Purpose – The purpose of this research is to propose a hybrid simulation framework which can take into account both the continuous and operational variables affecting the performance of construction projects. Design/methodology/approach – System dynamics (SD) simulation paradigm is implemented for the modelling of the complex inter-related structure of continuous variables and discrete event simulation (DES) is implemented for the modelling of operational influencing factors. A hybrid modelling framework is then proposed through combination of SD and DES to simulate the construction projects. Findings – This paper discusses the deficiencies of two traditional simulation methods – SD and DES – for simulation of construction projects which can be compensated by implementing hybrid SD–DES model. Different types of basic hybrid structures and synchronisation methods of SD and DES models are introduced. Practical implications – The proposed hybrid framework discussed in this research will be beneficial to modellers to simulate construction projects. Originality/value – The paper introduces a theoretical framework for a hybrid continuous- discrete simulation approach which can take into account the dynamics of project environment arising from the complex inter-related structure of various continuous influencing factors as well as the construction operations. Different steps required to develop the hybrid SD–DES model and synchronisation of SD and DES simulation methods are illustrated.

Physical and operational inspection of sewer pipelines is critical to sustaining an acceptable level of system serviceability. Emerging inspection tools in addition to developments in sensor and lens technologies have facilitated sewer condition assessment and increased the quality and consistency of provided data. Meanwhile, sewer networks are too vast to be adequately investigated manually so the development of innovative computer vision techniques for automation applications has become an interest point of recent studies. This review paper presents the current state of inspection technology practices in sewer pipelines. An overall inspection tool comparison was conducted and the advantages and disadvantages of each method were discussed. This was followed by a comprehensive review of recent studies on visual inspection automation using computer vision and machine learning techniques. Finally, current achievements and limitations of existing automation methods were debated to outline open challenges and future research for both infrastructure management and computer science researchers.

Abstract. Labor productivity is one of the most signi cant factors in the evaluation of the performance of construction projects. Improvement of labor productivity is believed to have direct impact on outperformance of the project. This research argues about a hybrid SD-DES approach to model labor productivity considering the e ects of both the context and operational level factors. The complex inter-related structure of di erent context factors a ecting the labor productivity is modeled using System Dynamics (SD) approach. Discrete Event Simulation (DES) is implemented to model the operational variables and their e ects on labor productivity. Using the proposed hybrid SD-DES model, the labor productivity can be determined more precisely since the e ects of both context and operational variables are taken into account. The proposed hybrid model is implemented in a real-world case and the value of labor productivity is simulated considering the e ects of both context and operational variables.

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