192,818 research outputs found
Design Guide for Precast UHPC Waffle Deck Panel System, including Connections, June 2013
No full textAbstract: As a part of an innovation project funded by the Federal Highway Administration (FHWA) Highways for LIFE program, a full-depth precast, ultra-high-performance concrete (UHPC) waffle deck panel and appropriate connections suitable for field implementation of waffle decks were developed. Following a successful full-scale validation test on a unit consisting of two panels with various types of connections under laboratory conditions, the waffle deck was installed successfully on a replacement bridge in Wapello County, Iowa. The subsequent load testing confirmed the desirable performance of the UHPC waffle deck bridge. Using the lessons from the completed project and outcomes from a series of simple and detailed finite element analyses of waffle decks, this report was developed to serve as a guide for broadening the design and installation of the UHPC waffle deck panel in new and existing bridges. Following an introduction to UHPC and waffle deck panels and a summary of completed work, this document presents information on waffle deck design, design of connections, redecking using waffle deck panels, and guidance on precast fabrication, construction, and installation of UHPC waffle deck panels
Comprehensive Bridge Deck Deterioration Mapping of Nine Bridges by Nondestructive Evaluation Technologies Final Report, January 2011
No full textThe primary objective of this research was to demonstrate the benefits of NDT technologies for effectively detecting and characterizing deterioration in bridge decks. In particular, the objectives were to demonstrate the capabilities of ground-penetrating radar (GPR) and impact echo (IE), and to evaluate and describe the condition of nine bridge decks proposed by Iowa DOT. The first part of the report provides a detailed review of the most important deterioration processes in concrete decks, followed by a discussion of the five NDT technologies utilized in this project. In addition to GPR and IE methods, three other technologies were utilized, namely: half-cell (HC) potential,
electrical resistivity (ER), and ultrasonic surface waves (USW) method. The review includes a description of the principles of operation, field implementation, data analysis, and interpretation; information regarding their advantages and limitations in bridge deck evaluations and condition monitoring are also implicitly provided.. The
second part of the report provides descriptions and bridge deck evaluation results from the nine bridges. The results of the NDT surveys are described in terms of condition assessment maps and are compared with the observations obtained from the recovered cores or conducted bridge deck rehabilitation. Results from this study confirm that the
used technologies can provide detailed and accurate information about a certain type of deterioration, electrochemical environment, or defect. However, they also show that a comprehensive condition assessment of bridge decks can be achieved only through a complementary use of multiple technologies at this stage,. Recommendations are provided
for the optimum implementation of NDT technologies for the condition assessment and monitoring of bridge decks
Using SHERPA to predict design-induced error on the flight deck.
No full textHuman factors certification criteria are being developed for large civil aircraft.
The objective is to reduce the incidence of design induced error on the flight deck.
Many formal error identification techniques currently exist, however none of
these have been validated for their use in an aviation context. This paper
evaluates SHERPA (Systematic Human Error Reduction and Prediction
Approach) as a means for predicting design induced pilot error. Since SHERPA
was developed for predicting human error in the petrochemical and nuclear
industries, a series of validation studies have suggested that it is amongst the best
human error prediction tools available. This study provides some evidence for the
reliability and validity of SHERPA in a flight deck context and concludes that it
may form the basis for a successful human error identification tool
Numerical investigation of the effects of pedestrian barriers on aeroelastic stability of a proposed footbridge
No full textA numerical investigation into the aerodynamic characteristics and aeroelastic stability of a proposed footbridge across a motorway in the north of England has been undertaken. The longer than usual span, along with the unusual nature of the pedestrian barriers, indicated that the deck configuration was likely to be beyond the reliable limits of the British design code BD 49/01. In particular, the investigation focussed on the susceptibility of the bridge due to flutter, and to assess if the design wind speeds could be met satisfactorily. The calculations were performed using the discrete vortex method, DIVEX, developed at the Universities of Glasgow and Strathclyde. DIVEX has been successfully validated on a wide range of problems, including the aeroelastic response of bridge deck sections. The proposed deck configuration, which incorporated a pedestrian barrier comprised of angled flat plates, was found to be unstable at low wind speeds with the plates having a strong turning effect on the flow at the leading edge of the deck. DIVEX was used to assess a number of alternative design options, investigating the stability with respect to flutter for each configuration. Reducing the number of flat plates and their angle to the deck lessened the effect of the barrier on the overall aerodynamic characteristics and increased the stability of the bridge to an acceptable level, with the critical flutter speed in excess of the specified design speed
A sunrise deck scene [picture] /
No full textCondition: Good.; Part of the collection: Souvenir of the visit of the Federal Parliamentary Party to the Northern Territory, April - May, 1912.; Caption: "A sunrise deck scene"--Handwritten in ink to left of image.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-an24189404. Shows seamen working on the deck of the S.S. Eastern
Fatigue resistance of rib to deck, crossbeam to deck and deck to deck welds in orthotropic decks using structural stress
No full textThis study derives the fatigue resistance of welded details in orthotropic decks using structural stress (hot-spot stress where possible) based on tests described in literature and tests by the authors. The data are supported with linear elastic fracture mechanics simulations. Details covered are the rib to deck weld, the crossbeam to deck weld and the deck butt weld. High fatigue resistances are found, caused by favourable loading modes (bending and compression) and reduced driving force with the growth of cracks. The technical specification TS 1993-1-901, part of the new generation of Eurocodes, is based on the results of this study.</p
Simulation of multi-deck medium temperature display cabinets with the integration of CFD and cooling coil models
No full textThis is the post-print version of the final paper published in Applied Energy. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.In this paper, the model for the multi-deck medium temperature display cabinets is developed with the integration of CFD and cooling coil sub-models. The distributed method is used to develop the cooling coil model with the airside inputs from the outputs of the CFD model. Inversely, the airside outputs from the cooling coil model are used to update the boundary conditions of the CFD model. To validate this cabinet model, a multi-deck medium temperature display cabinet refrigerated with a secondary refrigerant cooling coil was selected as a prototype and mounted in an air conditioned chamber. Extensive tests were conducted at constant space air temperature and varied relative humilities. The cabinet model has been validated by comparing with the test results for the parameters of air at different locations of the flow path, and temperatures of refrigerant and food product, etc. The validated model is therefore used to explore and analyse the cabinet performance and control strategies at various operating and design conditions.DEFR
Aircraft Passenger Comfort Enhancement by Utilization of a Wide-Body Lower Deck Compartment
No full textGrowing passenger dimensions and the demand for more comfort in the economy class cabin is a trend that is becoming more important during aircraft conceptual design. Based on recent investigations, it is known that current aircraft seat dimensions are not suitable and safe for a large part of the world population. Therefore, a change in aircraft conceptual design thinking, by taking human anthropometry into account, is required. This thesis investigates the opportunity to change the aircraft during conceptual design as well as the opportunity to change current aircraft in order to provide a higher level of passenger comfort and safety. To measure the latter, a comfort model is created, based on scientific research and human dimensions, allowing for the measurement of comfort related to seating configurations, seat characteristics, and cabin dimensions. By establishing the ideal seat dimensions, it is shown that conceptual aircraft designs for the worldwide 95 percentile passenger require wider, but shorter, fuselages. Using the Initiator as a conceptual design tool, four short-haul and four long-haul aircraft are modeled for a range of seat dimensions. Based on an inside-out aircraft design approach, it is shown that similar aircraft performance characteristics are obtained when designing for the worldwide 95 passenger percentile. Moreover, a similar level of direct operating costs, and hence profitability, is attained. However, designing for the worldwide 99 passenger percentile yields considerably higher fuel burn rates and operating costs. An average increase of 3.9 % among all modeled aircraft is seen for the harmonic fuel burn, leading to an increase of 4.2 % in direct operating costs. Considering existing aircraft, use is made of an outside-in aircraft design approach to assess a set of performance characteristics. Based on an average utilization of 37 % of the cargo space in commercial transport aircraft, a potential is shown for a different utilization of the aircraft lower deck, allowing the airline to provide more passenger comfort while retaining a similar level of profitability. Using the Airbus A340-300 as reference aircraft, it is shown that the placement of passengers in the lower hold is feasible from a regulatory, ergonomical, economical, and structural point of view. Based on a reference three-class layout with 267 passengers, it is shown that a lower deck seating compartment provides an increase of 14.6 % in the number of passengers when similar seat properties are used as on the main passenger deck. The installment of additional furnishing and required structural reinforcements results in a decrease of 12 % in maximum structural payload weight. Nevertheless, it is shown that the placement of passengers in the lower deck yields higher profitability rates for the airline when compared to the carriage of additional freight. Secondly, the placement of lavatories and galleys in the aircraft lower deck is investigated, allowing for a maximum increase of 13 % in passenger seats. To allow for the installment of galley lift systems, staircases, and required safety measures, a decrease of 6.27 % in maximum structural payload is attained. By subsequently increasing seat characteristics on the main deck, an increase of 12 % in passenger comfort is achieved for the worldwide 95 passenger percentile. The airline profitability level associated to this comfort layout in turn relates to an average carriage of 5300 kg of freight during the aircraft service life, being equal to the current average. For both the lower deck seating and service utilization, it is concluded that the flying experience of the passenger is increased, while a similar level of airline and manufacturer profitability is obtained. Aircraft lower deck utilization can therefore be seen as a feasible replacement for conventional aircraft configurations.Flight Performance and PropulsionAerospace Engineerin
The influence of human factors on operational efficiency
No full textThis paper adopts a socio-technical systems approach is taken to examine how airline operational efficiency can be enhanced from a human factors perspective. Four case studies are examined from this viewpoint: increasing operating efficiency on the airport ramp; increasing efficiency through flight crew rostering; increasing
efficiency by promoting direct routing; and increasing efficiency through greater flight deck automation. It is argued that the increases in operational efficiency (which is taken to be almost synonymous with cost) taking solely a human factors perspective will be minimal. To truly enhance operating efficiency the human component in any system cannot be examined in isolation from all other components
Structural Performance of FRP Bridge Deck
No full textThe purpose of this paper is to present fatigue and strength experimental qualifications performed for an all-composite bridge deck. This bridge deck, made up of fiber-reinforced polymer (FRP) was installed on the campus at University of Missouri at Rolla on July 29th, 2000. The materials used for the fabrication of this 30 foot (9.144 m) long by 9 foot (2.743 m) wide deck were 3 inches (76.2 mm) pultruded square hollow glass and carbon FRP tubes of varying lengths. These tubes were bonded using an epoxy adhesive and mechanically fastened together using screws in seven different layers to form the bridge deck with tubes running both longitudinal and transverse to the traffic direction. The cross-section of the deck was in the form of four identical I-beams running along the length of the bridge. Fatigue and failure tests were conducted on a 30 foot (9.144 m) long by 2 foot (609.6 mm) wide prototype deck sample, equivalent to a quarter portion of the bridge deck. The loads for these tests were computed so as to meet American Association of State Highway and Transportation Officials (AASHTO) H-20 truckload requirements based on strength and maximum deflection. The sample was fatigued to 2 million cycles under service loading and a nominal frequency of 4 Hz. Stiffness changes were monitored by periodically interrupting the run to perform a quasi-static test to service load. Results from these tests indicated no loss in stiffness up to 2 million cycles. Following the fatigue testing, the test sample was tested to failure and no loss in strength was observed. The testing program, specimen detail, experimental setup and instrumentation, testing procedure, and the results of these tests are discussed in detail. A finite-element model of the laboratory test was also developed. The results from the model showed good correlation to deflections and longitudinal strains measured during the tests. The design of the bridge deck has been discussed in detail
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