Deck Length Research Articles

Ambient vibration testing of Berta Highway Bridge with post-tension tendons

The aim of this study is to determine the dynamic characteristics of long reinforced concrete highway bridges with post-tension tendons using analytical and experimental methods. It is known that the deck length and height of bridges are affected the dynamic characteristics considerably. For this purpose, Berta Bridge constructed in deep valley, in Artvin, Turkey, is selected as an application. The Bridge has two piers with height of 109.245 m and 85.193 m, and the total length of deck is 340.0 m. Analytical and experimental studies are carried out on Berta Bridge which was built in accordance with the balanced cantilever method. Finite Element Method (FEM) and Operational Modal Analysis (OMA) which considers ambient vibration data were used in analytical and experimental studies, respectively. Finite element model of the bridge is created by using SAP2000 program to obtain analytical dynamic characteristics such as the natural frequencies and mode shapes. The ambient vibration tests are performed using Operational Modal Analysis under wind and human loads. Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods are used to obtain experimental dynamic characteristics like natural frequencies, mode shapes and damping ratios. At the end of the study, analytical and experimental dynamic characteristic are compared with each other and the finite element model of the bridge was updated considering the material properties and boundary conditions. It is emphasized that Operational Modal Analysis method based on the ambient vibrations can be used safely to determine the dynamic characteristics, to update the finite element models, and to monitor the structural health of long reinforced concrete highway bridges constructed with the balanced cantilever method.

DEM simulation of particle flow on a single deck banana screen

A mathematical study of particle flow on a banana screen deck using the discrete element method (DEM) was presented in this paper. The motion characteristics and penetrating mechanisms of particles on the screen deck were studied. Effects of geometric parameters of screen deck on banana screening process were also investigated. The results show that when the values of inclination of discharge and increment of screen deck inclination are 10° and 5° respectively, the banana screening process get a good screening performance in the simulation. The relationship between screen deck length and screening efficiency was further confirmed. The conclusion that the screening efficiency will not significantly increase when the deck length L⩾430mm (L/B⩾3.5) was obtained, which can provide theoretical basis for the optimization of banana screen.

Banana Screening Method and Simulation of Banana Screening Process Using Discrete Element Method

This paper presented the fundamentals of banana screening method and the structural features of the banana screen. Based on soft-dry ball contact model, banana screening process was simulated by using 3D discrete element method. The results show that the material bed on banana screen possesses a characteristic of thin and constant thickness along the screen plate. The particles velocity on the screen deck shows a decreasing distribution along the screen deck length and the decrease of velocity changes from steep at the feed end to flat at the discharge end. The instantaneous efficiency of banana screen can reach to above 0.95 and the efficiency of steady state is about 0.83. Numerical simulation results can provide references for insight understanding of the banana screening mechanism and optimization of banana screen.

Impact of Pontoon Vessel Geometry on Allowable Passenger Weight Using USCG Pontoon Simplified Stability Test

A parametric analysis of stability was performed for more than 30,000 geometric variants of cylindrical-hulled pontoon vessels to quantify the impacts of vessel geometry and prepassenger displacement on the maximum passenger weight allowed by the US Coast Guard (USCG) Pontoon Simplified Stability Test (PSST). Variables examined included pontoon diameter, pontoon length, pontoon separation, deck height, passenger deck width, location of forward and aft edges of the passenger deck, prepassenger displacement prior to loading, and trim. Each pontoon vessel variant was evaluated using General Hydrostatics Software to apply the PSST to determine the maximum passenger weight allowed for that vessel. Graphical analysis of the data demonstrated that a vessel's allowable passenger weight increases with: an increased pontoon diameter or length of pontoon, a decreased deck height, a limited increase in pontoon separation or beam ratio, and a symmetrically decreased passenger deck width or length. Additionally, it was found that each specific vessel has an optimum prepassenger displacement, unique to its pontoon diameter and length of pontoons, which maximizes the allowable passenger weight. Finally, a method is provided to correlate the present results with prior related work by other authors that characterized pontoon vessel stability in the context of pontoon percent submergence.

Safety in Big Jumps: Relationship Between Landing Shape and Impact Energy Determined by Computer Simulation

Abstract With the increasing popularity of freestyle skiing and snowboarding many ski resorts constructed their own terrain parks including several jumps, rails, and pipes. In order to prevent risks of high-impact injuries in jumping, an adequate construction of the landing hill is very important. In professional ski jumping this can be achieved by designing the landing area profile so that its curvature follows the flight path of the jumping athlete. Classical kicker shapes do not follow this principle. They consist of a ramp subsequently followed by a flat table and a descending landing area. Construction of these kickers is commonly made by trial and error. To make the construction process safer and reduce unnecessary risks, a guideline for save kicker construction based on multiple simplifications of the real situation was published in the literature. The purpose of this study was to investigate how this guideline applies to the situation in a real kicker. Two skiers and three snowboarders performed a total of eleven jumps on one expert’s kicker (table length 17 m, transition angle 20°, and kick-off height 2.5 m). Computer simulations, based on the take-off velocities of the eleven jumps measured, were used to calculate the impact energy during landing on different table lengths combined with different landing slopes. If the jumper fails to adjust take-off velocity to account for the shorter deck length, the sum of the impact energies of the simulated jumps will increase dramatically at table lengths smaller than 15 m combined with a landing steepness greater than 20. The predictions based on the guideline (16 m table length and 33° landing steepness) are within a safe region. The guideline is therefore applicable for the experts kicker investigated.

Application of dam-break flow to green water prediction

The present study investigates, through analysis of laboratory measurements, the practice of applying Ritter’s dam-break flow solution to the prediction of overtopping green water on an offshore structure. The flow field of green water has been very difficult to obtain from either numerical computation or laboratory measurement. The dam-break flow model has been used in design to approximate the effect of green water due to the possible resemblance of the two flows, the simplicity of the dam-break flow, and the availability of analytical solutions of dam-break flow. In this study, the velocity of green water on a two-dimensional simplified model structure was measured using a newly developed technique called bubble image velocimetry (BIV). The profiles of horizontal green water velocity along the model deck are presented herein. Ritter’s analytical solution for the dam-break flow problem is examined and compared with the measurements. Two alternative approaches for quantifying the initial water depth, a parameter required in the analytical dam-break flow model, are investigated. The solution with the initial water depth estimated using the front velocity of green water is found to be in good agreement with the green water measurements. In addition, the influence of the deck length on green water velocity is examined.

The earth pressure behind full-height frame integral abutments supporting granular fill

Compared with conventional bridges, integral bridges have no bearings or joints between the deck and abutments and thus can significantly reduce maintenance requirements and costs over the bridge's lifetime. However, there is uncertainty about the ultimate magnitude of the lateral earth pressure behind such abutments, as they are forced to move with the deck length change caused, for example, by daily and annual variations in the effective bridge temperature. This research investigated the earth pressure that would be expected to occur behind full-height frame integral abutments backfilled by granular materials. Radial strain-controlled cyclic stress path testing has been conducted on coarse sand specimens and a glass ballotini specimen. The results suggest that for integral abutments retaining uniform coarse sand, the lateral earth pressure will experience systematic increases for almost all cyclic strain levels, eventually reaching states of stress close to both active and passive. The mechanism of the buildup of lateral stress is explored, and it appears to be associated with nonspherical granular particle shape. The implications for frame integral abutment design are discussed.Key words: integral abutments, granular, particle shape, earth pressure, stiffness.

The influence of the section shape of box-girder decks on the steady aerodynamic yawing moment of double cantilever bridges under construction

The yawing moment acting on the box-girder deck of reinforced concrete bridges constructed using the balanced cantilever method during the erection stage has been experimentally analyzed by testing different types of bridge cross-sections. Experimental results show that the yawing moment coefficient decreases as the bridge decks become streamlined, and that the yawing moment coefficient reaches a maximum when the bridge deck length is nearly twice the deck width.

Parametric studies on seaworthiness of SWATH ships

This paper reports seakeeping studies performed on a parametrically varied set of SWATH hull forms. The SWATH form, because of its de-linked nature of design affords many variations of the underwater hull geometry without affecting overall deck length and beam. For a given displacement, the hull form can be varied in terms of length, basic section shape, maximum area of cross section of under water hull and strut water plane shape. Using these variants, a parametric family of hull forms has been generated employing Chebychev polynomial scheme for representing sectional area distribution and using a bi-quintic B-spline based surface definition scheme. Not all designs offer optimal performance in a given sea state. A twin-hull motion analysis program SEDOS has been used to study the motions and other dynamic effects. Setting criteria for operability, these dynamic effects have been quantified into a single value namely, operability index. The approach here fulfils an investigation at the design stage in order to tap the full advantage of the SWATH form. The study brings out a methodology for assessment of the SWATH at the design stage highlighting interesting results related to section shapes and sectional area distribution. Thus, combining a newly developed interactive surface generation scheme with an analysis package, a rapid assessment tool is offered for new design.

The Tamaraceite Viaduct

The Tamaraceite Viaduct is an intermediate deck Arch Bridge with several peculiarities making it an interesting structure; both for its design and construction method, both closely linked to each other. The arch, which is mixed concrete-steel, has a 162-meter span. Its steel part was mounted by cantilever advance and making use of provisional pylons and stays, whilst the buttresses acted as counter-weights. The deck is prestressed concrete and was built in-situ on scaffolding at the end areas close to the abutments, whilst in the center area (approximately half the deck's length) it was prefabricated in five parts or segments of 650 tons weight each. These segments were lifted using hydraulic jacks following a procedure expressly developed for building this bridge. The lifting was, in turn, the method for putting the arch under load, and the transfer of the segment loads from the lifting cables to the final suspenders was directly performed. These two aspects are deemed to be unique in the histories of Arch Bridge construction and lifting methodology. Besides, it is unusual to find so many construction methods together to build a single structure, in Tamaraceite Viaduct this was the best way to optimize construction. This is only achievable through full cooperation between construction and design teams.

The use of air decks in production blasting in an open pit coal mine

The influence of air deck blasting on blast performance and blast economics and its feasibility has been studied in the production blasting of soft and medium strength sandstone overburden rocks in an open pit coal mine in India. The air deck blasting technique was very effective in soft and medium strength rocks. Its main effects resulted in reducing fines, in producing more uniform fragmentation and in improving blast economics. The fines were reduced by 60–70% in homogeneous sandstones. Oversize boulders were reduced by 80% and shovel loading efficiency was improved by 20–40% in blocky sandstones. The explosive cost was reduced by 10–35% dependent on the type of rock mass. Throw, backbreak and ground vibration were reduced by 10–35%, 50–80% and 30–94% respectively. For a particular rock mass and blast design environment, air deck length (ADL) significantly influenced the fragmentation. ADL as represented by air deck factor (ADF) in the range of 0.10–0.35 times the original charge length (OCL) produced optimum results. ADF beyond 0.35 resulted in poor fragmentation and in inadequate burden movement.

A Diverging Belt Screen for Farmer Stock Peanuts1

Abstract Separating farmer stock (FS) peanut materials into more than two diameters with conventional belt screens requires more than one screen with different spacings between belts. A new type of belt screen (diverging belt) was developed which separates materials into six sizes. The effects of varying the diverging belt screen operational parameters on separating farmer stock peanuts (cv. Florunner), loose shelled kernels (LSK), and foreign materials (FM) were evaluated with three replications. The operational parameters for two of the replicates were six consecutive positions along the deck length (30.5, 20.3, 50.8, 50.8, 50.8 cm and riding the entire deck length); six belt speeds (101.6, 111.8, 122.1, 132.3, 142.6, and 152.4 cm/sec); and six material feed rates (MatFR) (0.9, 1.8, 2.7, 3.6, 4.5, and 5.4 Mg/hr). Deck lengths and belt speeds were the same for the third replicate but MatFRs of 1.4, 2.7, 4.1, 5.4, 6.8, and 8.2 Mg/hr were used to evaluate performance of the screen at higher flow rates. Materials were collected into six compartments according to where they fell through the screen. The amount of materials falling through the screen deck varied directly with screen deck length, belt speed, and material feed rate. Screen deck length had the greatest effect on the amount of materials falling through. The diverging belt screen provides an alternative for multi-separation of FS peanut materials based on diameter.

Effects of Belt Screen Operational Settings on Separations of Farmers Stock Peanut Materials

Abstract The effects of varying belt screen operational parameters on separating farmers stock peanuts (cv. Florunner), loose shelled kernels (LSK), and foreign materials (FM) were evaluated. The operational parameters evaluated were four screen deck lengths (40.6, 81.3, 121.9, and 162.6 cm); four belt spacings (0.87, 0.95, 1.03, and 1.11 cm); four belt speeds (81.3, 91.4, 101.6, and 111.8 cm/sec); and four feed rates (0.45, 0.91, 1.36, and 1.81 t/hr). The amount of materials falling through the screen varied directly with screen deck length and belt spacing. Screen deck length had the greatest effect on the amount of LSK, total FM, sticks from FM, dirt from FM, and rocks from FM falling through the screen. Belt speeds and material feed rates had less effect on the separations made than screen deck length and belt spacing.

Some kinetic aspects of continuous screening

Continuous screening of ferrous sinter mixtures was studied in a laboratory screen (310 × 600) incorporating continuous weighing of the underflow and overlfow streams with the aim of checking the applicability of recent batch sieving results [1] to continuous screening. The results of the study show that the two operations are comparable in all respects if deck length in continuous screening and time in batch sieving are interchanged. The effect of oversize particles is again found to be beneficial in speeding up the screening of near-mesh material. Calculated screening rate constants with and without the presence of oversize, unfortunately, also parallel the results of batch sieving and this problem of theory is, therefore, still unresolved.

Notes and Queries

NOTES AND QUERIES Edited by Boyd B. Stutter 517 Main Street Charleston 2, West Virginia This department is designed as an open forum for researchers into Civil War themes and for readers of Civil War History in general. It is open for questions on, and discussion of, aU phases of die Great Conflict and its personnel. Also, notes on newly-discovered or Uttíe-known sidehghts of die war are welcomed. Address Notes and Queries Editor. NOTES Correspondence of Harvard Classmates Wanted: Enrolled in die class of 1855 at Harvard CoUege wereJames Benjamin Clarke, whosehome wasnear Jackson, Mississippi, and Thomas WilUam Clarke, of Roxbury, Massachusetts. These two classmates became fast friends and this friendship endured through the years of the Civil War. Thetwo Clarkes exchanged letters during die war years—those of James Benjamin Clarke are reported to contain valuable information concerning wartime conditions in Mississippi. Unfortunately die letters of the Massachusetts Clarke to Mississippian James Benjamin Clarke appear to have been lost; perhaps some reader of Civil War History may know of dieir present location or parts of the correspondence that have so far evaded researchers. Any information about the location of the letters or about die correspondence would be greatly appreciated by Professor Rodney C. Loehr, Department of History, University of Minnesota , MinneapoUs 14. Hungarian Archives Yield Papers of General Julius Stahel: A number of official papers and letters once belonging to Hungarianborn Union General Julius Stahel were recently discovered in die Budapest archives, including three papers signed by President Abraham Lincoln. The documents bearing Lincoln's signature are two commissions and a letter to Union General Carl Schurz. General Stahel, who came to the United States in 1856, joined the 207 208BO YD B. STU TLER Federal forces as a Ueutenant colonel at the outbreak of the war. He was later placed in command of cavalry units around Washington, but on promotion to brigadier and major general had active and distinguished field service as a cavalry commander. He won a Medal of Honor at Piedmont, Virginia, on June 5, 1864, when, though severely wounded, he continued to lead his division through the engagement. Other documents found in his estate include letters from Presidents Andrew Johnson and Rudierford B. Hayes, and from five Union generals . General Stahel died in 1912 at the age of eighty-seven, and is buried in Arlington National Cemetery. Nystrom's Armored Steam Corvette: Contributed by Richard G. Wood, MontpeUer, Vt. On August 29, 1861, John W. Nystrom of Philadelphia submitted to die Secretary of the Navy, Gideon WeUes, a set of "Plans and Specifications for an Armored Steam Corvette." In coming forward widi diis suggestion for an ironclad vessel he was in good company, as over a hundred proposals for ironclads were submitted prior to the classic struggle between die Monitor and die Merrimack, some of diem even before the fall of Sumter. Nystrom had been in Washington earlier on August 1, when he wrote Secretary WeUes on the subject of manufacturing iron plate, and from this letter we learn that he was ". . . an Engineer by profession and a naturalized Citizen of die United States." He was die recipient of a certificate from the Royal Technological Institute of Stockholm in 1846. (See Miscellaneous Letters, Aug., 1861, 1, Naval Record CoUection, National Archives.) Nystrom submitted a diirty-five page manuscript of specifications, with several drawings including a frontispiece in color, which now reposes in the Records of die Bureau of Yards and Docks, National Archives. Placed beside sketches of die utilitarian Monitor or the early Mississippi River ironclads, die design for an armored corvette proposed by Nystrom is elaborate, with some of the details bordering on die fantastic . In appearance the vessel did not seem a radical departure from die other craft of the day because it had masts and superstructure. Only die bulge of armor between deck and water line revealed die innovation . For dimensions, Nystrom's corvette was to have the following: length of deck, 175 feet; breadtii of beam, 27 feet; breaddi over the armored guards, 32 feet; draft, 10 feet; displacement, 875 tons; speed, 12 knots. But die central feature was, of course, the armor. As Nystrom noted, The science...