Supply-chain transparency within industrialized construction projects

Computers in Industry 65 (2014) 345–353

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Supply-chain transparency within industrialized construction projects ˇ usˇ-Babicˇ *, Danijel Rebolj, Matjazˇ Nekrep-Perc, Peter Podbreznik Nenad C Faculty of Civil Engineering, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia

A R T I C L E I N F O

A B S T R A C T

Article history: Received 11 January 2013 Received in revised form 20 November 2013 Accepted 4 December 2013 Available online 27 December 2013

This paper addresses those issues relating to the integration of information flows in relation to material management throughout the construction industry supply-chain. Based on a case study, it shows how to bridge any gaps between those information systems used within the design, prefabrication, and on-site construction processes. The information requirements of the aforementioned three key processes are analysed regarding an industrialized construction project, and any gaps identified between their three sets of requirements. A theoretical model for information mapping is proposed using these requirements. The solution is then verified through a case study, performed within the operational environment of a construction company. This case study represents one approach for applying the proposed information mapping model, and possible benefits for the industry. The information analysis highlights significant distinctions among particular views on the information required for supporting the tasks during the three above-mentioned processes. The main difference lies in the levels of data granularity important for particular tasks. Building Information Modelling based construction (BIM-based construction) proved itself to be an adequate context for bridging the information gaps. BIM-based construction can accommodate the proposed model for information mapping across the processes. Within this context it is possible to separate the identities of physical building elements from those of designed building elements, which is required when mapping. This study shows that it is feasible to automate the proposed information mapping in the form of a computer algorithm. It explains the value and necessity of building information model (BIM) usage, in order to provide the context for information mapping. The integration of design, manufacturing, and construction processes, and a transparency of information about material resources across these processes, would bring significant benefits for all stakeholders within the supply-chain. In the case study, the architecture and a prototype of the software system were developed in order to implement the proposed idea. Specifically, the case study showed that the proposed information mapping improved the project’s progress monitoring, detailed planning, and management of material flows, across the construction supply-chain. ß 2013 Elsevier B.V. All rights reserved.

Keywords: Construction industry Building an information-model Interoperability Supply-chain management Material management Project management.

1. Introduction Industrialization regarding construction started several years ago [1] and is an important trend within the construction industry. It aims to achieve several improvements within the sector, such as higher productivity levels and better quality construction products. Reports and case studies from different parts of the world have shown that prefabrication and on-site assembly are becoming common practices [2,3]. Industrialization regarding construction tries to address the problems of low profit-margins in comparison

* Corresponding author. Tel.: +386 31 627 609; fax: +00 386 222 94 179. ˇ usˇ-Babicˇ), E-mail addresses: [email protected], [email protected] (N. C [email protected] (D. Rebolj), [email protected] (M. Nekrep-Perc), [email protected] (P. Podbreznik). 0166-3615/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.compind.2013.12.003

to other industries, and a shortage of skilled workers [4,5]. The prefabrication of building components at a remote facility is shown to save space for material storage on-site, assures better qualitycontrol during the parts’ production, reduces waste and enables reengineering, and more efficient supply-chain management [3]. All of the above benefits are the result of industrialization partially shifting activities from a construction sites to remote locations. Therefore, industrialization of the construction process requires a higher level of integration among partners within a construction project, since the manpower, materials, and equipment within a project have to remain coordinated. This coordination is maintained by frequent exchanges of information. Within construction projects, this exchange takes place in the context of linkages between independent organizations. Such contexts require high level of interoperability among partners, which increasingly contributes to the success in current highly dynamic

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field of construction [6]. Co-ordination is especially important within the context of industrialized construction because many construction sites receive prefabricated building elements from the same manufacturer. Hence the production and supply of the building elements must fit into the overall project schedule at each construction site. Actually, a prefabrication manufacturer works within a multi-project environment. At the same time, we have to take into account that companies engaged in prefabrication usually produce products in ‘make-to-order’ standard and configurable products [7]. Love identifies [8] that construction projects are increasingly performed as concurrent processes and, therefore, require strong information coordination and integration amongst the partners. The impact of such coordination on project effectiveness is identified. Information from the supply-chain management system could significantly improve the detailed planning of prefabrication and on-site activities. Since the manufacturers have to deliver building elements to several sites, the production process and logistics should be aligned with the construction site schedules. In regard to ‘last planner’ principles, information-flow integration between partners within the construction supply-chain, significantly improves any overseeing of ‘what can be done’ compared to ‘what should be done’ [8]. In a similar manner, research in the fields of enterprise resource planning (ERP) and supply-chain management (SCM) show that the integration of many isolated systems, modules, and strategies for effective planning, control and the execution of large projects across both manufacturing and distribution environments significantly improves planning, control and execution in comparison to interfaced or loosely-integrated systems [9]. In addition to the planning of on-site activities, information technologies significantly help to distribute changes in those designs that occur during the later project stages among several partners throughout the supply-chain, who are affected by the change [10]. However, with regard to information flows within partner organisations and between project partners, the construction industry still faces many problems. As described in [11], to achieve interoperability among the systems, information must be physically exchanged, must be understood and also conceptual and organisational interoperability must be reached. Construction companies as well as other types of organizations that try to implement ERP systems are confronted with very high complexity of the task [12]. This paper focuses on a particular problem identified when working with construction companies and which was also clearly pointed out by [2]. Information technologies and those tools used to support tasks within a construction project, such as computer-aided design (CAD) tools, are unsuitable for integration within those enterprise resource planning systems that support manufacturing processes. Also certain systems developed for manufacturing possess insufficient abilities for supporting construction tasks such as structural design and detailing. Presented research focused on bridging the gap between data structures relating to a building from the perspectives of design, detailing, and on-site work, and those data structures used during enterprise resource planning (ERP) for supporting the prefabrication of construction elements used for the actual erection of the building. The goal was to bridge the gap between these two specific semantic views regarding the building, with the aim of establishing better integration among partners within the construction supply-chain. In order to achieve this goal, the presented work was structured into tasks which included: analysis of work processes; synthesis of common information needs for building design processes, prefabrication processes and construction-site processes; and the development of those data transformations needed to overcome the gaps identified within the flow of information. A use-case was designed and implemented to serve as proof of the concept, which demonstrated the appropriateness of the transformations.

2. Work process analysis The processes across the construction project supply-chain were analysed as the first step of this work. It should be pointed out that the processes described here are actually performed by the same business entity. However, a company plays only one of the described roles within a particular project but is interconnected with other parties responsible for other roles. Within other projects these companies may perform different roles. This case study directly reflected the situation referenced by Segerstedt and Olofsson [13], where the construction company is often flexible within its supply chain. It can be positioned as a supplier on one tier of the supply chain for a certain project but on another tier for other projects. Hence, the results and principles discussed in this paper are applicable to the whole supply chain of a construction project, despite the fact that its analysis was always performed within the same company. The company providing the environment for the analysis is involved in projects as a supplier of prefabricated building elements and also as a contractor responsible for detailed design and construction. The company is large sized and is involved in several projects both within Slovenia and abroad. Primarily it produces storage-house buildings, industrial halls, and large storage facilities. These buildings consist of load-bearing steel or concrete structures, and are enclosed with metal roofs and fac¸ade elements. In addition to their construction projects, the company also manufactures roof and fac¸ade elements for the general market. The scope of the presented work and the case study was centred on these types of buildings and related processes. From a time perspective, the scope of this research targeted those project workflows that start after the project contract has been signed and continue until the end of the construction phase. The work processes at the company can be divided into three groups of activities—(1) detailed design, (2) prefabrication and (3) construction site activities. Detailed design inputs customers’ requirements and architectural design, and has two outputs. It is the basis for the manufacturing of prefabricated building elements whilst also producing blueprints for the construction. The work is well supported by computer-aided design tools (CAD) for both the load-bearing construction and fac¸ade elements’ designs. Prefabrication is organized as a massproduction, and is highly automated. The industrialized production of building elements is integrated within other business activities such as sales, purchasing, and logistics via the Enterprise Resource Planning (ERP) system. Construction site activities are projected in relation to and including the organization of the construction site, construction work, project progress monitoring and management activities, and the tracking of material flows to and on the construction sites. The analysis showed that this group of activities is insufficiently supported by software tools. Detailed planning and data collection concerning the performed construction work were handled inconsistently, using software tools selected individually by a particular project manager. The project managers often used spreadsheets for the planning and tracking of activities, yet sometimes used project management tools such as MS Project, and even performed in a more relaxed manner using text editors. Note-taking and reporting were implemented by the use of text editors, emails, phone calls, or even just written on paper. In addition, the structure and scope of the documentation varied across the projects. The consequence of these inconsistencies resulted in difficulties when trying to synchronise activities across the above-mentioned groups. The synchronisation and close coordination of all three activity groups is necessary, especially because the prefabrication and

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construction processes run in parallel. At a construction site, costly delays can occur if the manufacturing plant does not provide enough building elements on time. On the other hand, early production of building elements when they are not needed increases the storage costs. It makes on-site material manipulation more complex, and seriously affects other projects supplied by the same manufacturing plant within a multi-project environment. The presented process analysis identified two main areas for improvement, which could significantly improve the overall project’s performance. Firstly, an integration of building design and industrialized production should be achieved in such a way that prefabrication can directly use up-to-date building design data for the automatic calculation of those material quantities required for the building elements’ production. This would improve the planning and organization of the prefabrication processes. Secondly, on-site project management and project documentation-related activities should be consolidated and integrated within the manufacturing, thus improving the efficiencies of logistics, on-site material handling, and overall project progress tracking. As the first improvement step, two specific goals were set on a short-term scale: (1) project progress monitoring should be improved within a new system, and (2) the tracking of building elements’ statuses should cover both the prefabrication processes and the construction site works, and become transparent throughout the company or between the involved partners. 3. Overview of relevant building information modelling (BIM) aspects Besides industrialized construction, integration and interoperability have been very important topics throughout the construction industry for several years. Research and development efforts have led the community towards product modelling and nD modelling, and finally to building information models. All these efforts have always and repeatedly produced the need for data exchange between tasks, stakeholders or systems [14]. The results of these developments guided us to base our integration efforts on an extensible BIM platform, which would provide the basis for future developments within the company. As described elsewhere, the building information models [15,16] contain the information needed for particular phases of a building’s life-cycle (scheduling, analyses, cost evaluation, etc.). It is much more than just a data-container for the building model; it is an object-oriented building design. The information structures of the design are presented as objects (walls, columns, windows, doors, etc.) with attributes and relationships between building elements. BIM provides logical and consistent access to these objects, using standardized approaches such as via STEP or IFC standards. Early ideas were more optimistic when applying a complete BIM for the purpose of the whole building’s life-cycle. In this regard, feasibility studies and tests were performed to check whether existing standards such as STEP and IFC could be applied as in HUT 600 [17,18]. Efforts were made to extend the usage of building information-modelling beyond its early designs and construction, mostly in a search for solutions that would provide accurate information about the building, and would also be suitable for maintenance and support. At this point in time there are significant efforts going-on to apply the ICF standard in various parts of the world. A short overview of BIM-related projects was done by Eastman [19], where several initiatives were mentioned, such as: (1) CORENET as driven by the Singaporean Building and Construction Authority in collaboration with other public and private organizations [20], (2) the Australian trademark of DesingCheckTM [21] was undertaken as a similar effort to that of Singapore, (3) the International Code Council in the USA developed a plan for BIM implementation that went down a different path

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from the CORENET efforts, called SMARTcodes [22], (4) The Norwegian government and construction industry worked together to initiate changes within the Norwegian construction industry, including building control, planning, and the integration of design, building and facility management [23], (5) The General Services Administration of the USA government undertook a series of BIM demonstration projects, addressing various applications, many relying on exchanges based on the IFC. These were published on the webpage of IAI [23], (6) the GSA building project started in 2007 utilized BIM design tools and the use of an exported model in IFC format, to support the checking of preliminary concept designs against a specific project’s programmable spatial requirements. These activities led to the draft development of GSA BIM guidelines to be followed for all new GSA projects [24]. In Europe, major research was undertaken organized and financially-supported under the auspices of the EU Research Framework Programmes (FP). During the last ten years BIM-related developments could be tracked within Europe by following large projects such as ROADCON [25] and InPro [26]. The main focus of these two projects was the radical transformation of traditional construction work practices aimed at creating an efficient collaborative construction-project environment, based on BIM. This rich body of knowledge within the field of BIM was utilized during the presented efforts to create a link between the partproduction information handled by the ERP system, on the one hand, and the design information traditionally handled by CAD systems, on the other. The building information-model was placed within a central position of the system as a vehicle for the reliable exchange of information. It served as a platform for the integration of different building information aspects. The model became the common denominator that made the construction process more transparent. All three aspects became interconnected with the usage of a common model for the design, prefabrication, and construction site activities. All three aspects became interconnected, thus also contributing to a better understanding of the project’s boundaries, and an understanding of the financial consequences of building design-related decisions. Transparency between the construction work and the manufacturing processes, made short-term planning more accurate, which then led to a shorter construction process with reduced delays and a lower demand for material buffering. Similar results have also been recognized by other authors [27]. 4. Interoperability between CAD and ERP A building information-model establishes the basis for interoperability between CAD and ERP information technology systems. This model stores information about those building elements that, when assembled together, represent the whole building. This information should flow from the design stage, through prefabrication, to the construction site. A building information-model represents a consistent way to store and access this information. However, there is a need for a mapping algorithm that enables an exchange of information between the worlds of CAD (design, construction) and ERP world (prefabrication). The previously described work process analysis revealed that interoperability between CAD and ERP systems and the transfer of information in both directions is mostly affected when transferring building element identity from the design, through prefabrication, to the construction site processes. The transfer of building element identity requires special attention and causes the necessity for a mapping algorithm. This problem has its roots in the very nature of on-site construction processes. Enforcement of traceability on the level of a particular building element from the design stage to the construction stage would generate big organizational and logistical problems, because many building elements are interchangeable.

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Fig. 1. Handling of building elements in design-prefabrication-construction.

Fig. 1 illustrates the differences when handling building elements during different processes’ stages. Upper image in the figure schematically presents the wall covered with panels (marked with P) and building elements named ‘details’ (marked with D). The sketch shows organization of the elements needed to cover the fac¸ade. The panels are single item elements and the details are assemblies consisted of many separate building elements. All parts of the detail are always mounted together; therefore they are represented as one block. The concept of details significantly simplifies planning of logistic processes. For each building element, specific attributes are available, like material and geometry. During design stage, building elements are designed as unique objects with a set of properties like element placement, geometry, material, etc. When modelling, designers create a building model. They define element shapes, place the element on specific position in a building and define material and other required properties. The result is complete building model made of the building elements in 3D. In prefabrication stage, elements with the same characteristics are grouped together. For example, all fac¸ade panels of the same type and dimensions are collectively represented by one generic production item. Quantities of those elements are

distributed among ‘handling units’ (HU) for logistic purposes. Middle image schematically shows three such HU, each containing several types of building elements. For example, HU1 contains 6 panels of type A (from a set of small panels) and 2 details of type B (from a set of details). Production process is planned, organized and tracked by HU. When all elements belonging to one HU are ready, HU can be delivered to construction site. In construction stage, the process is planned and tracked using design model linked to detailed project schedule (4D) and to the status of HU. Bottom image sketches the same wall as the top image, but here the order of mounting is displayed. Each particular building element in the model is assigned to a task (depicted by dotted line) in the schedule and mounting sequence inside the particular task is defined. Material requirements for particular tasks are derived from the building model. The status of (as designed) building elements is tracked and compared to the plan. From the completion status of HU and the content of HU, it is always possible to calculate availability of the material needed for particular task on the construction site. In order to track a building element’s status throughout the supply-chain using BIM, the model should handle all the views of

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Fig. 2. Data model for integration of CAD and ERP.

the data described above. As a consequence, it is insufficient to store building elements from the design-model into BIM without taking into consideration the mapping to the prefabrication stage data-model and back to design-data model. Fig. 2 illustrates a common data-model, which ensures a merging of the views, and connects the CAD world with the ERP world. The presented data model is, of course, simplified and incomplete, and is only presented here to expose the CAD-ERP interoperability issue. In the above data-model, information about the Building Section (e.g. storey, wall or roof) and the Building Element (ex. particular fac¸ade element, beam or roof element) data come from CAD. In the ERP, on the other hand, the information is used regarding the Handling Unit and corresponding elements. The integration of both systems is, of course, possible via a direct link between the Building Element and the Handling Unit Element. However, such a solution would have serious consequences for data management in ERP, where such a detailed view is unnecessary and hence unacceptable for the ERP work process. It would also heavily affect the logistics of the manufactured building elements, because a strict link between the building element and the handling unit poses too many constraints on building element handling. Therefore, it is necessary to introduce a generalization of the Building Element in the form of a Building Element Type, which contains the common properties of several interchangeable Building Elements. In this way, the identity of a designed element is not linked to any manufactured physical building element, although it is still possible to link the CAD data with the needed information from the ERP, and the query and transfer information between the systems. The mapping between the CAD data and ERP data is shown within the mapping model in Fig. 3. When the building elements have been designed, this information-flow crosses the border between the CAD and the manufacturing. At least at this point, building element generalization occurs and all interchangeable building elements are linked together by a Building Element Type object. This step should have already been performed on the CAD side. For example, the designer can identify groups of elements from the same type. The quantities are then calculated for the particular element types. On the prefabrication side, the production and shipment processes should be planned in such a way as to be compatible with the construction plan. According to the needs of the construction site, handling units are created for logistical purposes, and the quantities of the building element types are distributed among the handling units. As a result of this process, all the common information (such as the geometry needed for the production or material definitions) of a set of building elements is available directly from BIM during the prefabrication stage. In the opposite direction, the mapping of information from ERP to CAD starts with the step of aggregating the handling unit

elements. This aggregation depends on the needs and purposes of the mapping. For example, if information is needed about the production stage of a particular building element, aggregation would be based on the production status of the handling unit. In order to utilize the time-related constraints posed on the construction process, a definition of the building element’s consumption sequence should be defined. Finally, the building elements could be linked back to those ERP handling units based on the available aggregated quantities from step 1 and the construction sequence from step 2. For this mapping, Information about the building element-type is needed for this mapping. Since a link is established between both systems, the processes performed at the construction site can use the information about prefabrication for planning purposes. The statuses of the building elements become transparent throughout the supply-chain and can be visualized on a 3D building-model. Reporting from the construction site is linked to the financial information in ERP, and is used for project management purposes.

Fig. 3. Mapping from CAD to ERP and from ERP to CAD.

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5. System architecture The concept described in the previous chapter, established the basis for information exchange throughout the processes within the construction project. In order to confirm the concept of the proposed mapping between CAD and ERP, a pilot information system was implemented and used during the case study in a Construction Company. Previous experiences with BIM, also reported by other authors [28], clearly show that a pragmatic and stepwise approach should be used when introducing modelbased work into construction. Therefore, the initial BIM for the interconnection of subsystems within the company was rather simple. At this stage, the model was not, as yet, the main repository of the building information that serves all the processes within the building life-cycle. However, open architecture based on the IFC standard provides the basis for future developments in this direction. The overall system architecture is presented in Fig. 4. Fig. 4 shows the connections between the pre-existing ERP system, the CAD tools, and the construction site via the building information-model based on the IFC standard. In addition to these three main parts, the architecture was rounded-up with a document management system (DMS) that handles non-structured project information, and a project portal as an infrastructure for improving project communication inside the company, which also serves the needs of outside stakeholders. The following few paragraphs describe the characteristics of each system’s architectural elements. Within the company from the case study, two different modellers (CAD tools) were used during the detailed design, one for modelling a load-bearing construction and one for modelling a roof and the fac¸ade elements. Blueprints were prepared from these designs, for the construction stage. Before integration, a bill for those materials needed for the construction work, was transferred

into the ERP system as a set of requirements for prefabrication. The transfer was performed in a semi-automated way that contains a lot of manual data entries. The introduction of BIM integrated these two models into one consistent model of a complete building. In general, any number of sub-models or domain specific model views can be merged into an integrated BIM. After the integration, the bill for materials was loaded into the ERP system directly from the BIM, using the mapping algorithms. This mapping was necessary since the problem had to be faced, that the design and prefabrication stages use different granularity levels when storing information about building elements. The identity of a particular building element was crucial for the design but was sometimes unimportant for the prefabrication process. In the presented case, it was only sufficient to keep information about building elements in a more aggregated way, in the form of transportation units during the manufacturing and distribution of the building elements. During the prefabrication stage, the overall project planning, pre-sales activities, purchasing, manufacturing and logistics are handled by the ERP system. The building elements, either purchased from other suppliers or company-made, are tracked by the ERP at the aggregated level described above, until delivered to the construction site. The status of a particular transportation unit (e.g. ‘planned’, ‘in production’, ‘on stock’, etc.) also determines the status of a particular building element. In order to achieve the goal of tracking the statuses of building elements throughout the whole building process, further mapping should be done to support the planning, control, and execution of construction-site activities. At the construction site, statuses such as ‘on-site’ or ‘mounted’ are important. Here, status information on a complete transportation unit has no real value anymore and it is necessary to track construction progress at a level of the particular building’s elements. Handling the building element status information from

Fig. 4. System architecture.

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the stage of detailed design, through manufacturing, to the construction site contributes to the transparency of the building elements’ flow through the supply-chain. This opens-up possibilities for automated material tracking using technologies such as RFID, and also enables quick visualization of the available and needed materials at the site. The IAI IFC standard was used in order to implement BIM. At the moment, the CAD tools used at this company do not provide an IFC interface. However, it is reasonable to assume that, in the future, this situation will improve. For the purpose of this research, IFC interfaces were developed for CAD tools and the ERP system. It is important to point out that libraries for reading IFC data structures are already available, which significantly shortens the software development life-cycle. In the presented research, efforts were made to use TNO’s IFC Engine [29] and an IFC library developed by Secom IS Laboratory [30]. Within the building information model, information about geometry, progress tracking status, and the data needed for planning and control were stored for about every particular building element. Only the main building elements such as columns, beams, and fac¸ade plates were stored in BIM. Information about mounting material and minor items were not stored in the BIM, but were referenced via their transportation units into the ERP system and linked to the main elements. In order to create a 4D model, the main building elements were also linked to those activities within the construction site project plan, with the use of IFC property sets. It should be pointed-out that such a 4D model can be very detailed, however until a higher level of automation is invented for the creation of 4D models, the suggestion is to use such high-level 4D models as to avoid too much work by the project and site managers with regard to the detailed planning of construction site activities. In addition to the structured information about the building object, there were lots of unstructured documents in use during this project. A document management system in form of a project portal, was introduced for this reason. 6. Construction-site application The proposed architecture was used as a basis for the case study. This study was performed by implementing pilot projects, selected from the regular sets of projects run by the company. The aim of this study was to show that integrated architecture brings improvements in regard to project progress monitoring, and when tracking the statuses of building elements throughout a project’s lifecycle. The integration of design information produced and maintained by CAD tools with information relating to manufacturing and distribution, enabled the development of a software application that supports the planning and control of a construction site. A prototype application was developed to support the work of the site and project managers. Site managers track on-site activities and report to a project manager about the progress, using a construction diary and weekly field reports. Before new tools were put into service, field reports were produced in paper format, most of the time. The site manager prepared all the necessary sketches and manually calculated the quantities of the performed work. With the new application, the site manager recorded work in progress by assigning a new status to a particular building element using 3D graphical representation of the building model (see Fig. 5) or by using lists of elements and/or different grouping criteria, such as project activity or part of the building (e.g. storey 1, north fac¸ade, roof, etc.). Reports on the project’s progress were generated by this application and these reports also included automatically generated digital sketches. Information about the progress and statuses of building elements were propagated back to the manufacturing stage, which runs in parallel to the construction site’s activities.

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Fig. 5. Reporting of work progress via a 3D model.

Because of this back-loop, the planning of subsequent distributions regarding building elements was significantly improved, since the logistic managers at the prefabrication company could see the real needs of a particular construction site with regard to material requirements, and could act accordingly. The planning of construction site activities was also based on the 3D model. The site manager produced a detailed plan of activities and linked the building elements to particular activities. Scheduling was significantly improved since information about building element status from the prefabrication process was propagated to the construction site and was visible for the site manager. The site manager was thus informed about the manufacturing statuses of the building elements and their availability; hence the manager was immediately aware of any missing elements for the planned activities. The project manager, who is usually responsible for several projects and construction sites, obtained prompt information on the activities at different locations. He was informed either via receiving annotated blueprints and reports in electronic format or by directly connecting to the system where he could explore the model, where the statuses of the building elements were shown in different colours. The colours indicated the statuses of the building elements during all stages of the project, regardless of where within the supply-chain the building element was at certain points in time. The project manager could compare the ‘as planned’ and ‘as built’ situations at the construction site and also identify existing or forthcoming difficulties relating to the building elements’ production and delivery. On a more abstract level and accompanied by photographs from the site, the customer could also be informed on the project’s progress. Similarly to these examples, several other tasks could become automated. The site manager could obtain all the properties and details concerning the building elements. Specific assembly instructions could also be linked to the building elements and displayed on-site. Since all this information was available to both the production unit and construction site, this formed the basis for the automated tracking of material flows using technologies, such as RFID, etc. 7. Discussion Within the scope of industrialized construction, prefabrication has become a significant part of a construction project. For this reason, manufacturing and distribution processes should be integrated within traditional project organization where processes result in a ‘one of a kind’ product—the building. The same manufacturing plant supplies several construction sites. Therefore it works within a multi-project environment. The causes of delays at a construction site can be influenced by bad coordination between the manufacturing, distribution, and

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construction site activities. Therefore, the planning of manufacturing should be coordinated within all the construction sites to ensure the timely distribution of building elements. A construction site’s detailed plan imposes timing requirements on manufacturing and distribution, and detailed planning also depends on the availability of material delivered after manufacturing. The integration of manufacturing and construction site information systems contributes to better planning and coordination of activities. Building an information model serves as a common repository for building information with the purpose of collaborating and exchanging information about a building amongst construction project stakeholders. A model is the basis for integrating construction processes. In a similar manner, manufacturing processes can also benefit from information about a building, as stored in BIM. BIM is the source of information about building elements that should be produced during prefabrication. It stores the design and material requirements of the required building elements. The integration of design and manufacturing via BIM reduces errors in data transfer from one project stage to another and requires less communication effort by designers and production planners. Consequently, better communication reduces waste and any delays caused by erroneous prefabrication. This is especially important in scenarios where changes are needed. For example, when change request comes from the construction site, designers make changes on the model and logistic planners have to change the content of handling units, which is of the outmost importance for production process planning and delivery of material to the construction site. In this scenario, designers, planners and site manager cooperate on the model. When designer changes the model, logistic planners are informed which handling units are affected by this change. With the updates on handling units made by the logistic planners, the site manager gets immediate overview on material availability and is able to adjust on-site tasks accordingly. This was really appreciated by the site managers and planners. Also there were some direct financial benefits because of better micro planning of the construction site activities. For managers, the cost of the new system is important, and as in any software project, it is difficult to establish a direct relation between cost and potential savings. A stepwise approach is therefore advisable. It assures quick feedback from the production environment and also quickly shows progress in the performance. Prompt information about positive results encourage management to further invest into model based building and also motivate end users in the efforts needed for the change of previous work practices. In our case, introduction of BIM based progress monitoring resulted in effective tracking of rework. For example, when there is a need for un-mounting and re-mounting of some fac¸ade panel, this was easily forgotten or hard to document in its complete extent when manually handling construction project log book. With the new system, it is now possible to track status changes for every single construction element and display complete history of the handling process. Site manager spends less time for preparation of daily records and has more time for managing exceptions and for negotiations with owners regarding additional work and deviations. This results in some direct and immediate financial benefits, which are so important for upper management when deciding on future investments. Beside exact records of the work performed and charged, responsibility for rework can also be recorded, which helps in management of disputes and contract extensions. There are many difficulties when connecting construction engineering-related data (CAD) with manufacturing-related data (ERP). These systems have different views on the construction object. From the manufacturing and distribution point of view it is

important as to which type of material or building element is purchased or produced, and in what quantities. From the design and construction perspective, the position and geometry of a particular element within a building is important. We therefore face a problem regarding the different levels of granularity when trying to link these systems. Mapping should be implemented in order to overcome these differences in data structures. Mapping requires a generalization of building elements on the level of BIM in the form of building element types, which separates the handling of such as a designed building element identity from the physical building element identity. In daily practice, this has some important impacts on logistic planners. From the beginning, they were reluctant about the system because planning of handling units which link to CAD and to as designed models requires much more data records to be prepared in the ERP system. With careful design of the mapping process, the amount of records can be greatly reduced. As a consequence, the burden put on logistic planners does not grow and system acceptance is therefore improved. Mapping between CAD and ERP data structures can be automated by computer algorithms. The use of generalized information about building elements in form of building element types, allows for the aggregation and disaggregation of building elements, which is necessary for the efficiency of manufacturing, distribution, and construction site activity implementation. Those generalizations impact specificity of later data analysis, therefore the goal is to retain as much detail as possible inside the BIM and at the same time not overburden the roles where those details are not important. For this reason, the design process and work practices should be adjusted. Designers were asked to add some additional information into the model, which is related to the model structure important in later stages, especially at construction site. Therefore, some additional responsibility was put on designers, which is not related to the design itself. To avoid overloading designers with tasks not important for their work, we contacted developers of the design software with some specific requirements with this regard. Later on, designers found these changes and the additional information useful for their own tasks, especially when changes in design were required. 8. Conclusion From the literature review and our own experiences, we have identified an opportunity for enhancing construction project planning, execution, and control via the integration of software tools for design within construction (CAD tools) and ERP systems. The problem that prevented seamless integration of these systems in the past lay in the incompatible data structures used during particular phases of a construction project. On the other hand, building information modelling (BIM) is used in the construction industry with the aim of overcoming problems of interoperability among different software tools. By our efforts, we have introduced BIM as a basis for integrating the CAD and ERP systems. Within the building information model, a complete building is encoded as a hierarchy of the building elements. In order to bring data structures from both types of tools onto common ground within an integrated model, there is a need for a mapping algorithm. This algorithm solves the problem of building element identity, because the identity of a physically built element is handled differently during the stages of detailed building design, the manufacturing of building elements, and at the construction site. A useful case study was performed containing several pilot projects using CAD tools and ERP systems, and where software tools and systems were integrated by the system architecture proposed in this paper. This case study serves as a ‘proof of concept’. During the pilotedprojects, we identified benefits within the process of construction

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project planning in terms of more accurate scheduling and proactive change management due to transparency of material flows throughout the project supply-chain. The manufacturing and distribution of prefabricated building elements can also be optimized because of integrating prefabrication with the design and construction processes. Both the short-term goals set at the beginning of the project were achieved, which were the improvement of project progress monitoring and an improved transparency regarding the statuses of building elements throughout the construction supply-chain. Therefore, we can conclude that this work provides a contribution to better transparency of information flows within construction processes and brings added-value to the broader context of a construction supply-chain. References [1] L. Koskela, Application of the New Production Philosophy to Construction, CIFE, Stanford University, 1992. [2] H. Johnsson, L. Malmgren, S. Persson, ICT support for industrial production of houses—the Swedish case, in: Proc. W78 Bringing ITC Knowledge to Work, Maribor, Slovenia, (2007), pp. 407–414. [3] V.W.Y. Tam, C.M. Tam, S.X. Zeng, W.C.Y. Ng, Towards adoption of prefabrication in construction, Building and Environment 42 (10) (2007) 3642–3654. [4] P. Paevere, C. MacKenzie, Emerging Technologies and Timber Products in Construction, Australian Forest and Wood Products Research and Development Corporation, 2006. [5] S. McGuinness, J. Doyle, Examining the link between skill shortages, training composition and productivity levels in the construction industry: evidence from Northern Ireland1, International Journal of Human Resource Management 17 (2) (2005) 265–279. [6] R. Jardim-Goncalves, K. Popplewell, A. Grilo, Sustainable interoperability: the future of Internet based industrial enterprises, Computers in Industry 63 (8) (2012) 731–738. [7] J.C.P. Cheng, K.H. Law, H. Bjornsson, A. Jones, R.D. Sriram, Modeling and monitoring of construction supply chains, Advanced Engineering Informatics 24 (4) (2010) 435–455. [8] P.E.D. Love, Z. Irani, D.J. Edwards, A seamless supply chain management model for construction, Supply Chain Management: An International Journal 9 (1) (2004) 43–56. [9] P. Samaranayake, D. Toncich, Integration of production planning, project management and logistics systems for supply chain management, International Journal of Production Research 45 (22) (2007) 5417–5447. [10] C. Xie, D. Wu, J. Luo, X. Hu, A case study of multi-team communications in construction design under supply chain partnering, Supply Chain Management: An International Journal 15 (5) (2010) 363–370. [11] M. Lezoche, E. Yahia, A. Aubry, H. Panetto, M. Zdravkovic´, Conceptualising and structuring semantics in cooperative enterprise information systems models, Computers in Industry 63 (8) (2012) 775–787. [12] P.M. Wognum, J.J. Krabbendam, H. Buhl, X. Ma, R. Kenett, Improving enterprise system support—a case-based approach, Advanced Engineering Informatics 18 (4) (2004) 241–253. [13] A. Segerstedt, T. Olofsson, Supply chains in the construction industry, Supply Chain Management: An International Journal 15 (5) (2010) 347–353. [14] A. Watson, Digital buildings—Challenges and opportunities, Advanced Engineering Informatics 25 (4) (2011) 573–581. [15] C. Fu, G. Aouad, A. Lee, A. Mashall-Ponting, S. Wu, IFC model viewer to support nD model application, Automation in Construction 15 (2) (2006) 178–185. [16] T. Hkkinen, S. Vares, P. Huovila, E. Vesikari, J. Porkka, L.O. Nilsson, A˚. Toger, C. Jonsson, K. Suber, R. Andersson, R. Larsson, I. Nuorkivi, ICT for whole life optimization of residential buildings, Technical report, VTT (2007). [17] M. Fischer, C. Kam, PM4D final report, CIFE, Stanford University, 2002. [18] C. Kam, M. Fischer, R. Hnninen, S. Lehto, J. Laitinen, Capitalizing on early project opportunities to improve facility life-cycle performance, Proc. International Symposium on Automation and Robotics in Construction and 19th (ISARC), (2002), pp. 73–78. [19] C. Eastman, P. Teicholz, R. Sacks, K. Liston, BIM Handbook A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers and Contractors, John Wiley & Sons, Inc., Canada, 2007.

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[20] CORENET, Integrated Plan Checking systems, http://www.corenet.gov.sg (accessed 4 May 2012). [21] L. Ding, R. Drogemuller, M. Rosenman, D. Marchant, J. Gero, Automating Code Checking for Building Designs—DesignCheck, in: Clients Driving Innovation: Moving Ideas into Practice, CRC for Construction Innovation for Icon.Net Pty Ltd, Sydney, Australia, 2006. [22] ICC, SMARTcodesTM, available at http://www.iccsafe.org.(accessed 4 May 2012). [23] IAI, BuildingSMART and Interoperability, available at http://www.iai-international.org.(accessed 4 May 2012). [24] GSA, GSA Performance-Based Acquisition, available at http://www.gsa.gov,.(accessed 4 May 2012). [25] ROADCON, Strategic Roadmap towards Knowledge Driven Sustainable Construction, available at http://cic.vtt.fi/projects/roadcon/docs/roadcon_d11.pdf.(accessed 9 May 2012). [26] InPro, Open Information Environment for Knowledge-Based Collaborative Processes throughout the Lifecycle of a Building, available at http://www.inproproject.eu/main.asp.(accessed 9 May 2012). [27] G. Ballard, The Last Planner System of Production Control, Doctoral Thesis, University of Birmingham, 2000. [28] C. Robinson, Structural BIM. Discussion, case studies and latest developments,, Structural Design of Tall and Special Buildings 16 (2007) 519–533. [29] TNO, IFC. engine, http://www.ifcbrowser.com.(accessed 4 May 2012). [30] SECOM, IFC Model Server, available at http://www.secom.co.jp/isl/e2/research/ cs/report02/.(accessed 4 May 2012). ˇ usˇ Babicˇ, Researcher and associate professor at Nenad C the University of Maribor. He received his PhD degree at the Faculty of Civil Engineering at University of Maribor. Main research interests are related to building information modelling, dissemination of technology innovation and integration of construction processes. He leads the Construction IT Centre, is visiting lecturer at the Dublin Institute of Technology and is coordinator of the e-Learning group at the University of Maribor.

Danijel Rebolj, professor of Construction and Transportation Informatics at University of Maribor. In 2009 visiting professor of Civil and Environmental Engineering at Stanford University. Coordinator of the international postgraduate program in Construction informatics. Research interests involve issues on system integration, product and process modelling, automated building, mobile and ubiquitous computing, web based collaboration and communication, virtual design and construction as well as other high potential IT for Architecture, Engineering and Construction. Since 5.5.2011 rector of the University of Maribor.

Matjazˇ Nekrep Perc is a Senior Lecturer and Head of Centre for Hydraulics at the University of Maribor, Slovenia.

Peter Podbreznik received his Ph.D. degree in Computer Science in 2011 from the University of Maribor, Slovenia. Currently he works as Assistant Professor at the Faculty of Civil Engineering at University of Maribor. His research interests are construction information technologies, signal and image processing, computer vision and biomedicine.