1 Introduction

As building construction projects have become more complex and larger in magnitude, enhancing the interface between the design and construction has become more important for their successful completion (Kwon and Kim 2003). Most decisions in the pre-construction phase affect the construction performance (Pulaski and Horman 2005), and those impacts increase with the projects’ size. However, the traditional procurement approach tends to separate the design from the construction, which hinders contractors from providing designers with suggestions and feedback, based on their construction expertise during the design phase (Lam et al. 2006). In addition, many designers have indicated that failure to consider constructability is a major problem in the design process (Bae et al. 2006). This leads to increased waste, e.g., design changes and reworking in the construction stage, as well as losing opportunities for design enhancement (Motsa et al. 2008).

Thus, continuous efforts have been made to minimize the fragmentation between participants and to make better use of construction knowledge in the design process. The Construction Industry Institute published guidelines for implementing constructability programs (CII 1993), and Singapore introduced the Buildable Design Appraisal System for making more buildable and labor-efficient designs (Poh and Chen 2010). Several programs, e.g., design reviews, constructability reviews, and value engineering, have been introduced to enhance the design quality and project performance (Pulaski and Horman 2005; Park et al. 2009; Li et al. 2018).

Although these methods have led to improvements in project performance, they are relatively unsophisticated and inefficient and rely heavily on reviews. In addition, existing approaches tend not to consider the appropriate timing when applying knowledge or the level of detail for efficient decision-making in the design process (O’Connor and Miller 1995). This can result in productivity loss by frequent reworking at the design stage, as well as adversarial relationships among the participants. Thus, to utilize constructability knowledge effectively, the right information at the proper time should be provided to the design team. The information should also have appropriate levels of detail to enable its successful integration with specific design activities.

This study proposes a process model for integrating constructability activities (CA) into the design phase in high-rise concrete building construction. In this study, the CA focuses on the temporary work including facilities, equipment, and construction methods. This is because there have been lack of efforts and attempts to enhance the constructability of temporary work from the design phase, even though this can greatly affect the construction efficiency of permanent structures as well as cost and time during the construction phase. The model organizes activities for constructability improvements based on appropriate timing and detail levels. The proposed model considers the information-exchange efficiency and minimizes overlapping activities in the design process.

2 Literature Review and Methodology Overview

2.1 Constructability

The concept of constructability, which initially focused on productivity, was first studied in the United Kingdom in the 1970s. It has been developed into an integrated concept for each production phase, including planning, design, and construction, to improve the cost effectiveness and quality of the construction industry (Griffith and Sidwell 1995; Oh et al. 2002). The definition of constructability varies slightly from country to country, but the common concept is to foster efficient decision-making by fully reflecting construction knowledge and experience from the early stages of the project. As observed in Table 1, existing studies have focused on investigating constructability factors and proposing efficient methods for constructability improvement. However, the approaches do not consider the timing or level of detail in applying the CA for an effective decision-making process in the design phase.

Table 1 Literature review of constructability.
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2.2 Constructability Activities for Temporary Work

Lee et al. (2017a) investigated the CA related to temporary work for constructability improvement at the design phase in high-rise building construction. Based on questionnaires and statistical analyses, they derived 22 activities classified into five categories: (1) structural methods and surveying, (2) vertical transportation of resources, (3) space zoning, (4) water supply, and (5) temporary facilities and services (Table 2). However, it is difficult to apply the activities in the design phase because no information is available on when the activity should be applied or who should be involved in carrying it out.

Table 2 Constructability activities for temporary work and regrouping for integration with design activities.
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Thus, Lee et al. (2017b) investigated the above matters through interviews with experts to effectively reflect the CA in the design process. Based on the similarity of execution subjects, applicable design stage, and characteristics of each activity, they presented 13 regrouped activities, shown in Table 2. In addition, 22 subdivided activities were provided, considering the work scope at each design stage. It allows appropriate levels of the CA to be applied at each design stage, which include schematic design, design development, and construction documentation.

For example, a regrouped activity “Construction methods for structures” includes three constructability activities: “Zoning for concrete placement,” “Rebar placing and splicing method,” and “Formwork operation method.” Following the subdivided activities, alternative construction methods are compared in the design-development stage, and the final method selection and construction planning are carried out in the construction documentation stage. In this study, we try to link those subdivided CA with specific design activities at each design stage.

2.3 Dependency Structure Matrix

In modeling the design process, there have been several ways such as critical path method and integration definition functional modeling. However, those methods have limitations on representing the precedence relationships between activities clearly or the repetitive activities. On the other hand, the Dependency Structure Matrix (DSM), proposed by Steward (1965), has been widely used as an effective tool for identifying information exchanges between activities and handling the iterative process (Steward 1965; 1981). Thus, this study uses the DSM methodology to create an efficient process for integrating the CA with design activities. It uses a square N × N matrix to represent the information-flow dependencies and sequences among N activities.

In the matrix, the information dependencies between activities are generally represented with an Χ mark in the off-diagonal cells according to the type of relationship between activities, as shown in Fig. 1 (Park et al. 2012; Ahn et al. 2013). For example, if activity B requires information from activity A to start and progress, the Χ mark lies at the intersection of column A and row B. In other words, the activities along the columns become “gives information to” and the activities along the rows become “needs information from.” When the marks are below the diagonal, it is called “feedforward”. It is called “feedback” when the marks are above the diagonal.

Fig. 1
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Types of relationship between activities and their representations in the DSM.

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To appropriately sequence the activities, the rows and columns in the matrix should be reordered. Partitioning the DSM means reordering the activities by moving the feedback marks below the diagonal and as close as possible to the diagonal. This minimizes the need for activities that use information assumptions and avoids the possibility of reworking because a mark’s distance from the diagonal roughly indicates the scope of the feedback (Browning 2001; DSM 2018). This study optimizes the information flows between the CA and design activities using a partitioning algorithm.

3 Process for Integrating Constructability with Design Activities Based on the DSM

3.1 Construction Design Activities

It is necessary to investigate the existing design process to reflect the constructability activities in the design phase. The construction design process can be generally divided into three stages: (1) schematic design (SD), (2) design development (DD), and (3) construction documentation (CD). In this study, the design activities classified into design disciplines (architectural, structural, mechanical and electrical (M&E), and fire/disaster prevention) at each design stage are derived from literature reviews (Kim 2005; Shon 2013; Kwon et al. 2016) and interviews with design experts (Table 3). In this study, design activities only include the activities affecting decision-making in the design process.

Table 3 Design activities at each design stage.
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At the schematic-design stage, architectural design concepts should be established to clarify the client’s requirements, and the basic system architecture of the building structure, M&E facilities, etc. should be reviewed. Starting from sketches and study models, the architect prepares a schematic building design and preliminary cost estimates. In the structural design, structural materials and systems are reviewed and compared. M&E systems are also reviewed based on rough load calculations.

The design-development stage involves finalizing the design and specifying major components, e.g., materials, preliminary structure, and general details. The M&E and fire-protection systems are also selected based on preliminary capacity calculations. During this stage, efficient coordination and information exchanges among participants become more important because numerous decisions should be made.

The construction-documentation stage completes the design to the optimal levels for bidding and construction. Detail drawings of all design disciplines are created. Construction documents include a complete set of architectural drawings, combined with structural and M&E drawings, specifications, and a final cost estimate.

3.2 Constructability Integration into the Design Phase

3.2.1 Dependency Relationship Analysis and DSM Application

To create the CA integration process, the information-dependency relationships between activities are firstly analyzed. In this study, the activities include both the 33 design activities in Table 3 and the 22 constructability activities (i.e., subdivided activities in Table 2). In this study, the constructability activities are to improve the efficiency of temporary work and equipment operation and to find optimal solutions by considering along with ease of construction for permanent structures. By applying these activities in the design process and reflecting into the drawings and specifications, inefficient project operations such as design changes and reworks are minimized at the construction phase. The dependency relationships also include information flows between design activities, between constructability activities, and between design and constructability activities. Thus, in this study, information dependencies among the activities are derived through iterative interviews and feedback from experts with over 20 years’ experience in both the design and construction fields. Table 4 shows the survey results of the precedence relationships among all 55 activities, along with the information dependencies.

Table 4 Analysis of precedence relationships among the activities.
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Once the activity DSM is formed, based on the activity list and precedence relationship in Table 4, the matrix is partitioned to reduce feedback, as shown in Fig. 2. In the partitioned DSM, shaded elements are the constructability activities, and different marks represent information flows between design activities (Χ mark), between constructability activities (● mark), and between design and constructability activities (◎ mark). Here, eight blocks (A–H) with interdependent relationships between activities have been identified; they have a relatively short cycle including two to three activities.

Fig. 2
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Partitioned dependency structure matrix.

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Most information exchanges between design and constructability activities occur during the design development stage (C–E, G blocks), which implies that the design team should actively cooperate with the construction experts at this stage to produce a better output. In contrast, no feedback loops appeared between the design and constructability activities in the construction-documentation stage, although 11 constructability activities exist; i.e., information flows sequentially between the design and construction teams. Blocks F and H show the interdependence between the constructability activities, which only requires simultaneous review and decision-making within the construction team.

During the schematic-design stage, a design activity “Review of structural materials (4)” has an interdependent relationship with a constructability activity “Discussions about separation plan (35)”. In high-rise building construction, the separation between the built and working zones can be discussed to enhance the business value, and requires the participation of the owner and construction experts for proper decision-making. Only after the preliminary building design is completed, the necessity review and discussion about the separation can be carried out. The structural materials should be reviewed at the same time because they can directly influence the necessity and economic feasibility.

In the design-development stage, a design activity “Preliminary capacity calculation and selection of M&E systems (17)” has a feedback loop with two constructability activities, “Comparison of alternatives for water supply (42), and electricity and lighting (43)”. The plans for M&E systems should be established with consideration for temporary water and electric power supplies during construction stage and switching plan to permanent systems. These constructability activities should also be conducted based on the capacity calculation and economic feasibility review, according to each alternative. For similar reasons, “Systems selection for fire/disaster prevention (18)” should be implemented with “Alternatives review of evacuation floors and routes (44)” by considering disaster occurrence and effective evacuation during construction stage. In addition, “Appropriate surveying methods and locations (40)” should be investigated to effectively monitor the column shortening and structural health while “Determining the preliminary structural systems (16)”.

3.2.2 Constructability Integration Process Based on Optimized Information Flows

Based on the information flows of the partitioned DSM in Fig. 2, a work process integrating the CA on temporary work with existing design activities is proposed, as shown in Fig. 3. The proposed work process clearly specifies the timing for applying the CA with appropriate levels of detail, considering the efficiency of the information exchange. Thus, it allows proper construction knowledge to be effectively utilized in the decision-making process during the design phase. It can also minimize productivity losses at the design stage through optimizing information transfers and exchanges among the activities.

Fig. 3
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Work process integrating constructability into the design phase.

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The proposed process model represents the relationship between the activities and related expertise for performing each activity. The project manager can recognize how each person collaborates with whom, based on the information dependency. The activities involved in the blocks (in Fig. 2) require close cooperation and the continuous exchange of information and ideas between the related design and construction teams, while one-way collaboration is enough for the other activities. Thus, the proposed model can facilitate efficient collaboration and communication among the working groups. Consequently, it enables a project team to address constructability issues at the appropriate time during the design process and contributes to enhancing the efficiency of the overall project operation in high-rise building construction.

4 Summary and Limitations

With the increasing number of high-rise building construction projects, utilizing construction knowledge and expertise during the design phase has a significant effect on the successful project completion. It enables the minimization of inefficiencies, e.g., design changes and reworking, and allows constructability improvements in the construction phase. Thus, this study proposed a process integrating constructability activities related to temporary work into the design phase for high-rise concrete buildings. The proposed model organized constructability activities based on appropriate timing considering the information flows of the existing design activities. As a result, the interdependence relationships between design and constructability activities were mostly occurred in the design development stage, implying that the design team during this stage needs active cooperation and information exchange with construction experts to make better design outputs. On the other hand, the construction documentation stage only required sequential information transfer between the design and constructability activities because major decisions should be made in preceding stages. The proposed process, as a useful mechanism to organize constructability issues, can help to utilize construction knowledge most effectively during the design decision-making. Consequently, it could contribute to improve the constructability by minimizing design changes and reworking at the construction stage, as well as enhancing the design quality.

The limitations of this study are as follows. First, this study focused on constructing an efficient process for utilizing the CI in each design stage. However, the quantitative effectiveness of applying the proposed process was not fully investigated, even though the process was made through iterative review from both design and construction experts. Thus, it is necessary to verify how useful the proposed activities and processes are in terms of reducing the reworking, time, cost, etc. Second, the proposed model specified the timing and related participants for each activity and interrelationships among activities. Although it is helpful to recognize the decision-making points and necessary participants, the simple introduction of different participants at each decision-making point is not enough to take full advantage of the proposed process. Further research is required to determine how best to organize the project participants and use information at each design point to optimize the decision-making process.