Span Structures Research Articles

Omnidirectional Printing of PEDOT:PSS for High-Conductivity Spanning Structures.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a prominent conducting polymer, holds significance in both industry and academia. However, prevailing fabrication techniques struggle to build spanning features of PEDOT:PSS with both high electrical conductivity and fine resolution due to layerwise assembly in the xy plane. Here, we report an "omnidirectional printing and secondary doping" strategy to construct spanning, filamentary and out-of-plane 3D PEDOT:PSS with high conductivity. The pristine PEDOT:PSS suspension is homogeneously concentrated to form a printable ink with high solids (∼15 wt %) consisting of entangled PEDOT:PSS nanofibrils. Such ink shows a high storage modulus G' (43531 Pa) and a high yield stress τy (4325 Pa), thereby enabling omnidirectional printing. Secondary doping with sulfuric acid or other polar solvents is used to induce a synergetic process of PSS loss, conformational change, phase separation, and crystallinity enhancement in the printed structures, resulting in a remarkable enhancement of conductivity in dehydrated (65,378 S/m) and swollen (7190 S/m) states. As a proof-of-concept, 2D grids with a feature size of 15 μm and 3D overhanging arches are fabricated for high-performance transparent glass heaters and 3D interconnection, respectively. This work promises great potential for the development of advanced flexible electronics, wearable devices, and bioelectronics.

TIME DEPENDENT DEFORMATIONS OF A COUPLED BRIDGE: A CASE STUDY

<p>The bridge's span structure comprises a connected beam designed to support a concrete slab poured over parallel steel supports. Simultaneously, segmental construction, shrinkage, and the flow of concrete play a significant role in stress redistribution over time. The span construction is statically indeterminate due to its connections with the abutments, and temporal deformations occur under additional complex conditions. In this analysis, we employed a calculation model based on the layered finite elements method developed by the authors. This model can be utilized to analyse both statically indeterminate supports and the predicted phased construction method. It accounts for changes in the static system and loading, as well as variations in the layers within the coupled section and the viscous properties of the concrete over time. The calculation analysis results reveal that viscous concrete deformations, combined with different moments of activation of individual segments, have a significant impact on stress redistribution over time. Such intricate analyses are indispensable for ensuring the required safety and cost-effectiveness of the bridge span construction.</p>

Analysis of drilling vibration characteristics of anchoring system in coal mine

A new type of parallel operation unit for excavating and supporting anchors is proposed to address the issue of imbalanced excavation anchor ratio in coal mines. By equipping a straddle type anchoring drilling rig group, the synchronous parallel and fast operation mode for excavating and supporting anchors is achieved; Consider the problem of poor drilling stability of drill pipes in coal mines due to the coupling vibration between surrounding rock and anchoring equipment. Firstly, taking the multi drilling rig anchoring system as the research object, considering the influence of the equipment itself as an influencing factor on the vibration of the drill pipe, a dynamic model of the system is constructed using Lagrangian equations, and analytical solutions for the vibration displacement of each mass block are obtained; In order to more intuitively represent the vibration process of the drill pipe, Ansys is used to conduct modal analysis on the key components of the anchoring drilling rig system, and obtain the natural frequencies and vibration modes of each order of the key components; Using Adams to solve the rigid flexible coupling dynamic model of the anchoring drilling rig system, the vibration response laws of the drill pipe under different operating states were obtained. Secondly, Abaqus was used to simulate the drilling process of the drill pipe and obtain the vibration response law generated by the interaction between the drill pipe and the surrounding rock; The results indicate that the anchoring equipment has a greater impact on the vibration of the drill pipe, and the surrounding rock has a more stable impact on the vibration of the drill pipe. Due to the short body and large span structure of the anchoring system crossbeam expansion frame, the vibration response of the drill pipe is significantly greater than that of the retracted state of the drilling rig due to being in an unstable cantilever state when the drilling rig is extended. The theoretical reliability of the vibration response law of the drill pipe under different states has been further verified through drilling experiments of the anchoring system prototype. The relevant theories can provide a theoretical basis for the implementation of automatic anchoring technology in the anchoring system.

Kinetics of Light-Responsive CNT / PNIPAM Hydrogel Microactuators.

Light-responsive microactuators composed of vertically aligned carbon nanotube (CNT) forests mixed with poly(N-isopropylacrylamide) (PNIPAM) hydrogel composites are studied. The benefit of this composite is that CNTs act as a black absorber to efficiently capture radiative heating and trigger PNIPAM contraction. In addition, CNT forests can be patterned accurately using lithography to span structures ranging from a few micrometers to several millimeters in size, and these CNT-PNIPAM composites can achieve response times as fast as 15ms. The kinetics of these microactuators are investigated through detailed analysis of high-speed videos. These are compared to a theoretical model for the deswelling dynamics, which combines thermal convection and polymer diffusion, and shows that polymer diffusion is the rate-limiting factor in this system. Applications of such CNT/hydrogel actuators as microswimmers are discussed, with light-actuating micro-jellyfish designs exemplified, and >1500 cycles demonstrated.

Powers of Hamilton cycles in dense graphs perturbed by a random geometric graph

Let G be a graph obtained as the union of some n-vertex graph Hn with minimum degree δ(Hn)≥αn and a d-dimensional random geometric graph Gd(n,r). We investigate under which conditions for r the graph G will a.a.s. contain the kth power of a Hamilton cycle, for any choice of Hn. We provide asymptotically optimal conditions for r for all values of α, d and k. This has applications in the containment of other spanning structures, such as F-factors.

On lift enhancement and noise reduction in serrated gurney flap airfoil of wind turbines using proper orthogonal decomposition

Based on the steady simulation results obtained by the SST k-ω turbulence model, large eddy simulation (LES) and proper orthogonal decomposition (POD) are used to examine the static pressure and vorticity modes of the wind turbine airfoil with serrated Gurney flaps (SGFs) and the baseline at α = 12° and 20°. The effect of SGF on the aerodynamic performance and radiated noise is investigated, and the influence of serration's span structure on the vorticity mode distribution is discussed. By analyzing the main modes and mode coefficients of the flow field, the mechanism of lift enhancement and noise reduction of SGF is explained. The results indicate that an airfoil with a SGF(ASGF) of 6.7%c width and 0.8%c height can effectively improve the lift coefficient within the investigated attack angles, delay stall by about 3°, and reduce the radiated noise of the airfoil by 0.51 and 4.40 dB, respectively, at 12° and 20°. Static pressure distribution analysis reveals that the SGF can significantly widen the positive pressure zone of the pressure surface, improve the ultra-low pressure regime of the suction surface, and make the pressure distribution on the suction surface more uniform, which increase the lift-drag ratio of ASGF. The POD method effectively extracts the most relevant mode of the airfoil surface radiated noise. The unsteady feature of the main flow of the airfoil is the vortices on the suction surface. The ASGF can effectively restrain the vortex separation on the suction surface and reduce the vorticity, delaying the stall and reducing the radiated noise of the airfoil surface.

ПОРІВНЯННЯ ЕФЕКТИВНОСТІ МЕТОДІВ РЕКОНСТРУКЦІЇ СТАЛЕЗАЛІЗОБЕТОННИХ ОДНОПРОЛІТНИХ МОСТІВ

The paper contains developed the method of strengthening steel-reinforced concrete single-span bridge structures that have undergone wear and tear due to long-term operation and require expansion. Have been described the structural solution and the principle of operation under load of the existing typical steel-reinforced concrete single-span bridges. As an example have been considered real emergency bridge structure in the village of Dashiv of the Haysyn district of the Vinnytsia region, in need of urgent reconstruction. Have been described in detail its main structural elements and technical condition. Have been shown possible rational ways of expanding and strengthening the structure in two variants. Variant 1 – reinforcement of existing steel and reinforced concrete structures with partial blocking of road traffic. Variant 2 – replacement of the span structure with a complete shutdown of the bridge for the duration of the construction and installation works. Have been developed basic constructive schemes for the reconstruction of the structure for the first and second variants. Have been described the technological sequence of strengthening the bridge structure according to both mentioned methods, have been analyzed the advantages and disadvantages and have been estimated the cost indicators of the reconstruction of each of the proposed variants. Have been proven that the strengthening method (variant 1) is more appropriate if it is necessary to partially operate the structure during construction and installation works. This method makes it possible to restore the design load-bearing capacity of the bridge structure with the provision of modern dimensional requirements and traffic safety requirements for less cost. The method of complete replacement of the span structure (variant 2), despite the higher cost, should be preferred in all other cases according to dynamics of constant growth of traffic flow in our country. With variant 2, it is possible to achieve not only the required dimensions, but also higher load-bearing characteristics of the bridge structure in a shorter period of time. The reliability and efficiency of each of the methods is confirmed by the corresponding strength calculations.

Spanning -cycles in random graphs

AbstractWe extend a recent argument of Kahn, Narayanan and Park ((2021) Proceedings of the AMS 149 3201–3208) about the threshold for the appearance of the square of a Hamilton cycle to other spanning structures. In particular, for any spanning graph, we give a sufficient condition under which we may determine its threshold. As an application, we find the threshold for a set of cyclically ordered copies of $C_4$ that span the entire vertex set, so that any two consecutive copies overlap in exactly one edge and all overlapping edges are disjoint. This answers a question of Frieze. We also determine the threshold for edge-overlapping spanning $K_r$ -cycles.

Finite element analysis of the span structures dynamics under a moving load influence

Introduction: Providing the span structure durability under dynamic influences is one of the main tasks in their design and construction. This task is accomplished mainly by studying the dynamic behavior of railway bridges when a train is moving. The paper considers the study of building a span structure finite element model under dynamic influences caused by a moving load on the main beam of railway bridge crossings. Methods: Construction members are designed by the finite element method in the Midas civil software package using rod finite elements. The dynamical analysis is carried out by the direct dynamic method in a linear setting. Fixed loads on the structure are transferred to the mass to meet the requirements of dynamic analysis. The rail is designed as a linear elastic Bernoulli-Euler beam of finite length, and the bridge is designed as a series of multi-span continuous Bernoulli-Euler beams. The interaction of the system (train — track — bridge) is designed by elastic elements. Results: An algorithm for calculating span structures under dynamic influences was created and a dynamic response of the structure was built. As a result of all the above, the dependences of the greatest vertical dynamic displacement and dynamic acceleration on time for different speeds were obtained. Discussion: This work made it possible to understand the principle of creating a linear mathematical model of the dynamic interaction of the system (bridge — train — railway) by the finite element method and presented an algorithm for calculating span structures under dynamic influences. The article showed the influence of train speed on the dynamic behavior of span structures, so it is necessary to take into account this influence on the parameters of the stress-strain state (vertical displacements).

Floor vibrations and rectification

Excessive floor vibration due to human excitation is a significant serviceability concern in buildings and other long span structures. The use of lightweight materials, nominal furniture and open plan layouts is resulting in lighter floors with lower damping than traditional older floors and hence an increased risk of excessive vibration response. This paper provides insights into walking excitation, floor response and remedial actions for floors with excessive vibrations.

Fatigue life of unified riveted superstructures designed by Transmostproject with the introduction of increased axle loads

The article presents a study of the residual fatigue life of superstructures during the introduction of trains with increased axial loads on bridges with riveted superstructures, designed in the fifties of the last century. Unified metal superstructures have been in relatively heavy duty conditions for more than 60 years. During lcontinuous operation, processes occur in elements and joints that lead to the appearance and development of various damages and varying degree failures of hazard, so it is necessary to decide on the further operation of old bridge spans and their replacement. When determining the fatigue life, the linear addition hypothesis of fatigue damage accumulation was used, taking into account the increase in stresses with the introduction of increased axial loads. As a critical measure of damage, providing a given reliability, the value obtained from the calculation results of several hundred cracks in riveted superstructures of older design standards was adopted. The increase in load from the installation of a ballastless bridge floor is taken into account. To determine the residual fatigue life, fatigue data is used depending on the concentration of stresses magnitude in the attachments of the main truss elements. For a more accurate determination of the rivet joints operation stage, the author carried out a wear-out calculation through operation period. The introduction of heavier train loads will lead to an increase in the accumulation of fatigue damage in the elements. If weak rivets in attachments are found during inspection, they must be replaced with high-strength bolts to increase fatigue life. The author obtained that the residual fatigue life of the span structures designed by Transmostproekt has not yet been fully exhausted even with the introduction of heavy trains with a wagon axle load of 27–30 tons.

FEATURES OF CONSTRUCTIVE, ORGANIZATIONAL AND TECHNOLOGICAL SOLUTIONS FOR THE RESTORATION OF REINFORCED CONCRETE BRIDGE STRUCTURES

The article provides information on effective structural and organizational-technological solutions for surveying, designing and restoring the bridge structure, which was partially destroyed as a result of the armed aggression of the Russian Federation. It was established that information from scientific and regulatory sources does not sufficiently reflect the situation with bridges, where a part of the load-bearing structures has been completely lost and it is necessary to carry out work on the construction of new structures with the possible use of a part of the old (undamaged) ones. The current operating condition of the main elements of the structure (bridge web, span structure, supports and support parts, foundations, approaches) is determined. When predicting the term of accident-free operation, it was established that the remaining resource of the bridge, taking into account the actual technical condition of the main elements at the time of the inspection (destruction), which is determined from the equation of element degradation, is completely exhausted. The obtained data made it possible to predict the technical condition of the bridge in accordance with regulatory requirements and to prescribe operational and restoration measures. The use of undamaged underground structures for the construction of new reinforced concrete supports is substantiated, where preparatory work is provided with the use of complex mechanization tools. When concreting the bodies of the supports, the rationality of the new fastening of the braces of the formwork blocks was confirmed, which ensured increased rigidity and stability of the assembled formwork, for which it was proposed to install one plate between the supports on a rigid metal frame structure with a height of corresponds to the lower limit of the concreting massif, with the possibility of attaching braces working in different planes to it. It is proposed not to change the position of the two slabs intended for braces along the axis of the bridge, while they were also placed on similar metal frames. Placing the plates for fastening the braces at the mentioned height made it possible to reduce the length of the braces and ensure their working angles within the most effective limits.

Kosciuszko Bridge, USA: New York City's first cable-stayed highway bridge

The Kosciuszko Bridge carries a 1.8 km long segment of the Brooklyn–Queens Expressway over Newtown Creek between Brooklyn and Queens in New York City, USA. The roadway is a vital link in the region's transportation network, carrying over 170 000 vehicles/day. Owing to structural and operational deficiencies, the existing structure was replaced. The new bridge consists of two parallel structures, one eastbound and one westbound, with main spans mirroring one another. Each structure consists of a single-tower cable-stayed main span over Newtown Creek with unbalanced main and back spans. This was the first cable-stayed bridge to be constructed in New York City, joining the ranks of the city's most iconic bridges. Here, two main span structures are discussed, with the focus primarily on the design and construction of the westbound, phase 2 bridge. Some key design aspects are outlined, including outboard cable anchorages, a concrete-filled counterweight and other details intended to facilitate construction, maintenance and inspection. The eastbound, phase 1 bridge was constructed under a design–build contract, and the westbound, phase 2 bridge as a design–bid–build. The paper also touches on some of the design aspects that were refined during the second phase.

Resistance of Gable Structure of Nuclear Island to Progressive Collapse in Conventional Island Shield Building of Nuclear Power Plants

The gable wall of the conventional island of a nuclear power plant carries various pipeline loads connecting the nuclear island and the conventional island. If the gable wall collapses and is damaged due to the progressive collapse of the main plant structure of the conventional island, it will directly threaten the safety of the nuclear island. Therefore, it is of great significance to systematically study the resistance of the gable structure of the nuclear island to progressive collapse for the safe operation of nuclear power plants. Based on the SAP2000 finite element analysis platform, this paper established a model of the reinforced concrete frame structure of the first span of the shield building on the conventional island of a nuclear power plant, including the gable. According to the alternate path method, the node displacement and bearing capacity responses were used to determine the critical components in the gable, and single column failures of the top four in importance were selected as different analysis conditions. Nonlinear static and dynamic methods were used to analyze the displacement, internal force change, hinge sequence of the gable structure on the side of the nuclear island, and the ability of the gable to resist progressive collapse. The analysis results showed that the gable structure of the nuclear island had good resistance to progressive collapse under four single column failure conditions, whether by nonlinear static or dynamic analysis, and the overall vertical displacement obtained by the nonlinear static analysis was larger than that obtained by the dynamic analysis.

ДОСЛІДЖЕННЯ АРМАТУРИ ПЕРІОДИЧНОГО ПРОФІЛЮ А-ІІІВ ТА ПЕРСПЕКТИВИ ЇЇ ЗАСТОСУВАННЯ ДЛЯ ПЛИТ ПРОГОНОВИХ БУДОВ МОСТІВ

Introduction. Metal reinforcement A-IIIв, manufactured from reinforcement A-III in accordance with GOST 5781 by pulling, was quite widely used for slabs of span structures of bridges in the period before 1991, as well as later. There is a need to repair such structures due to the exhaustion of their resource due to a significant duration of operation, damage due to the impact of means of destruction during hostilities. Often, the best option for repairing such spans is to replace a separate plate or plates with similar ones, since in this case there are no problems with the size of height, resting on existing supports, etc. Problem Statement. The vast majority of bridges in Ukraine, built in the period 1960-1991 and, to a large extent, in subsequent years, were designed according to typical projects. A large number of these bridges were built from girder slabs according to typical designs, where class A-IIIв reinforcement was used as prestressed reinforcement. These reinforcements were produced directly at the factories producing slabs structures from reinforcements of class A-III in accordance with GOST 5781 by pulling. To perform such works, the manufacturing plant must have appropriate equipment, qualified specialists, documentation, and obtain reinforcements of the required quality. As for the documentation, in the period up to 1991, such documentation was developed centrally and distributed to factories manufacturing structures. After 1991, this does not happen, the documentation is often not updated, which can be the reason for not ensuring the quality of the structures. Purpose. To analyze the documentation for the manufacture and use of reinforcement A-IIIв for the manufacture of slabs of span structures of bridges with a length of 12 m in accordance with the documentation VTP 21-86 (addition). To research the reinforcement A-IIIв, which is manufactured in accordance with the documentation YN 218 USSR – 026-84 directly at the manufacturing plant from the reinforcement of class A-III in accordance with GOST 5781 by pulling it for further use for the manufacture of slabs of span structures of bridges with a length of 12 m in accordance with documentation VTP 21‑86 (addition). Establish the possibility of using reinforcement A-IIIв in today’s conditions for the manufacture of slabs of span structures 12 m long in accordance with the documentation VTP 21-86 (addition) for the repair and construction of bridges.

Investigation of the effect of a monolithic reinforced concrete slab on the force distribution between the main components of a span structure, taking into account their collective performance

Abstract. Problem. The issue of bridge repair and reconstruction mostly for bridges on motorways has become especially pressing in the last few years, and especially in the year of military invasion. In the article, one of the options for creating a finite element model of a plate girder structure for analysis and calculation is presented. The studies provided in the article investigate the effect of the newly established monolithic reinforced concrete plate, which serves to unify the primary beams (plates) of the truss structure into a temperature-resistant construction, on the distribution of forces between the main constituents of the truss structure in case of their collective operation. The objective of the study is to develop a suitable finite-element model of a composite beam structure joined by a monolithic overlay plate and to analyze the effect of this plate on the spatial performance of the beam structure. Methodology. An analysis was conducted of the forces in the span structure elements in accordance with the standard project, as well as the forces in these elements after the monolithic slab was merged. The comparison results demonstrated that the use of a monolithic overlay slab to create a temperature-proof span structure permits a decrease in forces in the main elements of 27% and 20%, respectively. The scientific innovation presented herein is a finite element model of a plate girder structure, composed of several rods which model individual components of the plate. The practical implications of this work are that the proposed finite element model can be used to accurately calculate both existing girder structures and new reinforcement designs.

The impact of bridge crossing span damage under moving load

The structure of the bridge crossing span structure is simulated in order to determine the most informative parameters, which need to be measured in the process of monitoring system operation. To assess the influence of structural component integrity on the static deflections and dynamic response, damages were introduced into the model, which were simulated by removal of a part of the structural components. On the basis of a numerical model of calculating a span structure under static and dynamic moving load, it is shown how increasing damage changes deflection and natural frequencies, which can be reliably recorded by the monitoring system.

Seismic Response of Cable-Stayed Spanning Pipeline Considering Medium-Pipeline Fluid–Solid Coupling Dynamic Effect

With the aim of determining the influence of the fluid–structure coupling dynamic effect of the oil and gas transmission medium and pipeline on the seismic response, an oil pipeline supported by a cable-stayed spanning structure was taken as the study object. Kinetic equations taking into account the action of oil and gas medium were studied, and a finite element model structure considering the additional-mass method and the fluid–structure coupling effect were established separately. In addition, the mechanism of the oil–gas–pipeline coupling action on the seismic response of pipeline structure was analyzed, and the results were obtained. The results show that the pipeline has a minimal seismic response at the abutment location, the seismic response gradually increases along the abutment to the main tower, and the seismic response reach is maximized at about one-fifth of the bridge platform. The seismic response of the oil and gas pipeline model structure using the additional-mass method is generally more significant than that based on the fluid–solid coupled dynamic model; moreover, the maximum displacement response differs by about 24%, and the maximum acceleration response differs by approximately 30%, indicating that the oil and gas medium has a certain viscoelastic damping effect on the seismic response of the oil pipeline, which provides a reference for the seismic response calculation theory and analysis method of cable-stayed spanning oil pipelines.

Calculation of Continuous Reinforced Concrete Bridges And Overpasses Inseismically Hazardous Areas

In recent years, in the Republic, the design and construction of continuous reinforced concrete bridges and overpasses were conducted at a colossal pace. Foreign advanced technologies, methods, and software systems were taken into account. Foreign experience in studying rubber-metal bearing parts of bridges and overpasses was analyzed. The article presents the calculation of a continuous reinforced concrete overpass for seismic impacts using the finite element method in the framework of the linear spectral theory. Numerical calculations have shown that the bearing part of the right end of the overpass does not allow the span to fall from the abutment because the maximum displacement of the rubber-metal bearing part is 0.2 m. As a result, the span structure and overpass supports have an overestimated margin of safety for an 8-point earthquake, according to MSK-64.

Calculation of the stress-strain state of monolithic bridges on the action of real seismic impacts

To improve the transport infrastructure of the Republic of Uzbekistan, there is a tendency to build monolithic structures of bridges and overpasses. The article presents the calculation of a monolithic bridge on the 1083rd km of the M-39 highway passing through the city of Samarkand. The results of the monolithic bridge calculation on dynamic loads are presented, based on the records of two real seismograms of two dangerous earthquakes registered for a system with a spectral composition: the Gazli (Uzbekistan) and Manjil (Iran) earthquakes. The results of calculations of longitudinal and vertical displacements, and normal stress in the upper and lower parts of the span along the length of the bridge were analyzed. The calculations performed, show that the span structure and bridge supports have an overestimated margin of safety for an 8-point earthquake according to MSK-64. To ensure the guaranteed seismic safety of bridge structures, it is required to conduct design calculations based on a set of records of earthquake events that are close in dominant frequencies to the characteristics of the construction site. This provision must be included in the relevant regulatory documents.