土木毕业论文英汉对译.docVIP

9.4 Defining Precedence Relationships Among Activities 9.4 定义活动之间的优先级关系Once work activities have been defined, the relationships among the 一旦工作活动被定义,联系可以被指定。activities can be specified. Precedence relations between activities 活动优先级关系意味的活动必 signify that the activities must take place in a particular sequence. 须发生在一个特定的序列。Numerous natural sequences exist for construction activities due to 序列存在众多的自然要求建设活动于结构上的完整性,法规和其requirements for structural integrity, regulations, and other technical 他技术要求。 requirements. For example, design drawings cannot be checked before they 例如,设计图纸不能检查之前被他们。are drawn. Diagramatically, precedence relationships can be illustrated 活动之间的优先级关系可以被描述,通过一个网络或图形by a network or graph in which the activities are represented by arrows 的活动表现为如图9 as in Figure 9-0. The arrows in Figure 9-3 are called branches or links 图9 - 3的箭头被称为分支机构或链接在了活动in the activity network, while the circles marking the beginning or end 网络图,而圆圈标记开始或结束每支箭的被称为节点或事件。of each arrow are called nodes or events. In this figure, links represent 在这个图里,链接表示特殊的 particular activities, while the nodes represent milestone events. 活动,而节点代表里程碑事件 Figure 9-3? Illustrative Set of Four Activities with Precedences 图9 - 3说明活动More complicated precedence relationships can also be specified. For 更复杂的优先级关系也可以被指定。 example, one activity might not be able to start for several days after 例如,一个活动可能无法开始后几天,完成其它活动。 the completion of another activity. As a common example, concrete might 作为一个普通的例子,具体可能have to cure (or set) for several days before formwork is removed. This 要。restriction on the removal of forms activity is called a lag between the 这一限制对撤消形式活动叫做时间差完成一项活动(例如,浇注混completion of one activity (i.e., pouring concrete in this case) and the 凝土在这种情况下),开始准备下一个活动(例如,除模板在这种情 start of another activity (i.e., removing formwork in this case). Many 况下)。computer based