A Constructability Methodology to Integrate Planning and Design for Workers’ Safety in Construction Management

There are two important reasons for accidents resulting in injuries and fatalities on construction sites, i.e. the interference of different activities and the fact that aspects of workers‟ safety are considered to be only a concern of the construction phase. The main objective of this research was to incorporate a new workers‟ safety model into the existing critical path method (CPM) which is used as a supplemented tool in the planning and design phases to identify, remove or minimise the risk of accidents. In a first task the WSiCPM framework (integrating Workers‟ Safety into CPM) was developed. A matrix in the database was automated to analyse all interfering activities and to evaluate potential hazards. Besides the usual qualitative risk assessment based on expert judgment, the probability of an accident is calculated for each pair of interfering activities using new equations depending on parameters such as overlapping duration, overlapping working area, number of workers and type of hazard. The severity of an accident is estimated analogously to the compensation of casualties by insurance companies and is transformed to a monetary value representing the accident cost. In addition, the framework makes suggestions to eliminate or minimise the risk, e.g. by separating the activities spatially or temporally, modifying the path or re-scheduling the activities. In a second task the concept of „schedule for safety‟ was introduced by linking building design for safety (BDS) with CPM. The supplemented BDS can be applied in both the construction and control phases. New safety indicators were derived to assess the level of an accident and the impact on the project cost. The WSiCPM framework can help to overcome existing deficiencies of workers‟ safety through the link between schedule and design and between temporal and spatial attributes, and by considering the safety issues in all phases of the project. The example application demonstrates that this can lead to significant improvements in health and safety on construction sites.