• Title/Summary/Keyword: experimental campaign

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The structural performance of arches made of few vossoirs with dry-joints

  • Bernat-Maso, Ernest;Gil, Lluis;Marce-Nogue, Jordi
    • Structural Engineering and Mechanics
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    • v.44 no.6
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    • pp.775-799
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    • 2012
  • This work approaches the structural performance of masonry arches that have a small ratio between number of vossoirs and span length. The aim of this research is to compare and validate three different methods of analysis (funicular limit analysis F.L.A., kinematic limit analysis K.L.A. and plane stress Finite Element Analysis F.E.A.) with an experimental campaign. 18 failure tests with arches of different shapes and boundary conditions have been performed. The basic failure mechanism was the formation of enough hinges in the geometry. Nevertheless, in few cases, sliding between vossoirs also played a relevant influence. Moreover, few arches didn't reach the collapse. The FLA and KLA didn't find a solution close to the experimental values for some of the tests. The low number of vossoirs and joints become a drawback for an agreement between kinematic mechanism, equilibrium of forces and geometry constraints. FLA finds a lower bound whereas KLA finds an upper bound of the ultimate load of the arch. FEA is the most reliable and robust method and it can reproduce most of the mechanism and ultimate loads. However, special care is required in the definition of boundary conditions for FEA analysis. Scientific justification of the more suitability of numerical methods in front of classic methods at calculating arches with a few vossoirs is the main original contribution of the paper.

Influence of the shape of head anchors on the durability of reinforced concrete elements

  • Martinez-Echeverria, M. Jose;Gil-Martin, Luisa Maria;Montero, Jose Rodriguez;Hernandez-Montes, Enrique
    • Advances in concrete construction
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    • v.10 no.1
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    • pp.61-69
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    • 2020
  • This paper looks into how the shape of headed bars may influence the durability of reinforced concrete structures. Nowadays the only heads used in site works are cylindrical in shape. An alternative shape of head is studied in this piece of work. The new head reduces the concentration of stresses and so the appearance of cracks. In this work durability is studied based on both, first cracking and failure mode. An experimental campaign of 12 specimens and finite element modelling are described. The specimens were subjected to an accelerated corrosion process using an electrical current supply. Direct current was impressed on the specimens until breaking. Test results and the results obtained from numerical models are presented. Results are presented in term of comparison between the two shapes of heads studied. It was shown that the shape of the head has a significant influence on durability of reinforced concrete structures with headed reinforcing bars.

Review of Active Rotor Control Research in Canada

  • Feszty, Daniel;Nitzsche, Fred
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.2
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    • pp.93-114
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    • 2011
  • The current status of Canadian research on rotor-based actively controlled technologies for helicopters is reviewed in this paper. First, worldwide research in this field is overviewed to put Canadian research into context. Then, the unique hybrid control concept of Carleton University is described, along with its key element, the "stiffness control" concept. Next, the smart hybrid active rotor control system (SHARCS) projected's history and organization is presented, which aims to demonstrate the hybrid control concept in a wind tunnel test campaign. To support the activities of SHARCS, unique computational tools, novel experimental facilities and new know-how had to be developed in Canada, among them the state-of-the-art Carleton Whirl Tower facility or the ability to design and manufacture aeroelastically scaled helicopter rotors for wind tunnel testing. In the second half of the paper, details are provided on the current status of development on the three subsystems of SHARCS, i.e. that of the actively controlled tip, the actively controlled flap and the unique stiffness-control device, the active pitch link.

Warning Labels on Cigarette Packages: A Special Stimulus for Moslem Smokers to Quit Smoking

  • Halim, Rizal Edy;Sumiyarto, Sumiyarto;Muttaqin, Faisal
    • Asian Journal of Business Environment
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    • v.5 no.1
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    • pp.5-11
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    • 2015
  • Purpose - This study aims to explore the influence of combining "non-halal" labels with visual and textual warning labels on cigarette packages to induce the intention to quit smoking and boost the stop-smoking campaign. Research design, data, and methodology - This study examines"non-halal" labeling on cigarette packages using an experimental method. A total of 120 smokers, aged 18-23, were chosen from among Universitas Indonesia students. Data obtained were analyzed using ANOVA and T-Test. Results - The use of a "non-halal" label as a warning on cigarette packages is more effective to influence Muslim smokers to quit smoking. The results also suggest that "non-halal" labels more effectively increase intentions to quit smoking when use din combination with textual-visual labels. Conclusions - The study found that the addition of "non-halal" labels in textual or textual-visual warning labels on cigarette packages would significantly increase the intention of Moslems smokers to quit smoking. These results support previous research findings, that if cigarettes are labeled as "non-halal" (haram) products for Moslem teenagers, it will induce them to quit smoking.

Upward Flame Spread for Fire Risk Classification of High-Rise Buildings

  • McLaggan, Martyn S.;Gupta, Vinny;Hidalgo, Juan P.;Torero, Jose L.
    • International Journal of High-Rise Buildings
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    • v.10 no.4
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    • pp.299-310
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    • 2021
  • External fire spread has the potential to breach vertical compartmentation and violate the fire safety strategy of a building. The traditional design solution to this has been the use of non-combustible materials and spandrel panels but recent audits show that combustible materials are widespread and included in highly complex systems. Furthermore, most jurisdictions no longer require detailing of spandrel panels under many different circumstances. These buildings require rapid investigation using rational scientific methods to be able to adequately classify the fire risk. In this work, we use an extensive experimental campaign of material-scale data to explore the critical parameters driving upward flame spread. Two criteria are outlined using two different approaches. The first evaluates the time to ignition and the time to burnout to assess the ability for a fire to spread, and can be easily determined using traditional means. The second evaluates the preheated flame length as the critical parameter driving flame spread. A wide range of cladding materials are ranked according to these criteria to show their potential propensity to flame spread. From this, designers can use conservative approaches to perform fire risk assessments for buildings with combustible materials or can be used to aid decision-making. Precise estimates of flame spread rates within complex façade systems are not achievable with the current level of knowledge and will require a substantial amount of work to make progress.

Vision-based support in the characterization of superelastic U-shaped SMA elements

  • Casciati, F.;Casciati, S.;Colnaghi, A.;Faravelli, L.;Rosadini, L.;Zhu, S.
    • Smart Structures and Systems
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    • v.24 no.5
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    • pp.641-648
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    • 2019
  • The authors investigate the feasibility of applying a vision-based displacement-measurement technique in the characterization of a SMA damper recently introduced in the literature. The experimental campaign tests a steel frame on a uni-axial shaking table driven by sinusoidal signals in the frequency range from 1Hz to 5Hz. Three different cameras are used to collect the images, namely an industrial camera and two commercial smartphones. The achieved results are compared. The camera showing the better performance is then used to test the same frame after its base isolation. U-shaped, shape-memory-alloy (SMA) elements are installed as dampers at the isolation level. The accelerations of the shaking table and those of the frame basement are measured by accelerometers. A system of markers is glued on these system components, as well as along the U-shaped elements serving as dampers. The different phases of the test are discussed, in the attempt to obtain as much possible information on the behavior of the SMA elements. Several tests were carried out until the thinner U-shaped element went to failure.

Conditions to avoid synchronization effects in lateral vibration of footbridges

  • Andrade, Alexandre R.;Pimentel, Roberto L.;Silva, Simplicio A. da;Souto, Cicero da R.
    • Structural Monitoring and Maintenance
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    • v.9 no.2
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    • pp.201-220
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    • 2022
  • Lateral vibrations of footbridges may induce synchronization between pedestrians and structure itself, resulting in amplification of such vibrations, a phenomenon identified by lock-in. However, investigations about accelerations and frequencies of the structural movement that are related to the occurrence of synchronization are still incipient. The aim of this paper is to investigate conditions that could lead to avoidance of synchronization among pedestrians themselves and footbridge, expressed in terms of peak acceleration. The focus is on the low acceleration range, employed in some guidelines as a criterion to avoid synchronization. An experimental campaign was carried out, employing a prototype footbridge that was set into oscillatory motion through a pneumatic exciter controlled by a fuzzy system, with controlled frequency and amplitude. Test subjects were then asked to cross the oscillating structure, and accelerations were simultaneously recorded at the structure and at the subject's waist. Pattern and phase differences between these signals were analysed. The results showed that test subjects tended to keep their walking patterns without synchronization induced by the vibration of the structure, for structural peak acceleration values up to 0.18 m/s2, when frequencies of oscillation were around 0.8 to 0.9 Hz. On the other hand, for frequencies of oscillation below 0.7 Hz, structural peak accelerations up to 0.30 m/s2 did not induce synchronization.

Identification of bridge bending frequencies through drive-by monitoring compensating vehicle pitch detrimental effect

  • Lorenzo Benedetti;Lorenzo Bernardini;Antonio Argentino;Gabriele Cazzulani;Claudio Somaschini ;Marco Belloli
    • Structural Monitoring and Maintenance
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    • v.9 no.4
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    • pp.305-321
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    • 2022
  • Bridge structural health monitoring with the aim of continuously assessing structural safety and reliability represents a topic of major importance for worldwide infrastructure managers. In the last two decades, due to their potential economic and operational advantages, drive-by approaches experienced growing consideration from researcher and engineers. This work addresses two technical topics regarding indirect frequency estimation methods: bridge and vehicle dynamics overlapping, and bridge expansion joints impact. The experimental campaign was conducted on a mixed multi-span bridge located in Lombardy using a Ford Galaxy instrumented with a mesh of wireless accelerometers. The onboard time series were acquired for a number of 10 passages over the bridge,performed at a travelling speed of 30 km/h, with no limitations imposed to traffic. Exploiting an ad-hoc sensors positioning, pitch vehicle motion was compensated, allowing to estimate the first two bridge bending frequencies from PSD functions; moreover, the herein adopted approach proved to be insensitive to joints disturbance. Conclusively, a sensitivity study has been conducted to trace the relationship between estimation accuracy and number of trips considered in the analysis. Promising results were found, pointing out a clear positive correlation especially for the first bending frequency.

A Novel Framework for APT Attack Detection Based on Network Traffic

  • Vu Ngoc Son
    • International Journal of Computer Science & Network Security
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    • v.24 no.1
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    • pp.52-60
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    • 2024
  • APT (Advanced Persistent Threat) attack is a dangerous, targeted attack form with clear targets. APT attack campaigns have huge consequences. Therefore, the problem of researching and developing the APT attack detection solution is very urgent and necessary nowadays. On the other hand, no matter how advanced the APT attack, it has clear processes and lifecycles. Taking advantage of this point, security experts recommend that could develop APT attack detection solutions for each of their life cycles and processes. In APT attacks, hackers often use phishing techniques to perform attacks and steal data. If this attack and phishing phase is detected, the entire APT attack campaign will be crash. Therefore, it is necessary to research and deploy technology and solutions that could detect early the APT attack when it is in the stages of attacking and stealing data. This paper proposes an APT attack detection framework based on the Network traffic analysis technique using open-source tools and deep learning models. This research focuses on analyzing Network traffic into different components, then finds ways to extract abnormal behaviors on those components, and finally uses deep learning algorithms to classify Network traffic based on the extracted abnormal behaviors. The abnormal behavior analysis process is presented in detail in section III.A of the paper. The APT attack detection method based on Network traffic is presented in section III.B of this paper. Finally, the experimental process of the proposal is performed in section IV of the paper.

Exploring the Impact of Consumer Benefits and Altruistic Attitudes on Consumer Attributions and Donation Intentions (소비자 혜택 유형 및 타인지향 성향이 패션기업의 기부 활동에 대한 소비자 귀인과 기부 의도에 미치는 영향)

  • Xi Chen;Sojin Jung
    • Journal of the Korean Society of Clothing and Textiles
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    • v.48 no.4
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    • pp.657-672
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    • 2024
  • This experimental study aimed to investigate the determinants of fashion products donation intentions built on two consumer attributions: strategic and value-driven motives. While consumers may perceive that the underlying motivations of a firm's CSR initiatives are to sincerely help society, they may also believe that such initiatives are strategically motivated and that the firm only engages in CSR to improve its corporate image. Therefore, this study tested how extrinsic factors (consumer monetary and non-monetary- benefits for participating in a donation campaign) and intrinsic factors (i.e., altruistic attitudes) influenced perceived value- and strategic-driven motives, which in turn promote donation intentions. An analysis of 268 responses revealed that monetary benefits, such as offering discount coupons, increased consumers'perception of strategic motives, while non-monetary benefits, such as offering a ring and acertificate, enhanced their perception of value-driven motives. In addition, consumers who tended to have a positive altruistic attitude were more likely to perceive value-driven motives, and this orientation also directly increased donation intentions. These findings also confirmed that only value-driven motives promoted donation intentions. However, consumer benefits did not directly affect donation intentions. The findings of this study suggest valuable managerial implications as well as academic contributions.