This paper attempts to use evolutionary algorithms to solve the problem of minimizing construction project duration in deterministic conditions, with in-time changeable and limited accessibility of renewable resources (workforce, machines, and equipment). Particular construction processes (with various levels of complexity) must be conducted in the established technological order and can be executed with different technological and organizational variants (different contractors, technologies, and ways of using resources). Such a description of realization conditions allows the method to also be applied to solving more complex problems that occur in construction practice (e.g., scheduling resources for a whole company, not only for a single project). The method’s versatility distinguishes it from other approaches presented in numerous publications. To assess the solutions generated by the evolutionary algorithm, the writers worked a heuristic algorithm (for the allocation of resources and the calculation of the shortest project duration). The results obtained by means of this methodology seem to be similar to outcomes of other comparable methodologies. The proposed methodology (the model and the computer system) may be of great significance to the construction industry. The paper contains some examples of the practical use of the evolutionary algorithm for project planning with time constraints.

A significant number of construction projects involve repetitive processes. Planning them occurs to be a complex task. Network methods traditionally applied to construction scheduling prove inefficient in the case of repetitive construction projects (RCPs) due to the increased number of relationships among processes, locations (units), and resources. Frequently, the aim of scheduling RCPs is making the full use of the resources’ capacity, thereby ensuring continuity of the crews’ work. To achieve this, the planner typically allows discontinuity of some secondary processes to shift resources to the key processes, allowing optional modes of process delivery and introducing soft precedence relations between processes. This paper presents a new way of increasing the continuity of work of a general contractor’s crews in RCPs by employing subcontractors’ crews. A deterministic mathematical model of the mixed-integer linear problem of a repetitive (nonlinear) project was formulated to find a schedule that minimizes the downtime of the general contractor’s crews under constraints of a maximum acceptable total project duration and a maximum acceptable cost of the works commissioned to subcontractors; the model accounts for the limited availability of crews. Application of the model is illustrated by an example.

The selection of a general contractor for construction works is one of the most important decisions made throughout the entire construction project. It may be decisive in the success or failure of the project (e.g. delays in the commissioning of works, exceeding the budget, low quality of works). The article presents a method for supporting group decision-making in the contractor qualification process. The proposed method is a development of Mikhailov's approach to Fuzzy Analytic Hierarchy Process. It consists in the aggregation of the decision makers' judgments using type-2 fuzzy sets, allowing for inaccuracy of the decision-maker’s assessment. The use of an unbiased estimator of standard deviation for determining compromise evaluation enables the small size of the expert group and deviations in their evaluations to be taken into consideration. The quality of the solution obtained through this method was compared with the results obtained by means of Mikhailov’s Fuzzy Preference Programming and Enea & Piazza Method. The use of the proposed method generated better results for this example of preparing a ranking of contractors than the two other methods discussed. The method presented herein may also be proposed for solving decision-making problems in other spheres.

Current network techniques used for project scheduling presume that there is only one logical sequence of activities. However, in reality, the precedence logic of activities is not necessarily unchangeable. There are two types of relations between activities: fixed (hard) and soft. Current scheduling methods do not differentiate between these two types of relations and require a planner to choose one particular logical sequence based on some assumptions. The paper presents a model that allows for “weakening” the links between activities, i.e. that permits concurrent execution of activities or reversing their order, but this may require additional resource-consuming works or expenditures. The model involves two subtypes of soft logic: REVERSED and CANCELED to represent the soft relations between activities. Its mathematical form is a mixed linear integer programming model of minimizing the project duration without exceeding the allowed budget. The paper presents an example of practical application of the method to scheduling interior finishing works. The results support the argument that using soft logic relations between construction activities provides more flexibility in reducing project duration, activities timing and resource allocation.