Project Benefits of Digital Fabrication in Irregular-Shaped Buildings

,e 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. ,is 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.


Introduction
e 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].
is 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 irregularshaped buildings to construct the complicated structures [15].Digital fabrication represents innovative, computercontrolled 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].
e number of studies analyzing the effects of digital fabrication on sustainability is gradually increasing [22][23][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.us, 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 irregularshaped buildings implemented with digital fabrication are investigated to quantitatively evaluate the benefits of digital fabrication for construction project management.

Trend of Manufacturing Paradigms.
e 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]. is 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.is trend closely resembles mass customization, but the niches are different in nature.erefore, 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.is manufacturing method leads many industries to the concept of direct digital manufacturing (DDM).
e 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].erefore, 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.erefore, 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.

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,

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Advances in Civil Engineering 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 Figure 1 [33].It is evident that sustainability has conjoined with cost and evolved as a main decision-making factor in manufacturing [4].
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, reallife 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.

Limitation of Assessment for Benefits of Digital
Fabrication.Sustainability is the latest main interest in many industries [38,39].e 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][44][45].
However, studies evaluating the sustainability aspects of particular technologies of AM and DDM are very limited in terms of their findings [46][47][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 irregularshaped 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].
us, this study aims at evaluating the benefits of using digital fabrication for construction project management through data collection of irregular-shaped buildings.
e research method for this task is explained in the next section.

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].e secondary data of this study were collected from projects using digital fabrication utilizing innovative computer control processes and technologies.e sources of secondary data on overseas projects were collected through the AIA BIM TAP Awards Advances in Civil Engineering (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 rms and construction rms of each project, and manufacturing rms that directly manufactured irregular-shaped members. is 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 bene ts 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 signi cant bene ts to construction projects.

Success Criteria.
Evaluation criteria were established to analyze data on the types of bene ts introduced due to digital fabrication, or if any bene ts were introduced at all. is 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 e ective scope management and communications.
ese success criteria re ected the idea of multidimensional success of construction projects by including not only the projects themselves but also project management [55].e success criteria can also be referred to as "critical success factors" or "key results areas" in project management [37].
e success criteria were classi ed 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 bene ts of digital fabrication for construction projects [56].ese 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 bene ts of digital fabrication on irregular-shaped buildings with those expected from a project manager.

Content Analysis.
It is very di cult to objectively evaluate the impact of digital fabrication on construction projects.However, researchers have di culty in securing the expert pool by applying digital fabrication to the irregularshaped 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 bene ts of BIM on construction projects through content analysis of secondary data [37].
A content analysis process suggested by Harris was carried out to con rm the positive and negative bene ts of digital fabrication for construction projects using secondary data for each irregular-shaped building.e unit of analysis adopted was the "phrase," which may vary from a single word to a whole sentence [52].e phrase in this study refers to "project bene t" [37].e phrase associated with "project bene t" 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.e projects were then organized using the added score for each of them (positive bene ts minus negative bene ts).
is is not an attempt to nd which case demonstrates the 4 Advances in Civil Engineering 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." is 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.

Assessment of Project Benefits of Digital Fabrication
4.1.Case Description.Table 2 summarizes the study cases where digital fabrication was applied to the construction of irregular-shaped buildings.e total area, area of irregularshaped 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 irregularshaped segments comprising an area of 10,000 m 2 and 4 projects had an area of 50,000 m 2 .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.e 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 fiberreinforced concrete (GFRC), and ultrahigh performance concrete (UHPC).e production method for irregularshaped segments differed according to material.
A 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.

Positive and Negative Benefits of Using Digital Fabrication.
Table 3 summarizes the evaluation results of the benefits of digital fabrication for construction project management  Advances in Civil Engineering Org. Com.

Risk
Soft.
Mat. e 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.is is shown in the score column in Table 3.

Score
e focus of evaluation was not on how effectively each case study used digital fabrication but on highlighting the positive benefits over the negative benefits.erefore, the values in the score column in Table 3 do not serve as an index to determine the success of a project.ese 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.
is 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.

Success Criteria Ranking of Using Digital Fabrication.
Each success criterion was defined with the frequency of occurrence for positive and negative benefits (Table 4) 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]."

Quality Success Criterion.
ere 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][59][60][61]. is document includes "design and engineering methodology," "design optimization," "fabrication of panels," and "methodology of survey works" for irregular-shaped segments.

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.us, 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. is is because not all participants in the supply chain related to digital fabrication have the resources to use high-end software.

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.e 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 irregularshaped buildings.
e design optimization results for irregular-shaped segments for case study P8 (KEB Hana Bank, Samsung-dong, Seoul) are shown in Figure 2 [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 Advances in Civil Engineering design to 8 through design optimization.
is allowed manufacture and construction to be completed within the project period.

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 regularshaped 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.
e 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.is 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.
e 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.

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.

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.e 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.is 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.

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.

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.e 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.
erefore, the study results cannot solely stand as a premise for digital fabrication with meager positive benefits for communication improvement.

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.
is 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 irregularshaped 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.

Discussion
is 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 irregularshaped 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.e 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 Advances in Civil Engineering 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.erefore, the analyzed results are more reliable.Among the positive bene ts 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 bene ts that were mentioned as challenging or causing di culties 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.

Conclusion
e purpose of evaluation in this study was not to nd the project that used digital fabrication in the most e ective way, but to nd success criteria that should be considered and managed relatively more when managing projects wherein digital fabrication is applied to irregular-shaped buildings.
e average score for 27 projects in the score column in Table 3 was 2.740.As shown in Figure 3, there are 13 projects with a higher score than the average.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 signi cant positive bene ts for construction project management.e 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 re ect the characteristics of digital fabrication technology.In particular, quantitative cost factors need to be considered.

Figure 1 :
Figure1: Manufacturing decision-making attributes in the 1990s and at the present time[27].

Figure 2 :
Figure 2: Design optimization for exterior cladding.(a) Original design with 12 types of formwork and (b) optimized design with 8 types of formwork.

Table 1 :
Success criteria based on PMBOK knowledge area.

Table 2 :
Details of cases.

Table 3 :
Positive and negative benefits of using digital fabrication on selected cases.

Table 4 :
Success criteria ranking of using digital fabrication.