팽창재와 수축저감제를 사용한 고성능 콘크리트의 수축 특성

고경택(Koh Kyung Taek),박정준(Park Jung Jun),류금성(Ryu Gum Sung),강수태(Kang Su Tae) 대한토목학회 2006 대한토목학회논문집 A Vol.26 No.4A

고성능 콘크리트는 물-결합재비를 작게 하고, 단위결합재량을 다량으로 시용하므로 콘크리트의 수화열 및 자기수축이 증대 되는 경향이 있다. 본 연구에서는 고성능 콘크리트의 수축저감 기술을 구축하는 연구의 일환으로 팽창재와 수축저감제 사용이 고성능 콘크리트의 수축특성에 미치는 영향을 검토하였다. 그 결과, 팽창쟁와 수축저감제는 고성능 콘크리트의 수축을 저감시키는 데 효과가 뛰어나며, 특히 팽창재와 수축저감제를 조합하여 사용할 경우, 각각 단독으로 사용하는 경우보다는 수축 저감 효과가 큰 것으로 확인되었다. 또한 시공성, 강도 및 수축특성을 종합적으로 고려하여 팽창재 5.0%와 수축저감제 1.0%의 조합이 적정배합으로 분석되었다. Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

Autogenous shrinkage of ultra high performance concrete considering early age coefficient of thermal expansion

Park, Jung-Jun,Yoo, Doo-Yeol,Kim, Sung-Wook,Yoon, Young-Soo Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.6

The recently developed Ultra High Performance Concrete (UHPC) displays outstanding compressive strength and ductility but is also subjected to very large autogenous shrinkage. In addition, the use of forms and reinforcement to confine this autogenous shrinkage increases the risk of shrinkage cracking. Accordingly, this study adopts a combination of shrinkage reducing admixture and expansive admixture as a solution to reduce the shrinkage of UHPC and estimates its appropriateness by evaluating the compressive and flexural strengths as well as the autogenous shrinkage according to the age. Moreover, the coefficient of thermal expansion known to experience sudden variations at early age is measured in order to evaluate exactly the autogenous shrinkage and the thermal expansion is compensated considering these measurements. The experimental results show that the compressive and flexural strengths decreased slightly at early age when mixing 7.5% of expansive admixture and 1% of shrinkage reducing admixture but that this decrease becomes insignificant after 7 days. The use of expansive admixture tended to premature the setting of UHPC and the start of sudden increase of autogenous shrinkage. Finally, the combined use of shrinkage reducing admixture and expansive admixture appeared to reduce effectively the autogenous shrinkage by about 47% at 15 days.

콘크리트 배합조건에 따른 수축저감제의 건조수축 특성

김영선 ( Kim Young-sun ),김광기 ( Kim Kwang-ki ),박순전 ( Park Soon-jeon ),김정선 ( Kim Jung-sun ) 한국건축시공학회 2017 한국건축시공학회지 Vol.17 No.3

최근 소비패턴의 변화에 따라 대형마트, 아울렛 및 물류창고 등과 같은 구조물들이 증가하고 있다. 이와 같은 구조물들은 초평탄 바닥부재를 포함하고 있기 때문에 소성 및 건조수축에 의한 슬래브 부재의 균열 억제 관리를 철저하게 실시한다. 슬래브 부재의 균열을 억제하기 위한 방안으로 화학적 균열저감 방법을 사용하고 있으며, 특히 수축저감제에 대한 사용검토가 증가하고 있다. 그러나 이에 대한 국내 연구결과는 부족한 상황이다. 본 연구에서는 수축저감제를 사용한 콘크리트의 수축특성과 배합요인 변동에 따른 건조수축 특성을 검토하였다. 국내 수축저감제는 해외 고급형 수축저감제와 성능이 유사한 것으로 나타났으며, 수축저감제 사용량이 증가할수록 건조수축 억제 효과는 높아지는 것으로 나타났다. 수축저감제 1.5%를 사용한 시험체는 재령 100일에서 수축저감제를 사용하지 않은 시험체에 비해 건조수축량이 약 절반으로 나타났다. 또한, 혼화재료 사용에 대해 특별한 성능변화는 없는 것으로 확인되었다. Recently, structures such as large retailers, outlets and warehouses have been increasing in accordance with changes in consumption patterns. Since these structures include ultra-flat slab members, they are thoroughly managed to control slab cracking by the plastic and drying shrinkage. In order to control the cracking of the slab member, a chemical crack reduction method is used. In particular, the use of the shrinkage reducing agent has been examined. However, domestic research results are limited. In this study, the shrinkage properties of concrete using shrinkage reducing agent and the drying shrinkage properties according to the mixing factors were investigated. The performance of domestic shrinkage reducing agent was appeared similar to that of overseas high-grade shrinkage reducing agent. As the shrinkage reducing agent usage increased, the drying shrinkage reduction effect increased. At the age of 100 days, the dry shrinkage rate of specimen with the shrinkage reducing agent of 1.5%was shown about half that of the specimen without the shrinkage reducing agent. The shrinkage reducing agent was gound to have no specific performance change for the use of the admixture.

THE EFFECT OF MONOMER TO POWDER RATIO ON POLYMERIZATION SHRINKAGE-STRAIN KINETICS OF POLYMER-BASED PROVISIONAL CROWN AND FIXED PARTIAL DENTURE MATERIALS

Kim, Sung-Hun The Korean Academy of Prosthodonitics 2007 대한치과보철학회지 Vol.45 No.6

Statement of problem. Although a number of previous investigations have been carried out on the polymerization shrinkage-strain kinetics of provisional crown and fixed partial denture (FPD) materials, the effect of the changes of liquid monomer to powder ratio on its polymerization shrinkage-strain kinetics has not been reported. Purpose. The purpose of this study was to investigate the influence of liquid monomer to powder ratio of polymer-based provisional crown and FPD materials on the polymerization shrinkage-strain kinetics. Material and methods. Chemically activated acrylic provisional materials (Alike, Jet, Snap) were investigated. Each material was mixed with different liquid monomer to powder ratios by volume (1.0:3.0, 1.0:2.5, 1.0:2.0, 1.0:1.5, 1.0:1.0). Time dependent polymerization shrinkage- strain kinetics of all materials was measured by the bonded-disk method as a function of time at $23^{\circ}C$. Five recordings were taken for each ratio. The results were statistically analyzed using one-way ANOVA and the multiple comparison Scheffe test at the significance level of 0.05. Trends were also examined by linear regression. Results. At 5 minutes after mixing, the polymerization shrinkage-strains of all materials ranged from only 0.01% to 0.49%. At 10 minutes, the shrinkage-strain of Alike was the highest, 3.45% (liquid monomer to powder ratio=1.0:3.0). Jet and Snap were 2.69% (1.0:2.0) and 1.58% (1.0:3.0), respectively (P>0.05). Most shrinkage (94.3%-96.5%) occurred at 30 minutes after mixing for liquid monomer to powder ratio, ranging from 1.0:3.0 to 1.0:1.0. The highest polymerization shrinkage-strain values were observed for the liquid monomer to powder ratio of 1.0:3.0. At 120 minutes after mixing, the shrinkage-strain values were 4.67%, 4.18%, and 3.07% for Jet, Alike, and Snap, respectively. As the liquid monomer to powder ratio increased, the shrinkage-strain values tend to be decreased linearly (r=-0.769 for Alike, -0.717 for Jet, -0.435 for Snap, $r^2=0.592$ for Alike, 0.515 for Jet, 0.189 for Snap; P<0.05). Conclusion. The increase of the liquid monomer to powder ratio from 1.0:3.0 to 1.0:1.0 had a significant effect on the shrinkage-strain kinetics of polymer-based crown and FPD materials investigated. This increased the working time and decreased the shrinkage-strain during polymerization.

Silorane 복합레진의 중합수축의 동력학

권영철,이인복 大韓齒科保存學會 2010 Restorative Dentistry & Endodontics Vol.35 No.1

복합레진이 개발된 이후 많은 물성의 향상이 이루어졌으나 복합레진의 중합수축은 아직 해결되지 않은 주요 단점으로 남아있다. 중합수축이 적은 복합레진을 만들기 위한 많은 노력이 이루어졌고, 최근에 기존의 methacrylate 기질이 아닌 silorane 기질의 복합레진이 개발되었다. 본 연구에서는 silorane 기질의 복합레진과 methacrylate 기질의 복합레진의 중합수축거동을 측정하고 비교하고자 하였다. 온도변화에 민감하지 않으며 실시간으로 복합레진의 체적 중합수축을 측정할 수 있는 계측장치를 제작하여 사용하였다. 5종의 methacrylate 기질의 수복용 복합레진(Beautifil, Z100, Z250, Z350, Gradia X)과 silorane 기질 복합레진 (P90)의 중합수축을 10분 동안 측정하여, 중합수축량, 최대 중합수축률 그리고 최대수축시간을 비교하였다. 복합레진의 중합수축은 제품별로 많은 차이를 보였다. Silorane 기질의 P90복합레진의 중합수축이 1.48%로 가장 낮았고 Beautifil 복합레진의 중합수축이 2.80%로 가장 높았다. Methacrylate 계열의 복합레진 사이에도 중합수축량에 제품별로 유의한 차이를 보였다(p<0.05). 최대 중합수축률은 P90이 0.13%/s로 가장 낮았고 Z100이 0.34%/s로 가장 높았다. 최대 수축시간은 methacrylate기질의 복합레진(2.4-3.1초)에 비해, silorane 기질의 P90 복합레진이 6.7초로 두 배 이상 길었다. 최대중합수축률은 중합수축과 최대수축시간의 역수를 곱한 값과 강한 양의 상관관계를 보였다(R = 0.95). Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

Study on the Engineering Properties of 150MPa Ultra-high Strength Concrete

정상진,Yoshihiro MASUDA,김우재,이영란,하정수,김성덕 한국건축시공학회 2010 한국건축시공학회지 Vol.10 No.4

In this study, 150MPa ultra-high-strength concrete was manufactured, and its performance was reviewed. As technically meaningful autogenous shrinkage reportedly occurs at a W/B ratio of 40% or less, although it occurs in all concrete regardless of the W/B ratio, the effects of the use of expansive admixture and shrinkage reducer, or of the friction and restraint of forms that may result in the effective reduction of autogenous shrinkage, were reviewed. As a result, considering the flow and strength characteristics, it was found that the slump flow time was shorter with expansive admixture, and shortest with shrinkage reducer. All specimens with 30㎏/㎥expansive admixture showed high strength at early material age. Their strength decreased due to the expansion cracks when there was excessive use of expansive admixture, and the use of shrinkage reducer did not influence the change in the strength according to the material age. The expansive admixture had a shrinkage reduction effect of 80%, while the shrinkage reducer had a shrinkage reduction effect of 30%, indicating that the expansive admixture had a stronger effect. It seems that mixing the two will have a synergistic effect. The shrinkage reduction rate was highest when the W/B ratio was 20%. The form suppressed the expansion and shrinkage at the early period, and the demolding time did not significantly influence the shrinkage. The results of the study showed that the excessive addition of expansive admixture leads to expansion cracks, and the expansive admixture and shrinkage reducer have the highest shrinkage reduction effect when they are mixed

A new method to measure the polymerization shrinkage kinetics of light cured composites

LEE, I.B.,CHO, B.H.,SON, H.H.,UM, C.M. Blackwell Science Ltd 2005 Journal of oral rehabilitation Vol.32 No.4

<P><SMALL>SUMMARY</SMALL> </P><P>This study was undertaken to develop a new measurement method to determine the initial dynamic volumetric shrinkage of composite resins during polymerization, and to investigate the effect of curing light intensity on the polymerization shrinkage kinetics. The instrument was basically an electromagnetic balance that was constructed with a force transducer using a position sensitive photo detector (PSPD) and a negative feedback servo amplifier. The volumetric change of composites during polymerization was detected continuously as a buoyancy change in distilled water by means of the Archimedes’ principle. Using this new instrument, the dynamic patterns of the polymerization shrinkage of seven commercial composite resins were measured. The polymerization shrinkage of the composites was 1·92∼4·05 volume %. The shrinkage of a packable composite was the lowest, and that of a flowable composite was the highest. The maximum rate of polymerization shrinkage increased with increasing light intensity but the peak shrinkage rate time decreased with increasing light intensity. A strong positive relationship was observed between the square root of the light intensity and the maximum shrinkage rate. The shrinkage rate per unit time, <I>d</I>Vol%/<I>dt</I>, showed that the instrument can be a valuable research method for investigating the polymerization reaction kinetics. This new shrinkage-measuring instrument has some advantages that it was insensitive to temperature changes and could measure the dynamic volumetric shrinkage in real time without complicated processes. Therefore, it can be used to characterize the shrinkage kinetics in a wide range of commercial and experimental visible-light-cure materials in relation to their composition and chemistry.</P>

A Study on the Creep and Autogenous Shrinkage of High Performance Concrete with Expansive Additive and Shrinkage Reducing Admixtures at Early Age

Park, Sun-Gyu,Noguchi, Takafumi,Kim, Moo-Han Korea Concrete Institute 2006 International Journal of Concrete Structures and M Vol.18 No.e2

This paper shows a study of the efficiency of expansive additive and shrinkage reducing admixture in controlling restrained shrinkage cracking of high performance concrete at early age. Free autogenous shrinkage test of $100{\times}100{\times}400mm$ concrete specimens and simulated completely-restrained test with VRTM(variable restraint testing machine) were performed. Creep and autogenous shrinkage of high-performance concrete with and without expansive additive and shrinkage reducing admixture were investigated by experiments that provided data on free autogenous shrinkage and restrained shrinkage. The results showed that the addition of expansive additive and shrinkage reducing admixture effectively reduced autogenous shrinkage and tensile stress in the restrained conditions. Also, it was found that the shrinkage stress was relaxed by 90% in high-performance concrete with and without expansive additive and shrinkage reducing admixtures at early age.

Effects of mix proportion and curing condition on shrinkage behavior of HPFRCCs with silica fume and blast furnace slag

Yoo, Doo-Yeol,Kim, Min-Jae,Kim, Soonho,Ryu, Gum-Sung,Koh, Kyung-Taek Elsevier 2018 Construction and Building Materials Vol.166 No.-

<P><B>Abstract</B></P> <P>This study investigated the effects of mixture proportion and curing condition on the mechanical and shrinkage behaviors of high-performance fiber-reinforced cementitious composites (HPFRCCs). Different water-to-binder (W/B) ratios and amounts of mineral admixtures, such as zirconium silica fume (Zr SF) and blast furnace slag were evaluated. The test results indicate that initial steam-heat curing accelerated the strength development and was sufficient to develop its full strength. The ultimate autogenous shrinkage was insignificantly affected by the curing conditions, but the heat curing accelerated the development of autogenous shrinkage. HPFRCC with a lower W/B ratio and greater amount of Zr SF exhibited higher autogenous shrinkage but lower drying shrinkage. In addition, the amount of total shrinkage of HPFRCC was more effectively reduced by providing heat curing when a higher W/B ratio and a smaller amount of Zr SF were used. There were no increases in the autogenous and drying shrinkage for HPFRCC immediately after finishing the initial heat curing, meaning that there is no possibility of shrinkage cracks forming in HPFRCC elements after the heat curing process. Finally, the autogenous shrinkage behaviors of HPFRCC were simulated with several prediction models from literature and an optimized model, considering equivalent age, was suggested.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultimate autogenous shrinkage of HPFRCCs is insignificantly affected by curing condition. </LI> <LI> Lower W/B ratio and higher amount of Zr SF result in higher autogenous shrinkage but lower drying shrinkage. </LI> <LI> After heating curing, there are no increases of autogenous and drying shrinkage strains of HPFRCCs. </LI> <LI> Total shrinkage of SC150 and SC120 is effectively reduced by applying heat curing. </LI> </UL> </P>

지속가능한 도시관리를 위한 스마트 축소 모형 연구(Ⅰ)

박창석,신지영,송지연,박현주,이재경,송원경,김휘문,이은석,최희선 한국환경정책평가연구원 2020 사업보고서 Vol.2020 No.-

Ⅰ. 서론 1. 연구의 배경 및 필요성 ❏ 인구감소 및 저성장 기조에 따라 성장 중심의 도시정책을 전환하고 친환경적 스마트 축소를 위한 정책방안 마련 필요 ❏ 도시인구 감소는 도시경제 및 재정, 토지이용변화 등 다각적 영향을 미침 ㅇ 인구감소는 세수 부족을 유발하고, 과잉 공급된 도시기반시설의 유지·관리 비용은 증가하여 도시재정이 지속적으로 악화되고 있음 ㅇ UN SDGs와 UN Habitats는 지속가능 도시를 인류번영과 생존을 위한 기본사항으로 강조하고, 스마트 축소 등 사회경제적 여건변화와 기술혁신에 대한 적극적인 대책과 대응을 주문 ❏ 스마트 축소는 『제5차 국가종합계획(2020-2040)』, 『제5차 국토종합계획(2020-2040)』 등 국가 정책에서 시급한 과제임 2. 연구의 목적 ❏ 새로운 국면을 맞게 된 도시축소 현상이 해외 도시에서 나타나는 현상과 비교하여 어떠한 특징을 가지고 있는지와 더불어 이러한 현상이 전개되는 메커니즘 분석 ㅇ 도시축소 메커니즘을 토대로 주거소멸 및 생태복원 분석 방법론과 도시축소 모형을 구축하여 도시축소 시나리오별 주거·생태적 공간이용과 환경·공공서비스 접근성, 도시재정 변화를 검토 ❏ 스마트 축소를 통한 재자연화 등 삶의 질을 제고할 수 있는 지속가능한 도시로의 방향을 정립하고 이를 실현하기 위한 정책방안 제시 Ⅱ. 도시축소 개념과 주요 사례 1. 도시축소와 스마트 축소 ❏ 국내외 다양한 연구에서 인구감소를 도시축소의 가장 중요한 지표로 활용되고 있으며, 스마트 축소(smart shrinkage)는 감소하는 도시인구와 쇠퇴하는 산업구조에 맞춰 도시를 축소하려는 계획적 접근임 ❏ 도시축소로 인한 주거 소멸과 환경·공원녹지 확충, 환경·공공시설 접근성 관리 등은 앞으로 스마트 축소로 나타나는 도시관리 및 도시재정 패러다임의 변화를 수반함 ㅇ 삶의 질 향상에 초점을 맞추어 적정규모를 추구하는 축소와 안정화를 지향하는 패러다임으로 전환 2. 해외 사례와 대응노력 ❏ 독일, 미국, 일본 등에서는 도시의 축소에 따라 주거지, 인프라 등을 재조정하고 녹지로 돌리는 등 스마트한 축소 전략을 마련하여 추진 중 ㅇ 일본은 거점의 집적과 분산, 대중교통 네트워크를 통한 축소 전략 수립, 미국은 적정 규모화를 위해 ‘선택과 집중’ 전략 수립, 독일은 도심강화, 주거지 환경개선, 인프라 재편 등 적극적인 정책 마련 ❏ 인구감소 및 주거소멸에 대응한 스마트 축소 정책 마련과 지역특성을 반영한 선제적 대응이 필요하며, 지속가능한 도시관리를 위한 토지이용 및 환경·생태적 접근 방안 고민 필요 ㅇ 지역 특성에 맞는 거점 연결 방법, 외곽 거주민들의 유입을 위한 유도적 정책 필요 ㅇ 환경적, 물리적, 경제적으로 긍정적인 변화를 가져올 수 있는 체계적인 전략수립 및 수시 모니터링 필요 ㅇ 시민의 자발적 참여와 공감대 형성을 통한 정책 대응방안 마련 필요 Ⅲ. 우리나라의 도시축소 현황과 특징 1. 인구감소, 국토공간 및 지역소멸 추세와 전망 ❏ 우리나라 총 인구의 급격한 감소와 비수도권의 상대 인구 비중 하락 ㅇ 2019 통계청 인구전망 결과 인구감소 시점이 2028년으로 앞당겨짐 ㅇ 인구 자연증가에 의한 인구 정점 또한 시기가 앞당겨질 것으로 예상됨 ❏ 인구과소지역 및 무거주 지역의 증가가 지속되고, 공간 간 인구증감 추세의 양극화 현상 예상 ㅇ 인구과소지역은 2020년 49,634개에서 2040년 5만 8,932개로 전망 ㅇ 2040년 인구가 거주하지 않는 지역으로 추정되는 격자는 401개, 8개 지역으로 분석 ❏ 인구감소의 영향이 지역적으로 대칭적이지 않으며, 지역 차별적 소멸 위험 증가 ㅇ 전국적 소멸위험지수 증가 및 비수도권의 모든 ‘도’ 지역이 소멸주의단계 진입 2. 도시축소에 따른 영향과 주요 인자 분석 ❏ 지속적인 인구감소와 도시 축소, 도시의 기능 저하가 사회·경제·환경적 요인에 어떠한 영향을 미치는지 알아보기 위해 분석 진행 ㅇ 전국 시·군·구를 대상으로 20년 단위로 감소 정도를 분석하고, 2005~2018년 기준 시·군·구 단위 가용데이터를 기준으로 분야별 관련요인 도출 ㅇ 인구증감에 따라 지역을 그룹화하여 각 분야별 요인과의 영향 여부를 분석하고 상관관계 분석 진행 ❏ 노령화 지수 증가, 고령화에 따른 영향이 우리나라 축소도시의 원인으로 작용 ㅇ 노령화 지수가 증가하여 고령화가 심화될수록 여러 요인에 마이너스(-)의 영향을 미치는 것으로 해석 - 사회·경제적 요인 전체, 도시·공간 요인 중 기반시설(1인당, 전체), 환경 요인 중 1인당 생활폐기물, 대기오염배출량(NOx) ❏ 도시축소의 특성은 도시서비스와 기반시설이 축소되어 생활편리성이 저하되고 주거 소멸과 사회적 관계 저하로 인해 지역의 매력도가 저하되며, 우리나라 축소도시가 갖고 있는 거버넌스와 물리적 문제를 중심으로 지역 특성에 근거한 기후환경 증진 및 공간설계적 해법 제시 및 차별화 전략 마련 필요 Ⅳ. 스마트 축소를 위한 모형 개발과 적용, 정책적 시사점 1. 스마트 축소 모형 개발과 적용 ❏ 스마트 축소 전략의 특성상 인구변화, 지역의 경제상황, 도시민의 삶의 질 등 관련 변수를 토대로 대상지 선정(전주, 정읍) ❏ Multilevel Logistic Regression Model(MLRM) 기반의 빈집 확률 예측모형 개발 ㅇ 건축물 현황, 건축물이 입지한 토지의 특성, 지역의 인구학적 특성을 고려하여 대상지 내 건축물들의 향후 빈집이 될 확률에 대한 공간적 패턴 모형 설계 ㅇ 전주시와 정읍시 모두 행정동 레벨에서 노인 인구비율이 상대적으로 높아질수록, 건축물이 노후해질수록, 블록 및 목조 건축물일수록 공실의 확률이 높아짐 ㅇ 전주시와 정읍시의 개별 건축물의 평균 빈집 확률 예측 결과 각각 2.78%, 4.45%로, 정읍시의 건축물들이 향후 빈집 위험이 높을 것이며, 전주시는 구시가지를 중심으로, 정읍시는 산발적으로 빈집이 발생할 것으로 예측되어 지자체별 차별화 전략 필요 ❏ 공간그래프 이론 기반 생태네트워크 최적화 모형 및 시범적용 ㅇ 경관 연결성의 정량적 기준이 확보될 수 있는 공간그래프 이론(Conefor)을 생태네트워크 모형 방법으로 시범 적용하여, 현재 빈집 필지가 녹지가 된다는 시나리오에 따라 생태네트워크 연결성 중요도를 평가 ㅇ 빈집 예측 우선 필지에 대한 연결성을 우선적으로 고려함으로써 현재 낙후된 생태네트워크 지역의 연결성을 향상시킬 수 있는 잠재적 가치의 필지로 판단하여 지자체 개발 또는 보전에 대한 도시계획 의사결정 지원 가능 2. 지속가능한 스마트 축소 도시관리를 위한 정책제언 ❏ 스마트 축소를 위한 빈집관리 정보 구축과 기후생태화 인식 강화 ㅇ 축소도시 관련 부서 간 정보의 수집, 활용, 공유 등 체계적인 빈집 관련 통합 플랫폼 구축을 통한 지속적인 빈집 관리 필요 ㅇ 정책 결정 과정에서 시민의 의견을 적극 반영하고, 지역주민을 위한 그린인프라 등 생태녹지공간이나 도시생태가든, 커뮤니티 공간 등 빈집 활용 전략의 기후생태화 요구 ❏ 공간설계 인벤토리를 고려한 스마트 축소 전략화 ㅇ 인구감소가 가져오는 공간적 문제, 사회·경제적 문제, 환경적 문제를 유형화함으로써 선택가능한 공간적 해법을 공간설계 인벤토리를 구축해 적용 ㅇ 축소도시의 미래 시나리오(커뮤니티 재생, 지속가능성 확보, 점진적 소멸)에 따라 공간설계 인벤토리 적용 - 도시쇠퇴 특성에 따른 유형: 재생과 정비를 통한 재활성화 유형, 고령화에 따른 자연감소로 인한 소멸유형 - 적용대상: 건축물, 토지, 기반시설, 공원녹지, 교통시스템 ❏ 기후탄력성에 기초한 스마트 축소 전략화 ㅇ 도시 축소에 따라 발생하는 공간을 기후환경 측면에서 회복탄력성 증진을 위한 공간으로 전환 및 역할을 부여하여 기회의 공간으로 전환 가능 ㅇ 기후변화 취약성이 높은 지역에 위치한 빈집 공간에 쿨루프, 쿨페이브먼트, 쿨링로드, 녹지 확충 등 기후영향을 저감시킬 수 있는 요소와 사업 도입을 우선적으로 고려할 수 있음(VESTAP 활용 가능) ❏ 스마트 축소를 고려한 환경계획 강화와 국토-환경 통합관리 사업으로의 발전 ㅇ 지자체 단위에서 환경계획 수립 시 스마트 축소를 적용하고 도시계획과 연계할 수 있도록 환경계획 지침에 스마트 축소 관련사항을 고려하도록 환경계획 강화 필요 - 현안 및 여건분석: 인구감소와 노령화에 따른 도시 축소/쇠퇴 현상에 대한 분석과 진단 항목 추가 - 비전 및 목표 설정: 생태적 회복, 연결성 등의 가치를 고려한 계획 추가 ㅇ 빈집 정비를 점적(點的) 사업으로 보는 시각에서 벗어나 기후탄력도시 및 그린도시로의 전환사업으로 자리매김 필요 - 주민들에게 녹지화를 통한 생태계 서비스 공급, 커뮤니티 경관 개선, 유휴지를 수익성 있는 토지로 바꾸는 사업 등 Ⅴ. 결론 ❏ 스마트 축소는 공공성을 증대하고 삶의 질과 기후탄력성 등 지속가능한 도시가치를 높이는 새로운 기회의 성장전략이며, 도시계획적 접근뿐만 아니라 기후환경을 고려한 접근 강화 필요 ❏ 향후 도시의 공간환경 계획 수준에서 적용가능한 스마트 축소모형 구축과 전략개발 추진 필요 ㅇ 스마트 축소 모형으로 개발한 공실률 예측모형의 고도화를 위해 불법 건축물 정보반영, 건축물 관련 상세 정보의 구축과 변수화, 도시별 비교를 위한 지역특성을 고려한 변수 발굴 등의 노력이 지속적으로 필요 ㅇ 생태네트워크 연결성 평가는 빈집 필지의 연결성 가치를 우선 평가하였기 때문에 도시지역의 녹지 분포, 면적 등 공간적 특성과 폭염 등 기후위험수준, 주민 접근성 (accessibility) 등 기후·사회적 가치 고려 필요 ❏ 향후 지역별 빈집 발생 가능 공간의 활용전략 수립 근거로 활용 가능 ㅇ 빈집을 도시 기능 서비스 관점에서 유지할지 또는 기후생태적 관점에서 기후생태공간 등으로 조정하여 환경·공공서비스를 제공할지 또는 사회적·문화적 가치를 고려할지 등 효과적인 공간 활용 방식 제안 가능 ㅇ 지속가능한 도시관리를 위한 정책결정에 도움이 될 것으로 기대함 Ⅰ. Introduction 1. Background and necessity of research ❏ Due to population decline and low growth, changes in urban policy and eco-friendly smart shrinkage policy are necessary. ❏ A decrease in urban population causes various effects on urban economy and finance, as well as changes in land use. ㅇ The decrease in city population led to the aggravation of financial conditions of many cities due to low tax revenues and high maintenance cost of infrastructure. ㅇ UN SDGs and UN Habitats emphasize that sustainable cities are the basis for human prosperity and survival and request plans for responding to socioeconomic changes and innovation in technology such as smart shrinkage. ❏ Smart shrinkage is an urgent task in government policies, including the Fifth Comprehensive National Plan (2020~2040) and the Fifth Comprehensive National Land Use Plan (2020~2040). 2. Purpose of research ❏ This study aims to analyze the characteristics of shrinking cities in Korea compared to those abroad and to understand the mechanism of the shrinking city phenomenon. ㅇ A model of shrinking city will be built based on the mechanism of the phenomenon to observe the residential space usage, accessibility of public services, and financial change in the shrinking cities. ❏ Also, this study aims to prepare the basis for sustainable cities that can improve quality of life through smart shrinkage and to present policies that can realize the plan. Ⅱ. Concept and Case Studies of Shrinking City 1. Shrinking city phenomenon and smart shrinkage ❏ Various research projects use population decrease as an indicator for shrinking city phenomenon. Smartshrinkage is an approach that aims to shrink the city in accordance with the decline in population and industrial structures. ㅇ Smart shrinkage is a sustainable plan that can increase quality of life and establish a virtuous cycle between society, economy, and environment in shrinking cities by vacating overdeveloped areas and rearranging essential structures. ❏ Converting to a paradigm that pursues shrinkage to a reasonable size and stabilization of the city centered on maximizing quality of life is necessary. 2. Foreign cases and efforts to resolve problems ❏ Countries such as Germany, the USA, and Japan readjusted the landscape based on the reduced scale of the city to fulfil their smart shrinkage strategies. ㅇ Japan is developing shrinkage strategy focusing on centralization and decentralization of base areas and public transportation networks; the USA is developing ‘choose and focus’ strategy for the right downsizing; and Germany is developing active policy measures including strengthening urban centers, improving residential environments, and rearranging infrastructure. ❏ It is necessary to prepare a smart shrinkage policy in response to the population decline and disappearance of housing and to take preemptive actions that reflect regional characteristics, as well as consider land use and environmental and ecological approaches for sustainable city management. ㅇ Plans to connect bases that consider regional characteristics and policies to induce the influx of new residents are required. ㅇ Systematic strategy and frequent monitoring that can bring positive environmental, physical, and economic changes are required. Ⅲ. Current Status and Characteristics of Shrinking Cities in Korea 1. Trends and prospects of population decline, territorial space, and regional extinction ❏ The total population of Korea and the proportion of the relative population in non-capital regions are rapidly declining. ㅇ According to the 2019 Statistics Office’s population outlook, the point of population decline has been brought forward to 2028. ㅇ If the current trend continues, the natural population growth will reach its maximum in 2021. ❏ Underpopulated and unpopulated areas are continually increasing and the trend toward population polarization between spaces is expected. ❏ The impact of population decline is not regionally symmetric and the risk of extinction by region is increasing. 2. Analysis of the effects and major factors of the shrinking city phenomenon ❏ Analysis was conducted to find out how the continuous population decline, city shrinkage, and urban function decline affect social, economic, and environmental factors. ㅇ By grouping regions according to population change, the influence on each factor was analyzed and then correlation analysis was conducted. ❏ The increase in the aging index and the effects of aging are the cause of the shrinking cities in Korea. ㅇ As aging accelerates, it is interpreted as having a negative (-) effect on various factors. ❏ The characteristics of city shrinkage are as follows: the convenience of living is reduced due to the reduction of urban services and infrastructure and the attractiveness of the region decreases due to the disappearance of housing and the decline in social relations. ❏ It is necessary to improve climate environment focusing on regional properties, present spatial design solutions, and prepare differentiation strategies. Ⅳ. Model Development and Application for Smart Shrinkage and Policy Implications 1. Model development and application ❏ The target sites were selected based on related variables such as population change, regional economic conditions, and quality of life of urban residents (Jeonju and Jeongeup). ❏ Development of a vacant home probability prediction model based on the Multi-level Logistic Regression Model (MLRM) ㅇ A spatial pattern model was designed in consideration of the current state of the building, the characteristics of the land where the building is located, and the demographic characteristics of the region. ㅇ In both Jeonju and Jeongeup, the probability of vacancy was higher if the proportion of elderly population was higher, the building has aged more, and when the building was made out of blocks or wood. ❏ Ecological network analysis based on the spatial graph theory ㅇ The spatial graph theory (Conefor) that can secure a quantitative standard of landscape connectivity was selected and the importance of ecological connectivity was evaluated according to the scenario of the current vacant lots turning into green spaces. ㅇ By prioritizing the connectivity of areas with a high probability of vacant homes, these areas can be evaluated as having great potential value that can improve connectivity in underdeveloped areas. 2. Policy suggestion for sustainable smart shrinkage ❏ It is necessary to continuously manage vacant homes through the establishment of an integrated platform, promote voluntary participation and consensus of the citizens in the policy making process, and strengthen awareness of climate ecology. ❏ Constructing a spatial design inventory by categorizing the spatial, socioeconomic, and environmental problems brought about by population decline can provide selectable spatial solutions in each future scenario. ❏ Smart shrinkage strategy that considers climate resilience can preferentially reduce the climate impact in regions that are highly vulnerable to climate change and can convert areas created due to shrinkage into a space of opportunity (cool roof, cool pavement, cooling road, expansion of green space, etc.). ❏ It is necessary to reinforce environmental plans in consideration of smart shrinkage and to promote vacant home maintenance as a project to transform our cities into climate-resilient, green cities. Ⅴ. Conclusion ❏ Smart shrinkage is a growth strategy for new opportunities that increases public interest and values of sustainable city such as quality of life and climate resilience and it is necessary to strengthen not only the approach of urban planning but also the approach that considers climate environment. ❏ It is necessary to build a smart shrinkage model applicable at the level of urban spatial environment planning considering information on illegal buildings, detailed information on buildings in general, variables in consideration of regional characteristics, distribution of urban green space, the level of climate risks, and accessibility to residents. ❏ It is expected that the result of this study could be used in making policy decisions for sustainable city management, such as when deciding whether to maintain empty houses from the perspective of urban services, rearrange them as climate-ecological space to provide environmental /public services from the perspective of climate ecology, or to promote their social/cultural values.