Implementing bridge weigh-in-motion for railway traffic

This paper focuses on implementing existing bridge weigh-in-motion technology on railways. Using only simple instrumentation with four concrete embedded sensors, a complete WIM system with axle detection, weighing, track detection and attempted identification of locomotives was implemented on a bridge with multiple railway tracks. The results and the effectiveness of this type of sensor setup is discussed.     

Damage detection of truss bridge joints using Artificial Neural Networks

Recent developments in Artificial Neural Networks (ANNs) have opened up new possibilities in the domain of inverse problems. For inverse problems like structural identification of large structures (such as bridges) where in situ measured data are expected to be imprecise and often incomplete, ANNs may hold greater promise. This study presents a method for estimating the damage intensities of joints for truss bridge structures using a back-propagation based neural network. The technique that was employed to overcome the issues associated with many unknown parameters in a large structural system is the substructural identification. The natural frequencies and mode shapes were used as input parameters to the neural network for damage identification, particularly for the case with incomplete measurements of the mode shapes. Numerical example analyses on truss bridges are presented to demonstrate the accuracy and efficiency of the proposed method.     

铁路单体桥梁安全监测的仿真与分析

以典型黄河铁路桥桥梁健康状况评估为目标,通过使用ABAQUS工程模拟有限元软件,在建立连续梁模型的基础上,从横向摇摆力作用下变形,以及应变和应力关系上进行桥梁状况模拟及分析,并在此基础上设计基于光纤光栅传感器的桥梁安全监测网络,为工程技术人员在铁路桥梁结构分析上提供了有效的方法。     

高效自动化码头低架桥结构垂直挠度分析

为验证某高效自动化码头低架桥结构设计的合理性,利用ANSYS建立有限元模型,对其进行静力特性计算．比较用挠度数学模型计算出的理论值与用ANSYS计算的结果,表明该模型建立正确．研究表明垂直挠度比结构强度更难以满足实际工况的应用要求．     

大跨钢桁架拱桥地震响应有限元分析

采用ANSYS建立某大跨钢桁架拱桥有限元模型,对其进行模态分析;采用瑞利阻尼理论,通过拱桥前2阶圆频率计算质量阻尼和刚度阻尼;采用动力时程分析法对拱桥进行地震响应有限元分析.结果表明:横向位移的最大峰值由水平地震波载荷沿横桥向输入决定,纵向位移的最大峰值由水平地震波载荷沿纵桥向输入决定,竖向位移的最大峰值由重力载荷工况决定.     

铁路桥梁监测中基于短签名方案的数据传输协议

针对开放式互联网环境下铁路桥梁监测系统在数据交互过程中存在的信息泄露与篡改等网络安全问题,提出一种铁路桥梁监测中基于短签名方案的数据传输协议。首先,在Boneh短签名基础上构造了基于身份的短签名方案;然后,在随机预言机模型和逆计算性Diffie-Hellman问题（Inv-CDHP）假设下证明了该方案的安全性,并进一步把此方案运用在桥梁监测数据传输协议中;最后,给出了方案实现的关键代码并与另几种方案进行了实验比较。实验结果和分析表明,新方案的平均耗时与经典的Boneh方案接近,但与Fangguo Zhang方案和Leyou Zhang方案相比,平均耗时分别减少了6%和22%。因此,该方案在签名长度和效率方面较有优势,能有效解决监测数据缺乏完整性保护和身份可靠性认证的问题。     

Evolutionary optimization of a geometrically refined truss

Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection, and stress on a benchmark cantilever truss problem. Predominantly, traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This paper will present a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation—genetic algorithms and differential evolution—to successfully optimize a benchmark structural optimization problem. A nontraditional solution to the benchmark problem is presented in this paper, specifically, a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization tool set.     

抗蛇形减振器失效对车辆动力学性能的影响

为研究高速动车组车辆动力学性能对抗蛇形减振器失效的敏感性,以国内某型高速动车组为研究对象,以其实际动力学参数为依据,建立该型动车组的整车动力学模型。对抗蛇形减振器不同失效形式下的车辆动力学性能进行研究,结论认为：抗蛇形减振器失效对车辆动力学性能尤其是对列车的横向动力学性能影响显著;当列车行驶速度在250~380 km/h时,车辆系统动力学性能各项指标随列车行驶速度的增大而增大,随抗蛇形减振器失效个数的增加而增大。     

Optimum least-cost design of a truss roof system

An algorithm is presented encompassing the application of optimization methods to the least-cost elastic design of roof systems composed of rigid steel trusses, web joists and steel roof deck. The method is capable of designing rigid trusses that can be fabricated from various grades of steel and several types of standard sections. The selection of open web joist is presently limited to standard H-series, and decking material is standard 22 gage. The design is based upon AISC allowable values where combined stresses resulting from axial forces and secondary bending moments are considered. The effective column lengths are computed using the characteristic buckling equation for a member whose ends are elastically restrained against rotation. The procedure developed considers changes in the mechanical properties of the members, geometric variations in the truss configuration and changes in topology. Selected sets of members may be chosen to be identical, and chord members may be defined as continuous over several panels. Also investigated is the problem of finding the design containing the optimum number of trusses. A number of examples are presented which demonstrate the flexibility and generality of the design approach developed.     

Elastoplastic truss design using a displacement based optimization

A displacement based optimization (DBO) method is applied to truss design problems with material nonlinearities, to explore feasibility and verify efficiency of the method as compared to traditional structural optimization. Minimum-weight truss sizing problems with various path-independent elastoplastic laws, including elastic perfectly plastic, linear strain hardening, and Ramberg–Osgood models, are investigated. This type of material nonlinearity allows us to naturally extend the linear elastic truss sizing in the DBO setting to nonlinear problems. To implement the methodology a computer program that uses the commercially available optimizer DOT by VR&D and IMSL Linear Programming solver by Visual Numerics is developed. Several test problems are successfully solved using the DBO approach and solutions are compared to those available in the literature, demonstrating significant reduction of computational time in comparison to the traditional structural optimization method. In particular, the DBO approach is found to be suitable for truss topology design since the method allows member areas to have cross-sectional areas equal to zero exactly.     

Evolutionary truss topology optimization using a graph-based parameterization concept

A novel parameterization concept for the optimization of truss structures by means of evolutionary algorithms is presented. The main idea is to represent truss structures as mathematical graphs and directly apply genetic operators, i.e., mutation and crossover, on them. For this purpose, new genetic graph operators are introduced, which are combined with graph algorithms, e.g., Cuthill–McKee reordering, to raise their efficiency. This parameterization concept allows for the concurrent optimization of topology, geometry, and sizing of the truss structures. Furthermore, it is absolutely independent from any kind of ground structure normally reducing the number of possible topologies and sometimes preventing innovative design solutions. A further advantage of this parameterization concept compared to traditional encoding of evolutionary algorithms is the possibility of handling individuals of variable size. Finally, the effectiveness of the concept is demonstrated by examining three numerical examples.     

Optimal design of a truss configuration under multiloading conditions

The paper deals with the optimum structural design of a truss for which coordinates of structural nodes as well as member sizes constitute a set of design variables. The truss may be loaded by as many loading conditions as needed and is subjected to constraints imposed on stress displacements and complementary energy. An important relation between the cost function, Lagrange multipliers and limit values of constraints is derived. The paper presents the outline of an algorithm for the solution of a system of equations and inequality arising from the Kuhn-Tucker necessary condition for an optimum problem. Five numerical examples of 2D trusses are presented.Presented at the International Conference Structural Optimization '93, Rio de Janeiro, August 2–4, 1993.     

Some shortcomings in Michell's truss theory

This reply outlines further classes of problems for which Michell's original theory is valid. Struct. Optim. 12, 244–255     

Optimization of geometry in truss design

In this paper a method is presented which attempts to minimize the weight of a 3-dimensional truss structure subject to displacement-, stress- and buckling constraints under multiple load conditions. Both the cross section areas of the bars and the geometry (but not the topology) of the structure are permitted to vary during the optimization.The method generates a sequence of subproblems which are solved by a dual method of convex programming. The convergence of the overall algorithm is in evidence on some test problems.     

Design complexity control in truss optimization

Truss optimization based on the ground structure approach often leads to designs that are too complex for practical purposes. In this paper we present an approach for design complexity control in truss optimization. The approach is based on design complexity measures related to the number of bars (similar to Asadpoure et al. Struct Multidisc Optim 51(2):385–396 2015) and a novel complexity measure related to the number of nodes of the structure. Both complexity measures are continuously differentiable and thus can be used together with gradient based optimization algorithms. The numerical examples show that the proposed approach is able to reduce design complexity, leading to solutions that are more fit for engineering practice. Besides, the examples also indicate that in some cases it is possible to significantly reduce design complexity with little impact on structural performance. Since the complexity measures are non convex, a global gradient based optimization algorithm is employed. Finally, a detailed comparison to a classical approach is presented.     

Some shortcomings in Michell's truss theory

Michell (1904) derived his well-known optimality criteria for trusses in the context of unequal permissible stresses in tension and compression. For the same design constraints, Hemp (1973) and the author (e.g. 1989) have obtained optimality conditions which are different from those of Michell, and also lead, in general, to different, and lighter trusses. The reasons for this contradiction are examined and it is found that for unequal permissible stresses Michell's optimality conditions are only valid for a highly restricted class of support conditions.     

Nonlinear optimal design model of a concrete reinforcement truss plank

The reinforced concrete truss plank is one kind of specially-shaped reinforcement concrete composite slab that has been used in bridge structures, building structures, etc. in Hong Kong, Japan, America and European countries. Because of its complicated reinforcement distribution, this truss plank is analysed and designed by simplified methods that neglect the contributions from a combined reinforcement truss mechanism and the design is over-conservative. This paper describes a non-linear optimal design model for this plank, considering reinforcement truss action by a strain compatible method from a refined finite element model and experiment analysis.Communicated by J. Sobieski     

An evolutionary approach for layout optimization of a three-dimensional truss

Layout optimization is defined as the simultaneous optimization of three aspects, i.e. topology, size and geometry. In this paper, a new approach based on evolutionary genetic search is employed to find the optimal design. The proposed approach departs from standard Genetic Algorithms (GA) in that it does not use binary strings in the representation of the possible solutions. The approach is applied to a 2-D benchmark example and a well-known space truss example. This 25-bar-truss is solved by using the proposed approach, with good results. The effect of removing the restriction of area grouping and the free location of joints and supports in the 25-bar truss are also investigated, with and without symmetry. Major drawbacks in finding the optimal solution by using the ground structure approach are overcome in the proposed method.     

Discrete-event models of a railway network

This paper constructs discrete-event models for the basic elements of railway networks, i.e., a station-to-station block with a passing track, a segment (as a part of a station-tostation block), a segment section (a block section), a railway point, as well as train operation models. All models represent Petri nets with bounding arcs. The group control of the models under the parallel-conveyor movements of trains is implemented by special control elements (the so-called supervisors) that ensure railway traffic safety requirements.     

Human factors in support of a successful railway: a review

One of the critical infrastructure components in most economies across the world is the rail network. In different nations rail is responsible for ensuring that there is not complete gridlock on the roads in commuter hours, and for moving both people and freight for long distances in an as efficient manner as possible. This critical role, a number of high profile accidents and proposals for new network control philosophies and systems have led to a great upsurge in human factors rail research and applications in the past few years. This paper provides a retrospective on rail human factors research covering driving, signalling and control, maintenance, incident reporting systems, passengers and the public, planning and technical systems change. This research foundation, and also current major rail human factors programmes, are placed in the context of technology, investment, competition, cultural and safety requirements and constraints. The paper concludes with an examination of where rail human factors should and will be going into the future. Rail human factors research has grown rapidly in both quantity and quality of output over the past few years. There was an early base of work at a few institutions carried out over the 1960 s and 1970 s, followed by a lull in the 1980 s and early 1990 s. The continual influences of safety concerns, new technical system opportunities, reorganisation of the business, needs to increase effective, reliable and safe use of capacity, and increased society, media and government interest have now accelerated rail human factors research programmes in several countries. In this paper we review the literature on rail human factors research, covering driving, signalling and control, maintenance, reporting systems, passenger interests, planning and technical systems change. Current major rail human factors programmes are summarised and future research needs proposed. It is asserted that general human factors models and methods are being re-assessed, and new ones developed, to meet the requirements of the railways. This paper has, with the agreement of all editors concerned, been published in substantially similar form as: Wilson J. R. and Norris B. J., 2005, Rail human factors: past, present and future. Applied Ergonomics, 36, 6, 649–660.