本专栏涵盖了CPM和建筑法的问题。今天的博客涵盖了两者的互动 - CPM规范。
A little background on why this topic now. The Association for the Advancement of Cost Engineering annual conference ended June 30th. Two papers I presented covered issues of risk and issues of trend-based forecasting. (The second was covered in our blog of May 18 – and your comments were incorporated into the discussion by AACE members attending this session).
其他几篇论文涵盖了类似的范围。因此，我返回的那天晚上，我与吉姆·奥布赖恩（Jim O’Brien）共进晚餐，讨论了会议上提出的许多问题。
吉姆重申，CPM规范的主要目的是提供额外的保证，承包商可以（不）按时完成项目。此保证包括一些证据，表明承包商已经充分详细地通过项目思考。
我们讨论了该规范是用于商店图纸的 - 毕竟，该规范通常在规范的商店图纸部分中的CSI 01310下。
我们通常是否会在商店图纸的钢筋或砌体规范中看到有关付费应用程序和诉讼规则的条款？我们再次同意，这种语言也不属于CPM规范，并且规格仍然主要是为了提供所需的进一步保证。
我们注意到有关风险分析和基于蒙特卡洛模拟的计划的论文的复兴，吉姆发现了这种令人振奋的人。
While we all learned the臭名昭著PERT formula (O + 4M + P)/6, most practitioners do not know that the formula is incorrect and that the calculated PERT or CPM completion date for a project has only a 22% probability of achievement. Or as Jim stated in his 1964 text,CPM建筑管理:
“实际完成日期超过第一个CPM结束日期有明确的趋势。因此，合理的是允许CPM结束与实际所需的完成日期之间的某些意外情况。[这个]将随着项目的具体情况而变化。但是，如果您需要一个12个月的项目完成项目，请在大约11个月的时间内设定CPM目标，等等。”[Thus, a CPM calculated to finish in 11 months has a 22% likelihood of completion within 11 months, a 50% likelihood of completion within 12 months, and an 80% likelihood of completion within 12½ months, etc]。
虽然1960年代和1970年代的大型计算机（以及1980年代的微型计算机）的功能不足以在经济上calculate这是必要的安全因素，我们当前的计算机可以，并且可以使用软件来计算可能的原始CPM完成日期，但也可以使用统计验证的可能的完成日期。（软件的示例包括Oracle Primavera风险分析，又名Pertmaster，Deltek开放式计划以及诸如风险+和 @风险等附加组件。
我们来自石油和天然气部门的读者可能想知道为什么我要写所有这一切 - 他们很容易接受时间表风险评估的概念。
So Jim wants to know why our construction (read public) owners appear reluctant to change specs to read “Contractor shall provide a CPM which is calculated to have an 85% likelihood of completion on or before June 30, 2011”. Do these owners (and professional engineers providing them advice) suggest the contractor provide shop drawings showing the least amount of rebar that theoretically may hold up an elevated slab but ignoring factors of safety required by code? Why then require a CPM that shows possible but highly unlikely completion by the desired deadline and without the contingency understood to be required by the folks who first developed CPM?
吉姆（Jim）要求我采取这一任务，以对所有者和专业工程师进行有关此主题的教育。提供教育很容易。但是，我担心的任务超出了我，获得必要的受众，尤其是对惯性的行动。我需要您的帮助来说服业主询问他们想要的东西。
CPM会议更新
On a separate front, our Construction CPM Conference is indeed picking up steam. The conference will be held January 12-15, 2011, at the Swan Resort, Walt Disney World, Florida. AACE will be there hosting its PSP-certification exam as well as operating its bookstore. Oracle will be hosting the Wednesday Welcome Reception and Deltek will be hosting the Thursday Networking Reception. Most of our 100 sessions have already been spoken for and our pre-registration numbers continue to rise. For more信息，转到www.constructioncpm.com.
