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Delays in construction projects are both disruptive and expensive. Thus, potential causes of schedule deviation need to be identified and mitigated. In previous research, delay factors were predominantly identified through surveys administered to stakeholders in construction projects. Such delay factors are typically considered individually and presented at the same level without explicitly examining their sequence of occurrence and inter-relationships. In reality, owing to the complex structure of construction projects and long execution time, non-conformance to schedule occurs by a chain of cascading events. An understanding of these linkages is important not only for minimising the delays but also for revealing the liability of stakeholders. To explicitly illustrate the cause–effect and logical relationship between delay factors and further identify the primary factors which possess the highest significance toward the overall project schedule delay, the fault tree analysis (FTA) method, a widely implemented approach to root cause problems in safety-critical systems, has been systematically and rigorously executed.

Using a case study, the in-depth analysis for identifying the most fundamental delay factors has been fulfilled through FTA's tree structure. The logical deduction for mapping and visualising the chronological and cause–effect relationships between various delay factors has been conducted through the logical gate functions of FTA based on the data collected from the site event log, pre-fabricated structural component manufacturing log and face-to-face interview with project stakeholders.

The analysis identified multiple delay factors and showed how they are linked logically and chronologically from the primary causes to the ultimate undesired event in a rigorous manner. A comparison was performed between the proposed FTA model and the conventional investigation method for revealing the responsibility employed in the construction industry, consisting of event logs and problem reports. The results indicate that the FTA model provides richer information and a clearer picture of the network of delay factors. Importantly, the ability of FTA in revealing the causal connection between the events leading to the undesired delays and in comprehending their prominence in the real-world construction project has been clearly displayed.

This study demonstrates a new application of FTA in the construction sector allowing the delay factors to be understood and visualised from a new perspective. The new approach has practical use in finding and removing root causes of the delay, as well as clarifying the attribution of responsibility that causes the delay.

Although product design is a fundamental element in the transition towards the circular economy, the knowledge of practices, methods and tools oriented to circular product design has not been widely developed. This study aims to contribute to the circular economy research area by investigating and analyzing the main design approaches to circular products and their relationship to new product development.

The authors conducted a systematic review and qualitative analysis of 120 articles. In these studies, the authors analyzed aspects such as design strategies used, the barriers to the adoption of circular product design and the relationships between the phases of new product development processes with circular product design studies.

The findings revealed that the circular product design approach has added new design strategies to those already recommended by ecodesign, such as multiple use cycles, emotional durability and biomimicry. Furthermore, the results showed that most circular product design articles focus on the planning and concept development phases of the new product development process.

In this article, the authors systematized the findings of an emergent research area: the development of new products for the circular economy. Its main contributions lie in the identification of design strategies, the classification of Design for X approaches, analysis of such approaches during the new product development process and discussion of their main barriers. Finally, this study presents contributions for managers and designers who are starting the transition to a circular strategy.