High-Temperature Properties of a Long-Span Double-Deck Suspension Bridge under a Tanker Fire

This paper presents a numerical study on the high-temperature mechanical properties of a long-span double-deck suspension bridge. The main focus of this paper is the behavior analysis of Wuhan Yangtze River Bridge. A three-dimensional thermal model of the bridge was established by the Fire Dynamics software (FDS) to obtain the 3D temperature field distribution, and the thermal analysis result was then applied to the three-dimensional finite element model of the suspension bridge. The shortest failure time of the main cable and sling was determined to obtain the rescue time of a bridge fire. According to the calculation results of the suspension bridge under a tanker fire initiated at the upper deck of the bridge, the middle lane in the upper deck of the suspension bridge was determined to be a safe lane. Thus, the tanker should be guided to go in this lane of the bridge. The numerical analysis of the experimental results shows that when the fuel tanker is located on the upper and lower floors of the bridge, the bridge structure is affected by the fire. When the oil tanker burns in the outermost lane of the upper bridge, it will have a great impact on the main cables and slings of the bridge. When the fuel tanker burns in the lower nonmotorized lane of the bridge, it will have a great impact on the upper stiffening beam steel plates and truss rods.

First Application Micro Coiled Tubing in Indonesia at Offshore Mahakam

With a view to addressing the challenges of future offshore platform evolution, smaller footprint of coiled tubing set is required for pumping work in minimalist platform. Although coiled tubing (CT) is the most efficient service method for multiple wellsite operations, it can be difficult to capture all the benefits of applying it to some offshore wells. Limited crane capacity and platform’s upper deck space often present challenges to efficiently execute CT operation. Minimalist and crowded platforms may not allow a perfect condition to properly set up conventional CT system. As part of the continuous improvement in Well Intervention, smaller size of CT called Micro CT is deployed to unload the completion fluid using nitrogen pumping. This is in order to provide sufficient drawdown prior to clean up or perforation works. Micro CT is a small coiled tubing with an outside diameter of 1” and a length of 10,000ft. It is 46% lighter and 39% smaller compared to conventional CT. The firtst Micro CT start-up project in Indonesia was initiated with unloading jobs in Bekapai and South Mahakam wells. There were five unloading jobs and they were successfully performed within the allocated time frame and budget. There were no major safety issues occurred. Total 60% cost savings can be generated from reduced supply boat mobilization trips prior to equipment mobilization while 40% cost savings came from efficiency in diesel consumption. From an operational aspect, less annular friction can be achieved and gives us 35% efficiency in N2 consumption. Moreover, it saves 10 – 20% rig up time in comparison to conventional CT. On top of that, those five unloading jobs were completed with an efficiency of more than 70%. In conjunction with this paper, we would like to share Micro Coiled Tubing experience where this was the first application in Indonesia with safety and measurable milestones.

Evaluation of Behaviour of Plan Curved Structure Supported by Arch

New type of plan curved structure has been developed within the research of arch footbridges at Faculty of Civil Engineering of Brno University of Technology. Structural arrangement came out of study of behaviour of plan curved upper deck arch structures of various radii of curvature. The design method of such structures with ideal shape of arch was the outcome of the research. Results of numerical analysis were verified on physical model in scale 1:10, which has been built and tested. The model has been mounted with gauges – 41 strain gauges at various positions on concrete and steel part of the structure and 5 deflection sensors. Then the structure has been subjected to loads in various positions corresponding with load positions of variable loads in calculation model. The paper describes evaluation of measurement of stresses and deformations of physical model of plan curved structure supported by an arch. Obtained values of stresses and deformations were compared with values derived from FE calculation model.

Drift Motion of Floating Bodies Under the Action of Green Water

Numerical simulations are peformed to model the dynamic motions of a free floating body exposed to water waves. The solid body has low freeboard and draft, and its upper deck can be washed by the steep waves. Thus, the green water phenomenon occurs as large waves interact with the floating body. The aim of the research is to improve the understanding of the green water emerging above the upper deck of a floating plate. A thin floating body with barriers is also modeled. For the case of the body equipped with barriers, no green water occurs. Green water has been seen to affect the wave field and the dynamic motions of the plate. It is observed that when water can wash the upper surface of the floating object, drift speed is slightly decreased as a proportion of the energy of waves is dissipated above the body. Water waves are seen to impact the upper surface of the thin floating body as the green water flows over its upper deck. Furthermore, water is seen to impact the plate as its front edge re-enters the water. The first water impact only occurs when the floating body is not equipped with any barrier. By sampling the numerical simulations, it is observed that the non-dimensional value of the impact pressure, resulting from the green water, is larger for the case of smaller wavelength.

Mathematical modeling of the fatigue cracks propagation and fatigue life estimation of aluminum structures with slot welds

Объектом исследования является конструкция верхней палубы соединительного моста высокоскоростного катамарана, выполненного из алюминиевого сплава 1561 (АМг61). Высокая плотность компоновки моста технологически не позволяет выполнять приварку рёбер жёсткости к настилу верхней палубы непрерывным сварным ш вом. Целью работы является расчётная оценка усталостной трещиностойкости конструкции верхней палубы при выполнении сварки прорезным сварным швом. Указанная оценка выполнена на основе эмпирического закона Пэриса – Эрдогана. При этом поскольку конструкция верхней палубы находится в сложном напряжённом состоянии, требуется учёт совместного влияния всех трёх механизмов роста трещин. В результате расчёта получены зависимости длин трещин и коэффициентов интенсивности напряжений от числа циклов нагружения, а также характер роста трещин. Выявлено, что доминирующим механизмом роста трещин является механизм среза, а не отрыва или сдвига. Показано, что прорезные сварные швы могут быть использованы в слабонагруженных алюминиевых конструкциях. The object of research is the structure of the upper deck of the connecting bridge of a high-speed catamaran, made of 1561 (AMg61) aluminum alloy. The high density of the bridge layout technologically does not allow welding of the stiffeners to the upper deck flooring with a continuous weld. The aim of the work is to estimate the fatigue crack resistance of the upper deck structure when welding with a slot weld. The specified estimate is based on the empirical Paris – Erdogan equation. In this case, since the structure of the upper deck is in a complex stress state, it is required to take into account the joint influence of all three mechanisms of crack growth. As a result of the calculation, the dependences of the crack lengths and equivalent stress intensity factors on the number of loading cycles, as well as the nature of crack growth. It has been revealed that the dominant mechanism of crack growth is the tearing mode, not opening or shearing mode. It is shown that slot welds can be used in lightly loaded aluminum structures.

The generation of Tollmien–Schlichting waves by free-stream turbulence in transonic flow

This paper studies the generation of Tollmien–Schlichting waves by free-stream turbulence in transonic flow over a half-infinite flat plate with a roughness element using an asymptotic approach. It is assumed that the Reynolds number (denoted Re) is large, and that the free-stream turbulence is uniform so it can be modelled as vorticity waves. Close to the plate, a Blasius boundary layer forms at a thickness of $$O(\mathrm{{Re}}^{-{1}/{2}})$$ O ( Re - 1 / 2 ) , and a vorticity deformation layer is also present with thickness $$O(\mathrm{{Re}}^{-{1}/{4}})$$ O ( Re - 1 / 4 ) . The report shows that there is no mechanism by which the vorticity waves can penetrate from the vorticity deformation layer into the classical boundary layer; therefore, a transitional layer is introduced between them in order to prevent a discontinuity in vorticity. The flow in the interaction region in the vicinity of the roughness element is then analysed using the triple-deck model for transonic flow. A novel asymptotic expansion is used to analyse the upper deck, which enables a viscous–inviscid interaction problem to be derived. In order to make analytical progress, the height of the roughness element is assumed to be small, and from this, we find an explicit formula for the receptivity coefficient of the Tollmien–Schlichting wave far downstream of the roughness.

The Soviet Pushkin: Pushkin's Substratum of Aleksey N. Tolstoy's Self-Mythmaking of the 1930s

The aim of this article is to review Aleksey N. Tolstoy's self-projections on the figure of Pushkin, seen as the most important classic author in the USSR during the 1930s. The material for the study was the writer's journalism and program speeches - it was in them that he most actively appealed to the Pushkin myth. Such appeals allowed Tolstoy to assert his special status in the Soviet literary hierarchy. In his articles and public speeches, the writer actually declared himself the heir of Pushkin, since both, each in his own era, created a “new literary language” based on historical documents. The category of language was important since the discussion about it became one of the key ones in determining the main aesthetic features of the emerging socialist realism. Pushkin, relying on folk speech, created a new “living” literary language opposing the “academic” elegant phrase of nobility (works by Turgenev, in Tolstoy's opinion, later became the peak of this style). Tolstoy, in turn, also saw his own merit in the discovery of a “new” language - the language of Soviet literature in his case. According to Tolstoy, both Pushkin and himself, relied on historical documents that reflected “authentic common people's” language in the process of creation. When writing, e.g., The Captain's Daughter, Pushkin used documents about Pugachev's Rebellion; while Tolstoy, creating Peter the Great, employed torture protocols of Peter's era, the so-called “Slovo i Delo”. As a result, the succession scheme was built in the following way: “common people's language” with almost a thousand years of history - Pushkin (the creator of a “new” literary language based on common people's language) - Tolstoy (the author who modernized these traditions and created a normative Soviet literary language based on them). These rhetorical techniques allowed the Comrade Count to increase his status in the Soviet literary hierarchy. On the one hand, he used the symbolic potential inherent in the Pushkin myth (the culmination of the poet's canonization was the commemoration of 1937); on the other hand, the figure of Pushkin, in relation to whom the word “great” was used, was constantly projected on Stalin. In the end, even despite a biography which was dubious from the point of view of the authorities, by the mid-1930s, Tolstoy, indeed, received the status of the main Soviet author. This situation was evidenced, for example, by a cartoon where the writer alone was depicted on the upper deck of the “steamship of Soviet literature”. Besides, at the funeral of Gorky, Tolstoy, along with Stalin, carried the coffin of the “proletarian writer”, as if occupying the “empty” place after the death of his predecessor. The important role in obtaining this status was played by Tolstoy's regular and consistent efforts to create his own writer's reputation based on the figure of Pushkin.

A Novel Three-SPR Parallel Platform for Vessel Wave Compensation

A wave compensation platform based on 3-SPR parallel platform is designed for marine ships with a dynamic positioning system. It can compensate for the heave, rolling, and pitching movement of a vessel under level 4 sea state. The forward kinematics of the mechanism is used to draw the central point position workspace and the attitude workspace of the moving deck of the compensation platform. The compensation effects of the 3-RPS parallel compensation platform and the 3-SPR parallel compensation platform are compared, and the feasibility and superiority of the compensation scheme using the 3-SPR parallel compensation platform are proved. To lower the working height of the upper deck of the compensation platform and reduce the extension range of the support legs, the structure of the compensation platform is optimized, and a novel 3-SPR parallel platform is designed. Finally, a simulation model was established. Using the inverse kinematic model as a compensation movement solver which can online calculate the length of branch legs based on the measured heaving, rolling, and pitching values of vessels, the compensation effect of the new structure under a certain sea state is simulated. The result demonstrated the efficiency of the ship motion decoupling movement of the newly designed compensation platform and proved the competence of it.

Flutter mitigation of a superlong-span suspension bridge with a double-deck truss girder through wind tunnel tests

As flutter is a very dangerous wind-induced vibration phenomenon, the mitigation and control of flutter are crucial for the design of long-span bridges. In the present study, via a large number of section model wind tunnel tests, the flutter performance of a superlong-span suspension bridge with a double-deck truss girder was studied, and a series of aerodynamic and structural measures were used to mitigate and control its flutter instability. The results show that soft flutter characterized by a lack of an evident divergent point occurred for the double-deck truss girder. Upper central stabilizers on the upper deck, lower stabilizers below the lower deck, and horizontal flaps installed beside the bottoms of the sidewalks are all effective in suppressing flutter for this kind of truss girder. By combining the structural design with aerodynamic optimizations, a redesigned truss girder with widened upper carriers and sidewalks, and double lower stabilizers combined with the inspection vehicle rails is identified as the optimal flutter mitigation scheme. It was also found that the critical flutter wind speed increases with the torsional damping ratio, indicating that the dampers may be efficient in controlling soft flutter characterized by single-degree-of-freedom torsional vibration. This study aims to provide a useful reference and guidance for the flutter design optimization of long-span bridges with double-deck truss girders.