Showing papers on "Deck published in 2023"

Structural Behavior of Reinforced Concrete Hollow Beams under Partial Uniformly Distributed Load

Abstract: A Longitudinal opening is used to construct hollow core beam is a cast in site or precast or pre stressed concrete member with continuous voids provided to reduce weight, cost and, as a side benefit, to use for concealed electrical or mechanical runs. Primarily is used as floor beams or roof deck systems. This study investigate the behavior of six beams (solid or with opening) of dimension (length 1000 x height 180 x width120mm) simply support under partial uniformly distributed load, four of these beam contain long opening of varied section (40x40mm) or (80x40mm). The effect of vertical steel reinforcing, opening size and orientations are investigated to evaluate the response of beams. The experimental behavior based on load-deflection measured at central and quarter of tension zones. The experimental test result shows the presence of Hollow decrease the load carrying capacity by about (37.14% to 58.33%) and increased the deflections by about (71.6% for (Hollow ratio 7.4%) to 75.5% for (Hollow ratio 14.8%)) for same applied loadcompared with solid beams with the same properties. The increase shear steel reinforcing will decrease all the deformations at all stages of loading, but particularly after initial cracking and give enhancement in ultimate load capacity of beams by about 31.5% with increasing the amount of shear steel reinforcing by about 50%. Finally, ductility is increased in all cases under partial uniformly distributed load when hollow ratio decreased by about 50% or increased in shear steel reinforcing by about 50%

Numerical Simulation of Fatigue Cracking of Diaphragm Notch in Orthotropic Steel Deck Model

Abstract: Orthotropic steel deck (OSD) are widely used in steel bridges because of their many advantages, but the structures and stresses of OSD are complex and sensitive to fatigue. Based on the model test, the structural fatigue analysis of OSD is carried out by using the extended finite element method (XFEM) to understand and reveal the causes of fatigue detail cracks and the generation and propagation of fatigue cracks at the welding ends of diaphragms, U-ribs, and diaphragms, which are the main structural fatigue details of the deck. The results show that: the fatigue crack at the diaphragm opening is not caused by a single factor, but the horizontal relative displacement is the root-cause of the fatigue crack; the contribution of out-of-plane displacement to the fatigue crack is more significant than that of vertical displacement or in-plane stress, which often leads to the initiation and propagation of the fatigue crack; the crack-propagation direction is perpendicular to the contour of principal stress, and the crack propagates into the plate along the high-stress area in the horizontal direction, which is in accordance with the basic theory of crack propagation. The research methods can provide technical support for the design of similar structures.

Novel methods for reliability study of multi-dimensional non-linear dynamic systems

Abstract: This research presents two unique techniques for engineering system reliability analysis of multi-dimensional non-linear dynamic structures. First, the structural reliability technique works best for multi-dimensional structural responses that have been either numerically simulated or measured over a long enough length to produce an ergodic time series. Second, a novel extreme value prediction method that can be used in various engineering applications is proposed. In contrast to those currently used in engineering reliability methodologies, the novel method is easy to use, and even a limited amount of data can still be used to obtain robust system failure estimates. As demonstrated in this work, proposed methods also provide accurate confidence bands for system failure levels in the case of real-life measured structural response. Additionally, traditional reliability approaches that deal with time series do not have the benefit of being able to handle a system's high dimensionality and cross-correlation across several dimensions readily. Container ship that experiences significant deck panel pressures and high roll angles when travelling in bad weather was selected as the example for this study. The main concern for ship transportation is the potential loss of cargo owing to violent movements. Simulating such a situation is difficult since waves and ship motions are non-stationary and complicatedly non-linear. Extreme movements greatly enhance the role of nonlinearities, activating effects of second and higher order. Furthermore, laboratory testing may also be called into doubt due to the scale and the choice of the sea state. Therefore, data collected from actual ships during difficult weather journeys offer a unique perspective on the statistics of ship movements. This work aims to benchmark state-of-the-art methods, making it possible to extract necessary information about the extreme response from available on-board measured time histories. Both suggested methods can be used in combination, making them attractive and ready to use for engineers. Methods proposed in this paper open up possibilities to predict simply yet efficiently system failure probability for non-linear multi-dimensional dynamic structure.

Bio-inspired design, modeling, and 3D printing of lattice-based scale model scooter decks

Abstract: Abstract This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters.

Design Optimization of Ocean Renewable Energy Converter Using a Combined Bi-level Metaheuristic Approach

Abstract: In recent years, there has been an increasing interest in renewable energies in view of the fact that fossil fuels are the leading cause of catastrophic environmental consequences. Ocean wave energy is a renewable energy source that is particularly prevalent in coastal areas. Since many countries have tremendous potential to extract this type of energy, a number of researchers have sought to determine certain effective factors on wave converters’ performance, with a primary emphasis on ambient factors. In this study, we used metaheuristic optimization methods to investigate the effects of geometric factors on the performance of an Oscillating Surge Wave Energy Converter (OSWEC), in addition to the effects of hydrodynamic parameters. To do so, we used CATIA software to model different geometries which were then inserted into a numerical model developed in Flow3D software. A Ribed-surface design of the converter’s flap is also introduced in this study to maximize wave-converter interaction. Besides, a Bi-level Hill Climbing Multi-Verse Optimization (HCMVO) method was also developed for this application. The results showed that the converter performs better with greater wave heights, flap freeboard heights, and shorter wave periods. Additionally, the added ribs led to more wave-converter interaction and better performance, while the distance between the flap and flume bed negatively impacted the performance. Finally, tracking the changes in the five-dimensional objective function revealed the optimum value for each parameter in all scenarios. This is achieved by the newly developed optimization algorithm, which is much faster than other existing cutting-edge metaheuristic approaches.

Characterization of the road profile and the rotational stiffness of supports in a bridge based on axle accelerations of a crossing vehicle

Abstract: In an effort to find more cost-effective and proactive ways to keep bridges in good condition, the use of instrumented vehicles has gained great interest in the last decade. Two bridge components that can wear rapidly are the bearings and the road surface. However, past research on drive-by monitoring has placed focus mostly on detecting losses of bending stiffness in the bridge deck, while assuming ideal support conditions that may differ from real cases significantly, and ignoring the characterization of the road profile. Even further, the need for specialized vehicles equipped with high-tech instrumentation, low speeds, or very good road profiles has been a major obstacle preventing its practical implementation. This paper investigates the use of axle accelerations from an ordinary two-axle vehicle crossing the bridge to quantify the rotational stiffness of the supports and the height of the road irregularities while overcoming the limitations exposed above. In contrast to previous research where the response of the contact point has been derived from other vehicular locations based on complex differential equations of motion, transfer functions are employed here. The key advantage of transfer functions is their simple algebraic form that can be easily calibrated on the field. The road profile is then obtained by subtracting the displacement of the bridge under each axle from the displacement of the contact point. There is one prediction of the road profile per axle but only a unique value of rotational stiffness at each support that will yield the same prediction by both axles. The algorithm is successfully tested with a half-car traveling at 5, 10, 15, and 20 m/s, over a 15-m bridge beam model with ISO road classes “A,” “B,” and “C,” for boundary conditions ranging from simply supported to fixed. The solution's robustness to modeling inaccuracies and noisy data is also investigated.

Cable Force Optimization of Cable-Stayed Bridge Based on Multiobjective Particle Swarm Optimization Algorithm with Mutation Operation and the Influence Matrix

Abstract: To compensate the incapability of traditional cable force adjustment methods to automatically optimize cable forces, this paper proposes Midas/Civil and MATLAB as a structure calculator and a cable force optimizer, and external memory as a data transfer. Initial solutions from conventional methods can be optimized by internalizing the influence matrix into the multiobjective particle swarm optimization algorithm with mutation operation and constructing the mathematical model of cable force optimization, and then, a series of Pareto frontier solution sets are obtained. For the first time, fuzzy set theory is introduced for selecting Pareto presolution set for the optimization of cable-stayed bridges, to solve the final reasonable dead load state of bridges. By using this method, the peak vertical displacement of a main girder of the optimized cable-stayed bridge decreased from −11 mm to −6 mm, with a reduction of 45%. Before and after optimization, the difference of peak negative bending moment at the top of the pier was 34.8%, indicating that the main beam was more evenly stressed and the alignment was more reasonable.

Fatigue behavior and remaining life evaluation of rib-to-deck joints using interior repair welds

Abstract: The rib-to-deck joints are one of the most critical vulnerable details of orthotropic steel deck subjected to vehicle loads. Specially, fatigue cracks initiating from the weld root and propagating along the thickness of the deck at the rib-to-deck joints is most difficult to repair. In this study, the interior repair weld is adopted to enhance the fatigue resistance of rib-to-deck joint. Three specimens of rib-to-deck joint were designed and tested to investigate the effectiveness and applicability of the interior repair weld. The fracture mechanics method associated with numerical simulation is adopted to analyze the failure mechanism and remaining life of rib-to-deck joints after reinforcement. The results indicate that the region of fatigue crack initiation will be transferred from the interior weld root before repairing to the exterior weld toe after repairing. The interior repair weld can effectively prevent fatigue crack propagation and significantly improve the remaining fatigue life of the rib-to-deck joints. The simulated fatigue life agrees well with the measurement in fatigue tests, revealing the accuracy of fracture mechanics method to estimate the remaining life.

Effect of Tool Rotation Direction on Mechanical Strength of Single Lap Friction Stir Welded Joints between AA5083 Aluminum Alloy and S355J0 Steel for Maritime Applications

Abstract: This study aims to investigate a friction stir welded joint between steel and aluminum alloy that is employed in maritime applications (i.e., connection between the ship over-structures and the hull or deck). By changing the tool rotational direction, or the advancing or retreating side, a single lap configuration was studied. Tensile tests were conducted to evaluate the mechanical resistance and the surface fracture after a preliminary investigation consisting of morphological and microstructural analyses and microhardness measurements, with the goal of considering the possibility of replacing the typical joining processes, such as traditional welding or explosion welding, with friction stir welding. The testing showed that the joint produced on the advancing side performed better (+23.5% of the maximum load) than the joint made on the retreating side.

Optimal Design of Bubble Deck Concrete Slabs: Sensitivity Analysis and Numerical Homogenization

Abstract: The use of layered or hollow floors in the construction of buildings obviously reduces the self-weight of the slab, and their design requires some expertise. In the present work, a sensitivity analysis and numerical homogenization were used to select the most important characteristics of bubble deck floors that have a direct or indirect impact on their load capacity. From the extensive case study, conclusions were drawn regarding the optimal selection of geometry, materials, and the arrangement and size of air voids in such a way as to ensure high stiffness of the cross-section and at the same time maximally reduce the self-weight of the slabs. The conducted analyses showed that the height of the slab and the geometry of the voids had the greatest impact on the load-bearing capacity. The concrete class and reinforcement used are of secondary importance in the context of changes in load-bearing capacity. Both the type of steel and the amount of reinforcement has a rather small or negligible influence on the bubble deck stab stiffness. Of course, the geometry of the voids and their arrangement and shape have the greatest influence on the drop in the self-weight of the floor slabs. Based on the presented results of the sensitivity analysis combined with numerical homogenization, a set of the most important design parameters was ordered and selected for use in the optimization procedure.

Aerodynamic Force Distribution Characteristics around a Double-Slotted Box Girder of a Long-Span Bridge during Vortex-Induced Vibration

Abstract: Vortex-induced vibrations (VIVs) remain a key issue for slotted box girders. To clarify the influence of additional structural elements on the aerodynamic characteristics of a double-slotted box girder for highway and railway hybrid bridges, wind tunnel tests involving the pressure distribution, VIV responses, and wake measurements were performed. The wind pressures and vortex-shedding frequency characteristics of a bridge were compared under different additional structural element combinations of balustrades, wind barriers on highways and railway deck surfaces, maintenance rails, and so on. The results indicated that the maintenance rails had a limited influence on VIV characteristics and distributed pressures of the double-slotted box girder. However, owing to the stronger disturbance of the wind barriers and balustrades on the highway deck surface, unsteady shear flow separating from the wind barrier top acts on the middle and leeward girders, resulting in large-amplitude torsional VIVs to generate considerable excitation forces. Moreover, because wind flow across the slotted parts interacted with the girder and additional structural elements, stronger torque forces were generated. Consequently, correlation and contribution were enlarged, which corresponded to large-amplitude torsional VIVs. This provides a reasonable explanation for the considerable influence of wind barriers on highway decks on torsional VIVs. Moreover, with regard to the double-slotted box girder [especially the upper surface of the windward girder, upper and lower surfaces of the leeward girder, and windward gap of the three girders (Regions II to IV, VI, and X to XI, respectively)], the distributed wind pressures acting on the characteristic parts of bridge decks further contributed to the generation of torsional VIVs.

Location and actuation of flight deck controls for commercial transport type aircraft

Abstract: <div class="section abstract"> <div class="htmlview paragraph">The recommendations of this bulletin apply to commercial type, multi-engine transport aircraft utilizing reciprocating or turbine type powerplants.</div></div>