Design optimisation for off-site manufacture and assembly of MEP systems

Abstract

Modularisation and Standardisation for prefabrication of mechanical, electrical and plumbing (MEP) systems have become more prevalent during the last decade with the growth of the prefabricated construction industry. Speedy construction, minimum onsite labour, improved quality and waste reduction are the key benefits that make prefabrication superior to conventional construction.

However, in MEP, modularisation and standardisation are currently applied only to smaller systems, where integrated packaged units are used in heating, ventilation and air conditioning (HVAC) and other building services installations. Modular prefabrication is rarely practiced when services are located within the building due to limitations during installation and difficulty in coordination.

The term ‘optimum modularity’ is not accurately used in the field, and identification of modules is solely based on individual judgement than a structured method. The absence of a structured method for modularisation in MEP has made the identification of modules for prefabrication a time-consuming process, that often fails to achieve the optimum module division with minimum installation cost. In most cases, this has resulted in modular prefabrication of MEP being the same cost as conventional construction or even higher. This is one of the main reasons that impedes the use of modular prefabrication in the MEP industry.

Therefore, this research has formulated an algorithm for optimum module identification in MEP systems, considering the installation cost and the functional requirements of the system. The structured modularisation process developed in the thesis, identifies the optimum module configuration to achieve minimum installation cost, while satisfying the installation and operation constraints of MEP systems. This method assists engineers and researchers to evaluate the benefits of a modular configuration compared to conventional site build strategy, prior to implementing prefabrication in MEP projects.

In order to achieve these objectives, three case study project sites were visited during the construction period to identify the constraints in MEP construction and aspects to consider in the modularisation process. Chilled water central plants are chosen for the development of the modularisation algorithm, due to its complex installation process and popularity in the industry. This practical insight into the development of the method ensures that the configurations generated using the algorithm are practically constructable onsite. Structured modularisation methods practiced in various manufacturing industries such as Aerospace, Automotive, Shipbuilding and Consumer electronics were studied to identify their applicability to the construction industry.

The developed structured modularisation method presented in this thesis is the only study available to date in literature, that takes an algorithmic approach to modularisation in the construction industry. An automated process of module identification, using a combination of fuzzy logic, Dependency Structure Matrix (DSM) and Hierarchical Clustering and Partitioning Algorithm (HCPA) have minimum human intervention, where input data is extracted from the Building Information Model (BIM). This leads to significant time and cost savings during the design and construction stages of MEP systems. Although the development of the algorithm was based around chilled water plant construction, the methods proposed in this thesis can be used for modularisation of other MEP central plants, such as generator, transformer and pumps, with further research on limitations and assemblies associated with a particular system.

In addition to a structured method for modularisation, design engineers and researches would also require a model to evaluate the benefits of modular over conventional construction. In this regard, the output of the developed algorithm estimates the installation cost of the optimum configuration and compare the cost benefits with the conventional case, prior to implementing modular construction in MEP projects. This thesis provides a comparison of the modular approach to conventional construction, to identify a hybrid strategy to MEP plant construction. Furthermore, recommendations are provided to implement this research in other disciplines in the modular construction industry.