Bridge Problem Research Articles

Analysis and Countermeasures of Construction Quality Problems of Urban Road and Bridge

Analysis and Countermeasures of Construction Quality Problems of Urban Road and Bridge

A precise time-integration linear vehicle-bridge interaction method and dynamic sensitivity analysis

A linear dynamic vehicle-bridge interaction method is proposed in this paper. This VBI system can be easily simulated by a step-by-step solution technique based on precise time-integration method following discretization of the bridge and modal analysis of the finite element model. By selecting the target structural mode with high modal participation in finite element modal analysis, the huge computational overhead caused by the multi-degrees of freedom of large structures in the dynamic response analysis can be effectively reduced. In this integration process, the characteristics of precise time-integration method can be used to ensure the stability and accuracy of the iterative calculation when selecting a relatively large time integration step. This provides the possibility to investigate the VBI problem in large-scale bridges. In this work, a half-vehicle model case and an experiment on full-vehicle model are used to verify the application of the algorithm. Then the dynamic sensitivity of a beam is analyzed based on the dynamic amplification factor.

Nonlinear Flutter Analysis for a Long-Span Suspension Bridge

The wind-induced flutter of the long-span suspension bridge structure is extremely harmful to the bridge. Therefore, it is necessary to study the nonlinear problem of wind-induced flutter. Here, the nonlinear flutter problem of a long-span suspension bridge with cubic torsional stiffness is analyzed by the equivalent linearization method. The system has Hopf bifurcation and limit cycle oscillations (LCOs) under critical wind speed. Replacing the nonlinear stiffness term of the original nonlinear equation with the equivalent linear stiffness, we can obtain the equivalent linearized equation of the nonlinear flutter system and the solution, critical wind speed, and flutter frequency of the suspension bridge flutter system. At the same time, the system has a limit cycle vibration, and the Hopf bifurcation point is obtained. Compared with the numerical method, the calculation results are consistent. The influence of the damping ratio on the flutter system is analyzed. Increasing the system damping ratio can increase the flutter critical wind speed and reduce the amplitude of LCOs. The influence of cubic torsional stiffness on the flutter system is analyzed. The increase of the cubic stiffness coefficient does not change the critical state of flutter, but reduces the amplitude of LCOs.

First train timetabling and bus service bridging in intermodal bus-and-train transit networks

Subway system is the main mode of transportation for city dwellers and is a quite significant backbone to a city's operations. One of the challenges of subway network operation is the scheduling of the first trains each morning and its impact on transfers. To deal with this challenge, some cities (e.g. Beijing) use bus ‘bridging’ services, temporarily substituting segments of the subway network. The present paper optimally identifies when to start each train and bus bridging service in an intermodal transit network. Starting from a mixed integer nonlinear programming model for the first train timetabling problem, we linearize and reformulate the model using the auxiliary binary variables. Following that, the bus bridging model is developed to cooperate with the first train operation for reducing long transfer waiting times. After realizing the low computational efficiency of solving the integrated model, a tailored algorithm is designed to optimally solve the first train timetabling and bus service bridging problems. The exact models and algorithms are applied to the Beijing subway network to test their effectiveness and computational efficiency. Numerical results show that our approaches decrease the total passenger waiting time by 53.4% by a combined effect of adjusting the first train departure times and operating 27 bridging buses on 7 routes.

REVITALIZING POLICY OF PEDESTRIAN BRIDGE WITHOUT ROOF IN SUDIRMAN JAKARTA: DILEMMA BETWEEN FUNCTION AND AESTHETICS

Purpose survey research is to answer for dilemma of public service facilities to assess how much benefits of revitalizing the pedestrian bridge without a roof in Sudirman Jakarta, given the problem for the pedestrian bridge cannot protect its users from the heat and rain. In addition, this building structure can be adjusted to the aesthetic advantages layout of the modern city. The quantitative survey method uses the Analytical Hierarchy Process model approach, which is a decision-making method by comparing the selection criteria in pairs and the pairwise comparison between the available options. The results showed that respondents expected the pedestrian bridge to return to its function of safety and comfort to be the top priority. In addition, there are also advantages in improving the aesthetics of urban planning which is the attraction of public facilities. Thus the decision as a reference that revitalization pedestrian bridge must prioritize its function to cross, not enjoy the city view, besides that, the pedestrian bridge without a roof needs to adjust to the season and weather in Jakarta which has an impact on public concerns about the dangers of bridge conditions for its users

Conceptual Design of the Pedestrian Bridge

As the pedestrian bridge is in a period of rapid development, many issues such as design defects, lagging construction techniques and uncoordinated environmental boundaries have been exposed in the process of construction and maintenance. This article studies the conceptual design of the pedestrian bridge from the viewpoint of holistic engineering construction. By sorting out the developing context of existing pedestrian bridges at home and abroad, it analyzes the existing problems of pedestrian bridges and tracks their root causes. On this basis, combined with excellent international examples of pedestrian bridges, the developing trend of pedestrian bridges is summarized and fundamental design considerations for contemporary pedestrian bridges are proposed centering on the design concept, structural modeling and environmental landscape innovation. Based on design considerations for pedestrian bridges and the application of cutting-edge technologies such as new bridge materials, construction processes and innovative structures, conceptual design strategies for pedestrian bridges are approached by integrated assembling, digitizing, intelligentizing and humanizing design. The article also explores the feasibility of interdisciplinary and cross-cultural inspiration in the application of pedestrian bridge structures. This study attempts to develop a framework for integrating analytic process strategies, and the research content of this article can provide some reference for pedestrian bridge design.

Dynamical Schrödinger Bridge Problems on Graphs

We study a discrete dynamical Schrodinger bridge problem (SBP) as a dynamical variational problem on a finite graph. We prove that the discrete SBP exists a unique minimizer, which satisfies a boundary value Hamiltonian flow on probability simplex equipped with $$L^2$$ -Wasserstein metric. In our formulation, we establish the connection between discrete SBP problems and Hamiltonian flows.

Bridge structure safety assessment

With the passage of time, more and more highway bridges gradually enter the old age, and the safety assessment of bridge structures is particularly urgent. According to the use status of in-service reinforced concrete bridges and the actual problems of highway bridges, the necessity and urgency of this subject research are pointed out. At the same time, it comprehensively analyzes the technical specifications, research and application status of bridge structure safety assessment at home and abroad, and points out the advantages and disadvantages of existing technical specifications and research results in terms of content, methods and applications, and aims at the existing technical specifications and research results. Insufficiency, the main research content of this topic is proposed.

Equivalence between internal observability and exponential stabilization for suspension bridge problem

We study the fourth order semilinear suspension bridge problem with restoring force h(u) and linear damping $$\delta u_{t}$$ . Using the multiplier method, we first establish the observability inequality of the corresponding system without damping term. Then we show an equivalence between observability and exponential stabilization of this system by using an appropriate decomposition technique and the semigroup method.

Modeling ternary fluids in contact with elastic membranes.

We present a thermodynamically consistent model of a ternary fluid interacting with elastic membranes. Following a free-energy modeling approach for the fluid phases, we derive the governing equations for the dynamics of the ternary fluid flow and membranes. We also provide the numerical framework for simulating such fluid-structure interaction problems. It is based on the lattice Boltzmann method for the ternary fluid (Eulerian description) and a finite difference representation of the membrane (Lagrangian description). The ternary fluid and membrane solvers are coupled through the immersed boundary method. For validation purposes, we consider the relaxation dynamics of a two-dimensional elastic capsule placed at a fluid-fluid interface. The capsule shapes, resulting from the balance of surface tension and elastic forces, are compared with equilibrium numerical solutions obtained by surface evolver. Furthermore, the Galilean invariance of the proposed model is proven. The proposed approach is versatile, allowing for the simulation of a wide range of geometries. To demonstrate this, we address the problem of a capillary bridge formed between two deformable capsules.

Wasserstein Proximal Algorithms for the Schrödinger Bridge Problem: Density Control With Nonlinear Drift

In this article, we study the Schrödinger bridge problem (SBP) with nonlinear prior dynamics. In control-theoretic language, this is a problem of minimum effort steering of a given joint state probability density function (PDF) to another over a finite-time horizon, subject to a controlled stochastic differential evolution of the state vector. As such, it can be seen as a stochastic optimal control problem in continuous time with endpoint density constraints—A topic that originated in the physics literature in 1930s, and in the recent years, has garnered burgeoning interest in the systems-control community. For generic nonlinear drift, we reduce the SBP to solving a system of forward and backward Kolmogorov partial differential equations (PDEs) that are coupled through the boundary conditions, with unknowns being the “Schrödinger factors”—so named since their product at any time yields the optimal controlled joint state PDF at that time. We show that if the drift is a gradient vector field, or is of mixed conservative–dissipative nature, then it is possible to transform these PDEs into a pair of initial value problems (IVPs) involving the same forward Kolmogorov operator. Combined with a recently proposed fixed point recursion that is contractive in the Hilbert metric, this opens up the possibility to numerically solve the SBPs in these cases by computing the Schrödinger factors via a single IVP solver for the corresponding (uncontrolled) forward Kolmogorov PDE. The flows generated by such forward Kolmogorov PDEs, for the two aforementioned types of drift, in turn, enjoy gradient descent structures on the manifold of joint PDFs with respect to suitable distance functionals. We employ a proximal algorithm developed in our prior work that exploits this geometric viewpoint, to solve these IVPs and compute the Schrödinger factors via weighted scattered point cloud evolution in the state space. We provide the algorithmic details and illustrate the proposed framework of solving the SBPs with nonlinear prior dynamics by numerical examples.

Fire hazard in transportation infrastructure: Review, assessment, and mitigation strategies

This paper reviews the fire problem in critical transportation infrastructures such as bridges and tunnels. The magnitude of the fire problem is illustrated, and the recent increase in fire problems in bridges and tunnels is highlighted. Recent research undertaken to address fire problems in transportation structures is reviewed, as well as critical factors governing the performance of those structures. Furthermore, key strategies recommended for mitigating fire hazards in bridges and tunnels are presented, and their applicability to practical situations is demonstrated through a practical case study. Furthermore, research needs and emerging trends for enhancing the “state-of-the-art” in this area are discussed.

Multiobjective Optimization of Cable Forces and Counterweights for Universal Cable-Stayed Bridges

In cable-stayed bridges, especially asymmetric bridges, counterweights are always made to work together with cable pretension forces to get a reasonable finished state. To solve the optimization problem of the cable-stayed bridge considering the counterweights, the integrated optimization method (IOM) for estimating cable forces and counterweights is proposed. In this method, the counterweights are proposed to act on the anchor points. After that, the summary of the minimum weighted total bending energy and the summary of the counterweights are considered as two objective functions of a multiobjective problem. Finally, the dynamic weighted coefficient method is used to solve this problem and realize the Pareto solution set. IOM presents detailed procedures in a simple numerical model and is then applied to the Yong-ding special-shaped cable-stayed bridge. The results show that not only IOM can realize the priority selection of the loading position of the counterweights but also get a better reasonable finish state because of the introduction of the counterweight dimension; the dynamic weighted coefficient method can quickly find the Pareto optimal solution set and be further screened by decision-makers; counterweight is very helpful to reduce torsion and other spatial effects in cable-stayed bridges. IOM can be used as a universal optimization method for cable-stayed bridges.

Multimarginal Optimal Transport with a Tree-Structured Cost and the Schrödinger Bridge Problem

The optimal transport problem has recently developed into a powerful framework for various applications in estimation and control. Many of the recent advances in the theory and application of optimal transport are based on regularizing the problem with an entropy term, which connects it to the Schrödinger bridge problem and thus to stochastic optimal control. Moreover, the entropy regularization makes the otherwise computationally demanding optimal transport problem feasible even for large scale settings. This has led to an accelerated development of optimal transport based methods in a broad range of fields. Many of these applications have an underlying graph structure, for instance, information fusion and tracking problems can be described by trees. In this work we consider multimarginal optimal transport problems with a cost function that decouples according to a tree structure. The entropy regularized multimarginal optimal transport problem can be viewed as a generalization of the Schrödinger bridge problem with the same tree-structure, and by utilizing these connections we extend the computational methods for the classical optimal transport problem in order to solve structured multimarginal optimal transport problems in an efficient manner. In particular, the algorithm requires only matrix-vector multiplications of relatively small dimensions. We show that the multimarginal regularization introduces less diffusion, compared to the commonly used pairwise regularization, and is therefore more suitable for many applications. Numerical examples illustrate this, and we finally apply the proposed framework for the tracking of an ensemble of indistinguishable agents.

Objectivity as the Fruit of Authentic Subjectivity

One of the most important problems of philosophy is the “critical problem”, the problem of bridge between the human mind and the world, the external reality. It is the question of relations between the subject and the object. The interesting solution for this problem is given by Bernard Lonergan SJ (1904–1984), one of the most important Catholic English-speaking thinkers of the twentieth century. It would be difficult to point to someone who influenced the American Catholic philosophy and theology from the inside out more than he did: that is why he is called the “American Rahner „. He tries to connect the great tradition of Thomism and Augustinianism and, on the other hand, classical and modern philosophy, German idealism and English Empiricism. At the heart of his thinking is the theory of the human mind. With the help of transcendental and phenomenological methods, Lonergan demonstrates that the mental structure of man consists of five levels: the empirical level, the intellectual level, the rational level, the responsible level and the level of religious experience, which together create a cumulative process that leads to knowledge and decision. The most important point here is he act of understanding, the insight, which always has a creative moment, especially on the second and third levels, as an effect of the subject’s work. The correct understanding of this moment enables a mediation between the empirical, rational and idealistic understanding of the knowledge process. Correct action on all levels, faithfulness to the nature of the subject, leads to truth – according to Lonergan’s very apt maxim: objectivity is the fruit of the authentic subjectivity.

Mechanical System Evolution and Reasonable Structural Design Parameters of Long-Span Deck-Type Beam-Arch Composite Rigid Frame Bridge

Long-span deck-type beam-arch composite rigid frame (BACRF) bridge fully integrates the merits of arch bridges and beam bridges, and overcomes the cracking and deflection problems of continuous rigid frame bridges. As a perfect combination of beam bridges and arch bridges, the long-span deck-type BACRF bridge boasts a light structure, a strong bearing capacity, and a powerful spanning capability. From the perspective of mechanical system evolution, this paper theoretically analyzes the structural mechanics of the beam-arch composite system, establishes a half-bridge model for BACRF bridge, and derives the expressions of the internal force and displacement of the beam-arch composite system. Next, finite-element analysis was conducted to analyze how the variation of a single parameter, e.g., rise-span ratio, open web ratio, and side-to-middle span ratio, affects midspan displacement, arch-beam junction displacement, main beam bending moment, and main arch axial force. Finally, the calculation formula for deflection-span ratio of BACRF bridge was proposed based on the maximum hyperplane method. The research results provide a reference for the structural design of similar bridges.

A micromechanical model of fiber bridging including effects of large deflections of the bridging fibers

A micromechanical model of cross-over fiber bridging is developed for the prediction of macroscopic mixed-mode bridging laws (traction-separation laws). The model is based on non-linear beam theory and takes into account debonding between fiber and matrix as well as buckling of fibers in compression. Further, it is shown how failure of the bridging fibers can be taken into account through a Weibull distributed failure strain. Predictions made by the proposed model are compared with predictions made by detailed 3D finite element models, and a very good agreement was observed. It is shown that models based on linear beam theory are only valid for small transverse deflections of the bridging ligament and greatly underestimate the force transferred by ligaments subjected to moderately large deflections. The novel model, on the other hand, is applicable in the entire range where the bridging problem transitions from a beam bending problem to a bar-like problem. Finally, an example of how the proposed model can be used for parameter/sensitivity studies is given. A conclusion from this study is that reducing the fracture toughness, Gc, of the interface between fibers and matrix may lead to increased energy dissipation through cross-over fiber bridging as more fibres remain intact longer.

ASSESSMENT OF TECHNICAL STATE AND DESIGN OF RECONSTRUCTION OF THE SMALL BRIDGE OF THE SLOVINSKY SYSTEM

Abstract. In the 1950s and 1960s of the 20th century a lot of one- and two-span bridges with a span of 4-6 m were built on public roads on the territory of the former USSR. The paper describes the features of the design and construction of small four-hinged reinforced concrete bridges on lightweight supports of engineer Slovinsky system. The experience of surveying small bridges shows that in the context of a limited funding, compared to other types of bridges, maintenance and operation of these bridges does not get enough attention. There are relatively low material losses from their destruction and it is possible to restore them fairly easily. Therefore, many of them have a large number of defects and are in a poor physical condition. The purpose of the work is to draw attention of owners to the problems of small bridges using a specific example, as well as to present effective constructive solutions for the reconstruction of a small four-hinge bridge. These design solutions are developed on the basis of the research and development in Lviv National Polytechnic University and include the use of a reinforced concrete cover slab. The slab has been frequently used in other bridge reconstruction projects and proved its technical and economic efficiency in practice. The article gives characteristics of the bridge, the technical state of its structures, the main defects and damages, as well as the characteristics of the stream and its influence on the condition of the bridge. The design solutions for widening and strengthening the small bridge of the Slovinsky system can provide operational performance and consumer properties in accordance with the requirements of the current design standards for new bridges. These standards are able to ensure the service life of the reconstructed bridge.

Alternative solution for konigsberg bridge problem through the concept of matching

Alternative solution for konigsberg bridge problem through the concept of matching

Hopf–Cole transformation via generalized Schrödinger bridge problem

We study generalized Hopf–Cole transformations motivated by the Schrödinger bridge problem, which can be seen as a boundary value Hamiltonian system on the Wasserstein space. We prove that generalized Hopf–Cole transformations are symplectic submersions in the Wasserstein symplectic geometry. Based on this transformation, energy splitting inequalities are provided.