工期延误分析（3）

Feifei

As-planned v as-built analysis
基准计划与实施计划对比法

The method
This method is referred to in the SCL Protocol (2002)  and is described by Pickavance (2000)  as being a method that does not require CPM and that simply compares the durations of the planned activities in the contract programme with those of the as-built activities.  The difference is the measure of delay claimed by the contractor.   

方法
SCL Protocol和Pickavance的《Delay and Disruption in Construction Contracts》都提到过这种方法。Pickavance这样描述道：基准计划与实施计划对比法不要求基于关键路径法，它只是简单地将实际工期与计划工期作比较，两者之差就是承包商索赔的延误工期。

Selection criteria
The SCL protocol (2002) states that:
Where and as-planned programme and an as-built programme exist or the as-planned programme was regularly updated but little information is available in relation to the network logic followed, then and as-planned v as-built analysis may be appropriate.

选择标准
SCL Protocol建议选择基准与实施计划对比法的标准为：既有基准计划又有实施计划，或者基准计划虽然被定期更新，但却鲜少提及网络逻辑关系。

Rarely in the view of the authors will things be so one-sided that the difference between a planned and actual activity duration will be attributable only to one party.  Although this may nevertheless be the case and this method of analysis may be selected for relatively simple questions of liability, because of its various disadvantages rarely will this method of analysis be sufficient in its own right.

通常来说业主和承包商对计划工期和实际工期出现差距都负有责任，笔者认为很少出现一方全责的情况。但即使是出现了这种责任关系简单明了的情况，很多问题仅凭借该方法本身是无法解决的。诸多的缺陷使得这种方法在延误分析中很难单独使用。

However we agree with the Protocol (2002) at paragraph 4.5, where it states that it is useful as a starting point in relation to other more complex methods of analysis.  There is no question that it is useful to identify the difference between the planned and actual durations and sequence of events in order to focus the further investigation on areas which appear to have gone particularly wrong and which appear may have been critical.

虽然这种方法有局限性，但是对于其他比较复杂的分析法来说，基准与实施计划对比法是基础或者说是起点。这是SCL Protocol中第 4.5段的提法，笔者对此也持肯定态度。它的重要作用是毫无疑问的—识别有关活动在持续时间和活动顺序上的不用，找到那些和基准计划相比有明显偏差的关键点，这就为下一步分析论证指明方向。

Issues
Pickavance (2000) observes that the theory of this methodology is that if the only reason for inquiry into changes in durations is to quantify the time needed for variations, then provided the total extension of the time required for such variations to the critical path can be quantified, then there is no need to explore the individual effect of each sequential variation.

问题
Pickavance曾经对这种分析法的原理作出如下评价：如果调查实际工期变化仅仅是要量化工期变更的时间，进而量化由此产生的关键路线的延期，那么也就没必要知道每个变更带来的影响。

This is obviously a very simplistic method of analysis.  Rarely will variations be the only source of delay to an activity. Further the planned programme may well not be in sufficient detail to enable a credible conclusion that the difference between the planned and actual activity durations is explainable by the events relied upon.  

这种方法把问题想得过于简单了。通常来说变更不是唯一造成延误的原因。另外，我们的目的是目标延误事件是不是造成实际与计划工期差距的原因，但是如果基准计划编制不够精密信息不足，很难以此为基础得出可信的结论。

Advantages
This method of analysis is generally the cheapest and simplest to perform, although assuming a planned programme exists, it still requires the production of an as-built programme.  

优点
虽然在基准计划之外还需要编制实施计划，但是综合来说它还是成本最低操作最简单的一种分析法。

Disadvantages
Pickavance (2000)  observes that the fact that this is not a CPM based method means that it is impossible to demonstrate the effects of:
•concurrency or parallel delays;
•unproductive working;
•the effects of secondary or consequential delay;
•acceleration.

缺点
Pickavance 指出基准与实施计划对比法并不要求基于关键路径法，这也就意味着它将无法反映下列情况对工程的影响：
•同期延误或者平行延误
•unproductive working
•the effects of secondary or consequential delay;
•赶工

The Protocol (2002)  adds:
•resequencing; and
•mitigation

SCL Protocol还补充了另外两种情况：
•重新给施工活动排序
•弥补延误采取的措施

Since most projects involve these issues the use of this method of analysis is likely to be easily criticised.
上述这些情况在很多项目中都无法避免，基准与实施计划法对这些问题却束手无策，该方法会受到质疑与批评是可想而知的。