Work Density Method for Takt Planning of Construction Processes with Nonrepetitive Work

Abstract

A new method is presented for construction process planning. It is based on the concept of work density and called the Work Density Method (WDM), two terms coined for use in this context. Using the WDM, planners create one-piece workflow by dividing work space into zones while assigning each zone exclusively for each trade to complete their work, with trades working in consecutive process steps, each one taking up to the same fixed amount of time. The method supports development of a plan (using takt or not) for repetitive as well as nonrepetitive work thanks to work density serving as the common unit to describe workload. The WDM is an iterative method using work structuring to decide a sequence of process steps, zone the work space while lowering the peak of the cumulative work density (i.e., workload peak), determine a lower bound on the takt that can be met, and verify this meets customer requirements. The method was developed experimentally on a live project. This paper rationalizes the use of work density in planning, illustrates the WDM using examples, presents a paradox, and suggests method enhancements. The contribution to knowledge is the formulation of a new planning method that augments existing planning methods. On construction projects where speed is of the essence, activities must get scheduled in parallel and take place in multiple locations simultaneously. Those locations must be clearly demarcated in order to avoid the detrimental impact of trade stacking, and activity completion times must be strictly adhered to in order to avoid cascading delays. The WDM presented in this paper offers a systematic approach to determine such locations and to set a time limit within which activities must be completed. This new method is intended for use by superintendents together with their trade partners to develop an execution strategy so that they will be able to reliably hit milestones shown on their project master schedule. Some planners may already be familiar with the notion of work density and be using it intuitively when considering options to shorten a project’s duration. In this paper, a new, formal method is presented. It is illustrated by various examples. The use of computational support tools is suggested for practical implementation.