Selection of mobile cranes for building construction projects

The complicated process of selecting cranes for construction projects can be divided roughly into two main phases: (1) a general decision on the type of crane, mobile or tower; and (2) selection of the particular model according to the required size and technical specification. Several determinants of this second phase of the selection process in a typical mobile crane culture were investigated through on-site interviews with representatives of major construction companies. Factors affecting mobile crane selection were identified, classified, and rated according to their degree of influence. The involvement in equipment planning and crane selection was characterized with regard to project stages and planning parties. The findings were analysed with a view to the changing participation level of each party throughout project life. The conclusions of the study portray a picture that is different from the common assumptions about mobile crane selection, with respect to both influencing factors and the process itself. The study underlines the weight of non-project-specific factors, and shows that equipment planning is not merely a one-time technical exercise executed by a planner, but rather a process carried out throughout project life by a joint effort of several parties.     

An integrated decision support model for selecting the most feasible crane at heavy construction sites

Heavy industrial projects, especially oil refinery facilities, consist of numerous components such as modules and vessels, which are large, heavy, and long objects. The successful completion of these projects requires precise planning and selection of safe and efficient single- and/or tandem crane lifts, which are strongly influenced by the crane types and models used. Thus, selecting not only the best crane type and model, but also the most efficient crane operation among alternatives, can result in productivity and safety improvements. In this respect, this paper proposes an integrated decision support model which designs, simulates, and evaluates potential crane operations in accordance with feasible crane types and models based on equipment, cost, site, and environmental aspects of the project. The proposed methodology consists of two components: (1) 3D-based crane selection simulation, which enhances the process of crane selection by not only accurately verifying and identifying engineering factors, but also analyzing feasibility (procedures) of tandem and single-crane operations, from crane installation to lift completion and disassembly of the crane configuration, in a 3D environment; and (2) a crane selection matrix which calculates the crane evaluation scores by measuring various factors of each feasible crane against the project criteria and constraints. The methodology is tested in a case study in order to illustrate its effectiveness.     

Fuzzy-based MOGA approach to stochastic time–cost trade-off problem

In construction projects, time and cost are manageable objectives with significant interdependencies for which sets of trade-offs may exist. This study presents a new approach for the solution of time–cost trade off problems in an uncertain environment. Fuzzy numbers are used to address the uncertainties in the activities execution times and costs. Fuzzy sets theory is then explicitly embedded into the optimization procedure. A multi-objective genetic algorithm is specially tailored to solve the discontinuous and multi-objective fuzzy time- cost model with relatively large search space. The proposed approach identifies the best set of implementation options defined by the sets of non-dominated solutions Accepted risk level and optimism of the decision maker are addressed using α-cut approach and optimism index (β) respectively. To illustrate the application and performance of the model, two case examples are presented, for which separate Pareto fronts are developed. The fuzzy presentation of the non-dominated solution helps the project manager to apply his own level of risk acceptance and degree of optimism in decision making process. Different risk acceptance level and/or optimism leads to different scheduling and sets of Pareto solutions from which the project manager may select his preferred options.     

高桩承台PHC塔吊桩的设计与施工

本文通过工程实例,详细介绍PHC管桩作为高桩承台塔吊桩的设计与施工,着重说明了该种类型塔吊桩的施工要点。     

斜腿刚构桥设计的主要影响因素分析

以施工中的某斜腿刚构桥为工程实际背景,建立空间有限元模型对影响结构计算的温度、基础变位和斜腿支撑情况等因素进行分析,讨论各影响因素对结构内力的影响,总结出一些对同类桥型设计具有参考意义的规律。     

Modeling and evaluating construction project competencies and their relationship to project performance

In contemporary construction environments, construction organizations measure their performance against a set of predefined performance measures. These performance measures are governed by the ability of the organization to maintain necessary sets of “competencies” that assist in the successful execution of its construction projects. Competencies are often difficult to define and measure due to the multidimensional and subjective nature of their assessment. This paper identifies 41 project competencies with a total of 248 criteria for evaluating the different project competencies. This paper also identifies seven performance categories with 46 project key performance indicators. A systematic framework and methodology are presented in this paper to measure project competencies and project key performance indicators. A new modeling approach considering prioritized fuzzy aggregation, factor analysis, and fuzzy neural networks is presented to identify the relationship between project competencies and project key performance indicators. Data collected from seven construction projects are first aggregated using prioritized fuzzy aggregation to measure the different construction project competencies. The different project competencies are then analyzed using factor analysis. The factor analysis results are used with the prioritized fuzzy aggregation results to calculate inputs for the fuzzy neural networks. The fuzzy neural networks are then trained and tested using the data collected from the seven construction projects to identify and quantify the relationship between the different project competencies and project key performance indicators. This paper contributes to the current body of knowledge in project competencies and performance by establishing a standardized framework and methodology for evaluating the impact of construction project competencies on project key performance indicators. Furthermore, this paper incorporates advanced modeling techniques through the application of fuzzy set theory and neural networks to identify the relationship between the different project competencies and project key performance indicators. Identifying the relationship between construction project competencies and project key performance indicators allows construction organizations to improve their overall construction project performance by enhancing their projects competencies.     

基于模糊偏好及价值工程的矿业项目决策研究

针对不同优化方案进行项目决策时,为减少当前建设项目方案比选方法中存在的主观性,建立项目评审专家的个人模糊偏好矩阵并进行集结获得群模糊偏好关系,按照方案集结排序向量选出最优方案,进而总结出基于模糊偏好关系的建设项目方案比选程序。在此基础上,以某矿业工程项目为实证研究对象,对该矿的优化方案进行比选研究,得出最佳优化方案后运用价值工程分析对优化方案中的措施进行排序。综合运用模糊偏好关系和价值工程,为项目的方案和措施决策问题提出了解决方法。     

Climate and Architecture Torben Dahl (ed.), Routledge,London, 2010 168 pp., ISBN 978 0 415 56309 3, £25.99 (pb)

The purpose of this paper is to develop two efficient heuristic priority rules for the resource-constrained multiproject scheduling problem. The aptness of the two heuristic rules is analysed in terms of several dynamic characteristics of the scheduling problem. Fifteen heuristic rules presented in previous studies are used for comparison with the two heuristic rules on 4941 test problems which were generated by combining two, three or four projects from seven typical networks. The results indicate that the two proposed heuristics are superior to the other scheduling rules under the performance criteria of the minimum total project delay and the maximum number of times that a scheduling rule can obtain the best solution. Encouragingly, the two heuristic rules are proven to be adaptive and stable enough for scheduling under different problem sizes, network structures and degrees of resource tightness. As a result, the two proposed rules are the best representatives of the single priority rule method and the weighted combination search method, respectively. This study also includes a categorization process on which a project summary measure is based and then provides project schedulers with a convenient scheme to adopt appropriate scheduling rules.     

运用模糊神经网络研究混凝土AAR问题

提出运用模糊神经网络混凝土AAR问题。利用基于试验运算得到的模糊神经网络得到整体（系统）意义上的模糊规则，再利用训练好的网络扩充分析所需的其它模糊规则。通过对所有规则全面、深入的分析，从整体上找出引起混凝土AAR膨胀诸因素中每个因素作用的大小及其内在规律。研究表明，混凝土总碱量的大小对AAR膨胀起主要作用，水泥碱比外加碱对AAR膨胀的贡献更大。利用训练好的模糊神经网络可以对多因素作用下的混凝土AAR膨胀进行较准确的预测。     

Response modification factor for steel moment-resisting frames by different pushover analysis methods

The earthquake loads imposed to the structures are generally much more than what they are designed for. This reduction of design loads by seismic codes is through the application of response modification factor (R-factor). During moderate to severe earthquakes, structures usually behave inelastically, and therefore inelastic analysis is required for design. Inelastic dynamic analysis is time consuming and interpretation of its results demands high level of expertise. Pushover analysis, recently commonly used, is however, a simple way of estimating inelastic response of structures. Despite its capabilities, conventional pushover analysis (CPA) does not account for higher mode effects and member stiffness changes. Adaptive pushover analysis (APA) method however, overcomes these drawbacks. This research deals with derivation and comparison of some seismic demand parameters such as ductility based reduction factor, R_μ, overstrength factor, Ω, and in particular, response modification factor, R, from capacity curves obtained from different methods of APA and CPA. Three steel moment-resisting frames of 3, 9 and 20 stories adopted from SAC steel project are analyzed. In pushover analyses for each frame, eight different constant as well as adaptive lateral load patterns are used. Among the main conclusions drawn is that the maximum relative difference for response modification factors was about 16% obtained by the methods of conventional and adaptive pushover analyses.     

基于FG-MCGDM的水利工程施工进度方案优化

针对水利工程施工进度的多准则群决策问题,提出了一种新的模糊灰色多准则决策模型。该模型基于模糊集理论、灰色关联分析和折衷解的理论方法,将各决策属性和决策者权重的语言变量转化为梯形模糊数;采用改进的 GRA-VIKOR方法对模糊信息群体决策问题进行求解,并对各决策者的群体效益值和个体遗憾值进行聚合;通过折衷解对施工进度方案进行排序,获得最优方案。该模型有效地避免了信息的扭曲和丢失,确保了决策信息的完备性。通过在某水利工程施工进度方案优选的案例分析与计算,证明了该模型的有效性和实用性。     

高层住宅设计的个性化因素的影响与设计

住宅设计中针对不同的使用对象,对影响设计的若干因素中所考虑的重点也有所不同,因此体现出建筑的个性与多元化。综合考虑各影响因素的利弊,合理取舍和优化方案,使其功能更有针对性,为特定的使用者设计出理想的生活空间。     

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。     

Sequential ordering of crane service requests considering the pending times of the requests: An approach based on game theory and optimization techniques

Progress on a construction project can be derailed if its timetable is not met. Should a crane service request become overdue it may be preferable to minimize the pending time of the service request rather than minimize the crane's overall travel time. A novel approach was developed which minimizes and distributes the pending times uniformly, using a least deviation method to prioritize possible sequences according to the pending time for each requested crane service. An improved harmony search based on the power index method was then used to search for the sequence which led to the least deviation of priorities from their mean values. The efficiency of the proposed method was tested on a benchmark from the literature which involved solving 10, 50 or 100 service request problems. The proposed method achieved distribution of the deviation of pending times by approximately 40%, 50% and 10%, respectively.     

Automating motion trajectory Of crane-lifted loads

Crane Lifting Path Planning (CLPP) is an important task, especially in congested construction sites. This activity becomes extremely complex since, as the project advances, new (and sometimes unpredicted) constraints may occur. These constraints force lift engineers to explore the possibility of alternative paths for the objects still to be moved. Under severe time constraints, manual analysis of such paths is practically impossible, which makes it necessary to rely on computer implementations in order to avoid project delays. From a mathematical standpoint, if the crane payload trajectory is to be defined analytically, the polar coordinate system,(r, θ), is naturally the most suitable. As a result, this paper proposes an algorithm for CLPP in which the path is represented as a piece-wise continuous function where each portion is defined either by constant radius (rotation of the load) or a constant angle (translation of the load). In other words, rather than forcing a crane to adapt to un-natural rectilinear trajectories as obtained by traditional path searching procedures, it is the trajectory that is adapted to the crane motion. In fact, even though (mathematically) a precise balance between the rates of rotation and translation of the jib (or boom) will make the payload follow any continuous path (regardless of its complexity), the coupling between the rotations and translations increases the difficulty of the lifting activity. However, a crane lifting path in which these motions are uncoupled will lead to less stringent requirements in terms of controlling the balance between rotations and translations.     

Using fuzzy multiple criteria decision making approach to enhance risk assessment for metropolitan construction projects

The undertaking of construction projects in metropolitan areas is a risky, competitive, and dynamic proposition requiring a reliable risk assessment model for adequate planning. This study employs a fuzzy multiple criteria decision making (FMCDM) approach to systematically assess risk for a metropolitan construction project. Consistent fuzzy preference relations (CFPR) are used to measure and investigate the relative impact on project performance of twenty identified risk factors included in four risk dimensions. The fuzzy multiple attributes direct rating (FMADR) approach is employed to analyze the occurrence probability of multiple risk factors. Furthermore, the level of risk for the overall project caused by individual risk factor is evaluated with the synthesized analysis of the relative impacts and probability of occurrence. The implementation of FMCDM makes the proposed risk assessment approach more reliable and practical than the traditional statistical approach. The proposed approach can be employed to effectively evaluate the overall project risk, and can be benefited to efficiently identify significant risks of a metropolitan construction project.     

东方广场工程综合施工技术

北京东方广场工程总建筑面积９４万ｍ＾２，为亚洲最大的商业房地产建筑群。针对该工程面积大、设计变化多、管理难度大、场地狭小、工期紧等特点。采用了抽渗结合降水，基坑周边机械钻孔桩支护、ＵＥＡ补偿收缩混凝土，预应力混凝土、新型模架体系等先进技术、优质高速完成了结构工程。     

钢结构厂房空间刚度试验研究

文中介绍对钢结构厂房在吊车起重量升级前后,所作的两次空间刚度实测结果,通过静态和动态测试,给出了厂房空间工作的传播方式以及吊车综合力引起的位移大小,另外还得出吊车桥架起撑杆作用等一些有益的结论。     

模糊理论在变电站选址中的应用研究

本文分析了模糊理论在变电站选址中的应用,分析了变电站选址的一般规则,对变电站 GIS 系统进行了构建,然后利用模糊理论规则,对变电站进行选址,提高选址的效率和合理度。