Construction projects are swiftly growing in complexity that poses a significant challenge to project success, performance, schedule and cost. Cross-functional teams are commonly arranged for complex projects to facilitate comprehensive problem-solving and decision making. Shared leadership, a critical success factor in project management associated with various benefits for team effectiveness, plays a pivotal role in cross-functional teams. However, there is scant research how this manifests in practice. This study sets out to explore shared leadership behaviors in Dutch project design teams, to promote a comprehensive understanding how it influences and enhances team effectiveness. Two complex construction projects were studied; 50/10kV main station and 150/20kV main station. The main research question that this study aims to answer is what effects do shared leadership behaviors have on team effectiveness in Project-Based Cross-Functional Design Teams under different project delivery methods in the Dutch construction industry?

This study adopted the mixed methods approach, with a comparative case study as the research strategy. Data was collected through a context analysis, participatory observations, semi-structured interviews, and questionnaires. Qualitative data was analyzed by coding and annotating audio transcripts. Quantitative data was analyzed by calculating the baseline scores and team effectiveness scores. Subsequently, qualitative and quantitative data were integrated.

The study showed that that every task-focused and person-focused leadership behavior was exhibited, individually or in various combinations. This indicated that there is no one-size-fits-all leadership behavior. Moreover, the findings revealed the presence of situational leadership indicating the ability of individuals to adapt their leadership behaviors by prioritizing, steering and meeting the needs of the team. The second main finding suggested that high exhibition of leadership behaviors, especially person-focused behaviors during milestones, was associated with higher team effectiveness. Milestones were unveiled as critical moments that had a substantial impact on the exhibition of shared leadership behaviors and team effectiveness. An unexpected finding suggested that team composition -more than the project-delivery method- moderates the relationship between shared leadership and team effectiveness. Furthermore, the findings suggested that the project phase and responsibilities of individuals play a significant role in the involvement and presence during meetings. Hence, the study should be extended to fully observe and comprehend the influences of the project-delivery method on team composition. Therefore, two hypotheses are formulated that deserve further research, specifically suggesting that: 1) team composition moderates the relationship between shared leadership and team effectiveness in Project-Based Cross-Functional Design Teams; and 2) team composition in Project-Based Cross-Functional Design Teams are project phase-dependent.

In conclusion, this study provided valuable insights into the importance of shared leadership on team effectiveness in engineering design teams in the Dutch construction sector and has shown how various task-focused and person-focused leadership behaviors manifest in practice and how they can shape team effectiveness through time. The findings strengthen the idea that person-focused behaviors are equally important, if not, more important than task-focused behaviors in enhancing team effectiveness in Project-Based Cross-Functional Design Teams. Emphasizing person-focused behaviors should be beneficial to increasing overall performance, satisfaction and quality effectiveness. All team members can contribute to addressing this challenge, which promotes cohesion, satisfaction and improved team work.