装配式混凝土结构塔机吊装服务调度研究

随着我国装配率的提高,塔机吊装作业也面临新的挑战,塔式起重机现场的服务调度显得尤为重要。塔式起重机作业效率直接影响工程项目的施工进度与工程成本,同时还会带来施工事故和设备健康等安全隐患。通过把装配式构件任务吊装的时间约束转化为带有交货期的塔机任务,针对带有交货期约束的塔机服务调度问题,解析吊钩行程时间,设计了一种动态搜索启发式算法。通过对工程算例进行求解验证其有效性,试验结果表明所提模型和算法能够在满足物料请求任务时间窗的同时优化作业流程时间,为施工现场塔机作业管理提供决策依据。     

Hybrid of genetic algorithm and simulated annealing for multiple project scheduling with multiple resource constraints

Since scheduling of multiple projects is a complex and time-consuming task, a large number of heuristic rules have been proposed by researchers for such problems. However, each of these rules is usually appropriate for only one specific type of problem. In view of this, a hybrid of genetic algorithm and simulated annealing (GA-SA Hybrid) is proposed in this paper for generic multi-project scheduling problems with multiple resource constraints. The proposed GA-SA Hybrid is compared to the modified simulated annealing method (MSA), which is more powerful than genetic algorithm (GA) and simulated annealing (SA). As both GA and SA are generic search methods, the GA-SA Hybrid is also a generic search method. The random-search feature of GA, SA and GA-SA Hybrid makes them applicable to almost all kinds of optimization problems. In general, these methods are more effective than most heuristic rules. Three test projects and three real projects are presented to show the advantage of the proposed GA-SA Hybrid method. It can be seen that GA-SA Hybrid has better performance than GA, SA, MSA, and some most popular heuristic methods.     

An optimal scheduling model for ready mixed concrete supply with overtime considerations

The incorporation of overtime considerations in the production and dispatching of ready mixed concrete (RMC) is a complex real world problem. In this research, the authors develop a network flow model for an RMC carrier according to Taiwan's operation situation, that integrates RMC production scheduling and truck dispatching in the same framework, to decide on an optimal RMC supply schedule which also integrates overtime considerations. To build the model, the authors employ a time–space network technique to formulate the production of RMC and the truck fleet flows in the dimensions of time and space. The model is formulated as a mixed integer network flow problem with side constraints. To efficiently solve the problem a solution algorithm incorporating a mathematical programming solver is developed. The network flow model and the solution method are then evaluated using real operating data. The test results show that the model and the solution algorithm could be useful for actual operations.     

An approximation method for resonant response with coupling modes of structures under wind action

Effects of multi-mode coupling should be taken into account in computing the resonant buffeting response of some kinds of flexible structures with low damping and concentrated modes. In this paper, a new concept of “mode coupling factor” for computation of coupling effects between multi-mode resonant responses of the structures is proposed. On the base of the mode coupling factor, a modified SRSS method for computation of the resonant response contributed by multi-modes and their coupling effects of the structures is further raised. The roof structure of Shanghai Southern Railway Station is then taken as the case study to indicate the application and to verify the precision of the mode coupling factor and the modified SRSS method. The computaion results indicate that the mode coupling factor can quantitatively describe the contribution of mode coupling to the resonant response; and the modified SRSS method can make the computation of structural resonant response with consideration of mode coupling effects simpler.     

多工作台石材加工桥式切机研究

本文主要介绍了加工石材的多工作台桥式切机原理、加工工艺和设备结构.多工作台桥式切机主要由四个工作台和一个切割系统及真空机械手构成.工作台主要包括:上料工作台、主工作台、辅助工作台和卸料工作台.切割系统主要包括锯片切割头、横梁机构.真空机械手包括真空吸盘和其运动机构等.该设备带有激光自动扫描系统,可以对板材进行廓形扫描和自动优化排板,采用四个工作台对排板后的板材进行自动切割,实现石材排板切割一体化.     

大跨度桁架几何大变形结构分析的一种数值方法

基于ANSYS平台的二次开发,针对桁架结构几何大变形分析问题提出了一种有效的数值算法。主要思路为:采用两步交替迭代逐步逼近,使平衡状态与变形状态协调、统一,建立并求出变形后的平衡方程及其解;也就是说,首先由已知杆件内力建立计算节点位移的连续方程并求解,然后由已知节点位移建立计算杆件内力的平衡方程并求解,通过多次迭代求得平衡状态与变形状态协调统一的非线性大变形结构分析的精确解。本文方法在整个求解过程中仅需做一次结构分析,此在几何大变形桁架结构的优化设计中更突显其优点。本文方法对扁桁架、大跨度桁架尤其有用。通过编制相应的ANSYS二次开发程序,并由数值算例验证了本文方法的可行性、计算精确和计算效率。     

An optimal condition based maintenance scheduling for metal structures based on a multidisciplinary research approach

Abstract

Latest research findings show that the deterioration of metal coatings results due to complex combination of material and meteorological parameters. The classical maintenance scheduling do not consider complex interface of materials and meteorological parameters to determine optimal maintenance framework. The cost of recoating can be optimised through appropriate selection of coating specifications and maintenance strategy. This research provides a multidisciplinary algorithmic approach to determine cost-effective solutions for recoating. The specifications of red oxide primer coating and structural steel substrate system are considered for simulation analysis. The results show that the appropriate selection of 10% increase in coating thickness based on coating-substrate system specifications resulted in 20–25% reduction in annual patch failures which reduces 5–6% cost of recoating. Furthermore, the proposed model also simulated to compare Patch recoating and Part recoating strategy and algorithm show that the Part recoating is cost-effective as compared to Patch recoating if number of annual patch failure is greater than ‘2’ and area of the part is ‘2×’times larger than the area of the patch. Contrary, the Patch recoating results in low cost if the part area is ‘10×’ times larger than patch area and number of annual patch failures are less than ‘7’.     

An algorithm for improving the reliability of detection with processing of multiple sensors''signal

Recent surveys show that most of the false alarms of fire alarm systems are given by deceptive phenomena caused by human actions, such as cigarette smoking and cooking. Software-controlled systems have a potential ability in increasing the reliability of detection signals by data processing. However, it is rather difficult to distinguish an early stage fire from those deceptive phenomena only by processing the data of a single sensor. The authors' new algorithm utilizes the signals from three different sensors, i.e. temperature, smoke and gas (CO) concentration. Incorporating a mathematical fire model, these signals are translated into source parameters such as heat release rate, and smoke and gas generation rates. The conditions of the fire are then analyzed using the cross-correlation function between these source parameters. Testing the algorithm has been done using some experimental data and a promising result has been obtained.     

基于双三次B样条插值的空间结构自由曲面

双三次B样条插值曲面方法是工业造型、机械制造领域应用成熟的一种自由曲面设计方法,本在分析空间结构曲面设计现状、需求以及不足的基础上,提出了应用C^2连续的双三次B样条插值曲面方法进行空间结构自由曲面设计算法,并通过实例论证了该算法的可行性和有效性。     

基于轨道移动激光扫描的圆形隧道正射影像纠正算法

高质量的隧道内壁影像是隧道病害检测的基础,而基于轨道移动激光扫描技术采集的圆形隧道内壁影像,在断面方向和运动方向上存在较大的影像长度误差.本文提出一种基于轨道移动激光扫描的圆形隧道正射影像纠正算法,利用速度纠正和正射投影纠正,插值激光扫描数据生成隧道内壁影像.经实验证明,该算法可有效纠正圆形隧道内壁影像在断面方向和运动...