共查询到20条相似文献,搜索用时 171 毫秒
1.
文章以一座净跨为220m的钢管混凝土桁架式中承拱桥施工控制项目为依托,针对同一对吊杆上、下游索力偏差较大的情况,在常规影响矩阵的基础上,提出改进的单根索力影响矩阵方法,并结合数值仿真理论和迭代算法,提出确定混凝土桁架式中承拱桥吊杆成桥索力调整方案的方法。该方法利用有限元数值模型计算单根吊杆张拉的影响矩阵,通过迭代算法,求解吊杆索力调整值;同时对依托工程的吊杆张拉索力调整方案进行设计,通过有限次的迭代运算,可使最终的计算成桥吊杆索力与目标索力的偏差达到5%以下,并通过实测成桥索力与设计值对比验证了该方法的可行性。结果表明,实测成桥索力与目标成桥索力误差满足工程要求。 相似文献
2.
激光点云技术具有高精度、高密度和适应性良好的特点,将其应用于公路隧道形变监测中,研究基于固定站激光扫描数据的公路隧道断面连续提取、滤波和多期形变监测的方法。为保证多期形变的观测断面在同一位置,在隧道中安装位置固定的扫描仪,利用三维中轴线和配准算法保证多期断面的同一性。提出一种两次迭代的椭圆曲线拟合方法,该方法第一次迭代基于椭圆形状约束对隧道拱顶断面的非拱顶断面点云进行滤除,第二次迭代利用迭代最小二乘拟合算法对滤波后的拱顶断面进行椭圆曲线拟合。基于拟合的椭圆曲线和极坐标法监测断面的多期形变。与传统RANSAC方法进行对比,两次迭代的椭圆曲线拟合方法在提取隧道椭圆曲线方面表现出更好的滤波效果和更高的精度。搭建隧道模型进行形变模拟和监测试验,对提取的多期数据进行分析,结果表明所提出的方法在公路隧道多期形变监测中具有可行性,且中误差小于2 mm,具有较高的精度。 相似文献
3.
4.
5.
6.
7.
8.
9.
10.
11.
文章根据土质边坡安全系数计算原理和可靠度JC迭代计算方法,通过建立弹塑性本构模型,对某非均质边坡的稳定性进行了数值模拟分析。结果表明,该边坡处于稳定状态,该数值分析精度满足规范要求。 相似文献
12.
This paper introduces Simulation of Intelligent TRAnsport Systems (SITRAS), a massive multi-agent simulation system in which driver-vehicle objects are modelled as autonomous agents. The simulation outputs can be used for the evaluation of Intelligent Transport Systems applications such as congestion and incident management, public transport priority and dynamic route guidance. The model concepts and specifications, and the first applications of the model in the area of incident modelling in urban arterial networks were described in previous publications. This paper presents the details of the lane changing and merging algorithms developed for the SITRAS model. These models incorporate procedures for ‘forced’ and ‘co-operative’ lane changing which are essential for lane changing under congested (and incident-affected) traffic conditions. The paper describes the algorithms and presents simulation examples to demonstrate the effects of the implemented models. The results indicate that only the forced and cooperative lane changing models can produce realistic flow-speed relationships during congested conditions. 相似文献
13.
Planning a public transportation system is a multi-objective problem which includes among others line planning, timetabling, and vehicle scheduling. For each of these planning stages, models are known and advanced solution techniques exist. Some of the models focus on costs, others on passengers’ convenience. Setting up a transportation system is usually done by optimizing each of these stages sequentially.In this paper we argue that instead of optimizing each single step further and further it would be more beneficial to consider the whole process in an integrated way. To this end, we develop and discuss a generic, bi-objective model for integrating line planning, timetabling, and vehicle scheduling. We furthermore propose an eigenmodel which we apply for these three planning stages and show how it can be used for the design of iterative algorithms as heuristics for the integrated problem. The convergence of the resulting iterative approaches is analyzed from a theoretical point of view. Moreover, we propose an agenda for further research in this field. 相似文献
14.
A new concept of subway station capacity (SSC) is defined according to the gathering and scattering process. A queuing network analytical model of station is created for calculating SSC, which is built by M/G/C/C state dependent queuing network and discrete time Markov chain (DTMC). Based on the definition and the analytical queuing network, a SSC optimization model is developed, whose objective function is to optimize SSC with a satisfactory rate of remaining passengers. Besides, a solution to the model is proposed integrating response surface methodology with iterative generalized expansion method (IGEM) and DTMC. A case study of Beijing Station in Beijing subway line 2 is implemented to verify the validity and practicability of the proposed methods by comparison with simulation model in different experiments. Finally, some sensitivity analysis results are provided to identify the nodes that have the greatest impact on SSC. 相似文献
15.
This paper presents a time‐dependent origin‐destination (O‐D) matrix estimation procedure embedded with a dynamic traffic assignment model, in which the predictive dynamic user optimal conditions in congested networks are maintained. Two solution algorithms are proposed, namely: an iterative (ITR) scheme and a method of successive averages (MSA) scheme. It is found that the MSA scheme outperforms the ITR scheme. As a prior O‐D matrix is an important input for the problem, its quality is essential for the reliability of the matrix estimation procedure. Empirical constraints are set in relation to the quality of the prior O‐D matrix for the estimation procedure. Numerical examples are used to demonstrate the effectiveness of the proposed methodology. 相似文献
16.
《Transportation Research Part A: Policy and Practice》2006,40(7):572-586
Vehicle fleet routing and timetable setting are essential to the enhancement of an inter-city bus carrier’s operating cost, profit, level of service and competitiveness in the market. In past research the average passenger demand has usually served as input in the production of the final fleet routes and timetables, meaning that stochastic disturbances arising from variations in daily passenger demand in actual operations are neglected. To incorporate the stochastic disturbances of daily passenger demands that occur in actual operations, in this research, we established a stochastic-demand scheduling model. We applied a simulation technique, coupled with link-based and path-based routing strategies, to develop two heuristic algorithms to solve the model. To evaluate the performance of the proposed model and the two solution algorithms, we developed an evaluation method. The test results, regarding a major Taiwan inter-city bus operation, were good, showing that the model and the solution algorithms could be useful in practice. 相似文献
17.
This paper proposes simple and direct formulation and algorithms for the probit-based stochastic user equilibrium traffic assignment problem. It is only necessary to account for random variables independent of link flows by performing a simple transformation of the perceived link travel time with a normal distribution. At every iteration of a Monte-Carlo simulation procedure, the values of the random variables are sampled based on their probability distributions, and then a regular deterministic user equilibrium assignment is carried out to produce link flows. The link flows produced at each iteration of the Monte-Carlo simulation are averaged to yield the final flow pattern. Two test networks demonstrate that the proposed algorithms and the traditional algorithm (the Method of Successive Averages) produce similar results and that the proposed algorithms can be extended to the computation of the case in which the random error term depends on measured travel time. 相似文献
18.
19.
The tremendous use of hazardous materials has promoted the economic development, which also brings about a growing risk causing a widespread concern. In this work, we consider a location-scheduling problem on hazardous materials transportation under the assumption that transportation risks are time-dependent fuzzy random variables. First, we formulate a scheduling optimization model and design a fuzzy random simulation based genetic algorithm to optimize the departure time and dwell times for each depot–customer pair. Then we establish an expected value model and design a modified particle swarm optimization algorithm to minimize the en route risks and site risks. Finally, numerical examples are given to illustrate the effectiveness of the proposed models and algorithms. 相似文献
20.
A GA-based household scheduler 总被引:1,自引:0,他引:1
One way of making activity-based travel analysis operational for transport planning is multi-agent micro-simulation. Modelling activity and trip generation based on individual and social characteristics are central steps in this method. The model presented here generates complete daily activity schedules based on the structure of a household and its members’ activity calendars. The model assumes that the household is another basic decision-making unit for travel demand aside from individual mobility needs. Results of the model are schedules containing complete information about activity type and sequence, locations, and means of transportation, as well as activity start times and durations. The generated schedules are the outcome of a probabilistic optimisation using genetic algorithms. This iterative method improves solutions found in a random search according to the specification of a fitness criterion, which equals utility here. It contains behavioural assumptions about individuals as well as the household level. Individual utility is derived from the number of activities and their respective durations. It is reduced by costs of travelling and penalties for late, respectively early arrival. The household level is represented directly by the utility of joint activities, and indirectly by allocation of activities and means of transportation to household members. The paper presents initial tests with a three-person household, detailing resulting schedules, and discussing run-time experiences. A sensitivity analysis of the joint utility parameter impact is also included. 相似文献