KIEAE Journal

Research on the empirical construction of new Hanok style social welfare facilities and the development of tangible models¹⁾ was carried out to lay the foundation for the modern succession of traditional Korean architecture and convergence technology with the aim of disseminating new Hanok style buildings and securing practical research and development (R&D) technologies. After completing the second phase of the new Hanok style demonstration project (2014~2016), the third-stage demonstration project (2017~2021) is currently in progress. The new Hanok style demonstration is the phase in which the effectiveness of the building is verified through policy proposals and improvement measures for the dissemination of new Hanok style public buildings; it is a process in which the possibility of dissemination is evaluated through legal matters such as the ordinance and administrative procedures supporting Hanok, with great implications for the field of technical research. Particularly, the new Hanok R&D applied to public buildings is a new architectural style that combines traditional wooden structures and modern construction methods, which can be evaluated as a technology development field with a significant ripple effect on the wooden construction market as well as the social and cultural meaning of traditional heritage. Furthermore, considering that 72% of Hanok buildings (traditional and other Hanok buildings including cultural assets and historic buildings) constructed in South Korea are ordered by the public sector, the ripple effect of the New Hanok style public building model development and demonstration project at the national R&D level is expected to become the driving force to lead the market.

This study aims to analyze the scope of the empirical application of technology and specific cases in three public buildings constructed based on the new applied technology of the new Hanok R&D research as well as the Children's Forest Experience Center in Hongseong, a social welfare facility to be completed in 2021; it also aims to discuss the potential for the development of application technology considering the review of the prototype technology application and the efficiency of on-site construction. This study intends to provide the basic data for evaluating utilities such as the constructability, economic feasibility, aesthetics, and usability of the new Hanok style technology applied to public buildings, and for discussing the scalability in terms of region and purpose of application.

For this study, the results of the second phase demonstration projects [1] of the Public Daycare Center in Sunchang (2015), the Agricultural Fair Venue in Naju (2016), and the Community Center in Eunpyeong (2016), where the concept of the new Hanok style public building was first applied, and the third phase demonstration project [2], the Children's Forest Experience Center in Hongseong (2021), were reviewed, and the main contents were as follows.

First, the application range and reflection rate of the existing R&D technology in each case were compared. Among the R&D technologies, the unapplied technologies were identified and their problems were analyzed.

Second, the proposed design and construction technology and on-site application technology were analyzed [3] at the time of the demonstration for each phase. The degree and characteristics of the R&D technologies, such as the development of wood processing technique and the use of new materials, newly introduced and applied in the third phase demonstration project (Children's Forest Experience Center in Hongseong) were analyzed.

For this study, the existing research reports [4] and papers related to the second phase demonstration projects were reviewed. To examine the application and characteristics of the R&D technologies in the third stage demonstration project, the above reference data and design drawings for the demonstration were analyzed. Table 1. lists the site of the demonstration projects.

Hanok technology development R&D was a government-led technology development project organized by KAIA (2009 to 2016) which was followed by a tangible model study considering the expansion of application aand dissemination of the R&D technology that had already been developed through the 10m-class Large Space Hanok Design and Construction Technology Development project in 2017.

The construction of the new Hanok style building is economical with 1/3 ³⁾ of the cost of the traditional wooden Hanok. The construction performance has been reported to be comparable to the general construction cost of modern buildings. The new Hanok technology R&D is carried out to ensure structural safety and durability for maintenance. Through the demonstration projects from residential buildings to public and social welfare facilities, the technological prowess was exhibited with increased reliability [6].

In 2009, the first phase of the new Hanok technology R&D project focused on residential buildings, showing an inherent limitation in that the scope of technology application in non-residential public facilities was limited. From the second phase of the new Hanok technology R&D project, the scope of demonstration was expanded to a child care facility, a fair venue, and a community center, to verify the applicability of the R&D technology.

In particular, the third phase demonstration project, the Children's Forest Experience Center in Hongseong, which is under construction as part of the research on the development of a type model for a new Hanok style social welfare facility, is an example of the new Hanok style public facility emphasizing the hybrid convergence of tradition and modernity unlike the previous demonstration projects. In addition to the significance of forming a new architecture market, it has implications in terms of policy as it can lead to the effects of human resource development and job creation. This is considered to have laid the foundation for the establishment of a support system for the design and construction of new Hanok style welfare facilities as well as the establishment of a promotion system for the projects. It is meaningful as a site where the limitations of R&D technology manifested in the previous two phases of the new Hanok style public building demonstration project are identified to prepare supplementary measures.

New Hanok R&D technology has been applied to improve the current construction method, which relies on skilled workers who require long training and practical experience, and to improve the performance of the main materials. Furthermore, R&D has been conducted for the dissemination and generalization of the Hanok by reducing the cost of distribution and establishing a modular distribution structure based on mass production.

The technical requirements for design and construction according to each process are classified into essential (11), optional (16), and additional (58) items; essential technologies act as a key factor from the planning stage to the actual construction of the new Hanok style public facility. Among the 11 essential technology processes, there are five construction items⁵⁾ excluding the design software, and the additional group containing technology development for the detailed construction process accounts for approximately 69% of the total (Table 3.).

Each technology shows a difference in the application rate according to the characteristics of each use. For the technologies associated with roofing among the essential technologies, the dry construction method for the "Korean-style house tile roof structure" was applied to all sites, and the dry construction method for "wood structure construction insulation materials and structures" was applied to the demonstration projects for wall construction. The essential technology group shows a prototype application rate of approximately 72% in each project, whereas in the selective technology group, only the Eunpyeong Community Center has been applied with prototype technologies, showing a low prototype application rate.

Observing the application of the additional items, the application rate of technology is higher in the roof and wall construction. Including the technologies that can be applied in the construction process, the R&D technologies are applied the most in the roof construction process. Particularly, among the roof and wall processes, the dry construction method has a high application rate, which is regarded as a factor directly contributing to shortening the construction period as well as improving the construction performance and economic feasibility.

In each case, the scope of application has been set for R&D technology items to as many as an average of 31 processes. Except for the Naju Agricultural Fair project, the prototype technology seems to have been applied and reflected according to the field conditions. If this is evaluated only in the construction field among all processes, it can be observed that the application technology group is reflected at a value close to 1.5 times the prototype application rate.

The Children's Forest Experience Center in Hongseong is the demonstration site with the lowest prototype application rate, exhibiting a trend of the construction processes distinguished from the application technologies. Compared to the previous sites in Sunchang, Naju, and Eunpyeong, the Children's Forest Experience Center project in Hongseong is applied with more than four times the number of application technologies than the prototype technologies. It is evaluated as a construction site suggesting the possibility of expanding new Hanok style R&D technologies with remarkable adoption of carpentry and joinery technologies, which have been applied in a relatively passive manner in previous projects.

The application rate of the new Hanok R&D technology can be divided depending on the calculation method into the rate for the detailed technology in each process or the rate for the application range. The former is significant as a basis for data for discussing the evaluation and application method of technology that is directly related to the construction of the building; the latter is characterized by a relatively high application rate as it accommodates a wide range of technology applications focusing on the overall process range.

These can be considered as evaluations of the technology- and process scope-driven application rates. The technology-driven application rate is calculated by adding up the prototype and application technologies, focusing on 68 construction-related technologies excluding programs, landscaping, and other monitoring processes that correspond to the software in the planning stage among a total of 85 R&D technologies. The process scope-driven application rate is calculated by evaluating the application status in all 23 processes based on the range of technologies for each part and adding up the number of processes. Where, if the application of a prototype technology (a) is counted as 1, the application of an application technology (b) is counted as ×0.7⁶⁾ (Eq. 1).

The process scope-driven application rate was as high as 50% or more in all cases, which can be interpreted as a more favorable policy standard as an evaluation index for promoting the new Hanok style buildings.

However, the construction method can be analyzed more accurately and precisely through the quantitative evaluation of detailed technology using the technology-driven application rate. Therefore, complementary use of the two standards is required for evaluation.

In most cases, unapplied R&D technologies are mainly associated with unreasonable processes and increased construction costs. The R&D technologies devised for residential and living spaces were excluded owing to a different set of requirements for public facilities (Fig. 1.).

Fig. 1. 
Unapplied Technology Classification and Proportion

For example, for the wall construction, the steel reinforcement R&D technology, which had been discussed for application depending on actual necessities, was not applied as it did not seem necessary in the actual construction; the flooring technology, which had been excluded owing to different design conditions was applied by reflecting some construction methods. Nevertheless, many of them were not applied as they did not meet the on-site and design conditions.

As a result of classifying the unapplied technologies, excluding items in which the prototype technology was applied partially or reflected as an applied technology among the technologies in a total of 85 processes for each site, into the cases associated with different design conditions, an inevitable increase in the construction cost, or non-relevance with the construction was observed; the cases with the technology group differing from the design conditions accounted for the most. The proportion of unapplied technologies owing to the increase in the construction cost decreased with the progression of the demonstration projects, reported to have reached an insignificant level in the most recent project at the Hongseong site. When an increase in construction cost was expected, flexible adjustments and applications were made on site by modifying the planned prototype technology to change the material or reduce the scope of construction based on the technology accumulated through field experience. When looking at the unapplication rate by process, that of the carpentry technology group was the highest. The unapplication rate for joinery technologies was high in Naju, whereas that of the roofing technologies was high in Hongseong, indicating a large deviation depending on the design plan of each site.

The scope of the applied technology is largely divided into the construction for each part and the follow-up management program. Generally, the technologies proposed by the architect or contractor are reflected in the construction stage after the actual design. The technologies were proposed based on the rationality and suitability for the situation on site. To achieve a structural system advantageous in reducing the construction costs and construction period, the technologies were applied through consultation with the research team and construction company. R&D technologies applied based on the proposal of the design and construction were as follows.

2) Proposed design and construction technologies applied in roof such as roof tiles

The "Korean-style house tile roof structure" applied at Sunchang Public Daycare Center reduced the roof load by replacing the roof soil by assembling the roof neck member, facilitating the construction, while reducing costs by 20 to 50% compared to the traditional roof. It was applied to reduce the weight of the roof while having an appearance similar to the traditional Hanok tile roof using Hanok style assembly tiles (Fig. 8.).

Fig. 7. 
H-shaped Steel + Wood Junctional Structure - Eunpyeong Community Center

Fig. 8. 
New Hanok Style Assemble Roof Tile Application

The lightweight roof tiles are made of PVC or resin concrete material and include joints for binding. It is not in the form of the Japanese-style tile, but is configured in a way that the female and male roof tiles are assembled by connecting the joints allowing the easy placement and replacement (maintenance) of damaged tiles, not requiring an experienced tile worker for the construction. Although the lightweight roof tiles improved the sense of heterogeneity with modern materials by reproducing the exterior of the traditional Hanok roof tile with improved constructability and economic feasibility, cracks occurring in the process of joining the metal parts could reduce durability, and there is a limit to their application in various types of roofs as they are distributed as ready-made products rather than custom-made products. Various attempts on the shape and material will be required in this field to address these problems.

At the Eunpyeong Community Center, a vertical "skylight" was formed on the slope of the roof, which was attempted based on the proposed technology to increase the comfort of the indoor space and ventilate the stagnant upper air.

Despite the intensification of the copper plate and insulation reinforcement process for the roof insulation and leakage prevention, it was a significant attempt proving that a technical response to the modern demand, which had not been accommodated in the traditional Korean-style roof was possible (Fig. 9.).

Fig. 9. 
Skylight Window - Eunpyeong Community Center

The Children's Forest Experience Center in Hongseong, which was a project leading to the final results of the third phase of the Hanok technology R&D, was carried out with a focus on the realization of the New Hanok style public building in a more economical and modern form by relaxing the criteria for the application of selected essential items, unlike the previous demonstration projects. Consequently, the prototype application rate⁷⁾ of R&D technology was only 5% with one case, and 95% (19 cases) of the technologies were used as application technologies. The technology with rectangular stone and granite flagstone applied to the stylobate was applied to all demonstration sites, at the beginning of the interior finishing work after installing the foundation stone on the matte concrete and completing the carpentry and roofing work.

The traditional assembly of wooden structures was used for the woodwork joints, and the galvanized steel + bolted hardware joining method was applied to the cross-joining part. In the construction of the cornerstone and lower part of the column, the lateral force was reinforced by installing a "J-shaped anchor" that connected the mat foundation + the cornerstone + the lower part of the column. When connecting at a right angle to a column, a column hardware set was used; when connecting at a cross or oblique angle, a "T-shaped hardware" was installed. The lateral force was secured by connecting the lintel between the lower part of the column as well as the epoxy filling of the hardware joint.

While the previous demonstration construction sites generally reflected R&D technologies focusing on the roof and wall processes, in the Children's Forest Experience Center in Hongseong, various joinery technologies were applied as most of the exterior walls were composed of windows and doors along the curved wall forming a spiral plane. Among them, the Korean-style wooden system windows and doors were designed to cope with the problems of sagging and warping associated with the traditional Korean-style windows by reinforcing insulation and airtightness based on the aggregation technology for solid wood and aluminum.

Fig. 10. 
Mat Foundation+Cornerstone+Column Bottom Combination

The biggest cause of unapplied R&D technologies analyzed through the previous demonstration projects included the case in which the technology was excluded owing to differences in the design conditions, and the case in which an increase in construction cost was expected.

For the cases of R&D technologies applied to the Children's Forest Experience Center in Hongseong, 25 cases (29.4%) of existing technologies were reflected, of which the prototype application rate was below 20%, demonstrating a different trend from the previous demonstration projects. All unapplied technologies identified in the Children's Forest Experience Center in Hongseong were the cases of exclusion owing to differences from the design conditions, accounting for 70% of the total R&D technologies. This was a high number compared to the ratio of unapplied technologies of existing sites, which was counted as an average of 42%. Despite that the process of roof and wall construction was most frequently applied in the existing demonstration sites, 10 carpentry (40%) and joinery (24%) application technologies were applied, and technologies related to roof and wall construction were excluded in the Children's Forest Experience Center in Hongseong.

These results suggested that the scope of R&D technology application was limited in the first attempt of the curved planar structure. It was difficult to freely apply the technologies in design owing to the limits in terms of the use and shape of the building.