建设项目的成本与时间控制

1、建设项目的成本和时间控制:在实践中的制约因素和缓解措施 研究方法本研究采用了定量与定性相结合的方法。它在两个阶段中进行分析的。第一个阶段是通过定量的方法通过从大样本人口中做调查问卷来获得信息。研究的第二个阶段是利用定性的方法通过半结构访谈来分析。使用除了调查问卷调查之外的采访方法的原因是：尝试从调查问卷中获得数据；通过调查和详细阐述突出问题的方法加强，扩大，加深问卷调查的结果；并且通过探讨样本总体关于议题的经验显示对从问卷调查获得的数据的分析。 问卷调查法此调查的目的是在英国建筑业建立目前常用的时间和成本控制惯例，包括控制方法和被从业者使用的软件应用还有抑制因素。我们从一个深入的目前的研究调查

2、入手揭露建设时间和成本超支的大量问题。工程控制工具、技术、最新的思路和在建设工程控制领域的新发展。这形成了由22个多项选择题组成的调查表。此调查表被分为三个部分： 第一部分是以在调查对象和他们的团体的一般细节中获得信息为目的取得的背景资料，例如调查对象的经历，他们在组织中的职位，在组织中从事的项目类型等等。 第二部分是关于超出时限的。项目规划和时间控制做法这样的超出时限经验的频率，此技术用于计划和时间控制，关键在于阻碍受访者从有效地控制他们的项目等等。 第三部分包含相似的但是针对于成本控制时间的问题。总数为250位受访者的采访开始执行：150人去了英国按公司交易额来看的顶尖建筑企业，剩余的10

3、0人去了乡下的按被雇佣的专业人员和公司酬金收入来看的顶尖建设项目咨询公司。这份列表是从建筑杂志年刊排名表中获得的。这个排名表不包含公司地址因此有一个旨在引索到他们的地址和联系方式的详细资料的在线网页搜索。电话是后来给这些公司做出的用来确认地址并找出存在于组织中层次与结构的类型。这使得问卷要被送到适当部门。为了补充，一个建筑主管，经理或是在组织中对该建设项目管理负责的合适的人员的名字被写下来以确保问卷被正确地寄给适当的人员。这保证了一个非常好的回应，110份问卷（44%的回答率）被收回。表格1和表格2展示了从业者代表他们的公司对问卷做出回应的结果。将近72%完成问卷的回答者是董事（directo

4、r），高级管理者(senior manager)或者商务经理(commercial manager)。从他们的角色预计，这些受访者在建筑行业（construction industry）也有多年有意义的经验。接近一半（48%）的受访者有超过25年的经验。这显示受访者在经验中有大深度的体验。 面谈第二阶段是使用定性的方法-结构式访谈。目的是去更深入地探索在从业者问卷调查分析后发现的局部问题和经验。使用与定量阶段相同的人。该调查问卷在定量研究期间被发送到的公司办公室进行了接触，解释了研究的目的和请求相关的联系人（建设主管，项目主管，商务经理，高级项目经理等）可以接受采访。共15家公司提供了相应的从

5、业者来接受采访。本采访使用数字录音机，为了便于传输和储存电子信息。这份录音也被转录。 表格3提供了每个受访者的更多信息。从表中可以看出的受访者承包商和咨询公司（consultant）的组合有不同，但项目的类型往往相同。他们具有丰富经验的从业人员。15个受访者的总专业经验为402年（平均工作经验有26.8年）。大部分受访者是其公司的高级雇员，其中很多公司都是在英国国家或地区存在的大型组织；有的还具有国际覆盖面。 在时间中项目控制的调查结果成本和时间控制的重要性是被实践施工专业人员（professionals）广泛认可的。这项研究的问卷调查显示，58的受访者总是对他们的项目使用时间控制，另外29%

6、的受访者表明他们时常使用时间控制技术。只有11%的受访者表明他们极少或者没有在他们的项目中使用时间控制。成本控制的应用程序更受到欢迎，84受访者表示他们在项目中总是运用成本控制技术，16表示他们在项目中频繁使用成本控制方法。没有受访者表示，他们很少或不使用的成本控制技术，拱托出在英国成本控制在建设项目的重要性。项目从业者在英国。这证实苏海尔等人的建议（2002年）建设专业人士比起时间性能来似乎更注重项目的性能比。 最流行的时间规划和控制技术是甘特条形图，其用于35的承包商和33的咨询公司（见表4）。紧随其后的是被28的承包商和34的咨询公司使用的关键路径法（CPM-critical path

7、method）。这些技术的普及可能是由于这一事实，即他们是在工业中最成熟的技术，尽管施工工序（construction process）中的易用性和适用性还有争论也是它受欢迎的原因。其它常用的技术包括里程碑日期编程技术（milestone date programming)，计划评审技术（PERT-program evaluation review technique），优先网络图（PND-precedence network diagram），平衡的元素走势分析/线（LOB-line of balance），与仿真。使用软件支持是普遍的。三项清楚的应用软件是微软开发销售的项目管理软件程序（M

8、icrosoft Project），Asta Power Project和Primavera（表5）。微软项目被35的承包商和57的咨询公司使用; ASTA被44承包商和19咨询公司使用;Primavera被15的承包商和19%的咨询公司使用。 尽管成本和时间控制的技术和软件广泛应用，成本超支和超时在建设项目中仍然相当普遍。表8显示对承包商和咨询公司的调查中有这个问题的项目所占的比例。 受访者中，经历项目超时的仅仅不到10%，在他们之中，38%是时间超时，41%成本超支。这意味着，大约62%的受访者在项目中了时间经历了超时10%或者更多而且59%的受访者在项目中经历相似幅度的成本超支。 除了找

9、出成本和时间控制法的现状和确定存在超限的问题仍然困扰着建设工程，问卷调查旨在查明抑制建设项目从业者的项目控制力度的最重要的因素。 找出顶级抑制因素 调查之前，文献综述有助于确定最经常导致项目成本和时间超支的共同因素。初步确定了总共60多个来自不同研究的因素，其中的一些因素是相关或彼此重叠。分析后，20因素入围调查。这些因素及其来源表9列出。 这些出现在受访者的调查表中的确定因素使用了这个问题：“请评价以下每个影响你对你的项目进行有效的时间控制能力的因素的重要性。”以同样的方式，一个问题也分别被问及成本控制。受访者被要求将这些因素采用李克特量表排名，分为“非常重要”，“重要”，“不重要”或者“非

10、常不重要”。受访者还被要求提出和排列出他们认为的应当被包含的因素。被提到的只有一小部分被添加进了列表中，并且这些附加物总是与本来被受访者提出的20个因素众多1个或更多个相关联。受访者为了使分析简化通过分配1数值至4来评级如下：“非常重要= 4时，”“重要”= 3，“不重要”= 2，“非常不重要”=1。这四点等级尺度转化为一个对每个单独的因素来说相对重要的指数（RII），像Chan和 Kumaraswamy（1997）和Kumaraswamy和成龙（1998年），阿萨夫等。 （1995年）和艾耶和桑杰贾（2005）一样采用这个公式。相对重要性指标= w (HN) 其中w是由受访者给每个因子的总重

11、量，其范围从1到4，并通过对一个因素的所有受访者的各种权重以加法计算出来;H是可用的（即4在这种情况下）最高级别;N是已经回答了这个问题的受访者总数。 表10给出了影响从业者对项目进行时间控制的因素的相对重要性指数。这些因素已经通过相对重要性指数被分配相关等级。表格表明，“设计更改”被视为影响从业者对其项目时间控制的最重要的因素，相对重要性指数为0.94.这表明“错误的项目持续时间评估”重要性指数为0.86.其他因素前十名按排名来排分别是：工作的复杂性（RLL为0.86），项目的风险和不确定性（0.85 RII）,分包商和供应商违约（RII也是0.85）缺乏项目管理适当的训练和经验（0.78

12、RII），合同文件的差异（0.77 RII），低熟练度的劳动力（0.74 RII），项目各方之间的冲突（RII也是0.74）和不可预知的天气条件（也RII0.74）。应该注意到，一些因素具有相同的RII。在投标中，为了确定具有较高等级的因素，以“非常重要”等级的数值排名较高的来判别，因此例如即使工作的复杂性和对项目持续时间的错误估计的RLL都有0.86，但是对项目持续时间错误的评估等级还是高于工作的复杂性。 表11表示了成本控制的结果。有趣的是，“设计变更”拥有0.94的RLL，作为影响对建设项目的成本控制的最重要的因素，也来到了第一的位置，工程的风险和不确定性RLL是0.89，排名第二，“对

13、项目持续时间错误评估”（RLL为0.86）是紧接着的下一个。前十名中其他主导因素按他们的重要性排序依次是分包商违约（RII0.82），工程的复杂性（0.81 RII），项目各方之间的冲突（0.81 RII），合同文件的差异（RII0.80），合同规范的解释分歧（0.08 RII），物价上涨（0.79 RII）对已完成的工程融资和付款（0.78 RII）。 排名第一的抑制对建筑项目时间控制能力的影响因素与排名第一的抑制成本控制的因素相比，他们好像有一个很大的共同点。表1和表2的第一都是“设计变更”。设计变更确实是需要考虑的对抑制建筑项目时间和成本控制能力最重要的因素。毫无疑问，因为设计变更通常会

14、需要一些成本和时间而且如果设计变更的过程不好管理确实会影响时间安排，对项目成本也有同样的消极影响。在一个项目中的频繁地或偶然地设计变更请求经常可以成为有效控制的主要障碍物。对表1表2的一项更关键的分析显示影响时间和成本控制前七名中的六个是一样的。事实上更有趣的是，时间控制抑制因素中的前五名与成本控制抑制因素的前五名基本上由相同的因子组成。 抑制时间控制排名最低的因素是：薄弱的监管制度（weak regulation）与调控;项目欺诈和贪污;不稳定的政府政策;不稳定的利率;和货币/汇率波动。有趣的是，这些因素也构成了抑制成本控制中五个排名最低的因素。这说明，时间控制的排名和成本控制之间的排名看上

15、去有明显的相似点。以统计学确定这种观察，一种推论统计表是在两边排名中使用斯皮尔曼等级相关系数来测试在两个排名中相关或者不相关而得出的。斯皮尔曼等级相关系数是一个无参数检验。不同的相关系数1和-1，其中1表示完全正相关而-1表示完全负相关或不赞成。的公式斯皮尔曼等级相关系数为以下公式：是斯皮尔曼等级相关系数代表在不同情况下的不同等级，N是科目的编号或者承兑行列的数量（温伯格和阿布拉莫维茨，2008年）。此测试的结果为0.88，显示出很强的正相关性，并指示时间控制抑制因子和成本控制抑制因子的排名之间有很强的一致性。这与张的发现-很难分辨导致成本超支和时间超时的原因（2002）有争论。包括成本增长的

16、原因通常也是时间超时的原因。因此，也可以正确地认为是抑制项目有效时间控制的因素也可能抑制有效控制成本。 开发的缓解措施 调查结果的分析后,通过对经验丰富从业者为了找出原因，为什么他们让项目更难以控制的研究在更大的深度确定的顶级项目控制的抑制因素。这随后导致发展的一系列措施用于减轻这些因素。这一阶段的学习是通过一系列的深度访谈,已描述的研究方法部分。有必要限制了这部分的范围研究以达到足够的深度。前五名被选为主要的抑制因素关注,因为他们的重要性和他们的事实成本和时间控制的很常见。 使用半结构式访谈，为与这些因素有关的从业者提供了丰富的从业经验的信息源还有它们导致项目控制难的各种原因。为了最大限度地

17、发挥访谈会议的有效性，他们由一种考虑到问题流动的方式组成，在所有的采访中同样的问题在客观性和易分析方面被提出。问题是开放式的为了允许从业者充分地表达自己，尽管以一种规整的方式。采访会议的开始从从业者的项目控制的概念的理解的问题开始，引导他们讨论花费多少成本和时间是被输入控制在他们的组织中的，还有最后引导出前五确定的项目控制抑制因素的探讨过程的瓶颈。从承包组织的从业人员中获得的结果与那些从建筑咨询公司得到的结果没有区别，因为调查问卷显示在最影响项目控制实践中没有显著差别。承包商及咨询公司的抑制因素的排序也有统计地一致（YAKUBU和SUN，2009）。本研究也不是旨在找出他们的经验是否有任何差异

18、；相反，正如前面提到的，采访是面向探索更深入的围绕着导致在实践中的抑制因子的问题而建立，为了建立可以用于解决他们提出关系到工程控制措施探讨的问题对策。 访谈被全部转录而且随后缓解措施通过对采访结果的详细分析被综合起来。 值得一提的是，尽管这些措施被称为“鉴定”实践，重要的是要记住这些措施并没有樱桃的采摘面试是很重要的;而是一个过程，开始着手这使拟设立的措施。这个过程中所涉及的访谈记录，并通过不同的报价，从一些新兴的受访者表示问题或需求，揭示了采访分析。这些问题进行了严格的评估考虑到已在主题方面进行了审查的文献，问卷调查等方式，之后被开发，可用于减轻所确定的问题的措施的结果。然后评估这些措施，以

19、确定他们可以最好地根据五大制约因素和措施的性质分类。图1描绘了显影的措施的过程。This research adopts a combination of quantitative andqualitative methods. It was conducted in two stages.The first stage was conducted using a quantitativemethod through a questionnaire survey in a bid togenerate information from a large sample population.The

20、 second stage of the study was conducted using thequalitative method using semi-structured interviews.The reasons for using the interview in addition to thequestionnaire survey were: to triangulate data obtainedfrom the questionnaire survey; to enhance, expand andcreate depth to the results of the q

21、uestionnaire surveyby investigating and elaborating on some of the issueshighlighted; and to explore the experiences of thesample population in relation to the topical issuesrevealed after analysis of the data obtained from thequestionnaire survey.Questionnaire surveyThe aim of the survey is to esta

22、blish the currentcommon practice of time and cost control in the UKconstruction industry, including control methods andsoftware applications being used by practitioners aswell as inhibiting factors. We started with a thoroughreview of existing studies that revealed a lot of issues onconstruction pro

23、ject time and cost overruns, projectcontrol tools and techniques and latest thinking andnew developments in the field of construction projectcontrol. This led to the development of a questionnairemade up of 22 multiple choice questions. The questionnairewas divided into three sections:Section one wa

24、s background information whichwas targeted at obtaining information on thegeneral particulars of the respondents and theirorganization, such as the experience of therespondents, their position within the organization,the type of project embarked on by the organization,etc.The second section was abou

25、t time overrun,project planning and time control practice suchthe frequency of time overrun experienced, thetechniques used for planning and time control,the factors that hamper respondents from effectivelycontrolling their projects, etc.The third section contained similar questions butspecific to c

26、ost control practices.A total of 250 questionnaires were administered: 150 tothe top construction companies in the UK by companyturnover and the remaining 100 to the top constructionproject consultancies in the country by the number ofprofessional staff employed and company fee earnings.This list wa

27、s obtained from theBuildingmagazineannual league tables. The league tables did not containthe addresses of the companies so an online web searchwas conducted to find their addresses and contactdetails. Telephone calls were subsequently made tothese companies to confirm the addresses and to findout t

28、he type of hierarchy and structure that existswithin the organization.This enabled the questionnairesto be sent to the appropriate department. Tosupplement this, the name of a construction director,manager or the appropriate personnel responsible forthe management of construction projects in the org

29、anizationwas obtained to ensure that the questionnaireswere correctly addressed to the appropriate personnel.This ensured a very good response as 110 questionnaires(44% response rate) were returned. Tables 1 and2 show the profiles of the practitioners that respondedto questionnaires on behalf of the

30、ir companies.Nearly72% of the respondents that completed the questionnaireswere directors, senior managers or commercialmanagers. As would be expected from their roles, theserespondents also had significant years of experience inthe construction industry. Nearly half (48%) of respondentshad more tha

31、n 25 years of experience. Thissho wed that there was great depth in the experiencepossessed by the respondents.InterviewsThe second stage was conducted using a qualitativemethodsemi-structured interviews. The aim is toexplore the topical issues revealed after analysis of thequestionnaire survey and

32、experiences of practitioners ingreater depth. The same population used for the quantitativestage of the research was used. The offices ofthe companies that the questionnaires were sent toduring the quantitative study were contacted, explainingthe objective of the research and requesting a relevantco

33、ntact (construction directors, project directors,commercial directors, senior project managers, etc.)that could be interviewed. A total of 15 companiespresented relevant practitioners for interviews. Theinterviews conducted were recorded using a digitaldictation machine for ease of transferring and

34、storingelectronically. The recordings were also transcribed.Table 3 provides more information on each of theinterviewees. As can be seen from the table the intervieweeswere a mix of contractors and consultants withvarying but quite often similar kinds of projects. Theywere highly experienced practit

35、ioners. The total professionalexperience of the 15 interviewees is 402 years(average experience of 26.8 years). The majority of theinterviewees are senior employees of their company andmany of these companies are large organizations withnational or regional presence in the UK; some alsohave internat

36、ional coverage.Survey findings of project controlsin practiceThe importance of cost and time control is widelyrecognized by construction professionals in practice.The questionnaire survey of this study revealed that58% of respondents always apply time controls to theirproject and a further 29% indic

37、ated that theyfrequently apply time control techniques. Only 11% ofrespondents indicated that they rarely or do not applytime control during their projects. The application ofcost control is more overwhelming with 84% of respondentsindicating that they always apply their costcontrol method and 16% i

38、ndicating that theyfrequently applied cost control methods to theirprojects. None of the respondents indicated that theyrarely or do not use cost control techniques buttressingthe importance placed on cost control by constructionproject practitioners in the UK. This confirms thesuggestion of Sohaile

39、t al. (2002) that constructionprofessionals seem to pay more attention to cost performanceof projects than time performance.The most popular time planning and control techniqueis Gantt Bar Chart, which is used by 35% ofcontractors and 33% of consultants (Table 4). This isclosely followed by Critical

40、 Path Method (CPM) usedby 28% of contractors and 34% of consultants. Thepopularity of these techniques might be due to the factthat they are the most established techniques in theindustry, though ease of use and applicability to theconstruction process can also be argued as beingresponsible for thei

41、r popularity. Other used techniquesinclude the Milestone Date Programming Technique,Program Evaluation Review Technique (PERT), PrecedenceNetwork Diagram (PND), Elemental TrendAnalysis/Line of Balance (LOB), and Simulation. Theuse of software support is widespread. Three clear leadingapplications ar

42、e Microsoft Project, Asta PowerProject and Primavera (Table 5). Microsoft Project isused by 35% contractors and 57% consultants; AstaPower Project by 44% of contractors and 19% ofconsultants; and Primavera by 15% of contractors and19% of consultants.The survey results in relation to cost control tec

43、hniquesused in practice are presented in Table 6.Unlike time control techniques where two methodswere found to be dominant, cost control techniques aremore diverse. Several techniques, such as project costvalue reconciliation, overall profit and loss, profit andloss at valuation dates, unit costing

44、and earned valueanalysis, have some degrees of usage. However, nonecan be regarded as the overwhelming choice. Similarly,the use of support software is also more varied (Table7). Some of the same time control packages are on thelist, such as Microsoft Project and Asta Power Project.Others are specia

45、list cost control software, includingProject Costing System (PCS), Construction IndustrySoftware (COINS) and WinQS. The general purposeMicrosoft Excel spreadsheet is also used by someprofessionals. In fact, the largest option is bespoke/inhousesystems, used by 29% of contractors and 38% ofconsultant

46、s.Despite the wide application of cost and time controltechniques and software, cost and time overruns arestill quite common in construction projects. Table 8shows the proportion of projects that suffer from thisproblem as reported by the leading contractors andconsultants during this survey.The pro

47、portion of respondents that experience overrunon just less than 10% of their projects is 38% fortime overrun and 41% for cost overrun. This meansthat about 62% of respondents experience time overrunon 10% or more of their projects and 59% ofrespondents experience cost overrun on a similarmagnitude o

48、f their projects.In addition to finding out the current status of costand time control practice and ascertaining existingoverrun problems still besetting construction projects,the questionnaire survey seeks to identify the mostimportant factors that inhibit the project control effortsof construction

49、 projects practitioners.Identify top inhibiting factorsPrior to the survey, a literature review helped to identifymost of the common factors that often lead to projectcost and time overruns. In total more than 60 factorswere initially identified from different studies. Some ofthese factors are relat

50、ed or overlap each other. After ananalysis, 20 factors were shortlisted for the survey.These factors and their sources are outlined in Table 9.These identified factors were presented to respondentsin the questionnaire using this question: Pleaserate the level of importance for each of the followingf

51、actors in affecting your ability to effectively control thetime of your construction projects. In the same way, aquestion was also asked separately about cost control.Respondents were asked to rank the factors, using aLikert scale, as extremely important, important,unimportant or extremely unimporta

52、nt. Respondentswere also asked to include and rate other factors theythink should be among the factors put forward to them.It should be mentioned that only a few additions weremade to the list, and these additions were always relatedto one or more of the 20 factors originally presented tothe respond

53、ents. Responses were simplified to facilitateanalysis by assigning numerical values of 1 to 4 to theratings as follows: extremely important = 4, important= 3, unimportant = 2, extremely unimportant= 1. This four-point scale was converted to a relativeimportance index (RII) for each individual factor

54、, usingthe following formula, as adopted by Chan andKumaraswamy (1997) and Kumaraswamy and Chan(1998), Assafet al. (1995) and Iyer and Jha (2005):Relative importance index (RII)= w (HN)where w is the total weight given to each factor by therespondents, which ranges from 1 to 4 and is calculatedby an

55、 addition of the various weightings given to afactor by all the respondents; H is the highest rankingavailable (i.e. 4 in this case); and N is the total numberof respondents that have answered the questionTable 10 gives the RII of the factors that are consideredby practitioners as affecting their ab

56、ility to controltime of construction projects. The factors have beenassigned ranks in relation to their RII. The table indicatesthat design changes is considered as the mostimportant factor that inhibits the ability of practitionersto control the time duration of their projects with anRII of 0.94. T

57、his was followed by inaccurate evaluationof projects time/duration with an RII of 0.86.The other factors making up the leading top 10 factorsin order of the ranking are: complexity of works (RII of0.86), project risks and uncertainties (RII of 0.85) andnon-performance of subcontractor and suppliers

58、(alsoRII of 0.85), lack of proper training and experience ofthe PM (RII of 0.78), discrepancies in contract documentation(RII of 0.77), low skilled manpower (RII of0.74), conflict between project parties (also RII of0.74) and unpredictable weather conditions (also RIIof 0.74). It will be noticed tha

59、t some factors have thesame RII; in a bid to determine the factor with thehigher rank, the factor with the greatest number ofvery important ranking was ranked higher, hence forexample inaccurate evaluation of project time durationwas ranked higher than complexity of works eventhough both have an RII

60、 of 0.86.Table 11 shows the result for cost control. It is interestingthat design changes also came top as the mostimportant factor that affects the ability to control costof construction projects with a RII of 0.94, risk anduncertainty associated with projects was ranked secondwith and RII of 0.89,