Conference Proceedings – distributing knowledge in building Theme: Title: Requirements Identification for 4D Constraintbased Construction Planning and Control System

Abstract: Construction planning and control are identified among the top potential areas needing improvements. A traditional technique known as the Critical Path Method (CPM) has been widely criticised in terms of its inability to cope with nonprecedence constraints, difficulty to evaluate and communicate interdependencies, and inadequacy for work-face productions. Attempting to treat these deficiencies, substantial research efforts have resulted in a wide range of advancements including design of new planning and control methodologies and development of sophisticated computerised applications. However, these efforts have not effectively overcome all of the above CPM drawbacks and, therefore, have not yet provided a solution to the industry. This paper identifies requirements for the next generation of the planning and control as multi-constraints, visual, and lean-based system. In order to achieve this goal, important construction constraints and their characteristics are derived from previous literature. Various constraint detection and satisfaction techniques such as knowledge-based system, advanced computational algorithm, and 4D visualisation are also investigated. As a part of the Lean Enterprise Web-based Information System (LEWIS) presented in the companion paper, a developing prototype called 4D constraint-based planning and control system is briefly demonstrated. It is anticipated that successful implementation of this system will enable generation of reliable plans and constraint-free assignments, which will, in turn, reduce production risks and improve on-site productivity

Construction scheduling using multi-constraint and genetic algorithms approach

Reliable construction schedules are important for effective co-ordination across the supply chain and various trades at the construction work face. Reliability of construction schedules can be enhanced and improved through satisfying all potential constraints prior to execution on site. Availability of resources, execution space, execution logic, physical dependency of construction products, client instructions and others can be regarded as potential constraints. Current scheduling tools and techniques are fragmented and designed to deal with a limited set of construction constraints. In this context, a methodology termed 'multi-constraint scheduling' is introduced in which four major groups of construction constraints including physical, contract, resource and information constraints are considered to demonstrate the approach. A genetic algorithm (GA) has been developed and used for a multi-constraint optimization problem. Given multiple constraints such as activity dependency, limited working area, and resource and information readiness, the GA alters tasks' priorities and construction methods so as to arrive at an optimum or near optimum set of project duration, cost, and smooth resource profiles. The multi-constraints approach has been practically developed as an embedded macro in MS Project. Several experiments were conducted using a simple project and it was concluded that GA can provide near optimum and constraint-free schedules within an acceptable searching time. This will be vital to improve the productivity and predictability of construction sites