단부매립철물로 단순접합된 PSC보의 구조성능평가

Abstract

최근 건설시장은 건축물의 고층화와 대형화에 따른 층고 절감, 장스팬화 및 친환경성 등의 건축적 요구와 함께 급변하는 원자재의 가격 등락과 중장기적 상승세, 건설 현장의 환경 개선 및 건설 폐기물 발생 감소를 위한 노력 등이 이루어지고 있다. 건설에서 발생되는 폐기물의 문제는 수없이 지적되고 있으며 폐기물의 재활용 방법을 연구하는 큰 틀을 유지하고 있다. 그러나 폐기물의 재활용률은 매우 낮은 것이 현실이며 건설단계에서 발생되는 부수적인 폐기물에 대한 대책은 미비한 실정이다. 건설폐기물에서 발생하는 이산화탄소 등의 GHG(green house gas)는 지구 온난화 등 환경재앙으로 인한 급격한 기후 변화를 일으켜 지속적으로 인간의 삶을 위협하고 있다. 이러한 문제점을 해결하기 위해 건축 부재의 계획적 생산에 의한 고품질화, 거푸집 등 가설자재의 감량, 구조물의 안전성, 내구성, 신뢰성, 비용 절감 효과를 위한 실용적인 수단으로 철근콘크리트와 철골의 구조적 장점을 결합하여 효율성을 극대화시켜 경제적 효과를 증가시킬 수 있는 프리캐스트 프리스트레스트 콘크리트(precast prestressed concrete: PSC) 공법이 주목을 받고 있다. 하지만, PSC 기술의 한계로 인해 접합부에 대한 시공성 및 경제성 확보의 어려움으로 인하여 일부 형태만이 주로 사용되고 있는 실정이며, 이러한 접합부 시공성 저하는 PSC 공법의 단점으로 작용하고 있다. 일반적인 PSC 공법은 큰 보에 레져(ledger)를 설치하고 작은 보에 댑단부(dapped end)를 설치하여 얹어놓는 형식의 접합 방법이 이용되고 있으며, 효율적인 응력 전달을 위해 별도의 기계적 이음을 위한 철물, 철근 및 보강 철물의 용접 등 복잡한 시공 능력을 요구 하여 시공성 저하를 가중시키는 결과를 초래하였다. 보강 철물을 이용한 PSC 보의 접합 방법에 대하여 국내 건축구조기준(KBC2009) 및 콘크리트구조기준(KCI2012), 미국의 ACI(2011) 및 PCI Design handbook(2010) 등에서 일부분에 대한 설계 기준은 제시되어 있지만 정확한 기준은 제시되어 있지 않으며, 적절한 실험과 해석적 연구결과를 요구하고 있다. 현재 PSC 보 접합부의 시공성 향상을 위해 PSC 보 내부에 H 형강, T 형강 등의 철골이 삽입된 새로운 합성보 형태의 접합부가 제안되어 왔다. 하지만, 매립형 PSC 공법으로 인해 PSC 공법의 장점이 반감되고 자중이 증가하여 접합부 물량이 증가하는 등의 단점이 나타나는 것으로 확인되었으며, 접합부에 대한 실험 및 해석적 연구결과는 미비한 상황이다. 따라서, 본 연구에서는 접합부의 시공 능력을 향상시키면서 자중 증가로 인한 접합부 물량을 최소화하기 위해 PSC 보 단부에 매립 플레이트를 이용한 접합 상세를 제안하였으며, 실물 크기의 시험체를 제작하여 매립 플레이트를 접합한 PSC 보의 구조성능 평가를 수행하고, 실험을 통해 확인하기 어려운 접합부에 대한 구조성능을 평가하기 위하여 범용 유한요소해석 프로그램인 Midas FEA를 이용하여 해석적 연구를 수행하였다.

본 연구는 총 6장으로 구성되었으며, 각 장의 내용을 간략화하면 다음과 같다.

제1장에서는 연구의 배경 및 목적을 기술하였고, 연구의 범위 및 방법을 명시하였다.

제2장에서는 기존 공법 및 연구 분석으로 PC 및 PSC 공법 접합부에 대한 기존 연구 분석을 통하여 기존 PC 및 PSC 공법 접합부에 대한 문제점을 파악하고 PC 및 PSC 공법 접합부 설계식에 대하여 고찰하였다.

제3장에서는 PSC 보 단부에 매립 플레이트를 이용한 접합 상세를 제안하고 제안된 접합부의 특징 및 각각의 접합 방법, 제작 순서에 대하여 기술하였다.

제4장에서는 단부 매립 플레이트로 접합된 PSC 보에 대하여 스터드 커넥터의 개수 및 수평 플레이트의 길이, 시험체의 길이를 주요 변수로 선정하여 실물크기의 시험체를 제작하여 실험을 실시하였다. 단부 매립 플레이트로 접합된 PSC 보의 실험 결과 PSC 보에 대한 구조성능은 파악할 수 있었으나, 시험체 제작 과정 및 운반 과정, 실험 과정에서 접합부 스터드에 부착된 변형률 게이지의 파손 및 탈락에 의해 접합부에 대한 역학적 구조성능을 파악하지 못하였다.

제5장에서는 실험적 연구에서 규명하기 어려운 접합부의 응력집중 현상 등의 역학적 거동을 파악하기 위하여 스터드 커넥터의 개수를 주요 변수로 비선형 정적 해석을 수행하였으며, 매립 플레이트 접합부의 설계식을 제안하였다.

제6장에서는 이상의 실험 및 해석적 연구를 통하여 얻은 결론을 기술하였다.| In response to the trend of buildings towards high-rise and large scale in construction market, efforts are being made in reduction of story height, increase in span, sustainability as an architectural demand, and reduction of raw material cost fluctuation, interim and long term increase, improvement of environment in construction field and reduction of construction waste. Construction waste problems in construction have been numerously pointed out, and study of recycling method using construction waste is maintained in the large frame of research. However, recycling of construction is realistically low, and the countermeasure against the waste arising in the construction is minimal. Green house gas such as carbon monoxide generated from the construction waste is threatening human life continuously by causing the climate change due to environmental disaster. To resolve such problems, Precast Prestressed Concrete method is regarded as the method to improve the economic effect by maximizing the efficiency by combining the advantages of reinforced concrete and steel structures as the practical means for high quality, reduction of form work and temporary work, stability of structures, durability, reliability, and cost reduction effect. However, partial shape is only used due to the difficulties of securing constructability and economy for the connections because of limitation of PSC technology, and such reduction of connection constructability is regarded as the drawback of PSC construction method. PSC method generally uses connection method that ledger is installed on larger beam and dapped end is installed on small beam, and small beam rests on larger beam, and PSC method caused the reduction of constructability as it requires complex construction ability such as fasteners for the separate mechanical connection for stress transfer, and weld of re-bar and reinforcing fastener. Although the design criteria of connection method of PSC beam using connectors are partially provided in KBC(2009), KCI(2012), ACI(2011) and PCI Design handbook(2010), but accurate criteria is not provided, and the appropriate experiment and analytical research result are required. Currently new types of composite beam have been proposed for the improvement of connection constructability in PSC beam that H type, T type steels are embedded in PSC beam. However, due to embedded PSC method, the advantage of PSC method has been decreased, and the results of experimental and analytical researches are not recognizable. Accordingly, this research proposed the connection detail using embedded connectors at the end of PSC beam for minimizing the connection material quantity due to the increase of self weight with improving the connection constructability, evaluated the structural performance of PSC beam that embedded connectors on the mock-up specimens, and conducted numerical research using finite element method, Midas FEA to evaluate the structural performance at the end connection which may be difficult to verify through experiment.

This research consists of total 6 chapters, the content of each chapter is summarized as follows.

In chapter 1, research background and objective have been written, and the scope of research and methodology is specified.

In chapter 2, it covers existing construction method and research analysis that the problems of existing PC and PSC connection method is examined through the literature survey of PC and PSC method connection, and studied the design equation of connection on the PC and PSC method.

In chapter 3, connnection detail is proposed using the end embedded connector at the end of the PSC beam, and the characteristics, connection method, manufacturing sequence of the proposed connection are written.

In chapter 4, the experiment using mock-up size specimen with the selected variables of number of stud connector, length of horizontal plate, specimen length has been conducted on the PSC beam connected using end embedded plate. Although the structural performance of PSC beam has been evaluated as the result of PSC beam test connected with the end embedded plate, the mechanical structural performance of embedded connectors has not been obtained due to the failure and dislocation of strain gauges attached in the connection studs in the process of specimen preparation, transportation, and experiment.

In chapter 5, nonlinear static analysis has been performed based on the important variable such as number of stud connector to examine the mechanical behavior of stress concentration, etc. at the connection which is difficult to verify using the test, and proposed the design equation of embedded connector.

In chapter 6, the conclusion obtained through above experiments and analytical research is written.; In response to the trend of buildings towards high-rise and large scale in construction market, efforts are being made in reduction of story height, increase in span, sustainability as an architectural demand, and reduction of raw material cost fluctuation, interim and long term increase, improvement of environment in construction field and reduction of construction waste. Construction waste problems in construction have been numerously pointed out, and study of recycling method using construction waste is maintained in the large frame of research. However, recycling of construction is realistically low, and the countermeasure against the waste arising in the construction is minimal. Green house gas such as carbon monoxide generated from the construction waste is threatening human life continuously by causing the climate change due to environmental disaster. To resolve such problems, Precast Prestressed Concrete method is regarded as the method to improve the economic effect by maximizing the efficiency by combining the advantages of reinforced concrete and steel structures as the practical means for high quality, reduction of form work and temporary work, stability of structures, durability, reliability, and cost reduction effect. However, partial shape is only used due to the difficulties of securing constructability and economy for the connections because of limitation of PSC technology, and such reduction of connection constructability is regarded as the drawback of PSC construction method. PSC method generally uses connection method that ledger is installed on larger beam and dapped end is installed on small beam, and small beam rests on larger beam, and PSC method caused the reduction of constructability as it requires complex construction ability such as fasteners for the separate mechanical connection for stress transfer, and weld of re-bar and reinforcing fastener. Although the design criteria of connection method of PSC beam using connectors are partially provided in KBC(2009), KCI(2012), ACI(2011) and PCI Design handbook(2010), but accurate criteria is not provided, and the appropriate experiment and analytical research result are required. Currently new types of composite beam have been proposed for the improvement of connection constructability in PSC beam that H type, T type steels are embedded in PSC beam. However, due to embedded PSC method, the advantage of PSC method has been decreased, and the results of experimental and analytical researches are not recognizable. Accordingly, this research proposed the connection detail using embedded connectors at the end of PSC beam for minimizing the connection material quantity due to the increase of self weight with improving the connection constructability, evaluated the structural performance of PSC beam that embedded connectors on the mock-up specimens, and conducted numerical research using finite element method, Midas FEA to evaluate the structural performance at the end connection which may be difficult to verify through experiment.

This research consists of total 6 chapters, the content of each chapter is summarized as follows.

In chapter 1, research background and objective have been written, and the scope of research and methodology is specified.

In chapter 2, it covers existing construction method and research analysis that the problems of existing PC and PSC connection method is examined through the literature survey of PC and PSC method connection, and studied the design equation of connection on the PC and PSC method.

In chapter 3, connnection detail is proposed using the end embedded connector at the end of the PSC beam, and the characteristics, connection method, manufacturing sequence of the proposed connection are written.

In chapter 4, the experiment using mock-up size specimen with the selected variables of number of stud connector, length of horizontal plate, specimen length has been conducted on the PSC beam connected using end embedded plate. Although the structural performance of PSC beam has been evaluated as the result of PSC beam test connected with the end embedded plate, the mechanical structural performance of embedded connectors has not been obtained due to the failure and dislocation of strain gauges attached in the connection studs in the process of specimen preparation, transportation, and experiment.

In chapter 5, nonlinear static analysis has been performed based on the important variable such as number of stud connector to examine the mechanical behavior of stress concentration, etc. at the connection which is difficult to verify using the test, and proposed the design equation of embedded connector.

In chapter 6, the conclusion obtained through above experiments and analytical research is written.