Showing papers on "Deck published in 2011"

Staple cartridge including collapsible deck arrangement

Abstract: A staple cartridge for use with a surgical stapler can comprise a cartridge deck and a plurality of staples at least partially positioned within the cartridge deck. In various embodiments, the staples can comprise legs which extend upwardly from the deck wherein the deck can further include supports, or guides, which are configured to hold the staple legs in a particular alignment. In at least one such embodiment, the staple legs can extend upwardly from the supports into a tissue thickness compensator.

Fatigue Evaluation of Rib-to-Deck Welded Joints of Orthotropic Steel Bridge Deck

Abstract: This study reported fatigue test results of 300-mm-wide specimens with three details: 80% partial joint penetration (80%PJP), weld melt-through (WMT), and both The specimens were cut out from full-scale orthotropic deck specimens of 16-mm-thick deck plate In the fatigue test, the deck plate was subjected to cyclic bending loading and the rib was free from loading The fatigue fracture surfaces showed that the presence of WMT may affect the initiation of fatigue cracks A propensity to root cracking rather than toe cracking was observed Plotting fatigue test results in an S-N diagram showed that the specimens with WMT seemed to have slightly lower fatigue strengths than the 80%PJP specimens, but the difference is more likely to be within a usual scatter of test data, which means that both details have comparable fatigue strength The present test results satisfied the S-N curves of JSSC-E (80 MPa at 2×106 cycles) or AASHTO-C (89 MPa at 2×106 cycles)

Simulation of the screening process on a circularly vibrating screen using 3D-DEM

Abstract: A numerical study of the motion particulates follow along a circularly vibrating screen deck was done using the three dimensional Discrete Element Method (DEM). The motion of the particles was analyzed. The effects of vibration amplitude, throwing index, and screen deck inclination angle on the screening process are discussed. The results show that the average velocity of the particles increases along the longitudinal direction of the deck. The screening efficiency is highest when the vibration amplitude, throwing index, and screen deck inclination angle are 3–3.5 mm, 2.7 and 15°, respectively. This work is helpful for developing a deep understanding of particle motion and for optimizing screen separator designs.

Ultra-High-Performance Concrete Bridge Deck Reinforced with High-Strength Steel

Abstract: Open-grid steel bridge decks are lightweight, but present noise, fatigue damage, ride comfort and maintenance challenges. A lightweight bridge deck system with a solid riding surface could eliminate these problems. Ultra-high-performance concrete (UHPC) shows promise as a material for a new lightweight bridge deck system. This paper describes the development of a low-profile UHPC deck system that addresses the concerns with open-grid steel decks, satisfies strength and serviceability requirements, and meets the strict self-weight requirements for movable bridges. The experimental study shows that the proposed system has great potential to serve as an alternative to open-grid steel decks. The ultimate load capacity of all specimens exceeded the target load for the bridge deck. Although shear was the governing mode of failure in most of the specimens, it was not as abrupt and catastrophic as the commonly seen shear failure mode. The use of standard 180-degree hooks on both ends of the flexural reinforcement helped avoid bond failure. Further research is needed before field implementation of the proposed deck system.

Experimental evaluation of thin composite floor assemblies under fire loading

Abstract: This paper presents the behavior observations, results, and findings from experimental investigations of the structural behavior of thin composite floor systems subjected to combined gravity loads and fire loading. The 3.96×4.57 m floor systems consisted of A992 steel W10×15 interior beams and W12×16 girders acting composite with a 38.1-mm-deep ribbed steel deck with 63.5 mm of lightweight concrete on top. Three composite floor-assembly specimens were tested with two different shear connection types (welded-bolted shear tab and all-bolted double-angle connection), two different fire scenarios (realistic fires with standard heating and uncontrolled or controlled cooling paths), and two different fire protection scenarios (i.e., interior beams with or without fire protection). The experimental results indicate that removal of fireproofing from the interior beams causes them to heat, deflect, and fail more rapidly. The beams and girders have similar deflection-versus-temperature behaviors irrespective of th...

Concrete bridge deck condition assessment with automated multisensor techniques

Abstract: Early and accurate detection, location and assessment of damage in reinforced concrete bridge decks may be beneficial in the scheduling and performance of maintenance and rehabilitation activities. This article presents the results of a multiple sensor study of the condition of the reinforced concrete deck of the Van Buren Road Bridge in Dumfries, VA. The tests compared the following five different methods: (1) visual inspection and photographic recording; (2) half-cell electrochemical potential; (3) impulse type multipoint scanning ground penetrating radar; (4) chain drag and (5) impact echo. The bridge was tested on two separate occasions. The results of the tests were that each instrument nominally performed and collected data as expected, but that the condition assessments did not necessarily agree. The data are registered, overlaid and compared. The potential for developing automated multisensor systems that fuse data for efficient and effective bridge deck measurements is discussed.

Reliability of Bridge Decks in Wisconsin

Abstract: An accurate reliability model for bridge decks is important for effective long-term bridge deck management. The main objectives of this paper are to identify the most suitable reliability model for bridge decks in Wisconsin, and to utilize that model for detailed analyzes of bridge deck reliability and failure rates. The 2005 National Bridge Inventory (NBI) data for the State of Wisconsin were used. In this paper, the hypertabastic, Weibull, log logistic, and lognormal distributions are investigated. The end of service life is defined as the age of deck when rehabilitation or replacement is required (herein defined as a deck rating of between 4 and 5). The effects on NBI deck rating of average daily traffic (ADT), type of bridge superstructure (steel or concrete), and the deck surface area were considered. Based on the Akaike information criteria, the hypertabastic accelerated failure time model was selected as the most appropriate model for this study. Results show that deck area, type of superstructure ...

Hospital bed lift and braking mechanisms

Abstract: A patient support including a frame, plurality of wheels coupled to the frame, a deck, and a scissor mechanism coupled to the frame and the deck to move the deck from a raised position to a lowered position. The support includes brake mechanism including a brake pad to contact the floor to prevent the patient support from rolling.

Summary of cast-in-place concrete connections for precast deck systems

Abstract: This report contains recommended design specifications, construction specifications, and five illustrative examples of durable cast-in-place (CIP) reinforced concrete connections for precast deck systems that emulate monolithic construction, considering issues including speed of construction, durability, and fatigue. Included in the report is the supporting research that led to these recommendations. This research focused on systems that reduce the need to place and remove formwork thus accelerating on-site construction and improving safety. The three systems considered to accomplish these objectives were: (1) a precast composite slab span system (PCSSS) for short to moderate span structures, (2) full-depth prefabricated concrete decks, and (3) deck joint closure details (e.g., decked-bulb-tee (DBT) flange connections) for precast prestressed concrete girder systems for long span structures. Depending on the system, the connections are either transverse (i.e., across the width of the bridge) or longitudinal (i.e., along the length of the bridge). The first system, PCSSS, is an entire bridge system; whereas the other two systems investigated in the project represented transverse and longitudinal joint details to transfer moment and shear in precast deck panels and flanges of decked bulb tees. Two types of connection concepts were explored with these details, looped bar details and two layers of headed bar details.

Extension of bridging capacity of cable-supported bridges using double main spans or twin parallel decks solutions

Abstract: Technical investigation of current bridging capacity of cable-supported bridges shows that its single main span is up to 2 kilometres for suspension bridge and 1 kilometre for cable-stayed bridge respectively with the total deck width of about 40 metres. Approaches to extend bridging capacity by utilising double main span suspension structure and twin parallel deck cable-stayed structure are introduced. Special emphasis is placed on longitudinal stiffness design of central pylon for double main span suspension bridge. Both inversed Y-shaped pylons in Jiangsu Taizhou Bridge and I-shaped pylon with fixed connection of deck and central pylon in Anhui Maanshan Bridge can provide proper longitudinal stiffness for the central pylon. Two types of pylon and three kinds of deck section have been checked in the early design stage for a twin parallel deck cable-stayed bridge called Ningbo Yongjiang Bridge. Finally, a composite cross section with two diamond pylon has been decided on when considering structural durab...

Structural Behavior of Waffle Bridge Deck Panels and Connections of Precast Ultra-High-Performance Concrete: Experimental Evaluation

Abstract: The AASHTO strategic plan in 2005 identified extending the service life of bridges and accelerating bridge construction as two of the grand challenges in bridge engineering. Previous studies have shown that using a prefabricated full-depth precast concrete deck system not only accelerated the bridge deck rehabilitation process but also extended its service life with reduced user delays and lower life-cycle costs. The recent use of ultra-high-performance concrete (UHPC) in the United States for bridge applications has proved efficient and economical because of its superior structural and durability characteristics. On the basis of the advantages of UHPC and precast systems, a design for a full-depth UHPC waffle deck panel system was developed. A full-scale, single-span, 60-ft long by 33-ft wide prototype bridge with full-depth prefabricated UHPC waffle deck panels has been planned as a replacement bridge in Wapello County, Iowa. In support of this project, structural performance and constructability of the...

Flexural Testing of Precast Bridge Deck Panel Connections

Abstract: Precast deck panels are increasingly being utilized to reduce construction times and traffic delays as many departments of transportation (DOTs) emphasize accelerated bridge construction. Despite the short-term benefits, the connections between panels have a history of service failure. This research focused on the evaluation of the service and ultimate capacities of five precast deck panel connections. Full-scale tests were developed to determine the cracking and ultimate flexural strengths of two welded connections, a conventionally posttensioned connection, and two newly proposed, posttensioned, curved bolt connections. The conventionally posttensioned specimens were shown to perform well with the highest cracking loads and 0.42 times the theoretical capacity of a continuously reinforced concrete deck panel. The proposed curved bolt connections were shown to be a promising connection detail with approximately 0.5 times the theoretical capacity of a continuously reinforced panel. Data from the welded specimens showed that some welded connection types perform significantly better than others. The experimental results also compared closely with values calculated on the basis of finite-element modeling, which can be used for future analytical studies.

Nonlinear Rail-Structure Interaction Analysis of an Elevated Skewed Steel Guideway

Abstract: The use of continuous welded rail (CWR) with direct fixation of track on concrete deck is typical of most modern light-rail aerial structures. The interaction between the CWR and the elevated structure takes place through direct-fixation rail fasteners, which have a nonlinear force-displacement relationship. Factors that have significant influence on this interaction include the following: the bearing arrangement at the substructure units, trackwork terminating on the aerial structure, type of deck construction, and type of rail fasteners. To better understand the interaction mechanism, a nonlinear three-dimensional (3D) finite-element analysis of a straight, skewed, elevated steel guideway was carried out using the commercially available software GT STRUDL. The load cases considered in this study are temperature change, temperature change with rail breaking, and train braking. Results are presented in the form of rail axial stresses along the length of the bridge and normal bearing forces at both abutments and at all pier locations. The study shows that nonlinear 3D modeling can give a comprehensive insight into the rail-structure interaction (RSI) forces.

Nonlinear dynamic v elastic analysis for seismic deformation demands in concrete bridges having deck integral with the piers

Abstract: Seismic deformations in concrete bridges having fairly long continuous deck integral with the piers and restrained transversely at the abutments but free to slide there longitudinally, are estimated via nonlinear dynamic analysis and compared to the corresponding outcomes of modal response spectrum analysis with 5% damping. Eight bridge configurations are studied, all with a box girder deck prestressed with bonded tendons, having three or five spans and piers of various cross-sections and about equal or very different heights. Two versions of each bridge are considered: one of conventional, force-based design and another having much less overstrength in the piers and developing less inelastic action in the deck. The piers are taken in the analysis with effective elastic stiffness equal to the secant stiffness to the yield point of their end section(s). The deck is discretized longitudinally into a string of nonlinear elements, whose moment-rotation relations are derived from moment-curvature analysis of the section in the two main directions of bending. Seven spectrum-compatible motions with Peak Ground Acceleration (PGA) of 0.25, 0.35 and 0.45 g on rock are applied in the longitudinal or transverse direction. Modal response spectrum analysis with 5% damping gives on average good—or at least safe-sided—predictions of inelastic deformation demands at the deck and the piers of regular bridges, especially under longitudinal earthquake. However, it underestimates inelastic deformation demands in bridges having piers of very different height, even when design measures are taken to harmonize stiffness across the piers. The stronger the ground motion, the larger are on average the elastic predictions of deformations relative to those from nonlinear dynamic analysis.