Structural Intensity Analysis of Local Ship Structures Using Finite Element Method (유한요소법을 이용한 선체 국부 구조물의 진동인텐시티 해석)

  • Dong-Hwan Lee;Dae-Seung Cho
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.3
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    • pp.62-73
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    • 2001
  • The interest in evaluation of structural intensity arises for practical reasons, because net energy flow distribution offers information of energy transmission path, positions of sources, and sinks of vibration energy. In this paper, structural intensity analysis of local ship structures using finite element method(FEM) is carried out. The purpose of this analysis is to evaluate the relative accuracy according to mesh fineness. The structural intensity of unstiffened and stiffened plates varying their mesh fineness is analyzed and the results are compared with those obtained by the assumed mode method. As results, the proper mesh size in qualitative/quantitative structural intensity analysis of plate structures is proposed. In addition, the propagation phenomenon of vibration energy is investigated for the thickness-varying flat plate, L-type plate, and box-girder structures.

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Multi-Level and Multi-Objective Optimization of Framed Structures Using Automatic Differentiation (자동미분을 이용한 뼈대구조의 다단계 다목적 최적설계)

  • Cho, Hyo-Nam;Min, Dae-Hong;Lee, Kwang-Min;Kim, Hoan-Kee
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.04b
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    • pp.177-186
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    • 2000
  • An improved multi-level(IML) optimization algorithm using automatic differentiation (AD) for multi-objective optimum design of framed structures is proposed in this paper. In order to optimize the steel frames under seismic load, two main objective functions need to be considered for minimizing the structural weight and maximizing the strain energy. For the efficiency of the proposed algorithm, multi-level optimization techniques using decomposition method that separately utilizes both system-level and element-level optimizations and an artificial constraint deletion technique are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments, frequencies, and strain energy with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

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High-Temperature Structural Analysis on the Small-Scale PHE Prototype under the Test Condition of Small-Scale Gas Loop (소형가스루프 시험조건에서 소형 공정열교환기 시제품의 고온구조해석)

  • Song, Kee-nam;Hong, S-D;Park, H-Y
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.8 no.1
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    • pp.1-7
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    • 2012
  • A PHE (Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. A small-scale PHE prototype made of Hastelloy-X is being tested in a small-scale gas loop at Korea Atomic Energy Research Institute. In order to properly evaluate the high-temperature structural integrity of the small-scale PHE prototype, it is very important to impose a proper constraint condition on its structural analysis model. For this effort, we tried to impose several constraint conditions on the structural analysis model and consequently fixed a proper and effective displacement constraints.

Structural lightweight concrete containing expanded poly-styrene beads; Engineering properties

  • Vakhshouri, Behnam
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.581-597
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    • 2020
  • Light-Weight Concrete containing Expanded Poly-Styrene Beads (EPS-LWC) is an approved structural and non-structural material characterized by a considerably lower density and higher structural efficiency, compared to concrete containing ordinary aggregates. The experimental campaign carried out in this project provides new information on the mechanical properties of structural EPS-LWC, with reference to the strength and tension (by splitting and in bending), the modulus of elasticity, the stress-strain curve in unconfined compression, the absorbed energy under compression and reinforcement-concrete bond. The properties measured at seven ages since casting, from 3 days to 91 days, in order to investigate their in-time evolution. Mathematical relationships are formulated as well, between the previous properties and time, since casting. The dependence of the compressive strength on the other mechanical properties of EPS-LWC is also described through an empirical relationship, which is shown to fit satisfactorily the experimental results.

A Whole LCA of the Sustainable Aspects of Structural Systems in Tall Buildings

  • Trabucco, Dario;Wood, Antony;Vassart, Olivier;Popa, Nicoletta
    • International Journal of High-Rise Buildings
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    • v.5 no.2
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    • pp.71-86
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    • 2016
  • This paper summarizes the results of a two-year-long research project conducted by the CTBUH on the life cycle assessment (LCA) of tall building structural systems. The research project was made possible thanks to a $300,000 contribution from ArcelorMittal and the support of some of the most important structural engineering firms and players in the tall building industry. The research analyzed all life phases of a tall building's structural system: the extraction and production of its materials, transportation to the site, construction operations, final demolition of the building, and the end-of-life of the materials. The impact of the building structure during the operational phase (i.e., impact on daily energy consumption, maintenance, and suitability to changes) was also investigated, but no significant impacts were identified during this phase.