Top Deck Research Articles

Post-rehabilitation assessment of a centenary steel bridge through numerical and experimental analysis

This paper presents an experimental and numerical analysis regarding the structural assessment of an existing steel bridge – the Eiffel Bridge – after a recent rehabilitation. The Eiffel Bridge, a centenary road–rail truss bridge, comprising two superimposed decks, was subjected to major rehabilitation works involving the replacement of the top concrete deck, the strengthening of the upper chords of the main truss girders and the replacement of the support bearings. In this context a load test and an environmental test were carried out aiming at the assessment of the new structural condition and the evaluation of the effectiveness of the elements' strengthening. A structural analysis was carried out in order to characterize the most relevant aspects of the structural behavior and to support the discussion of the field results. Particular aspects concerning the main girders' bending, the nature of nodes' rotations, and the response under temperature changes are highlighted. The effectiveness of the strengthening of the top chords is verified based on the strains' measurements. Finally, it is shown that the thorough characterization of the structural behavior enabled the establishment of a reference condition for future assessments of the structure.

Underground Parking structure built with deep foundations and vault precast elements in Spain

In many cases the only places available for the construction of a new car park are the existing streets or roads. These streets may also have important or historic buildings very close to the structure, which means that they cannot be disturbed in any way during the construction of the parking structure. In this particular case, the novelty is that the top deck is solved with a unique structure: a vault that interacts with the pile wall not only for vertical but also for horizontal loads due to the arch mechanism. The construction of the vault is solved as a large precast element of one piece of more than 16 in length and 2.40m in width, which is built in the factory, transported with the help of trucks and erected on site with large cranes.

Mars Science Laboratory Mission and Science Investigation

Scheduled to land in August of 2012, the Mars Science Laboratory (MSL) Mission was initiated to explore the habitability of Mars. This includes both modern environments as well as ancient environments recorded by the stratigraphic rock record preserved at the Gale crater landing site. The Curiosity rover has a designed lifetime of at least one Mars year (∼23 months), and drive capability of at least 20 km. Curiosity’s science payload was specifically assembled to assess habitability and includes a gas chromatograph-mass spectrometer and gas analyzer that will search for organic carbon in rocks, regolith fines, and the atmosphere (SAM instrument); an x-ray diffractometer that will determine mineralogical diversity (CheMin instrument); focusable cameras that can image landscapes and rock/regolith textures in natural color (MAHLI, MARDI, and Mastcam instruments); an alpha-particle x-ray spectrometer for in situ determination of rock and soil chemistry (APXS instrument); a laser-induced breakdown spectrometer to remotely sense the chemical composition of rocks and minerals (ChemCam instrument); an active neutron spectrometer designed to search for water in rocks/regolith (DAN instrument); a weather station to measure modern-day environmental variables (REMS instrument); and a sensor designed for continuous monitoring of background solar and cosmic radiation (RAD instrument). The various payload elements will work together to detect and study potential sampling targets with remote and in situ measurements; to acquire samples of rock, soil, and atmosphere and analyze them in onboard analytical instruments; and to observe the environment around the rover. The 155-km diameter Gale crater was chosen as Curiosity’s field site based on several attributes: an interior mountain of ancient flat-lying strata extending almost 5 km above the elevation of the landing site; the lower few hundred meters of the mountain show a progression with relative age from clay-bearing to sulfate-bearing strata, separated by an unconformity from overlying likely anhydrous strata; the landing ellipse is characterized by a mixture of alluvial fan and high thermal inertia/high albedo stratified deposits; and a number of stratigraphically/geomorphically distinct fluvial features. Samples of the crater wall and rim rock, and more recent to currently active surface materials also may be studied. Gale has a well-defined regional context and strong evidence for a progression through multiple potentially habitable environments. These environments are represented by a stratigraphic record of extraordinary extent, and insure preservation of a rich record of the environmental history of early Mars. The interior mountain of Gale Crater has been informally designated at Mount Sharp, in honor of the pioneering planetary scientist Robert Sharp. The major subsystems of the MSL Project consist of a single rover (with science payload), a Multi-Mission Radioisotope Thermoelectric Generator, an Earth-Mars cruise stage, an entry, descent, and landing system, a launch vehicle, and the mission operations and ground data systems. The primary communication path for downlink is relay through the Mars Reconnaissance Orbiter. The primary path for uplink to the rover is Direct-from-Earth. The secondary paths for downlink are Direct-to-Earth and relay through the Mars Odyssey orbiter. Curiosity is a scaled version of the 6-wheel drive, 4-wheel steering, rocker bogie system from the Mars Exploration Rovers (MER) Spirit and Opportunity and the Mars Pathfinder Sojourner. Like Spirit and Opportunity, Curiosity offers three primary modes of navigation: blind-drive, visual odometry, and visual odometry with hazard avoidance. Creation of terrain maps based on HiRISE (High Resolution Imaging Science Experiment) and other remote sensing data were used to conduct simulated driving with Curiosity in these various modes, and allowed selection of the Gale crater landing site which requires climbing the base of a mountain to achieve its primary science goals. The Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem is responsible for the acquisition of rock and soil samples from the Martian surface and the processing of these samples into fine particles that are then distributed to the analytical science instruments. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments (APXS, MAHLI) on rock and soil targets. SA/SPaH consists of a robotic arm and turret-mounted devices on the end of the arm, which include a drill, brush, soil scoop, sample processing device, and the mechanical and electrical interfaces to the two contact science instruments. SA/SPaH also includes drill bit boxes, the organic check material, and an observation tray, which are all mounted on the front of the rover, and inlet cover mechanisms that are placed over the SAM and CheMin solid sample inlet tubes on the rover top deck.

Strengthening of Slab Action in Transverse Direction of Damaged Deck of Prestressed Box Girder Bridge

The deck slab of a prestressed concrete (PSC) box girder bridge serves as an integral part of the structural box section, and any damage to the deck may seriously affect the load-resistance mechanism of the bridge. This paper discusses a case study of a PSC box girder that developed early damage to the deck because of the poor placement of concrete at the time of construction as established by in situ non- destructive and core tests. The possibility of total replacement of the top deck was ruled out because of the disruptive and tedious nature of the process, which could have endangered the overall stability of the box girder. Strengthening of the deck was performed by installing a series ofsteeljoistsattheundersideofthedeckslabandaddingathinoverlayofconcreteatthetoptorestoreittotherequisitestrength.Thisapproach was bestsuited, foritnotonlyimprovedthestressdistributioninthedeck,butalsomaintainedtheoriginalloadresistancemechanism provided by the prestressing arrangement in thegirder. The presented scheme was easy to implement and could beused for similar damages occurring to the deck of PSC box girder bridges. DOI: 10.1061/(ASCE)BE.1943-5592.0000318. © 2013 American Society of Civil Engineers. CE Database subject headings: Rehabilitation; Bridge decks; Prestressing; Box girders; Case studies. Author keywords: Rehabilitation; Bridge deck; Prestressed; Box girder.

Effects of floor space during transport and journey time on indicators of stress and transport losses of market-weight pigs1

The effects of floor space on the trailer and journey time during transport from the farm to the packing plant on indicators of stress (open-mouth breathing, muscle tremors, and skin discoloration) and on the incidence of transport losses (dead on arrival, nonambulatory, noninjured, and nonambulatory, injured) were evaluated in a study involving 160 loads of market-weight pigs (BW 124.7 ± 4.38 kg) using a split-plot design with a 2 × 6 factorial arrangement of treatments: 1) journey time [main plot; short (<1 h) and long (3 h)] and 2) floor space (subplot; 0.396, 0.415, 0.437, 0.462, 0.489, and 0.520 m(2)/pig, which is equivalent to 0.317, 0.332, 0.350, 0.370, 0.391, and 0.416 m(2)/100 kg of BW, respectively). Two consecutively loaded trailers were randomly allotted to journey time treatment. Floor space treatments were compared in the front 3 compartments on the top and bottom decks of the trailer and were created by varying the number of pigs per compartment, which confounds the effect of floor space with group size. Of the 17,652 pigs transported in 954 test compartments, 0.24% died or became nonambulatory. Neither journey time nor floor space had an effect (P > 0.05) on the incidence of dead and nonambulatory, injured pigs, or on total transport losses. There were interactions (P < 0.05) between journey time and floor space treatments for the incidences of nonambulatory, noninjured pigs and open-mouth breathing. For 2 of the smallest floor spaces (0.415 and 0.437 m(2)/pig), the incidence of nonambulatory, noninjured pigs was greater on short than on long journeys; for the other 4 floor spaces there was no effect (P > 0.05) of journey time. The incidence of open-mouth breathing for the 3 smallest floor spaces was greater (P < 0.05) for short than long journeys, whereas there was no effect (P > 0.05) of journey time for the 3 greatest floor spaces. The frequency of skin discoloration was greater (P < 0.001) for pigs transported at the 2 smallest floor spaces compared with the other 4 floor spaces. In summary, short journey time increased the frequency of indicators of stress after unloading at the plant for pigs transported at smaller floor spaces and also increased the incidence of nonambulatory, noninjured pigs at 2 of the 3 smallest floor spaces. However, neither transport floor space nor journey time had an effect on total losses.

Rolling the Black Pearl Over: Analyzing the Physics of a Movie Clip

In the third movie (“At World's End”) in the Pirates of the Caribbean series, Jack Sparrow and his crew need to roll their ship (the Black Pearl) over in order to bring it back to the living world during a green flash at sunset. They do so by running back and forth from one side railing to the other on the top deck. In addition, Captain Barbossa orders that 18 cannons and a pile of barrels on the lower deck be cut loose to add mass to the running crew. In the movie they overturned the ship, but would they succeed under the same circumstances on a real galleon? In this paper, a numerical analysis using simple approximations is developed that suggests that what occurs in the movie is in fact realistic. Analyzing a popular film clip in this manner is a good way to arouse student interest, to teach about physics and numerical methods, and to model scientific reasoning when a situation is not as neatly defined as in a typical textbook problem.

Using SPH one-way coupled to DEM to model wet industrial banana screens

Large banana screens with multiple decks are used extensively in the process separation of many valuable export commodities. They are high capacity vibrating screens with a curved profile. Discrete Element Method (DEM) modelling using non-spherical particles has previously provided significant insight into the operation of these dry industrial screens. Here we introduce the use of Smoothed Particle Hydrodynamics (SPH) to model the flow of slurry (water and fine material) through a double deck banana screen. This paper firstly reports on the underlying DEM model of the coarse particulate flow on a full-scale banana screen. We then use Smoothed Particle Hydrodynamics (SPH) to model the transport of fine particle slurry over and through the double deck banana screen. Finally, we combine the DEM with SPH models using a one-way coupling to simulate the effects of adding a slurry flow to coarse particulates on the banana screen. The key outcomes from this study are that; SPH is ideally suited for the high speeds and the high fragmented and filamentary nature of the fluid flow through the screen deck openings; the fluid only (SPH) model of slurry behaves similarly to the DEM approach in that more fluid is screened as the velocity slows, except near the earlier panels on the top deck; and, use of a porous media derived from DEM in one-way coupled approach with SPH produces clear and reasonable changes in fluid structure, separation and wetting of the screens consistent with slurry behaviour. Specifically, the fluid layer was much thicker in the coupled case, with slurry being trapped inside a coarse particle bed and which is sensitive to the fluid viscosity.

CFD Verification of Engineering Options for Mitigating Liquid Sloshing in Topside Vessels on a Floating Production Facility

Summary This paper proposes an active-control concept that mitigates the liquid sloshing in a topside vessel by reducing the excitation source, thus extending the scope of sloshing mitigation. To verify the concept proposed, sloshing response in partially liquid-filled topside vessels was numerically investigated under various wave and vessel conditions. This study confirmed that vessel location on the top deck exhibits a weak correlation with the sloshing response. Although liquid sloshing is not very sensitive to the vessel location, it is beneficial to place the topside processing vessels as close as possible to gravity center of the floating production facilities (FPS/FPSO). It is evident that liquid sloshing in a topside vessel is closely related to the incident direction of the wave. The perpendicular incidence results in the minimum sloshing response; the parallel incidence leads to the maximum sloshing response. It is, therefore, essential to properly orient the vessel to establish perpendicular or close-to- perpendicular incidence status. It is also verified that liquid sloshing is significantly increased with length-to-diameter (L/D) ratio of a vessel. The horizontal vessels with larger L/D suffer from severe liquid sloshing. Because vertical vessels have a minimum L/D = 1.0, they always exhibit better antisloshing performance than the horizontal vessels. In addition, it is advisable to prevent a vessel from operating near the resonance-wave condition. Although the active control concept shows attractive advantages over the conventional approach, it is more feasible for layout of topside vessels on a newly built FPS/FPSO. Because most of the floating-production systems are not built from scratch such that the topside processing vessels can be placed in the optimal position and orientation but are retrofitted for a topside vessel to fit onto a limited deck space, the passive-control approach may be more applicable. Generally, a combination of the active and passive approaches should be considered to minimize liquid sloshing in a topside process vessel.

Associations of beef calf wellness and body weight gain with internal location in a truck during transportation

Cattle transportation by commercial truck carrier is common in the United States, and often cattle are placed within 1 of 8 potential compartments within the truck for the journey. The objective of this research was to determine potential associations between animal wellness (as measured by ADG and health outcomes) during a relatively short backgrounding phase (46.6 +/- 8.5 d) and location within the truck during transit. Data from 21 loads (average calves per load = 101.5; average BW = 210.1 +/- 19.4 kg) were included in the analysis. For each shipment, calves were divided among 8 compartments within the trailer: nose on top deck (NOT), nose on bottom deck (NOB), bottom deck middle forward (BDF), bottom deck middle rear (BDR), rear on the bottom (ROB), top deck middle forward (TDF), top deck middle rear (TDR), and rear on the top deck (ROT). General logistic (health outcomes) and mixed (ADG) models were employed to analyze the data accounting for effects due to truck section as well as the hierarchical data structure of multiple arrival times, loads, and pens. Cattle in the ROT section had less short-term BW gains compared with NOT and tended (P < 0.10) to be less than NOB. Cattle in the forward sections (NOT, NOB) were less (P = 0.02) likely [odds ratio (OR): 0.67, 95% confidence limits (CL): 0.50, 0.94] to be treated at least once compared with cattle in the middle sections (TDF, TDR, TOP, BDF, BDR, BOT). Calves in compartments with 15 head or less tended (P < 0.10) to have reduced odds of being treated compared with cattle in compartments with 16 to 30 head (OR: 0.79, 95% CL: 0.60, 1.0) or greater than 31 head (OR: 0.73, 95% CL: 0.53, 1.0). Our current project reveals that the location within the truck may affect calf health and performance.

Separation performance of double deck banana screens – Part 2: Quantitative predictions

Banana screens are often used for high capacity separation of iron ore, coal and aggregates into different size fractions. They consist of one or more curved decks that are fitted with screen panels with arrays of square or rectangular holes. The screen structure is vibrated while a dense stream of particles flows over it and is separated according to size. The material discharging from the top of the deck is the oversize and may become a coarse product or be crushed and recycled to the screen feed. The material falling through the deck can be further separated by additional decks below. Each lower deck returns a product stream and the material passing out through the bottom deck is the undersize. In this paper, Discrete Element Method (DEM) is used to explore the separation performance of a full industrial scale double deck banana screen for a peak acceleration of 5 g. The separation efficiency of each deck is analysed and the individual contributions of each screen panel are assessed using outputs from the model. Residence time distributions for particles on each deck provide insight into both the transport characteristics along the deck and the separation performance through each deck. The top and bottom decks have very different flow behaviour with very different bed structure and motion. The stresses applied by the flowing particles to the screen cloths and the impact and abrasive wear on the screen surfaces are evaluated. Finally, the energy absorbed by particles provides insight into the extent of particle degradation produced by transiting the screen.

Experimental Study on the Behavior of a Swimming Pool Onboard a Large Passenger Ship

The water in a swimming pool on the top deck of a large passenger ship can be excited to a resonant motion, even in a moderate sea state. The motion of the water in the pool is mainly caused by longitudinal acceleration, resulting from the ship's pitch and surge motions. At resonance, there can be high waves in the pool and splashing of water. In this study the behavior of the Solarium Pool of the Freedom of the Seas was examined in various sea states and operating conditions. The motions of the pool were calculated on the basis of a linear seakeeping method, and the behavior of the water in the pool was studied with experimental model tests. A large-scale model of the pool was constructed and fitted to a purpose-built test bench that could be axially moved by a computer-controlled hydraulic cylinder. Water elevation in the pool was measured, and all tests were video recorded. Different modifications of the pool were tested to improve the behavior of the pool. A strong correlation between the longitudinal motion and the behavior of the water in the pool was found.

Successful Drilling of Oil and Gas Wells by Optimal Drilling-Fluid/Solids Control— A Practical and Theoretical Evaluation

Summary Since the development of the drilling industry, the process for removing drill solids from the drilling fluid has culminated in the use of shaker screens as the primary or sole solution. It is, therefore, necessary to optimize both filtration efficiency and the screen life to hinder drilled solids from entering the drilling fluid. Optimum solids control can be obtained by using knowledge of how damage to the filtration cloth arises, of how to reduce it, and of how the particles in the circulation system influence the general picture of the drilling process. When this knowledge is accepted, established, and implemented in the drilling industry, it is possible to maintain efficient drilling. This paper describes, in detail, the theory and field examples on how wear arises on the shaker-screen cloth. As will be shown, this knowledge has been used to increase the solids-control efficiency and to reduce the screen wear by more than 90% in several field cases where 17½-in. sections have been drilled with oil-based mud. This has been achieved by use of a different screen configuration, running with top screens with finer cut points than normal. This leads to removal of 90 to 95% of the solids from the fluid using the top deck, thereby minimizing the wear on the finer bottom-deck screens. The documentation is based on practical off-shore results from these drilling operations, including data from the drilling log, laboratory analyses of the drilling fluid, and of the particle-size distribution (PSD) of the drilling fluid. The particular focus of this article is the application of double-deck shakers.

Vibration of a truss structure excited by a moving oscillator

This paper studies the vibration of a truss structure composed of a number of rigidly connected Timoshenko beams. The excitation is provided by a moving oscillator of an unsprung mass that supports another mass through a spring (oscillator) and moves on top of the truss structure. Each component beam of the structure is meshed with a number of Timoshenko beam elements. The finite-element (FE) modes of the whole structure are first obtained for the nodes of the FE mesh and then they are converted into an analytical form that is constructed over all the elements of the top deck of the truss through the element shape functions, whereby the location of the moving oscillator is easily tracked and the displacement continuity and force equilibrium conditions at the contact point can be easily implemented. This numerical–analytical combined approach has the advantage of the versatility of the FE method in dealing with structures (trusses or frames in this paper) of arbitrary configurations and the special efficiency and convenience of the analytical method in dealing with moving loads. Vibration of the truss structure and vibration of the oscillator are studied through simulated examples. It is found that the dynamic response can be several times higher than the relevant static response at high speeds. It is also found that the dynamic contact force can be much higher than its static value and may become negative if the contact between the oscillator and the truss is assumed to be constantly maintained. Interestingly, suitably chosen parameter values can bring the dynamic response and the dynamic contact force close to their respective static values.

Symposium on ‘Human evolution: ancestors and relatives’

Symposium on ‘Human evolution: ancestors and relatives’

Erha Floating Production, Storage, and Offloading Vessel

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 18659, "Erha and Erha North Development: Erha Floating Production, Storage, and Offloading Vessel," by S.M. Day and G.J. Parker, ExxonMobil, and P. Barclay and H. Boulais, Saipem, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May. The new-build Erha floating production, storage, and offloading vessel (FPSO) is one of the largest in the world, at 285 m long by 63 m wide, with a 2.2-million-bbl-capacity hull and capacity for 210,000 B/D oil processing, 340 MMscf/D gas injection, and 150,000 B/D water injection. The full-length paper discusses the development of the FPSO, including design and operational features incorporated to meet field-specific requirements. The paper also addresses the project-management challenges associated with each phase of the job, with emphasis on the safe and timely execution of a sequential drill center startup while managing simultaneous production operations and in-field development drilling. Introduction The Erha and Erha North development, in 1200 m of water approximately 97 km offshore Nigeria, consists of three subsea drill centers tied back to the FPSO by steel catenary risers (SCRs). Injection fluids are transferred from the FPSO by the SCRs and flowlines for subsea injection at the drill centers. The FPSO is a new-build, spread-moored vessel consisting of two trains of three-stage oil separation. Processed crude is stored in the hull and offloaded regularly to tankers through offloading lines and a catenary anchor leg mooring (CALM) buoy. Associated gas is compressed and dehydrated to provide fuel gas, with the remainder reinjected into the producing reservoir. Water injection facilities inject treated seawater into the reservoir for pressure maintenance to enhance oil production. The design, fabrication, integration, and startup of the Erha FPSO was a global undertaking, with engineering performed primarily in France, India, and Nigeria; hull fabrication in Korea; and topside fabrication in Singapore, Malaysia, and Nigeria. The hull and topside were integrated in Singapore, and the FPSO was towed to offshore Nigeria for installation. This work was carried out under a single prime contractor, Saipem S.A., and its in-country affiliate, Saipem Contracting Nigeria Ltd. (SCNL) and included key design and execution interfaces with the Erha tiebacks and subsea-system prime contractors. Facilities Description The Erha FPSO (Fig. 1) is a barge-shaped, new-build monohull with all of the processing equipment on its top deck. It has a 2.2-million-bbl oil-storage capacity. Processed oil is offloaded to export tankers by the CALM buoy offloading system. The FPSO also has the capability to offload crude to tandem moored export tankers in a "bow-to-bow" configuration in the event that the offshore loading system is not available.

Experimental Evaluation of Compressive Behavior of Orthotropic Steel Plates for the New San Francisco–Oakland Bay Bridge

Compression tests were conducted on two reduced-scale orthotropic plates to verify the design strength of steel box girders for the new San Francisco-Oakland Bay Bridge. The first specimen was composed of three longitudinal closed ribs and a top deck plate. It failed in global buckling, followed by local buckling in the deck plate and ribs. The second specimen, which was composed of four longitudinal T-shaped ribs and a bottom deck plate, experienced global buckling as well as local buckling in the ribs and the deck plate. The ultimate strength and failure mode of both specimens were evaluated by two bridge design specifications: the 1998 AASHTO load and resistance factor design specification and the 2002 Japanese JRA specification. Findings from code comparisons showed that: 1 Sufficient flexural rigidity of ribs were provided for both specimens; 2 the JRA specification slightly overestimated the ultimate strength of both specimens; and 3 neither specifications predicted the observed buckling sequence in Specimen 2. A general-purpose nonlinear finite element analysis program ABAQUS was used to perform correlation study. The analysis showed that the ultimate strength and postbuckling behavior of the specimens could be reliably predicted when both the effects of residual stresses and initial geometric imperfections were considered in the model.

CONUS Prepositioned Afloat Aircraft Carriers: A Concept for Mobilizing Heavy Brigades

Abstract This research breaks from current prepositioning paradigms in order to answer the question: Could re-commissioned aircraft carriers prepositioned with heavy brigades in CONUS ports enhance the United States' ability to respond to global contingencies? The methodology used was an open-ended panel interview conducted during two site visits. The first was to the Puget Sound Naval Shipyard's Inactive Ships facility in Bremerton, Washington to inspect the decommissioned USS Constellation aircraft carrier. This panel primarily focused on the generation of size and cost data. The second visit was to Goose Creek, South Carolina for a panel interview with DynCorp contractors responsible for the exercise and care of afloat stocks. This panel focused on the ability of the ship's elevators and top deck to increase readiness by enabling the use of more rigorous land-based maintenance and exercising criteria. The study concludes that reactivation cost estimates are far below those previously espoused by similar research efforts. The use of the top deck and modified ship and maintenance regulations can enhance readiness of prepositioned stocks. Finally, the carrier's speed makes projection from CONUS ports a critical enabler for homeland defense in the global war on terror.

CONUS Prepositioned Afloat Aircraft Carriers: A Concept for Mobilizing Heavy Brigades

Abstract This research breaks from current prepositioning paradigms in order to answer the question: Could re-commissioned aircraft carriers prepositioned with heavy brigades in CONUS ports enhance the United States' ability to respond to global contingencies? The methodology used was an open-ended panel interview conducted during two site visits. The first was to the Puget Sound Naval Shipyard's Inactive Ships facility in Bremerton, Washington to inspect the decommissioned USS Constellation aircraft carrier. This panel primarily focused on the generation of size and cost data. The second visit was to Goose Creek, South Carolina for a panel interview with DynCorp contractors responsible for the exercise and care of afloat stocks. This panel focused on the ability of the ship's elevators and top deck to increase readiness by enabling the use of more rigorous land-based maintenance and exercising criteria. The study concludes that reactivation cost estimates are far below those previously espoused by similar research efforts. The use of the top deck and modified ship and maintenance regulations can enhance readiness of prepositioned stocks. Finally, the carrier's speed makes projection from CONUS ports a critical enabler for homeland defense in the global war on terror.

A systematic approach towards the structural behaviour of a lightweight deck–side shell system

Lightweight structures are increasingly used for high-speed ships. This paper presents a systematic approach to analyse the structural behaviour of a lightweight deck–side shell system using high strength steel. An analytical model of the deck–side shell system was first given, which includes the effects of stiffeners for the deck and side shell, the support conditions of the centreline girder (CL-girder), the influence of transverse beams, and the interaction between the side shell and the lightweight deck as parts of problems to the solution. By changing several geometric parameters, the sensitivity of both overall and local stress and deflection for the deck–side shell system was investigated. The different geometric parameters analysed comprise the influence for variation in the thickness of the web for transverse beams, longitudinal stiffeners and the CL-girder, the thickness of lower flange for the transverse beam and, the thickness for the panel. Furthermore, the influence of the lightweight deck and loads from the deck above on the side shell, the effects of the side shell and loads from top deck on the deck, the support conditions for the CL-girder, and the influence of deck loads on the eigenmodes were also analysed. By evaluating the results obtained from FE simulation, the support conditions of the CL-girder, the thickness of the panels and the lower flange of the transverse beams were found to be the most relevant parameters affecting both the stress and the deflection distribution of the structure. The dynamic characteristics of the structure were also analysed. The FE analysis concerning buckling of the structure was present. The results enable naval architects and structural engineers to design new extreme lightweight deck structure more reliable and economical. And some suggestions for future research are also given.

FIELD EVALUATI ON OF A SPRINKLING SYSTEM FOR COOLING COMMERCIAL LAYI NG HENS IN IOWA

An economical, lowpressure (276 kPa, 40 psi) sprinkling system was tested for its efficacy of cooling laying hensin a commercial highrise layer house [14 130 m (46 426 ft)] in Iowa. The sprinklers, rated at 2.1 mL/s (2 gal/h) each,were equally spaced at 3 m (10 ft) apart and 2.4 m (8 ft) above the floor in each cage aisle of the layer house. They werecontrolled to operate 10 s every 10 min when the inside temperature exceeded 32_C (90_F). The system was shown to improveegg production by 2.6% overall and 5.6% for the top deck (P < 0.01). There was no sign of sprinkling damage to eggshellintegrity. Autocorrelation analysis has the potential to quantify the impact of heat stress history on subsequent egg productionresponse of the hen. Work is needed to optimize the layout of the sprinklers for uniform water distribution and waterapplication rate as a function of environmental conditions.