The paper presents methods of determining the location of cost buffers and corresponding contingency costs in the CPM schedule based on its work breakdown structure. Application of correctly located cost buffers with appropriately established reserve costs is justified by the common overrunning of scheduled costs in construction projects. Interpolated cost buffers (CB) as separate tasks have been combined with relevant summary tasks by the start–to–start (SS) relationship, whereas the time of their execution has been dynamically connected with the time of accomplishment of particular summary tasks using the “paste connection” option. Besides cost buffers linked with the group of tasks assigned to summary tasks, a definition of the cost buffer for the entire project (PCB) has been proposed, i.e. as one initial task of the entire project. Contingency costs corresponding to these buffers, depending on the data that the planner has at his disposal, can be determined using different methods, but always depend on the costs of all tasks protected by each buffer. The paper presents an exemplary schedule for a facility and the method of determining locations and cost for buffers CB and PCB, as well as their influence on the course of the curve illustrating the budgeted cost of work scheduled (BCWS). The proposed solution has been adjusted and presented with consideration of the possibilities created by the scheduling software MS Project, though its general assumptions may be implemented with application of other similar specialist tools.
The introduction of a baseline term to the dependency network most often results in a change, break and/or generation of a new sequence of critical path, depending on the type of such a baseline term and the exact date selected. Each of those situations has an impact on the location or need to include new time buffers in the modified Goldratt’s method. The purpose of this article was to identify possible effects brought by declaration of each type of baseline term and to point out actions to be taken in each case. It must be noted that guidelines provided should in each individual case be adapted to the specific character of schedule changes caused by implementation of the relevant baseline term. The example presented herein exemplifies one of such solutions to be implemented as a result of break of the critical path and need to introduce new time buffers.
Almost every construction investment should contain elements of risk forecasting, whose validity depends, among other things, on the correct assessment of potential threats. These risks were defined by the Authors as risk factors that were characterized and then grouped on the basis of performed research in the scope of their identification. Due to lack of method of scheduling railway investments on the construction market, including risk assessment, a research effort was undertaken [14-17], the result of which is the proposed method. The article presents the main assumptions of the original method of rail investment planning, which on the one hand, will take into account the impact of potential threats identified previously by the Authors, and, on the other, will allow project managers to refer to the conditions in which the implementation of a specific facility is planned. The assumption was made that the method, relatively easy to implement, supported by an appropriate computational program, will encourage teams planning the implementation of railway undertakings to its application and will improve the reliability of the schedules they develop.
During the planning and controlling of the construction process, most attention is focused on risk analysis, especially in the context of final costs and deadlines of the investment. In this analysis, the primary and most significant concern is the proper identification and quantification of events, which on a certain level of probability may affect the development process. This paper presents the result of a risk analysis for a particular building object, made after completion of the investment and accepting it for use. Knowledge of the planned values and the actual investment process allowed for the identification of the events and their effects that in this case have significantly disrupted the investment process. The limited total cost of the investment project in question had a considerable impact on the progress of the project execution. Despite three transitions of administrative procedures, the opening date of the shopping centre was delayed by only three weeks.
This paper identifies the adverse events occurring during the execution of water supply and sewerage systems construction. The basis for this paper is research conducted in 2010-2014 on the construction sites of water supply and sewerage systems located in the provinces of Lower Silesia and Opole. The research consisted of direct observations of construction sites and review of construction documentation. It showed that work stoppages on the examined construction sites were frequent. They were caused by violations of work discipline by the production employees, adverse weather conditions, and defects in the project documentation. The study demonstrated that in almost every case, these bad an adverse effect on the completion date and budget of the investment. The analyses show that in such important and expensive investments as water supply and sewerage systems, organizational structures in which a special role is assigned to middle-rank personnel should be adopted.