Automation of Time-Space Conflict Analysis Using 4D Models

Research performed by Burcu Akinci

Main Advisor: Martin Fischer

Sponsored by CIFE

With an increasing trend for shorter delivery schedules, construction managers encounter an increasing number of time-space conflict cases. Time-space conflicts create a variety of problems such as constructibility, productivity, safety, and damage problems, at construction sites. These problems translate into delays in activity onsets, reduction in productivity, and addition of non-value adding activities, such as double handling of materials and re-construction of damaged components. Current approaches for space management are reactive, leading to less than optimal solutions. If time-space conflicts in a given schedule were identified prior to construction, then a wider range of solutions could be explored. Burcu Akinci is working on developing a decision support system that represents work space requirements of activities on all x, y, z and time dimensions, identifies and analyzes time-space conflict situations in a given schedule, predicts the behaviors of interfering activities, and incorporates the schedule impacts of those behaviors. This decision support system provides an environment for what-if analyses. Through continuous analyses, construction managers will improve the reliability of their three-week look-ahead schedules; increase efficiency, constructibility and safety at their job sites; reduce project delays; and make proactive decisions about space management.



Figure 1a shows the initial look ahead schedule planned during the construction of a multi-story building project. A picture from the site is annotated to highlight the components that are involved in this initial schedule. Figure 1b shows the schedule achieved at the site when the initial schedule was tried to be implemented. The differences in the two schedules are consequences of spatial conflicts between activities.
This figure exemplifies one of the time-space conflict situations in this case. Here, the material path space required for installation of windows was blocked by the scaffolding used for c-channel installation. This results in a constructability problem where both c-channel and window installation activities cannot be performed at the same time. Since c-channel installation was of higher priority the window installation had to be interrupted until the c-channel activity was completed and the scaffolding was disassembled.



The categorization of time-space conflicts depending on the problem that they create at a construction site are: (1) Conflicts creating constructability problems, e.g., scaffolding blocking the material access path. (2) Conflicts creating safety problems, e.g., the conflict between the hazard space created by roof tiles falling off the roof conflicting with the crew space. (3) Conflicts creating productivity problems, e.g., congestion created by two interfering crew spaces. (4) Conflicts creating damage problems, e.g., the hazard space created by the roof tiles falling off the roof conflicts with the protected space required during the curing process. Time-space conflicts have varying schedule impacts depending on the problem that they create.