Özet:

Abstract The construction industry has a dynamic structure that takes quick decisions. This dynamic business culture also includes design changes. The purpose of design changes is to improve the quality and efficiency of projects in general. However, problems due to design changes can reduce project performance, cause rework, increase time and cost, and decrease quality. In this study, it is aimed to determine the causes of design changes that cause time and cost increases, quality problems and rework in the Turkish construction sector and the effects of these reasons on project performance through field study. To achieve this aim, firstly, the Competition Projects arranged according to the competition regulations of the Turkish Chamber of Architects are listed. Then, the ones whose construction was completed were selected from these projects. The design changes and their reasons during the construction phases of these projects were investigated. Within the scope of the study, eight completed projects were selected. This study aims to compare an award-winning project with its built state. Interviews were held with the design teams of the constructed structures. Design changes in the construction processes were determined through the interviews. The reasons for the design changes obtained from the interviews were compared with the literature. The reasons for the design change overlap with the literature. These are listed as; Regulations and incomplete definitions in the specification, addition/omission of functions, slow decision-making, constantly changing demands, lack of coordination between stakeholders, deficiencies/inconsistencies in design, lack of knowledge in the design phase, inexperienced teams / insufficient contractor/lack of expert personnel, unexpected conditions, and workmanship. According to the findings obtained from the field study, it is seen that the four most important effects of a design change on project performance are quality, time, cost and rework. Design changes lead to rework and rebuilds. Changes made cause project delays and cost overruns. Other effects of design change affecting project performance are poor quality and workmanship. It has been seen that effective project communication should be ensured to control design changes. To achieve this, a common understanding of problems, sharing of experiences, team harmony and a culture of cooperation are required. Success factors that increase the efficiency of building design management are listed as communication, decision-making, information management, performance evaluation, planning, risk management and team management. These factors help to address the difficulties to be experienced throughout the project early in the design phase. Collaboration between the design and construction phases is required for the design to be more productive and efficient.

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