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Enhancement of the buckling strength of glass beams by means of lateral restraints
Belis, J.,Impe, R. Van,Lagae, G.,Vanlaere, W. Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.15 No.5
New material applications and transparency are desired by contemporary architects. Its superb transparency and high strength make glass a very suitable building material -in spite of its brittleness- even for primary load bearing structures. Currently we will focus on load bearing glass beams, subjected to different loading types. Since glass beams have a very slender, rectangular cross section, they are sensitive to lateral torsional buckling. Glass beams fail under a critical buckling load at stresses that lie far below the theoretical simple bending strength, due to the complex combination of torsion and out-of-plane bending, which characterises the instability phenomenon. The critical load can be increased considerably by preventing the upper rim from moving out of the beam's plane. Different boundary conditions are examined for different loading types. The load carrying capacity of glass beams can be increased three times and more using relatively simple, cheap lateral restraints.
Vanlaere, Wesley,Impe, Rudy Van,Lagae, Guy,Maes, Thomas Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.2
A steel silo traditionally consists of a cylindrical and a conical shell. In order to facilitate emptying operations, the cylinder is placed on local supports. This may lead to dangerous stress concentrations and eventually to local instability of the cylindrical wall. In this contribution, the locally supported cylinder is strengthened by means of ring stiffeners and longitudinal stiffeners and the effect of their dimensions on the buckling stress is investigated. This study leads to a number of diagrams, each of them representing the effect of one of the dimensions on the buckling stress. In each diagram, the failure pattern corresponding to the buckling stress is indicated.
P1ane Strain Strength of Fine Sands
Yoon, Yeo-Won,Van, Impe W.F 한국지반공학회 1996 지반 : 한국지반공학회지 Vol.12 No.3
실리카질 모래에 대한 많은 시험결과로부터 삼축압축시첩과 평면변형시험간의 강도관계를 밀도와 파괴시 유효평균주응력의 함수로 표현하였다. 또한 파괴시 평균주응력과 축차응력간의 응력비가 내부마찰각의 함수로 잘 규정되었으며 그 비는 내부마찰각의 증가에 따라 감소하였다. 또한 중간주응력을 최대주응력과 최소주응력으로써 표현하였으며 이론적인 파괴면의 각도와 평면변형시험에서 관찰된 파괴면의 각도가 비교적 잘 일치함이 확인되었다. Based on many experimental results on fine silica sands, the strength relation between triaxial and plane strain tests is expressed as a function of both density and mean effective principal stress at failure. Stress ratio of mean normal stress to deviatoric stress at failure is a well defined function of shear angle of friction, This ratio decreases with increasing shear angle of friction. Intermediate principal stress is also expressed in terms of major and minor principal stresses and a relatively good agreement between theoretical and observed angles of failure plane in plane strain test is confirmed.
Tango, Charles Nkufi,Akkermans, Simen,Hussain, Mohammad Shakhawat,Khan, Imran,Van Impe, Jan,Jin, Yong-Guo,Oh, Deog Hwan Elsevier 2018 Food microbiology Vol.76 No.-
<P><B>Abstract</B></P> <P>In this work, the effect of environmental factors on <I>Staphylococcus aureus</I> (ATCC 13150) biofilm formation in tryptic soy broth was investigated under different ranges of pH (3.0–9.5), ethanol concentration (EtOH 0.0–20.0%), and a<SUB>w</SUB> (NaCl, 0.866–0.992). Biofilm formation was quantified using the crystal violet staining method and optical density (OD: 590 nm) measurements. Biofilm formation was significantly stronger at pH and a<SUB>w</SUB> close to <I>S. aureus</I> optimal growth conditions, while it was high at EtOH around 2.5–3.5%. Data sets from the difference between the OD measurements of the test and control (ΔOD) were fitted to the cardinal parameter model (CPM) and cardinal parameter model with inflection (CPMI) to describe the effect of the environmental factors. The models showed good quality of fit for the experimental data in terms of calculated RMSE, with the latter ranging from 0.276 to 0.455. CPM gave a good quality of fit compared to CPMI for the environmental factors tested. Optimal pH was close to neutral (6.76–6.81) and biofilm formation was possible till pH = 3.81–3.78 for CPM and CPMI, respectively. Optimum EtOH and a<SUB>w</SUB> conditions for biofilm formation were in the range of 1.99–2.75 and 0.98–0.97, respectively. Predicted OD values observed using strain 13150 were very closely correlated to the OD values predicted with strain 12600 with R<SUP>2</SUP> of 0.978, 0.991, and 0.947 for pH, EtOH, and a<SUB>w</SUB>, respectively. The cultivable bacterial cells within the biofilm were enumerated using standard plate counting and a linear model was applied to correlate the attached biofilm cells to ΔOD of biofilm formation. It was found that the biofilm formation correlated with <I>S. aureus</I> population growth. At 2.5–3.5% of EtOH the maximum population density was lower than that observed at 0.0% of EtOH. As 2.5–3.5% of EtOH initiated a stronger biofilm formation, biofilm formation seems to be induced by ethanol stress. The development of cardinal parameter models to describe the effect environmental factors of importance to biofilm formation, offers a promising predictive microbiology approach to decrypting the <I>S. aureus</I> population growth and survival ability on food processing surfaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biofilm formation was significantly stronger at pH and aw close <I>S. aureus</I> growth optimal conditions. </LI> <LI> Biofilm formation was significantly high at ethanol concentration around 2.5–3.5%. </LI> <LI> CPM showed a better quality of fit compare to CPMI whatever the environmental factors. </LI> <LI> High extracellular matrix production depend on stress induced by ethanol at non-lethal concentrations. </LI> </UL> </P>
Influence of the cylinder height on the elasto-plastic failure of locally supported cylinders
Arne Jansseune,Wouter De Corte,Wesley Vanlaere,Rudy Van Impe 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.4
Frequently, steel silos are supported by discrete supports or columns to permit easy access beneath the barrel. In such cases, large loads are transferred to the limited number of supports, causing locally high axial compressive stress concentrations in the shell wall above the supports. If not dealt with properly, these increased stresses will lead to premature failure of the silo due to local instability in the regions above the supports. Local stiffening near the supports is a way to improve the buckling resistance, as material is added in the region of elevated stresses, levelling these out to values found in uniformly supported silos. The aim of a study on the properties of local stiffening will then be to increase the failure load, governed by an interaction of plastic collapse and elastic instability, to that of a discrete supported silo. However, during the course of such a study it was found that, although the failure remains local, the cylinder height is also a parameter that influences the failure mechanism, a fact that is not properly taken into account in current design practice and codes. This paper describes the mechanism behind the effect of the cylinder height on the failure load, which is related to pre-buckling deformations of the shell structure. All results and conclusions are based on geometrically and materially non-linear finite element analyses.
Generation of High-Resolution Precise DEMs Through Airborne LIDAR Surveys on Huge Antarctic Regions
Lee Imp-yeong,CHOI Yun-soo,Lee, Jae-one Korean Society of Surveying 2004 Korean journal of geomatics Vol.3 No.2
NASA, NSF and USGS jointly conducted airborne LIDAR surveys to acquire numerous surface points with high densities over the Antarctic Dry Valleys and its vicinity, The huge set of these points retains two characteristics undesirable for DEM generation, which are unusually high blunder ratio and large variation of the local point densities. Hence, in order to not only reduce the undesirable effects due to these characteristics but also process the huge number of points within reasonable limits of time and resources, we developed an efficient, robust, nearly automatic approach to DEM generation. This paper reports about the application of this approach to generating high-resolution precise DEMs from the Antarctic LIDAR surveys and the evaluation of their accuracy.