# Project Benefits of Digital Fabrication in Irregular-Shaped Buildings

Authors: Namhyuk Ham; Sanghyo Lee
Journal: Advances in Civil Engineering
 (2019)

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## Abstract

The main purpose of this study is to investigate the advantages of digital fabrication pertaining to construction project management, in particular, in terms of different project management factors, using case studies of irregular-shaped buildings in which digital fabrication has versatile applications. This study collected secondary data corresponding to 27 construction projects of irregular-shaped buildings that implemented digital fabrication. Success criteria were developed based on the Project Management Body of Knowledge (PMBOK) to assess the benefits of implementing digital fabrication for management of the considered construction projects of irregular-shaped buildings. Content analysis was performed to investigate the degree of satisfaction for the success criteria of each project. With this approach, it is possible to see which success criterion appears more times as a positive factor and which ones appear as challenges or problems. Among the positive benefits of digital fabrication on construction project management, quality increase and control appeared in the highest number of projects (17 out of 27 projects) at the highest frequency (26 instances). However, among the negative benefits that were mentioned as challenging or causing difficulties of digital fabrication on construction project management, cost reduction and control appeared in the highest number of projects (14 out of 27 projects) at the highest frequency (21 instances). But it does not mean that the use of digital fabrication was overall negative.


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## Body

## 1. Introduction

The construction industry is responsible for up to 40% of energy consumption and greenhouse gas emission worldwide [1]. For such reasons, major international organizations (e.g., UNEP and IPCC) consider the construction industry as the main governing factor for carbon reduction activities [2]. This potential can be employed by implementing modern technologies including digital technology in place of traditional construction methods [3]. Digital technology is used widely in the manufacturing industry, and the method of directly manufacturing construction components using design data has become an essential part in recent product development [4]. However, the construction industry has an extremely disjointed production method, and since it is a risk-averse sector, manufacturing using digital technology still remains in the preliminary stages [5]. Not only do most construction companies lack resources to develop innovative technology through projects [6] but they also fail to systemize the developed knowledge, and therefore avoid using unfamiliar material and manufacturing methods [7].Despite this, interest in irregular-shaped buildings with considerably complicated structures compared to typical buildings is continuously growing [8]. An irregular-shaped building is used mainly in terms of “irregular-shaped buildings [8, 9],” “freeform building [10, 11],” “informal structure [12],” “complex-shaped buildings [13],” and “iconic building [14].” In general, it refers to a building to which an irregular design element such as a two-direction curved surface is applied to the interior or exterior of the building.It is common to introduce digital fabrication with new materials and manufacturing methods in such irregular-shaped buildings to construct the complicated structures [15]. Digital fabrication represents innovative, computer-controlled processes and technologies with the potential to expand the boundaries of conventional construction [6]. When it comes to project management, implementing digital fabrication requires managing not only the conventional supply chain but also supply chains for the new manufacturing methods [16]. Moreover, construction sites require managing the typical on-site construction as well as off-site construction and off-site and on-site deliveries [17]. Furthermore, in order to attend to problems that occur while constructing irregular-shaped buildings, various digital technologies are used including building information modeling (BIM) [18], reverse engineering with 3D laser scanning [19], computer-aided manufacturing (CAM) and computer-aided engineering (CAE) [4], and computerized numerical control (CNC) [20]. Such digital technologies directly support optimized design, factory production of construction segments from design data, and site assembly and installation; increase the quality of irregular-shaped buildings; and reduce the construction period and cost [21].The number of studies analyzing the effects of digital fabrication on sustainability is gradually increasing [22–24]. However, studies that quantitatively analyze the types of positive and negative effects that digital fabrication has on construction project management are hard to find. Thus, this study aims at constructing theoretical evidence concerning the effect of digital fabrication on construction projects through preliminary analyses of changes in the manufacturing paradigm and effects of digital fabrication on sustainability. Based on this, case studies on irregular-shaped buildings implemented with digital fabrication are investigated to quantitatively evaluate the benefits of digital fabrication for construction project management.


## 2. Literature Review

### 2.1. Trend of Manufacturing Paradigms

The manufacturing paradigm started from a very slow process of manual crafting. Mass production became possible through the industrial revolution in the early 20th century, and the manufacturing system has greatly evolved economically through endless technology development. Lean manufacturing allowed the mass production of standardized products with high quality [4]. Additionally, allocation for manufacturing reduced in size to allow customization [25]. This mass customization started with split demands from customers for high-quality low-cost products and the niche market for such products. A new trend of manufacturing is mass personalization. Products are created within the mass customization framework and include distinctive features according to the consumers. This trend closely resembles mass customization, but the niches are different in nature. Therefore, manufacturing systems must be flexible to meet such demands [26].In supporting this trend, additive manufacturing (AM) processes such as rapid prototyping and stereolithography play an important role in reducing the time and cost of development required for assessing designs using prototypes [27]. AM does not require formulating a processing plan before manufacturing, but rather, it manufactures artifacts (defined geometrically) directly derived from 3D CAD models. A large amount of AM-type technology started to develop in the 1980s including 3D printing. This manufacturing method leads many industries to the concept of direct digital manufacturing (DDM). The current manufacturing methods for products are redefined using DDM. Components are no longer manufactured in factories and then assembled to create the final product before being delivered to clients. Instead, these products are manufactured in close proximity to the clients using AM based on digital models [27]. Therefore, AM is evolving into DDM as a mutual link for computers and manufacturing software through manufacturing equipment and network (e.g., Internet and servers). Various forms of DDM have the potential for changing the efficiency of materials for product business models, process chain, and relationship with product consumers [4]. Furthermore, it is also possible to combine the advantages of such a production paradigm to produce customized high-quality products.Such changes in the production paradigm in the construction industry can be seen through the gradual increase in the number of large-scale irregular-shaped buildings with very complex structures. Irregular-shaped buildings face limitations, in which conventional construction materials and production methods cannot be applied effectively owing to the structural constraints. Moreover, construction projects are fundamentally involved with one-off teams based on a disjointed production system. Because the product size is large compared to that in the manufacturing industry, customization in advance is difficult. Consequently, digital fabrication is gradually being introduced to overcome the fundamental problems of a conventional production system. However, studies that analyze the effects of digital fabrication on actual construction projects are rare. In particular, a performance indicator for construction project management, which can be used by construction firms trying out the new manufacturing paradigm of digital fabrication, is not yet available. Therefore, this study aims at suggesting key performance indicators (KPIs) for assessing the benefits of digital fabrication for construction projects and verifying them through case studies.


### 2.2. Digital Fabrication for Sustainability

Recent studies have emphasized the benefits that AM brings regarding sustainability [28, 29]. However, these studies mostly focus on small-scale processes. For example, Kreiger and Pearce proved that distributed manufacturing through 3D printing potentially had lesser environmental impact and energy consumption compared to the conventional manufacturing method [22]. Faludi et al. pointed out that 3D printing could reduce processing efforts, which could eventually reduce the waste and energy consumption compared to that in conventional CNC milling [23]. Gebler et al. provided a general perspective on 3D printing technology from environmental, economic, and social perspectives [24]. However, quantitative studies were rarely found among these studies, and Ford and Despeisse stressed that significantly more applied studies on the environmental impacts of digital fabrication were required [28]. Agustí-Juan et al. evaluated the potential environmental benefits from applying conventional manufacturing and digital fabrication on different types of concrete walls in order to quantify environmental benefits that digital fabrication could bring to the construction industry [6].A new manufacturing method that clearly distinguishes itself from conventional production methods in the construction industry is digital fabrication, which is based on various digital technologies [6]. In the construction industry, digital fabrication is implemented through particular projects such as irregular-shaped buildings. It is through these particular construction projects that manufacturing processes superior to conventional manufacturing methods are developed from design aspirations and technological innovations [30]. Digital fabrication processes in the construction industry are based on computational design methods and robotic construction processes. In particular, irregular-shaped building segments are typically achieved by combining materials of additional manufacturing processes (e.g., assembly, lamination, extrusion, and other forms of 3D printing) using industrial robots [31]. Using this digital fabrication, technology has allowed the construction of customized complex buildings [32].However, questions still prevail concerning the positive benefits for sustainability in the manufacturing sector wherein digital fabrication is applied. Traditionally, the performance of a production system in the manufacturing stage was evaluated by monitoring four main factors: cost, time, quality, and flexibility. However, additional elements that are an integral part of sustainability such as energy and resource efficiency must be considered, as shown in Figure1 [33]. It is evident that sustainability has conjoined with cost and evolved as a main decision-making factor in manufacturing [4].Figure 1
Manufacturing decision-making attributes in the 1990s and at the present time [27].Digital fabrication is a technology that is crucial for the construction industry for constructing irregular-shaped buildings, but it cannot be regarded as the only system that is required for constructing buildings. Currently, real-life projects have a basis in conventional manufacturing and only apply digital fabrication to limited building segments. Lean construction refers to applying the concept and principles of the Toyota Production System (TPS) to construction fields and focuses on waste reduction, increase in customer value, and continuous improvement [34]. Lean construction is possible through the integrated project delivery (IPD) approach, and BIM is essential in effectively carrying out collaborations required for an IPD [35] and contributing in sharing data necessary for achieving lean construction [36]. Bryde et al. quantitatively evaluated the benefits of BIM for construction project management [37]. As such, benefits of digital fabrication for construction projects in the construction industry must be evaluated with a focus on its effects on the overall construction project management rather than the sustainability of manufacturing technologies.


### 2.3. Limitation of Assessment for Benefits of Digital Fabrication

Sustainability is the latest main interest in many industries [38, 39]. The KPIs related to sustainability allow manufacturers to monitor and evaluate all essential aspects including economic, social, and environmental factors [40, 41]. Many studies have tried evaluating sustainability for manufacturing systems and the life span of products [42]. Moreover, numerous tools were developed to support sustainable manufacturing including green supply chains, reverse logistics, design for environment, and design for disassembly [33, 43–45].However, studies evaluating the sustainability aspects of particular technologies of AM and DDM are very limited in terms of their findings [46–48]. Consequently, tools that allow the quantitative analysis of the benefits of digital fabrication for construction projects are rarely attainable. Moreover, although digital fabrication is a very important technological element in attaining the quality of irregular-shaped buildings, it cannot replace the entire system necessary for constructing buildings. To this day, real construction projects typically adopt the conventional manufacturing method and apply digital fabrication only to specific segments.Understanding the potential benefits of digital fabrication through projects is a challenge that must be addressed. By implementing new manufacturing technologies such as digital fabrication, changes occur in the roles of key parties (e.g., clients, architects, contractors, subcontractors, and suppliers) in a construction project, contract relations, and reengineered collaborative processes [49]. Specifically, construction project managers must undertake more managing tasks than before if digital fabrication is implemented. However, the ultimate effects of introducing a new manufacturing technology on the daily managing tasks of a construction project manager and project outcomes still remain unclear [50]. Moreover, it is uncertain whether a new manufacturing technology will be able to overcome the operational problems that arise from the disjointed nature of the construction industry [51]. Thus, this study aims at evaluating the benefits of using digital fabrication for construction project management through data collection of irregular-shaped buildings. The research method for this task is explained in the next section.


## 2.1. Trend of Manufacturing Paradigms

The manufacturing paradigm started from a very slow process of manual crafting. Mass production became possible through the industrial revolution in the early 20th century, and the manufacturing system has greatly evolved economically through endless technology development. Lean manufacturing allowed the mass production of standardized products with high quality [4]. Additionally, allocation for manufacturing reduced in size to allow customization [25]. This mass customization started with split demands from customers for high-quality low-cost products and the niche market for such products. A new trend of manufacturing is mass personalization. Products are created within the mass customization framework and include distinctive features according to the consumers. This trend closely resembles mass customization, but the niches are different in nature. Therefore, manufacturing systems must be flexible to meet such demands [26].In supporting this trend, additive manufacturing (AM) processes such as rapid prototyping and stereolithography play an important role in reducing the time and cost of development required for assessing designs using prototypes [27]. AM does not require formulating a processing plan before manufacturing, but rather, it manufactures artifacts (defined geometrically) directly derived from 3D CAD models. A large amount of AM-type technology started to develop in the 1980s including 3D printing. This manufacturing method leads many industries to the concept of direct digital manufacturing (DDM). The current manufacturing methods for products are redefined using DDM. Components are no longer manufactured in factories and then assembled to create the final product before being delivered to clients. Instead, these products are manufactured in close proximity to the clients using AM based on digital models [27]. Therefore, AM is evolving into DDM as a mutual link for computers and manufacturing software through manufacturing equipment and network (e.g., Internet and servers). Various forms of DDM have the potential for changing the efficiency of materials for product business models, process chain, and relationship with product consumers [4]. Furthermore, it is also possible to combine the advantages of such a production paradigm to produce customized high-quality products.Such changes in the production paradigm in the construction industry can be seen through the gradual increase in the number of large-scale irregular-shaped buildings with very complex structures. Irregular-shaped buildings face limitations, in which conventional construction materials and production methods cannot be applied effectively owing to the structural constraints. Moreover, construction projects are fundamentally involved with one-off teams based on a disjointed production system. Because the product size is large compared to that in the manufacturing industry, customization in advance is difficult. Consequently, digital fabrication is gradually being introduced to overcome the fundamental problems of a conventional production system. However, studies that analyze the effects of digital fabrication on actual construction projects are rare. In particular, a performance indicator for construction project management, which can be used by construction firms trying out the new manufacturing paradigm of digital fabrication, is not yet available. Therefore, this study aims at suggesting key performance indicators (KPIs) for assessing the benefits of digital fabrication for construction projects and verifying them through case studies.


## 2.2. Digital Fabrication for Sustainability

Recent studies have emphasized the benefits that AM brings regarding sustainability [28, 29]. However, these studies mostly focus on small-scale processes. For example, Kreiger and Pearce proved that distributed manufacturing through 3D printing potentially had lesser environmental impact and energy consumption compared to the conventional manufacturing method [22]. Faludi et al. pointed out that 3D printing could reduce processing efforts, which could eventually reduce the waste and energy consumption compared to that in conventional CNC milling [23]. Gebler et al. provided a general perspective on 3D printing technology from environmental, economic, and social perspectives [24]. However, quantitative studies were rarely found among these studies, and Ford and Despeisse stressed that significantly more applied studies on the environmental impacts of digital fabrication were required [28]. Agustí-Juan et al. evaluated the potential environmental benefits from applying conventional manufacturing and digital fabrication on different types of concrete walls in order to quantify environmental benefits that digital fabrication could bring to the construction industry [6].A new manufacturing method that clearly distinguishes itself from conventional production methods in the construction industry is digital fabrication, which is based on various digital technologies [6]. In the construction industry, digital fabrication is implemented through particular projects such as irregular-shaped buildings. It is through these particular construction projects that manufacturing processes superior to conventional manufacturing methods are developed from design aspirations and technological innovations [30]. Digital fabrication processes in the construction industry are based on computational design methods and robotic construction processes. In particular, irregular-shaped building segments are typically achieved by combining materials of additional manufacturing processes (e.g., assembly, lamination, extrusion, and other forms of 3D printing) using industrial robots [31]. Using this digital fabrication, technology has allowed the construction of customized complex buildings [32].However, questions still prevail concerning the positive benefits for sustainability in the manufacturing sector wherein digital fabrication is applied. Traditionally, the performance of a production system in the manufacturing stage was evaluated by monitoring four main factors: cost, time, quality, and flexibility. However, additional elements that are an integral part of sustainability such as energy and resource efficiency must be considered, as shown in Figure1 [33]. It is evident that sustainability has conjoined with cost and evolved as a main decision-making factor in manufacturing [4].Figure 1
Manufacturing decision-making attributes in the 1990s and at the present time [27].Digital fabrication is a technology that is crucial for the construction industry for constructing irregular-shaped buildings, but it cannot be regarded as the only system that is required for constructing buildings. Currently, real-life projects have a basis in conventional manufacturing and only apply digital fabrication to limited building segments. Lean construction refers to applying the concept and principles of the Toyota Production System (TPS) to construction fields and focuses on waste reduction, increase in customer value, and continuous improvement [34]. Lean construction is possible through the integrated project delivery (IPD) approach, and BIM is essential in effectively carrying out collaborations required for an IPD [35] and contributing in sharing data necessary for achieving lean construction [36]. Bryde et al. quantitatively evaluated the benefits of BIM for construction project management [37]. As such, benefits of digital fabrication for construction projects in the construction industry must be evaluated with a focus on its effects on the overall construction project management rather than the sustainability of manufacturing technologies.


## 2.3. Limitation of Assessment for Benefits of Digital Fabrication

Sustainability is the latest main interest in many industries [38, 39]. The KPIs related to sustainability allow manufacturers to monitor and evaluate all essential aspects including economic, social, and environmental factors [40, 41]. Many studies have tried evaluating sustainability for manufacturing systems and the life span of products [42]. Moreover, numerous tools were developed to support sustainable manufacturing including green supply chains, reverse logistics, design for environment, and design for disassembly [33, 43–45].However, studies evaluating the sustainability aspects of particular technologies of AM and DDM are very limited in terms of their findings [46–48]. Consequently, tools that allow the quantitative analysis of the benefits of digital fabrication for construction projects are rarely attainable. Moreover, although digital fabrication is a very important technological element in attaining the quality of irregular-shaped buildings, it cannot replace the entire system necessary for constructing buildings. To this day, real construction projects typically adopt the conventional manufacturing method and apply digital fabrication only to specific segments.Understanding the potential benefits of digital fabrication through projects is a challenge that must be addressed. By implementing new manufacturing technologies such as digital fabrication, changes occur in the roles of key parties (e.g., clients, architects, contractors, subcontractors, and suppliers) in a construction project, contract relations, and reengineered collaborative processes [49]. Specifically, construction project managers must undertake more managing tasks than before if digital fabrication is implemented. However, the ultimate effects of introducing a new manufacturing technology on the daily managing tasks of a construction project manager and project outcomes still remain unclear [50]. Moreover, it is uncertain whether a new manufacturing technology will be able to overcome the operational problems that arise from the disjointed nature of the construction industry [51]. Thus, this study aims at evaluating the benefits of using digital fabrication for construction project management through data collection of irregular-shaped buildings. The research method for this task is explained in the next section.


## 3. Research Method

### 3.1. Secondary Data Collection

In order to investigate the type of benefits of digital fabrication on construction project management, secondary data for irregular-shaped buildings in which digital fabrication was employed were collected. Empirical studies on tasks related to construction project management often use self-reported data [37]. However, an alternative approach using secondary data has the benefit of reducing inaccuracy that arises from self-reporting and accessing data on an event [52]. The secondary data of this study were collected from projects using digital fabrication utilizing innovative computer control processes and technologies. The sources of secondary data on overseas projects were collected through the AIA BIM TAP Awards (currently, AIA/TAP Innovation Awards Program) from 2005 to 2017 on irregular-shaped buildings that had implemented digital fabrication [53]. And the sources of secondary data on projects in Korea were collected through the previous research data of Korean BIM Journal (e.g., the BIM Vol. 1∼12, KIBIM Magazine 2011∼2016) and Korean BIM Award (e.g., Autodesk Korea BIM Awards 2014, Building Smart Korea BIM Award 2009∼2015) [54]. Data were supplemented from information available through public domains such as academic journals and conference publications, design firms and construction firms of each project, and manufacturing firms that directly manufactured irregular-shaped members. This was done in order to improve reliability of the secondary data. Furthermore, professional interviews were carried out for actual workers in digital fabrication to add overlooked study cases on irregular-shaped buildings and to verify the collected secondary data.Twenty-seven study cases on irregular-shaped buildings that mentioned positive and negative benefits of adapting digital fabrication were selected for further analyses. In order to evaluate the project advantages of digital fabrication in terms of the management of construction projects, case projects were selected considering the characteristics of the project. In other words, we selected a project to investigate the characteristics (e.g., an area of irregular-shaped segments, a number of unit materials, a size of unit material, a production method, and segments with irregular shapes) of digital fabrication. On the other hand, we excluded projects where the project size was small, or digital fabrication was applied only to some sections and did not bring significant benefits to construction projects.


### 3.2. Success Criteria

Evaluation criteria were established to analyze data on the types of benefits introduced due to digital fabrication, or if any benefits were introduced at all. This analysis was performed by deriving a “success criteria” that met the goals for time, cost, and quality of construction projects and was related to process management aspects including effective scope management and communications. These success criteria reflected the idea of multidimensional success of construction projects by including not only the projects themselves but also project management [55]. The success criteria can also be referred to as “critical success factors” or “key results areas” in project management [37].The success criteria were classified according to the Project Management Body of Knowledge (PMBOK) knowledge areas of the Project Management Institute (PMI) in order to establish the evaluation standards for the positive and negative benefits of digital fabrication for construction projects [56]. These knowledge areas were chosen as they provided an upper framework that was inclusive of all aspects of success in a project [37]. As shown in Table 1, the success criteria were used to compare the roles and benefits of digital fabrication on irregular-shaped buildings with those expected from a project manager.Table 1
Success criteria based on PMBOK knowledge area.
PMBOK knowledge area
Definition (after PMI, 2013)
Criterion
Positive consideration
Integration management
Unification, consolidation, articulation, and integrative actions
Integration
Improvement
Scope management
Defining and controlling what is and is not included in the project
Scope
Clarification
Time management
Manage the timely completion of the project
Time
Reduction or control
Cost management
Planning, estimating, budgeting, financing, funding, managing, and controlling costs
Cost
Reduction or control
Quality management
Quality planning, quality assurance, and quality control
Quality
Increase or control
Human resource management
Organize, manage, and lead the project team
Organization
Improvement
Communication management
Timely and appropriate planning, collection, creation, distribution, storage, retrieval, management, control, monitoring, and the ultimate disposition of project information
Communication
Improvement
Risk management
Increase the likelihood and impact of positive events and decrease the likelihood and impact of negative events in the project
Risk
Negative risk reduction
Procurement management
Purchase or acquire the products, services, or results needed from outside the project team
Procurement
Help
Stakeholder management
Develop appropriate management strategies for effectively engaging stakeholders in project decisions and execution
Stakeholder
Satisfaction


### 3.3. Content Analysis

It is very difficult to objectively evaluate the impact of digital fabrication on construction projects. However, researchers have difficulty in securing the expert pool by applying digital fabrication to the irregular-shaped buildings, and even if they have a pool of experts, interviews and expert interviews are limited. In this regard, Bryde et al. analyzed the project benefits of BIM on construction projects through content analysis of secondary data [37].A content analysis process suggested by Harris was carried out to confirm the positive and negative benefits of digital fabrication for construction projects using secondary data for each irregular-shaped building. The unit of analysis adopted was the “phrase,” which may vary from a single word to a whole sentence [52]. The phrase in this study refers to “project benefit” [37]. The phrase associated with “project benefit” found in each study case of irregular-shaped buildings was converted into the success criteria, as shown in Table 1. During the conversion process, the phrase related to procurement or stakeholder was rarely found among the success criteria. Consequently, the two factors, procurement and stakeholder, were omitted, and instead, software issues and materials of irregular-shaped segments were added as important factors related to the quality of irregular-shaped segments during content analysis for applying digital fabrication.The projects were then organized using the added score for each of them (positive benefits minus negative benefits). This is not an attempt to find which case demonstrates the most beneficial use of digital fabrication but to organize the data in a way that highlights were there are more positive than negative benefits. Hence, the numbers on the score column should not be seen as an indicator of how successful or unsuccessful those case study projects were, but simply how many success criteria were mentioned positively or negatively [37]. For example, the case study of P6 (Lotte World Tower Podium) in Table 3 shows that the cost-based success criterion is “−2” and the risk-based success criterion is “−1.” This means that there are two aspects of the digital fabrication related to the cost, risk success, and criteria that were mentioned as challenging or causing difficulties (negative benefit) but it does not mean that the use of digital fabrication was overall negative. With this approach, it is possible to see which success criterion appears more times as a positive factor and which ones appear as challenges or problems.


## 3.1. Secondary Data Collection

In order to investigate the type of benefits of digital fabrication on construction project management, secondary data for irregular-shaped buildings in which digital fabrication was employed were collected. Empirical studies on tasks related to construction project management often use self-reported data [37]. However, an alternative approach using secondary data has the benefit of reducing inaccuracy that arises from self-reporting and accessing data on an event [52]. The secondary data of this study were collected from projects using digital fabrication utilizing innovative computer control processes and technologies. The sources of secondary data on overseas projects were collected through the AIA BIM TAP Awards (currently, AIA/TAP Innovation Awards Program) from 2005 to 2017 on irregular-shaped buildings that had implemented digital fabrication [53]. And the sources of secondary data on projects in Korea were collected through the previous research data of Korean BIM Journal (e.g., the BIM Vol. 1∼12, KIBIM Magazine 2011∼2016) and Korean BIM Award (e.g., Autodesk Korea BIM Awards 2014, Building Smart Korea BIM Award 2009∼2015) [54]. Data were supplemented from information available through public domains such as academic journals and conference publications, design firms and construction firms of each project, and manufacturing firms that directly manufactured irregular-shaped members. This was done in order to improve reliability of the secondary data. Furthermore, professional interviews were carried out for actual workers in digital fabrication to add overlooked study cases on irregular-shaped buildings and to verify the collected secondary data.Twenty-seven study cases on irregular-shaped buildings that mentioned positive and negative benefits of adapting digital fabrication were selected for further analyses. In order to evaluate the project advantages of digital fabrication in terms of the management of construction projects, case projects were selected considering the characteristics of the project. In other words, we selected a project to investigate the characteristics (e.g., an area of irregular-shaped segments, a number of unit materials, a size of unit material, a production method, and segments with irregular shapes) of digital fabrication. On the other hand, we excluded projects where the project size was small, or digital fabrication was applied only to some sections and did not bring significant benefits to construction projects.


## 3.2. Success Criteria

Evaluation criteria were established to analyze data on the types of benefits introduced due to digital fabrication, or if any benefits were introduced at all. This analysis was performed by deriving a “success criteria” that met the goals for time, cost, and quality of construction projects and was related to process management aspects including effective scope management and communications. These success criteria reflected the idea of multidimensional success of construction projects by including not only the projects themselves but also project management [55]. The success criteria can also be referred to as “critical success factors” or “key results areas” in project management [37].The success criteria were classified according to the Project Management Body of Knowledge (PMBOK) knowledge areas of the Project Management Institute (PMI) in order to establish the evaluation standards for the positive and negative benefits of digital fabrication for construction projects [56]. These knowledge areas were chosen as they provided an upper framework that was inclusive of all aspects of success in a project [37]. As shown in Table 1, the success criteria were used to compare the roles and benefits of digital fabrication on irregular-shaped buildings with those expected from a project manager.Table 1
Success criteria based on PMBOK knowledge area.
PMBOK knowledge area
Definition (after PMI, 2013)
Criterion
Positive consideration
Integration management
Unification, consolidation, articulation, and integrative actions
Integration
Improvement
Scope management
Defining and controlling what is and is not included in the project
Scope
Clarification
Time management
Manage the timely completion of the project
Time
Reduction or control
Cost management
Planning, estimating, budgeting, financing, funding, managing, and controlling costs
Cost
Reduction or control
Quality management
Quality planning, quality assurance, and quality control
Quality
Increase or control
Human resource management
Organize, manage, and lead the project team
Organization
Improvement
Communication management
Timely and appropriate planning, collection, creation, distribution, storage, retrieval, management, control, monitoring, and the ultimate disposition of project information
Communication
Improvement
Risk management
Increase the likelihood and impact of positive events and decrease the likelihood and impact of negative events in the project
Risk
Negative risk reduction
Procurement management
Purchase or acquire the products, services, or results needed from outside the project team
Procurement
Help
Stakeholder management
Develop appropriate management strategies for effectively engaging stakeholders in project decisions and execution
Stakeholder
Satisfaction


## 3.3. Content Analysis

It is very difficult to objectively evaluate the impact of digital fabrication on construction projects. However, researchers have difficulty in securing the expert pool by applying digital fabrication to the irregular-shaped buildings, and even if they have a pool of experts, interviews and expert interviews are limited. In this regard, Bryde et al. analyzed the project benefits of BIM on construction projects through content analysis of secondary data [37].A content analysis process suggested by Harris was carried out to confirm the positive and negative benefits of digital fabrication for construction projects using secondary data for each irregular-shaped building. The unit of analysis adopted was the “phrase,” which may vary from a single word to a whole sentence [52]. The phrase in this study refers to “project benefit” [37]. The phrase associated with “project benefit” found in each study case of irregular-shaped buildings was converted into the success criteria, as shown in Table 1. During the conversion process, the phrase related to procurement or stakeholder was rarely found among the success criteria. Consequently, the two factors, procurement and stakeholder, were omitted, and instead, software issues and materials of irregular-shaped segments were added as important factors related to the quality of irregular-shaped segments during content analysis for applying digital fabrication.The projects were then organized using the added score for each of them (positive benefits minus negative benefits). This is not an attempt to find which case demonstrates the most beneficial use of digital fabrication but to organize the data in a way that highlights were there are more positive than negative benefits. Hence, the numbers on the score column should not be seen as an indicator of how successful or unsuccessful those case study projects were, but simply how many success criteria were mentioned positively or negatively [37]. For example, the case study of P6 (Lotte World Tower Podium) in Table 3 shows that the cost-based success criterion is “−2” and the risk-based success criterion is “−1.” This means that there are two aspects of the digital fabrication related to the cost, risk success, and criteria that were mentioned as challenging or causing difficulties (negative benefit) but it does not mean that the use of digital fabrication was overall negative. With this approach, it is possible to see which success criterion appears more times as a positive factor and which ones appear as challenges or problems.


## 4. Assessment of Project Benefits of Digital Fabrication

### 4.1. Case Description

Table2 summarizes the study cases where digital fabrication was applied to the construction of irregular-shaped buildings. The total area, area of irregular-shaped segments, material of irregular-shaped segments, number of unit material, size of unit material, production method, segments with irregular shapes (interior/exterior), construction work, construction period, and software were collected as data. Any data that were difficult to collect were supplemented through interviews of professionals from firms specializing in digital fabrication. Among the 27 projects from the study cases, 11 projects had irregular-shaped segments comprising an area of 10,000 m2 and 4 projects had an area of 50,000 m2. Irregular-shaped segments for which digital fabrication was applied were classified into interior and exterior. Digital fabrication was applied on the interior (4%) in 1 project, on the exterior (85%) in 23 projects, and on the interior and exterior (11%) in 3 projects. The results for construction work were similar to that for the irregular-shaped segments. Of all the projects, 26 (96%) corresponded to curtain wall and exterior finishing work, while 1 (4%) corresponded to interior finishing work. Various types of materials were used for irregular-shaped segments including those commonly used in conventional construction projects; for example, steel, concrete, aluminum, glass, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), glass fiber-reinforced polymer (GFRP), glass fiber-reinforced concrete (GFRC), and ultrahigh performance concrete (UHPC). The production method for irregular-shaped segments differed according to material.Table 2
Details of cases.
PJT no.
PJT name (city/country)
Total area (m2)
Irregular-shaped segments (m2)
Irregular-shaped segment material
Number of members
Fabrication method
Interior/exterior
Member size
Work type
Construction Period
Software
P1
GT tower (Seoul/Korea)
54,583
19,000
AL. BAR glass
22,000 EA12,500 EA
CNC machine
Exterior
1,400/1,450 mm × 4,500/6,000/7,000 mm1,400/1,450 mm × 550/1,100 mm
Curtain wall
12 months∗
CATIA
P2
Tri bowl (Incheon/Korea)
2,893
3,012
AL. panel
2,308 EA
CNC machine
Exterior
1,600 mm × 800 mm
Exterior finish
8 months∗
CATIA, Rhino
P3
DDP (Seoul/Korea)
83,024
33,228
AL. panel
45,133 EA
CNC machine and MDSF
Exterior
1,600 mm × 1,200 mm
Exterior finish
14 months∗
CATIA, Rhino, TEKLA
P4
Ecorium (Seocheon/Korea)
33,091
9,628
Glass
32,093 EA
CNC machine
Exterior
540 mm × 540 mm
Steel curtain wall
24 months∗
CATIA
P5
Theme Pavilion of Yeosu EXPO (Yeosu/Korea)
7,414
GFRP
98 EA
CNC machine and MDSF
Exterior
Exterior finish
20 months∗
CATIA
P6
Lotte World tower Podium (Seoul/Korea)
328,351
8,181
NT panelAL. BAR
17,934 EA 11,791 EA
CNC machine
Interior
1000 mm × 200 mm
Interior finish
10 months∗
CATIA
P7
The Arc (Daegu/Korea)
5,963
1,991
ETFE
336 EA
CNC machine
Exterior
3,000 mm × 2,500 mm
Steel exterior finish
5 months∗
CATIA
P8
KEB HANA Bank (Seoul/Korea)
16,287
3450
UHPC
256 EA
CNC machine and mold
Exterior
2,000 mm × 4,200/4,400/6,200 mm
Exterior finish
12 months∗
CATIA
P9
Korea National Maritime Museum (Busan/Korea)
25,803
CNC machine
Exterior
Curtain wall
TEKLA
P10
BEAT360 (Seoul/Korea)
1,880
Al. panelWood panel
7,553 EA; 8,800 EA
CNC machine
Interior/exterior
Interior/exterior finish
P11
Denver Art Museum (Denver/USA)
13,564
16,538
Titanium panel
9,000 EA
CNC machine
Exterior
2,100 mm × 800 mm
Exterior finish
39 months
CATIA, TEKLA
P12
Water Cube (Beijing/China)
90,000
52,000
ETFE
4,000 EA
CNC machine and pressure
Exterior
Diameter-7,500 mm Circle
Steel exterior finish
50 months
Rhino, 3D MAX, Microstation
P13
Bird’s Nest (Beijing/China)
260,000
38,50053,000
ETFEPTFE
884 EA1,044 EA
CNC machine and pressure
Exterior
Steel exterior finish
46 months
TEKLA
P14
Basra Sports City (Basra/Iraq)
65,000
GFRP
560 EA
Mold
Exterior
Length: 300,000 mm
Exterior finish
53 months
CATIA, TEKLA
P15
Louis Vuitton Foundation (Paris/France)
11,000
13,5009,000
ConcreteGlass
19,000 EA3,600 EA
CNC machine and MSV
Exterior
3,000 mm × 1,500 mm1,500 mm × 400 mm
Exterior finish
74 months
CATIA
P16
Louisiana State Museum and Sports Hall of fame (Natchitoches/USA)
28,000
1,380
Cast Stone panel
1,150 EA
CNC machine
Interior/exterior
2,000 mm × 500 mm
Interior/exterior finish
Navisworks
P17
Hangzhou Sports Park Stadium (Hangzhou/China)
400,000
15,000
AL. Panel
55 EA
CNC machine
Exterior
Height: 12 m–18 m
Exterior finish
84 months
Grasshopper
P18
Perot Museum of Nature and Science (Dallas/USA)
180,000
9,300
Concrete steel
700 EA8,400 EA
CNC machine and mold
Exterior
9,200 mm × 2,400 mm
Exterior finish
31 months
REVIT
P19
Phoenix Biomedical Campus: Health Sciences Education Building (Phoenix/USA)
24,898
8,910
Copper panel
6,000 EA
Press brake-punch-and-die machine
Exterior
3,300 mm × 300/450/760 mm
Exterior finish
27 months
REVIT
P20
Zlote Tarasy (Warszawa/Poland)
205,000
10,240
GlassSteel
4,788 EA7,123 EA
CNC machine
Exterior
2.14㎡ per panel
Exterior finish
52 months
P21
Weltstadthaus (Cologne/Germany)
14,400
4,900
Glass
6,800 EA
CNC machine
Exterior
0.72㎡ per a panel
Exterior finish
72 months
P22
BMW Welt (Munich/Germany)
16,500
8,000
Glass
4,500 EA
CNC machine
Interior/exterior
2.22㎡ per a module
Interior/exterior finish
56 months
Nemetschek Allplan
P23
Museo Soumaya (Mexico City/Mexico)
16,000
Steel
16,000 EA
CNC machine
Exterior
630 mm hexagon
Exterior finish
38 months
CATIA
P24
O-14 tower (Dubai/UAE)
28,000
Concrete
CNC machine and mold
Exterior
Exterior finish
48 months
Rhino, SAP2000
P25
Qatar National Museum (Doha/Qatar)
47,000
120,000
GFRC
75,000 EA
Mold
Exterior
400 m × 250 m per disc
Exterior finish
72 months
CATIA
P26
University of technology Sydney (Sydney/Australia)
16,030
5,594
Customized brick
320,000 EA
Mold
Exterior
Brick: 76 mm × 110 mm × 230 mm
Exterior finish
24 months
REVIT
P27
Benz Museum (Stuttgart/Germany)
16,500
6,1715,289
GlassAL. Panel
1,800 EA1,000 EA
Mold
Exterior
Exterior finish
36 monthsA CNC machine was used to produce AL. panels, AL. bars, wood panels, titanium panels, and molds, and the members were directly manufactured through cutting, welding, and milling. Materials such as concrete panels, UHPC, and customized bricks were produced into members using an irregular-shaped formwork manufactured with a CNC machine. For a unique material such as ETFE, members are produced using pressure. AL. panels were produced using conventional materials with the latest machine multipoint stretching forming (MDSF) machine depending on the design. High-end software such as CATIA, which can minimize the error range in the production, was found to be used frequently for digital fabrication to ensure the quality of the irregular-shaped segments.


### 4.2. Positive and Negative Benefits of Using Digital Fabrication

Table3 summarizes the evaluation results of the benefits of digital fabrication for construction project management obtained using 10 success criteria. The benefits of digital fabrication for construction project management were evaluated by subtracting the negative benefits from the positive benefits in order to obtain a score for each case study. This is shown in the score column in Table 3.Table 3
Positive and negative benefits of using digital fabrication on selected cases.
Project
Integ.
Scope
Time
Cost
Qual.
Org.
Com.
Risk
Soft.
Mat.
Score
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
P1
−1
1
−1
1
0
P2
1
1
1
1
4
P3
1
−2
2
1
1
2
5
P4
1
1
P5
1
1
1
3
P6
2
1
−2
2
1
1
−1
1
1
6
P7
1
1
−2
1
1
2
4
P8
2
1
−1
2
1
1
6
P9
−1
1
1
1
P10
1
1
P11
1
1
−2
1
−1
2
2
P12
2
−1
1
1
1
4
P13
1
−2
2
1
2
4
P14
−2
2
1
1
P15
1
2
2
2
7
P16
1
1
1
1
1
5
P17
−1
−1
1
−1
P18
1
1
1
1
4
P19
1
1
P20
−1
−1
P21
1
−1
−1
−1
P22
1
−2
2
2
3
P23
1
−1
1
1
2
P24
1
1
−1
1
2
P25
−2
1
1
1
1
P26
2
−1
1
3
2
−1
2
8
P27
2
2
Total
17
0
4
0
7
−6
1
−21
26
0
5
−1
3
0
7
−3
20
−1
16
0
74
Average
0.63
0.00
0.15
0.00
0.26
−0.22
0.04
−0.78
0.96
0.00
0.19
−0.04
0.11
0.00
0.26
−0.11
0.74
−0.04
0.59
0.00
2.74The focus of evaluation was not on how effectively each case study used digital fabrication but on highlighting the positive benefits over the negative benefits. Therefore, the values in the score column in Table3 do not serve as an index to determine the success of a project. These values simply indicate how many success criteria were mentioned positively and negatively from the secondary data of projects in the case studies. For example, case study P17 (Hangzhou Sports Park Stadium) expressed a negative experience owing to its challenges or difficulties with respect to time and cost, while a positive experience was observed in terms of material caused by achieving good quality irregular-shaped segments. Case study P20 (Zlote Tarasy) presented a negative experience in applying digital fabrication owing to its challenges or difficulties in terms of cost. Case study P21 (Weltstadthaus Cologne) expressed a negative experience in applying digital fabrication owing to its challenges or difficulties in terms of time and organization, while a positive experience was seen in terms of integration from digital fabrication. While the subtotal score of case studies P17, P20, and P21 was “−1,” this neither implies that introducing digital fabrication created losses in terms of construction project management nor that they were failed projects. Furthermore, the scores of positive and negative benefits for the case studies were not combined for each success criterion but divided into two separate columns (positive benefits and negative benefits), as listed in Table 3. This approach showed the success criteria that appeared more frequently as a positive element, which were challenges to be tackled, and what type of problems they had.


### 4.3. Success Criteria Ranking of Using Digital Fabrication

Each success criterion was defined with the frequency of occurrence for positive and negative benefits (Table4) and was ranked according to the summation of total instances and the total number of projects for positive benefits. Moreover, the total instances and total number of projects for negative benefits were shown together. An approach for quantifying the number of projects in which a success criterion had an influence as a positive benefit is fundamentally conservative [37]. In some cases, a success criterion was mentioned once in a positive manner and once in a negative manner. In such a situation, the success criteria were not counted as projects that had a positive effect (or negative), regardless of the impact of the project on the outcome. For example, on the Louis Vuitton Foundation, described by AIA TAP BIM Award, the integration success criterion was counted once as positive for the “Integration of construction modifications in the 3D model” and the quality success criterion was counted once as positive for the “Construction quality was monitored with on-site with laser equipment, and round-tripped back into the model [57].”Table 4
Success criteria ranking of using digital fabrication.
Success criterion
Positive benefit
Negative benefit
Total instances
Total number of projects
% of total projects
Total instances
Total number of projects
% of total projects
Quality increase or control
26
17
62.96
0
0
0.00
Software issues
20
16
59.26
1
1
3.70
Integration improvement
17
13
48.15
0
0
0.00
Material improvement
16
13
48.15
0
0
0.00
Negative risk reduction
7
5
18.52
3
3
11.11
Time reduction or control
7
7
25.93
6
5
18.52
Organization improvement
5
4
14.81
1
1
3.70
Scope clarification
4
4
14.81
0
0
0.00
Communication improvement
3
3
11.11
0
0
0.00
Cost reduction or control
1
1
3.70
21
14
51.85


#### 4.3.1. Quality Success Criterion

There were a total of 26 instances of positive benefits in terms of quality increase or control from applying digital fabrication in 17 (63%) projects; the negative benefits were not observed. Digital fabrication can evaluate constructability starting from the design stage to allow optimum design, as well as use latest equipment such as a CNC machine, MDSF, and MSV that allow precise production and minimize error down to the millimeter range to achieve the quality required for construction projects. Case study P25 (National Museum of Qatar) included quality standards for irregular-shaped segments in the request for proposal (RFP) [58–61]. This document includes “design and engineering methodology,” “design optimization,” “fabrication of panels,” and “methodology of survey works” for irregular-shaped segments.


#### 4.3.2. Software Issues Success Criterion

Positive benefits in terms of software issues from implementing digital fabrication were mentioned in 20 instances in 16 (59%) projects; a negative benefit was observed in one instance owing to the lack of experience in high-end software programming. Digital fabrication executes design, manufacture, and construction based on 3D models. Thus, software was used to generate 3D models in all studied projects. Most projects found positive benefits from using high-end software such as CATIA and TEKLA because it minimized error ranges in the manufacturing of irregular-shaped segments. In addition, a positive benefit of being able to swiftly and continuously provide necessary manufacturing information to the manufacturers by obtaining tens of thousands of 2D manufacturing blueprints from 3D models in a short period of time was observed [62]. Furthermore, collaboration, clash detection, and supply calculation were possible using 3D models. Although high-end software can support global collaboration systems based on server networks [63], the applicability is not up to par. This is because not all participants in the supply chain related to digital fabrication have the resources to use high-end software.


#### 4.3.3. Integration Success Criterion

Positive benefits in terms of integration improvement from applying digital fabrication were seen in 17 instances in 13 (48%) projects; negative benefits were not indicated. The integration process of increasing productivity by optimizing different and individually designed members from simultaneously considering design, manufacture, and construction is crucial for irregular-shaped buildings. Decisions on member size and production unit that consider materials and production methods were made by optimizing the design of irregular-shaped buildings. The design optimization results for irregular-shaped segments for case study P8 (KEB Hana Bank, Samsung-dong, Seoul) are shown in Figure2 [64]. Irregular-shaped segments can increase the construction cost or affect the construction period in the case of many types of formwork being presented according to unit size, and thus increasing the manufacturing time of the FRP formwork. Projects in the case studies minimized the number of mold types for formwork from 12 in the initial design to 8 through design optimization. This allowed manufacture and construction to be completed within the project period.Figure 2
Design optimization for exterior cladding. (a) Original design with 12 types of formwork and (b) optimized design with 8 types of formwork.
(a)
(b)


#### 4.3.4. Material Success Criterion

Positive benefits in terms of material improvement from applying digital fabrication were seen in 16 instances in 13 (48%) projects; negative benefits were not observed. Unlike conventional regular-shaped buildings constructed with traditional materials, latest materials such as UHPC, ETFE, and GRCP were applied to irregular-shaped buildings with digital fabrication, which allowed various and complex exterior envelopes. The members for irregular-shaped buildings were produced using manufacturing equipment such as a CNC machine, MDSF, MSV, and pressure using 2D manufacturing blueprints obtained through 3D models. This helps overcome the limitations of conventional construction materials. Moreover, AL. panels or copper panels that have been constantly used in the construction industry can be manufactured into three-dimensional panels depending on the design using manufacturing equipment such as press brake punches and dies tools. The irregular-shaped formwork was manufactured at a factory using a CNC machine for exposed concrete or concrete panel materials for complex shapes, and then, members were produced by placing and curing the material. In irregular-shaped buildings, the positive benefits related to quality, software issues, and integration from applying digital fabrication is inevitably associated with new material, new design, and production method.


#### 4.3.5. Risk Success Criterion

Positive benefits in terms of negative risk reduction from applying digital fabrication were seen in 7 instances in 5 (19%) projects; negative benefits were seen in 3 instances in 3 (11%) projects. Applying digital fabrication allows reducing risk that can arise during design, manufacture, and construction stages using 3D models to generate simulations and mock-ups. However, since irregular-shaped buildings are not considered as standard construction projects, discrepancies between initial plans and execution are inevitable, which becomes a potential risk. Currently, performance data or analysis data on the case studies of irregular-shaped buildings are not readily available, which makes it difficult to proactively avoid potential risks compared to typical construction projects [11]. Nonetheless, there were more instances of expressing positive benefits in terms of risk reduction from applying digital fabrication to irregular-shaped buildings.


#### 4.3.6. Time Success Criterion

Positive benefits in terms of time reduction or control from applying digital fabrication were seen in 7 instances in 7 (26%) projects; negative benefits were seen in 6 instances in 5 (19%) projects. Applying digital fabrication not only requires managing on-site construction but also additional off-site construction (e.g., fabrication factory). Moreover, managing new manufacturers introduced to the project because of the new manufacturing methods and consequential new supply chains becomes necessary. Such occurrences in the studied projects were either dealt with by going through trial and error in the early stages of a project before slowly learning to manage this as the project progressed or showed benefits that depended on management skills obtained from experience and skills gained throughout the project. When such management skills are put to use, great benefits, incomparable to that from the conventional production method can be achieved in the time reduction or control aspects. If not, a great amount of time may be consumed.


#### 4.3.7. Human Resource Success Criterion

Positive benefits in terms of organization improvement from applying digital fabrication were seen in 5 instances in 4 (15%) projects. Negative benefits were seen in 1 instance in 1 (3%) project. The application of digital fabrication is very similar to the concept of lean construction. New labor, material or resources, and equipment can be allocated in the right location with JIT (just-in-time) and increase productivity. Construction involving digital fabrication requires prefabrication in a factory and transporting to a site before installation takes place. This process is different from that of a conventional construction production method, which may result in negative benefits in terms of improving and integrating processes due to inexperience in digital fabrication.


#### 4.3.8. Scope Success Criterion

Positive benefits in terms of scope clarification from applying digital fabrication were seen in 4 instances in 4 (15%) projects; negative benefits were not observed. Digital fabrication requires defining the segments of the building, in which this production method is being applied to beforehand. Furthermore, the scope of work for design, manufacture, and construction firms responsible for digital fabrication and the scope of work and allocated tasks between initial production firms and new suppliers must be clearly defined.


#### 4.3.9. Communication Success Criterion

Positive benefits in terms of communication improvement from applying digital fabrication were seen in 3 instances in 3 (11%) projects; negative benefits were not observed. Design, manufacture, and construction processes were established based on 3D models for irregular-shaped segments that required digital fabrication. Moreover, construction project participants carried out communication, collaboration, and arbitration using 3D models, which increased the accuracy of the design. The positive benefits from obtaining tens of thousands 2D manufacturing blueprints from 3D models were already dealt above with software issues, which seemed to have caused the low number of instances of positive benefits for communication improvement. All blueprints produced during a construction project serve as the most primary method of communication. Therefore, the study results cannot solely stand as a premise for digital fabrication with meager positive benefits for communication improvement.


#### 4.3.10. Cost Success Criterion

Positive benefits in terms of cost reduction or control from applying digital fabrication were seen in 1 instance in 1 (4%) project; however, negative benefits were expressed in 21 instances in 14 (52%) projects. This was due to the burden of additional costs inevitably encountered when new technology is introduced in a construction project. New labor, software, and equipment are certainly required when digital fabrication is applied. Using the conventional construction method for irregular-shaped buildings can result in simultaneous loss in time, cost, and quality, which are important qualities in construction project management. On the contrary, construction project management that considers positive benefits of using digital fabrication not only allows attaining a certain quality for irregular-shaped segments but also allows reduction in time and cost.


## 4.1. Case Description

Table2 summarizes the study cases where digital fabrication was applied to the construction of irregular-shaped buildings. The total area, area of irregular-shaped segments, material of irregular-shaped segments, number of unit material, size of unit material, production method, segments with irregular shapes (interior/exterior), construction work, construction period, and software were collected as data. Any data that were difficult to collect were supplemented through interviews of professionals from firms specializing in digital fabrication. Among the 27 projects from the study cases, 11 projects had irregular-shaped segments comprising an area of 10,000 m2 and 4 projects had an area of 50,000 m2. Irregular-shaped segments for which digital fabrication was applied were classified into interior and exterior. Digital fabrication was applied on the interior (4%) in 1 project, on the exterior (85%) in 23 projects, and on the interior and exterior (11%) in 3 projects. The results for construction work were similar to that for the irregular-shaped segments. Of all the projects, 26 (96%) corresponded to curtain wall and exterior finishing work, while 1 (4%) corresponded to interior finishing work. Various types of materials were used for irregular-shaped segments including those commonly used in conventional construction projects; for example, steel, concrete, aluminum, glass, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), glass fiber-reinforced polymer (GFRP), glass fiber-reinforced concrete (GFRC), and ultrahigh performance concrete (UHPC). The production method for irregular-shaped segments differed according to material.Table 2
Details of cases.
PJT no.
PJT name (city/country)
Total area (m2)
Irregular-shaped segments (m2)
Irregular-shaped segment material
Number of members
Fabrication method
Interior/exterior
Member size
Work type
Construction Period
Software
P1
GT tower (Seoul/Korea)
54,583
19,000
AL. BAR glass
22,000 EA12,500 EA
CNC machine
Exterior
1,400/1,450 mm × 4,500/6,000/7,000 mm1,400/1,450 mm × 550/1,100 mm
Curtain wall
12 months∗
CATIA
P2
Tri bowl (Incheon/Korea)
2,893
3,012
AL. panel
2,308 EA
CNC machine
Exterior
1,600 mm × 800 mm
Exterior finish
8 months∗
CATIA, Rhino
P3
DDP (Seoul/Korea)
83,024
33,228
AL. panel
45,133 EA
CNC machine and MDSF
Exterior
1,600 mm × 1,200 mm
Exterior finish
14 months∗
CATIA, Rhino, TEKLA
P4
Ecorium (Seocheon/Korea)
33,091
9,628
Glass
32,093 EA
CNC machine
Exterior
540 mm × 540 mm
Steel curtain wall
24 months∗
CATIA
P5
Theme Pavilion of Yeosu EXPO (Yeosu/Korea)
7,414
GFRP
98 EA
CNC machine and MDSF
Exterior
Exterior finish
20 months∗
CATIA
P6
Lotte World tower Podium (Seoul/Korea)
328,351
8,181
NT panelAL. BAR
17,934 EA 11,791 EA
CNC machine
Interior
1000 mm × 200 mm
Interior finish
10 months∗
CATIA
P7
The Arc (Daegu/Korea)
5,963
1,991
ETFE
336 EA
CNC machine
Exterior
3,000 mm × 2,500 mm
Steel exterior finish
5 months∗
CATIA
P8
KEB HANA Bank (Seoul/Korea)
16,287
3450
UHPC
256 EA
CNC machine and mold
Exterior
2,000 mm × 4,200/4,400/6,200 mm
Exterior finish
12 months∗
CATIA
P9
Korea National Maritime Museum (Busan/Korea)
25,803
CNC machine
Exterior
Curtain wall
TEKLA
P10
BEAT360 (Seoul/Korea)
1,880
Al. panelWood panel
7,553 EA; 8,800 EA
CNC machine
Interior/exterior
Interior/exterior finish
P11
Denver Art Museum (Denver/USA)
13,564
16,538
Titanium panel
9,000 EA
CNC machine
Exterior
2,100 mm × 800 mm
Exterior finish
39 months
CATIA, TEKLA
P12
Water Cube (Beijing/China)
90,000
52,000
ETFE
4,000 EA
CNC machine and pressure
Exterior
Diameter-7,500 mm Circle
Steel exterior finish
50 months
Rhino, 3D MAX, Microstation
P13
Bird’s Nest (Beijing/China)
260,000
38,50053,000
ETFEPTFE
884 EA1,044 EA
CNC machine and pressure
Exterior
Steel exterior finish
46 months
TEKLA
P14
Basra Sports City (Basra/Iraq)
65,000
GFRP
560 EA
Mold
Exterior
Length: 300,000 mm
Exterior finish
53 months
CATIA, TEKLA
P15
Louis Vuitton Foundation (Paris/France)
11,000
13,5009,000
ConcreteGlass
19,000 EA3,600 EA
CNC machine and MSV
Exterior
3,000 mm × 1,500 mm1,500 mm × 400 mm
Exterior finish
74 months
CATIA
P16
Louisiana State Museum and Sports Hall of fame (Natchitoches/USA)
28,000
1,380
Cast Stone panel
1,150 EA
CNC machine
Interior/exterior
2,000 mm × 500 mm
Interior/exterior finish
Navisworks
P17
Hangzhou Sports Park Stadium (Hangzhou/China)
400,000
15,000
AL. Panel
55 EA
CNC machine
Exterior
Height: 12 m–18 m
Exterior finish
84 months
Grasshopper
P18
Perot Museum of Nature and Science (Dallas/USA)
180,000
9,300
Concrete steel
700 EA8,400 EA
CNC machine and mold
Exterior
9,200 mm × 2,400 mm
Exterior finish
31 months
REVIT
P19
Phoenix Biomedical Campus: Health Sciences Education Building (Phoenix/USA)
24,898
8,910
Copper panel
6,000 EA
Press brake-punch-and-die machine
Exterior
3,300 mm × 300/450/760 mm
Exterior finish
27 months
REVIT
P20
Zlote Tarasy (Warszawa/Poland)
205,000
10,240
GlassSteel
4,788 EA7,123 EA
CNC machine
Exterior
2.14㎡ per panel
Exterior finish
52 months
P21
Weltstadthaus (Cologne/Germany)
14,400
4,900
Glass
6,800 EA
CNC machine
Exterior
0.72㎡ per a panel
Exterior finish
72 months
P22
BMW Welt (Munich/Germany)
16,500
8,000
Glass
4,500 EA
CNC machine
Interior/exterior
2.22㎡ per a module
Interior/exterior finish
56 months
Nemetschek Allplan
P23
Museo Soumaya (Mexico City/Mexico)
16,000
Steel
16,000 EA
CNC machine
Exterior
630 mm hexagon
Exterior finish
38 months
CATIA
P24
O-14 tower (Dubai/UAE)
28,000
Concrete
CNC machine and mold
Exterior
Exterior finish
48 months
Rhino, SAP2000
P25
Qatar National Museum (Doha/Qatar)
47,000
120,000
GFRC
75,000 EA
Mold
Exterior
400 m × 250 m per disc
Exterior finish
72 months
CATIA
P26
University of technology Sydney (Sydney/Australia)
16,030
5,594
Customized brick
320,000 EA
Mold
Exterior
Brick: 76 mm × 110 mm × 230 mm
Exterior finish
24 months
REVIT
P27
Benz Museum (Stuttgart/Germany)
16,500
6,1715,289
GlassAL. Panel
1,800 EA1,000 EA
Mold
Exterior
Exterior finish
36 monthsA CNC machine was used to produce AL. panels, AL. bars, wood panels, titanium panels, and molds, and the members were directly manufactured through cutting, welding, and milling. Materials such as concrete panels, UHPC, and customized bricks were produced into members using an irregular-shaped formwork manufactured with a CNC machine. For a unique material such as ETFE, members are produced using pressure. AL. panels were produced using conventional materials with the latest machine multipoint stretching forming (MDSF) machine depending on the design. High-end software such as CATIA, which can minimize the error range in the production, was found to be used frequently for digital fabrication to ensure the quality of the irregular-shaped segments.


## 4.2. Positive and Negative Benefits of Using Digital Fabrication

Table3 summarizes the evaluation results of the benefits of digital fabrication for construction project management obtained using 10 success criteria. The benefits of digital fabrication for construction project management were evaluated by subtracting the negative benefits from the positive benefits in order to obtain a score for each case study. This is shown in the score column in Table 3.Table 3
Positive and negative benefits of using digital fabrication on selected cases.
Project
Integ.
Scope
Time
Cost
Qual.
Org.
Com.
Risk
Soft.
Mat.
Score
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
+
−
P1
−1
1
−1
1
0
P2
1
1
1
1
4
P3
1
−2
2
1
1
2
5
P4
1
1
P5
1
1
1
3
P6
2
1
−2
2
1
1
−1
1
1
6
P7
1
1
−2
1
1
2
4
P8
2
1
−1
2
1
1
6
P9
−1
1
1
1
P10
1
1
P11
1
1
−2
1
−1
2
2
P12
2
−1
1
1
1
4
P13
1
−2
2
1
2
4
P14
−2
2
1
1
P15
1
2
2
2
7
P16
1
1
1
1
1
5
P17
−1
−1
1
−1
P18
1
1
1
1
4
P19
1
1
P20
−1
−1
P21
1
−1
−1
−1
P22
1
−2
2
2
3
P23
1
−1
1
1
2
P24
1
1
−1
1
2
P25
−2
1
1
1
1
P26
2
−1
1
3
2
−1
2
8
P27
2
2
Total
17
0
4
0
7
−6
1
−21
26
0
5
−1
3
0
7
−3
20
−1
16
0
74
Average
0.63
0.00
0.15
0.00
0.26
−0.22
0.04
−0.78
0.96
0.00
0.19
−0.04
0.11
0.00
0.26
−0.11
0.74
−0.04
0.59
0.00
2.74The focus of evaluation was not on how effectively each case study used digital fabrication but on highlighting the positive benefits over the negative benefits. Therefore, the values in the score column in Table3 do not serve as an index to determine the success of a project. These values simply indicate how many success criteria were mentioned positively and negatively from the secondary data of projects in the case studies. For example, case study P17 (Hangzhou Sports Park Stadium) expressed a negative experience owing to its challenges or difficulties with respect to time and cost, while a positive experience was observed in terms of material caused by achieving good quality irregular-shaped segments. Case study P20 (Zlote Tarasy) presented a negative experience in applying digital fabrication owing to its challenges or difficulties in terms of cost. Case study P21 (Weltstadthaus Cologne) expressed a negative experience in applying digital fabrication owing to its challenges or difficulties in terms of time and organization, while a positive experience was seen in terms of integration from digital fabrication. While the subtotal score of case studies P17, P20, and P21 was “−1,” this neither implies that introducing digital fabrication created losses in terms of construction project management nor that they were failed projects. Furthermore, the scores of positive and negative benefits for the case studies were not combined for each success criterion but divided into two separate columns (positive benefits and negative benefits), as listed in Table 3. This approach showed the success criteria that appeared more frequently as a positive element, which were challenges to be tackled, and what type of problems they had.


## 4.3. Success Criteria Ranking of Using Digital Fabrication

Each success criterion was defined with the frequency of occurrence for positive and negative benefits (Table4) and was ranked according to the summation of total instances and the total number of projects for positive benefits. Moreover, the total instances and total number of projects for negative benefits were shown together. An approach for quantifying the number of projects in which a success criterion had an influence as a positive benefit is fundamentally conservative [37]. In some cases, a success criterion was mentioned once in a positive manner and once in a negative manner. In such a situation, the success criteria were not counted as projects that had a positive effect (or negative), regardless of the impact of the project on the outcome. For example, on the Louis Vuitton Foundation, described by AIA TAP BIM Award, the integration success criterion was counted once as positive for the “Integration of construction modifications in the 3D model” and the quality success criterion was counted once as positive for the “Construction quality was monitored with on-site with laser equipment, and round-tripped back into the model [57].”Table 4
Success criteria ranking of using digital fabrication.
Success criterion
Positive benefit
Negative benefit
Total instances
Total number of projects
% of total projects
Total instances
Total number of projects
% of total projects
Quality increase or control
26
17
62.96
0
0
0.00
Software issues
20
16
59.26
1
1
3.70
Integration improvement
17
13
48.15
0
0
0.00
Material improvement
16
13
48.15
0
0
0.00
Negative risk reduction
7
5
18.52
3
3
11.11
Time reduction or control
7
7
25.93
6
5
18.52
Organization improvement
5
4
14.81
1
1
3.70
Scope clarification
4
4
14.81
0
0
0.00
Communication improvement
3
3
11.11
0
0
0.00
Cost reduction or control
1
1
3.70
21
14
51.85


### 4.3.1. Quality Success Criterion

There were a total of 26 instances of positive benefits in terms of quality increase or control from applying digital fabrication in 17 (63%) projects; the negative benefits were not observed. Digital fabrication can evaluate constructability starting from the design stage to allow optimum design, as well as use latest equipment such as a CNC machine, MDSF, and MSV that allow precise production and minimize error down to the millimeter range to achieve the quality required for construction projects. Case study P25 (National Museum of Qatar) included quality standards for irregular-shaped segments in the request for proposal (RFP) [58–61]. This document includes “design and engineering methodology,” “design optimization,” “fabrication of panels,” and “methodology of survey works” for irregular-shaped segments.


### 4.3.2. Software Issues Success Criterion

Positive benefits in terms of software issues from implementing digital fabrication were mentioned in 20 instances in 16 (59%) projects; a negative benefit was observed in one instance owing to the lack of experience in high-end software programming. Digital fabrication executes design, manufacture, and construction based on 3D models. Thus, software was used to generate 3D models in all studied projects. Most projects found positive benefits from using high-end software such as CATIA and TEKLA because it minimized error ranges in the manufacturing of irregular-shaped segments. In addition, a positive benefit of being able to swiftly and continuously provide necessary manufacturing information to the manufacturers by obtaining tens of thousands of 2D manufacturing blueprints from 3D models in a short period of time was observed [62]. Furthermore, collaboration, clash detection, and supply calculation were possible using 3D models. Although high-end software can support global collaboration systems based on server networks [63], the applicability is not up to par. This is because not all participants in the supply chain related to digital fabrication have the resources to use high-end software.


### 4.3.3. Integration Success Criterion

Positive benefits in terms of integration improvement from applying digital fabrication were seen in 17 instances in 13 (48%) projects; negative benefits were not indicated. The integration process of increasing productivity by optimizing different and individually designed members from simultaneously considering design, manufacture, and construction is crucial for irregular-shaped buildings. Decisions on member size and production unit that consider materials and production methods were made by optimizing the design of irregular-shaped buildings. The design optimization results for irregular-shaped segments for case study P8 (KEB Hana Bank, Samsung-dong, Seoul) are shown in Figure2 [64]. Irregular-shaped segments can increase the construction cost or affect the construction period in the case of many types of formwork being presented according to unit size, and thus increasing the manufacturing time of the FRP formwork. Projects in the case studies minimized the number of mold types for formwork from 12 in the initial design to 8 through design optimization. This allowed manufacture and construction to be completed within the project period.Figure 2
Design optimization for exterior cladding. (a) Original design with 12 types of formwork and (b) optimized design with 8 types of formwork.
(a)
(b)


### 4.3.4. Material Success Criterion

Positive benefits in terms of material improvement from applying digital fabrication were seen in 16 instances in 13 (48%) projects; negative benefits were not observed. Unlike conventional regular-shaped buildings constructed with traditional materials, latest materials such as UHPC, ETFE, and GRCP were applied to irregular-shaped buildings with digital fabrication, which allowed various and complex exterior envelopes. The members for irregular-shaped buildings were produced using manufacturing equipment such as a CNC machine, MDSF, MSV, and pressure using 2D manufacturing blueprints obtained through 3D models. This helps overcome the limitations of conventional construction materials. Moreover, AL. panels or copper panels that have been constantly used in the construction industry can be manufactured into three-dimensional panels depending on the design using manufacturing equipment such as press brake punches and dies tools. The irregular-shaped formwork was manufactured at a factory using a CNC machine for exposed concrete or concrete panel materials for complex shapes, and then, members were produced by placing and curing the material. In irregular-shaped buildings, the positive benefits related to quality, software issues, and integration from applying digital fabrication is inevitably associated with new material, new design, and production method.


### 4.3.5. Risk Success Criterion

Positive benefits in terms of negative risk reduction from applying digital fabrication were seen in 7 instances in 5 (19%) projects; negative benefits were seen in 3 instances in 3 (11%) projects. Applying digital fabrication allows reducing risk that can arise during design, manufacture, and construction stages using 3D models to generate simulations and mock-ups. However, since irregular-shaped buildings are not considered as standard construction projects, discrepancies between initial plans and execution are inevitable, which becomes a potential risk. Currently, performance data or analysis data on the case studies of irregular-shaped buildings are not readily available, which makes it difficult to proactively avoid potential risks compared to typical construction projects [11]. Nonetheless, there were more instances of expressing positive benefits in terms of risk reduction from applying digital fabrication to irregular-shaped buildings.


### 4.3.6. Time Success Criterion

Positive benefits in terms of time reduction or control from applying digital fabrication were seen in 7 instances in 7 (26%) projects; negative benefits were seen in 6 instances in 5 (19%) projects. Applying digital fabrication not only requires managing on-site construction but also additional off-site construction (e.g., fabrication factory). Moreover, managing new manufacturers introduced to the project because of the new manufacturing methods and consequential new supply chains becomes necessary. Such occurrences in the studied projects were either dealt with by going through trial and error in the early stages of a project before slowly learning to manage this as the project progressed or showed benefits that depended on management skills obtained from experience and skills gained throughout the project. When such management skills are put to use, great benefits, incomparable to that from the conventional production method can be achieved in the time reduction or control aspects. If not, a great amount of time may be consumed.


### 4.3.7. Human Resource Success Criterion

Positive benefits in terms of organization improvement from applying digital fabrication were seen in 5 instances in 4 (15%) projects. Negative benefits were seen in 1 instance in 1 (3%) project. The application of digital fabrication is very similar to the concept of lean construction. New labor, material or resources, and equipment can be allocated in the right location with JIT (just-in-time) and increase productivity. Construction involving digital fabrication requires prefabrication in a factory and transporting to a site before installation takes place. This process is different from that of a conventional construction production method, which may result in negative benefits in terms of improving and integrating processes due to inexperience in digital fabrication.


### 4.3.8. Scope Success Criterion

Positive benefits in terms of scope clarification from applying digital fabrication were seen in 4 instances in 4 (15%) projects; negative benefits were not observed. Digital fabrication requires defining the segments of the building, in which this production method is being applied to beforehand. Furthermore, the scope of work for design, manufacture, and construction firms responsible for digital fabrication and the scope of work and allocated tasks between initial production firms and new suppliers must be clearly defined.


### 4.3.9. Communication Success Criterion

Positive benefits in terms of communication improvement from applying digital fabrication were seen in 3 instances in 3 (11%) projects; negative benefits were not observed. Design, manufacture, and construction processes were established based on 3D models for irregular-shaped segments that required digital fabrication. Moreover, construction project participants carried out communication, collaboration, and arbitration using 3D models, which increased the accuracy of the design. The positive benefits from obtaining tens of thousands 2D manufacturing blueprints from 3D models were already dealt above with software issues, which seemed to have caused the low number of instances of positive benefits for communication improvement. All blueprints produced during a construction project serve as the most primary method of communication. Therefore, the study results cannot solely stand as a premise for digital fabrication with meager positive benefits for communication improvement.


### 4.3.10. Cost Success Criterion

Positive benefits in terms of cost reduction or control from applying digital fabrication were seen in 1 instance in 1 (4%) project; however, negative benefits were expressed in 21 instances in 14 (52%) projects. This was due to the burden of additional costs inevitably encountered when new technology is introduced in a construction project. New labor, software, and equipment are certainly required when digital fabrication is applied. Using the conventional construction method for irregular-shaped buildings can result in simultaneous loss in time, cost, and quality, which are important qualities in construction project management. On the contrary, construction project management that considers positive benefits of using digital fabrication not only allows attaining a certain quality for irregular-shaped segments but also allows reduction in time and cost.


## 4.3.1. Quality Success Criterion

There were a total of 26 instances of positive benefits in terms of quality increase or control from applying digital fabrication in 17 (63%) projects; the negative benefits were not observed. Digital fabrication can evaluate constructability starting from the design stage to allow optimum design, as well as use latest equipment such as a CNC machine, MDSF, and MSV that allow precise production and minimize error down to the millimeter range to achieve the quality required for construction projects. Case study P25 (National Museum of Qatar) included quality standards for irregular-shaped segments in the request for proposal (RFP) [58–61]. This document includes “design and engineering methodology,” “design optimization,” “fabrication of panels,” and “methodology of survey works” for irregular-shaped segments.


## 4.3.2. Software Issues Success Criterion

Positive benefits in terms of software issues from implementing digital fabrication were mentioned in 20 instances in 16 (59%) projects; a negative benefit was observed in one instance owing to the lack of experience in high-end software programming. Digital fabrication executes design, manufacture, and construction based on 3D models. Thus, software was used to generate 3D models in all studied projects. Most projects found positive benefits from using high-end software such as CATIA and TEKLA because it minimized error ranges in the manufacturing of irregular-shaped segments. In addition, a positive benefit of being able to swiftly and continuously provide necessary manufacturing information to the manufacturers by obtaining tens of thousands of 2D manufacturing blueprints from 3D models in a short period of time was observed [62]. Furthermore, collaboration, clash detection, and supply calculation were possible using 3D models. Although high-end software can support global collaboration systems based on server networks [63], the applicability is not up to par. This is because not all participants in the supply chain related to digital fabrication have the resources to use high-end software.


## 4.3.3. Integration Success Criterion

Positive benefits in terms of integration improvement from applying digital fabrication were seen in 17 instances in 13 (48%) projects; negative benefits were not indicated. The integration process of increasing productivity by optimizing different and individually designed members from simultaneously considering design, manufacture, and construction is crucial for irregular-shaped buildings. Decisions on member size and production unit that consider materials and production methods were made by optimizing the design of irregular-shaped buildings. The design optimization results for irregular-shaped segments for case study P8 (KEB Hana Bank, Samsung-dong, Seoul) are shown in Figure2 [64]. Irregular-shaped segments can increase the construction cost or affect the construction period in the case of many types of formwork being presented according to unit size, and thus increasing the manufacturing time of the FRP formwork. Projects in the case studies minimized the number of mold types for formwork from 12 in the initial design to 8 through design optimization. This allowed manufacture and construction to be completed within the project period.Figure 2
Design optimization for exterior cladding. (a) Original design with 12 types of formwork and (b) optimized design with 8 types of formwork.
(a)
(b)


## 4.3.4. Material Success Criterion

Positive benefits in terms of material improvement from applying digital fabrication were seen in 16 instances in 13 (48%) projects; negative benefits were not observed. Unlike conventional regular-shaped buildings constructed with traditional materials, latest materials such as UHPC, ETFE, and GRCP were applied to irregular-shaped buildings with digital fabrication, which allowed various and complex exterior envelopes. The members for irregular-shaped buildings were produced using manufacturing equipment such as a CNC machine, MDSF, MSV, and pressure using 2D manufacturing blueprints obtained through 3D models. This helps overcome the limitations of conventional construction materials. Moreover, AL. panels or copper panels that have been constantly used in the construction industry can be manufactured into three-dimensional panels depending on the design using manufacturing equipment such as press brake punches and dies tools. The irregular-shaped formwork was manufactured at a factory using a CNC machine for exposed concrete or concrete panel materials for complex shapes, and then, members were produced by placing and curing the material. In irregular-shaped buildings, the positive benefits related to quality, software issues, and integration from applying digital fabrication is inevitably associated with new material, new design, and production method.


## 4.3.5. Risk Success Criterion

Positive benefits in terms of negative risk reduction from applying digital fabrication were seen in 7 instances in 5 (19%) projects; negative benefits were seen in 3 instances in 3 (11%) projects. Applying digital fabrication allows reducing risk that can arise during design, manufacture, and construction stages using 3D models to generate simulations and mock-ups. However, since irregular-shaped buildings are not considered as standard construction projects, discrepancies between initial plans and execution are inevitable, which becomes a potential risk. Currently, performance data or analysis data on the case studies of irregular-shaped buildings are not readily available, which makes it difficult to proactively avoid potential risks compared to typical construction projects [11]. Nonetheless, there were more instances of expressing positive benefits in terms of risk reduction from applying digital fabrication to irregular-shaped buildings.


## 4.3.6. Time Success Criterion

Positive benefits in terms of time reduction or control from applying digital fabrication were seen in 7 instances in 7 (26%) projects; negative benefits were seen in 6 instances in 5 (19%) projects. Applying digital fabrication not only requires managing on-site construction but also additional off-site construction (e.g., fabrication factory). Moreover, managing new manufacturers introduced to the project because of the new manufacturing methods and consequential new supply chains becomes necessary. Such occurrences in the studied projects were either dealt with by going through trial and error in the early stages of a project before slowly learning to manage this as the project progressed or showed benefits that depended on management skills obtained from experience and skills gained throughout the project. When such management skills are put to use, great benefits, incomparable to that from the conventional production method can be achieved in the time reduction or control aspects. If not, a great amount of time may be consumed.


## 4.3.7. Human Resource Success Criterion

Positive benefits in terms of organization improvement from applying digital fabrication were seen in 5 instances in 4 (15%) projects. Negative benefits were seen in 1 instance in 1 (3%) project. The application of digital fabrication is very similar to the concept of lean construction. New labor, material or resources, and equipment can be allocated in the right location with JIT (just-in-time) and increase productivity. Construction involving digital fabrication requires prefabrication in a factory and transporting to a site before installation takes place. This process is different from that of a conventional construction production method, which may result in negative benefits in terms of improving and integrating processes due to inexperience in digital fabrication.


## 4.3.8. Scope Success Criterion

Positive benefits in terms of scope clarification from applying digital fabrication were seen in 4 instances in 4 (15%) projects; negative benefits were not observed. Digital fabrication requires defining the segments of the building, in which this production method is being applied to beforehand. Furthermore, the scope of work for design, manufacture, and construction firms responsible for digital fabrication and the scope of work and allocated tasks between initial production firms and new suppliers must be clearly defined.


## 4.3.9. Communication Success Criterion

Positive benefits in terms of communication improvement from applying digital fabrication were seen in 3 instances in 3 (11%) projects; negative benefits were not observed. Design, manufacture, and construction processes were established based on 3D models for irregular-shaped segments that required digital fabrication. Moreover, construction project participants carried out communication, collaboration, and arbitration using 3D models, which increased the accuracy of the design. The positive benefits from obtaining tens of thousands 2D manufacturing blueprints from 3D models were already dealt above with software issues, which seemed to have caused the low number of instances of positive benefits for communication improvement. All blueprints produced during a construction project serve as the most primary method of communication. Therefore, the study results cannot solely stand as a premise for digital fabrication with meager positive benefits for communication improvement.


## 4.3.10. Cost Success Criterion

Positive benefits in terms of cost reduction or control from applying digital fabrication were seen in 1 instance in 1 (4%) project; however, negative benefits were expressed in 21 instances in 14 (52%) projects. This was due to the burden of additional costs inevitably encountered when new technology is introduced in a construction project. New labor, software, and equipment are certainly required when digital fabrication is applied. Using the conventional construction method for irregular-shaped buildings can result in simultaneous loss in time, cost, and quality, which are important qualities in construction project management. On the contrary, construction project management that considers positive benefits of using digital fabrication not only allows attaining a certain quality for irregular-shaped segments but also allows reduction in time and cost.


## 5. Discussion

This study collected secondary data from the AIA BIM TAP Awards, the Korean BIM journals, and the Korean BIM award, various publications from conferences, websites of corresponding projects, reports, and data from actual project progress reports from professional construction firms. However, challenges persisted in discovering in-depth data for every project, and it was difficult to compile secondary data owing to discrepancies in the amount and quality of data attainable for each project. Further, while it was relatively easy to obtain data on generally well-known irregular-shaped buildings and projects that had now been completed for years, it was impossible to obtain these data for the latest irregular-shaped buildings. Nonetheless, professional construction firms with direct experience in implementing digital fabrication were sought out to supplement the incomplete data in order to improve the quality of secondary data.In order to evaluate the benefits of applying digital fabrication for construction projects, the knowledge areas of the PMBOK were used. The success criteria on procurement management and stakeholder management were omitted because they were difficult to evaluate using the collected secondary data. It was difficult to find such terms in the secondary data because digital fabrication was still not universally implemented in the construction industry. Instead, software issues and material improvement were added as criteria to evaluate the benefits of digital fabrication for construction project management.Content analysis was performed to investigate the degree of satisfaction for the success criteria of each project. With this approach, it is possible to see which success criterion appears more times as a positive factor and which ones appear as challenges or problems. In the previous research, Bryde analyzed the impact of BIM on construction projects through the similar research method, while this study analyzed the impact of digital fabrication on construction projects. BIM supports construction as a virtual model and process, but digital fabrication is directly linked to the design, fabrication, and construction of the irregular-shaped buildings. Therefore, the analyzed results are more reliable. Among the positive benefits of digital fabrication on construction project management, quality increase and control appeared in the highest number of projects (17 out of 27 projects) at the highest frequency (26 instances). However, among the negative benefits that were mentioned as challenging or causing difficulties of digital fabrication on construction project management, cost reduction and control appeared in the highest number of projects (14 out of 27 projects) at the highest frequency (21 instances). But it does not mean that the use of digital fabrication was overall negative.


## 6. Conclusion

The purpose of evaluation in this study was not to find the project that used digital fabrication in the most effective way, but to find success criteria that should be considered and managed relatively more when managing projects wherein digital fabrication is applied to irregular-shaped buildings. The average score for 27 projects in the score column in Table3 was 2.740. As shown in Figure 3, there are 13 projects with a higher score than the average.Figure 3
Scores on positive and negative benefits of using digital fabrication.Among these, interviews with professionals revealed that compared to other projects, projects P15 (Louis Vuitton Foundation, Paris) and P26 (University of Technology, Sydney), each with a score of 7 and 8, were examples that could be referred to as the standard application of digital fabrication or quality achievement for applying digital fabrication in the future.Production methods employed by the construction industry are not as diverse as the currently employed manufacturing methods. However, investigating various case studies on irregular-shaped buildings showed that applying digital fabrication had significant positive benefits for construction project management. The limitation of this study is that we analyzed the advantages of digital fabrication by using highly generalized PMBOK. Future research will need to develop performance indicators that reflect the characteristics of digital fabrication technology. In particular, quantitative cost factors need to be considered.



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*Source: 3721397-2019-01-20.xml*