Construction Schedules of High Rise Buildings

Abstract

The construction of a high-rise building is a large project.  Each story contains similar tasks and procedures. The construction process is, therefore, considered to be repetitive.  In most projects, main

contractors usually hire subcontractors to carry out various activities.  In some cases, a particular activity is assigned to two or more subcontractors.  Given a number of participants associated within a project, the main contractor must have a very good plan to make sure that all activities can be performed productively, and are easily to be managed and monitored. The purpose of this research is to explore the current construction procedure of high-rise buildings.  The contractors of twenty-five buildings with more than 23 meters high were interviewed.  Twenty-four of them indicated that their projects are constructed with the post-tension system, and the other one is constructed with precast concrete structural panel system.

Given twenty-five construction schedules, the construction procedure of each floor in the tower zone can be grouped into 3 patterns: 1) perfect packaging work schedule – activities are grouped into several work packages with an equal duration to balance the production.  The grouping factors considered include technical constraints, space limitation, safety, and neat & clean work environment; 2) semi-packaging work schedule – the schedules of activities are determined with similar consideration as the previous pattern, but the packaging characteristics are not obvious; 3) early start work schedule – activities are scheduled to start as soon as possible, considering only technical constraints.   Given 25 projects, the perfect packaging work schedules are the most popular while the early start work schedules lead to the shortest duration.  In addition, construction durations were analyzed.  It is found that structural works require the least time with a very small deviation among different contractors whereas finishing works take half of the total duration with the most deviation among contractors.  Interestingly, the result shows that the size of the work area has no effects on duration.  It is because the main contractors usually hire working crews according to work quantity.  If to compare durations between post-tension system and precast concrete structural panel system, it is found that the precast concrete structural panel system takes 21 days less than those required by the post-tension system due to the advantages of no shoring and masonry.