하이브리드 거더 접합부의 설계 지침 제안

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 건설환경공학부, 2018. 2. 조재열.하이브리드 거더는 강거더와 콘크리트거더를 길이방향으로 접합하여 설계한 거더이다. 강거더와 콘크리트거더를 연결하는 하이브리드 거더 접합부는 일반적으로 강판과 속채움 콘크리트, 그리고 전단연결재로 구성되어있다. 접합부에서는 이종 재료 간의 강성 차이로 응력집중현상이 발생할 수 있어 설계 시 주의가 요구되는 부분이다. 현재 국내에는 하이브리드 교량 접합부 설계를 위한 설계기준이 존재하지 않는 상황이다. 전단연결재와 관련하여 국내 도로교 설계기준에는 강거더와 콘크리트바닥판으로 이루어진 합성단면에 대한 스터드형 전단연결재에 대한 규정이 존재하나 이를 접합부 설계에 적용 가능한지에 대해서는 검증 과정이 필요하다. 본 연구에서는 해당 규정의 적용 가능성을 확인하기 위해서 해석 및 실험적 연구를 수행하였다. 추가적으로 접합부를 구성하는 강판의 길이, 즉 접합부의 길이가 하이브리드 거더에 미치는 영향에 대해서 매개변수 연구를 추가적으로 수행하였다. 하이브리드 거더 접합부에서는 스터드의 휨변형으로 인해 부분합성거동이 발생하므로 접선 방향의 슬립물성을 고려한 해석모델을 정립하였다. 해석적 연구에 사용된 거더는 기존 연구자의 해석적 연구에서 사용한 거더를 사용하였다. 간단한 검증을 수행한 결과 정립한 해석모델은 접선 방향의 물성에 따라서 비합성 거동과 부분합성 거동, 완전합성 거동으로 구분되는 합성거동의 유형을 잘 모사할 수 있었다. 다음으로 해석 모델의 설계 상세를 기반으로 스터드의 개수를 실험 변수로 하여 총 3개의 실험체를 제작하고 하중재하실험을 수행하여 합성거동의 유형과의 관계를 분석하였다. 실험 결과 접합부 내부에 배치된 스터드의 개수에 따라 실험체는 비합성 거동과 완전합성 거동을 보이는 것을 확인할 수 있었다. 또한 도로교 설계기준에 제시된 합성단면에 적용하는 스터드에 대한 설계기준을 하이브리드 거더 접합부 설계에 적용할 경우 완전합성 거동을 보이므로 해당 규정을 적용 가능하다는 사실을 확인할 수 있었다. 접합부의 길이에 대한 영향을 확인하기 위해 매개변수연구를 수행하였다. 모든 해석에서 총 길이와 강거더의 길이는 동일하게 설정하였기 때문에 접합부의 길이가 증가할수록 PSC거더의 길이가 짧아지고 구조물의 강성이 커지므로 거더의 최대하중은 증가하게 된다. 증가된 구조물의 강성에 의한 효과를 제거한 순수한 접합부 길이에 대한 효과를 얻기 위해 동일한 길이에서 비합성 거동과 완전합성 거동의 최대하중 차이를 길이 효과로 가정하고 접합부 길이 증가에 따른 변화를 확인하였다. 매개변수연구 결과 접합부 길이가 증가함에 따라 발생하는 길이 효과는 최대하중 대비 약 1 % 내외로 미비한 것으로 나타났다.Hybrid girder consists of steel girder and concrete girder connecting in longitudinal direction. Joint in hybrid girder, connecting steel girder and concrete girder, is composed of the steel plate, filling concrete and shear connector. Joint is critical part because stress concentration can occur the difference of stiffness between two materials. For this reason, it is needed to be careful when design of joint. Currently there is no domestic design standard for design of joint in hybrid girder. The design standard about stud type shear connector for design of composite section combining steel girder and concrete slab is presented in Korean highway bridge design code, but the applicability of this standard for design of joint is not verified. In this thesis, finite element analysis and experimental test were conducted for suggestion of design guideline for joint in hybrid girder. Finite element model was developed using interface element to consider slip behavior in tangential direction at the interface between steel and concrete. Slip behavior should be considered because partial composite behavior was able to occur due to flexural deformation of stud. Target structure was selected which used in previous study conducted by other researcher. As a result of simple verification, the developed model was proper to simulate all types of composite behavior – non composite behavior, partial composite behavior and full composite behavior – just changing material properties of interface element. Total three specimens were fabricated and experimental test was conducted to find the relation between the number of stud and type of composite behavior. As experimental results, the specimen using the number of stud followed Korean highway bridge design code was shown full composite behavior and the other specimens which using less number of stud was shown non composite behavior. As a result, the design standard about stud in Korean highway bridge design code was applicable to design of joint in hybrid girder. Parametric study was conducted to find the effect of joint length. Equal total length and steel girder length were used in all analysis case. If the joint length was increased, PSC girder length was decreased. Therefore, the stiffness of structure was increased and finally the maximum load of hybrid girder was also increased. In order to exclude the effect of stiffness, the effect of joint length was calculated by the difference of maximum load increment between full composite behavior and non composite behavior. The results of parametric study showed that the effect of joint length was insignificant, less than about 1.5 % of maximum load.1. Introduction 1 1.1. Research Background 1 1.2. Research Objectives 3 1.3. Outline 3 2. Literature Review 5 2.1. Design of Joint in Hybrid Girder 5 2.1.1. Korean highway bridge design code (2010) (Korea) 5 2.1.2. Design of joint using prestressing tendon 6 2.1.3. Design of joint using stud type shear connector 7 2.2. Previous Studies 8 2.2.1. Kim, Kwang-Soo et al (2008) 8 2.2.2. Kim, Sang-Hyo et al (2011) 9 2.2.3. Park, Bong-Sik (2016) 10 2.2.4. Limitations of previous studies 10 3. Development of Finite Element Model using Interface Element 12 3.1. Interface Element 12 3.1.1. General 12 3.1.2. Slip properties 13 3.2. Finite Element Model 14 3.2.1. Geometry of target structure 14 3.2.2. Finite element type and mesh 16 3.2.3. Material models and properties 19 3.2.3.1. Concrete 19 3.2.3.2. Steel, reinforcing bar, stud and tendon 21 3.3.2.3. Interface 22 3.2.4. Constraint conditions 23 3.2.5. Boundary conditions 23 3.2.6. Loading conditions 23 3.3. Simple Verification 24 3.3.1. Comparison model for verification 24 3.3.1.1. Park (2016) model 24 3.3.1.2. Merging Nodes model 24 3.3.2. Analysis results 24 3.4. Conclusion 26 4. Experimental Verification 27 4.1. Experimental Program 27 4.1.1 Test specimens 27 4.1.2. Material properties 31 4.1.3. Test set-up 31 4.2 Test Result 33 4.2.1. Failure mode and crack pattern 33 4.2.2. Measurement position-deflection relationship 35 4.2.3. Load-deflection relationship 36 4.3. Finite Element Analysis 36 4.4. Conclusion 39 5. Parametric study 40 5.1 Finite Element Model 40 5.1.1 Geometry of target structure 40 5.1.2. Finite element type and mesh 41 5.1.3. Material models and properties 41 5.1.4. Constraint conditions 44 5.1.5. Boundary conditions 44 5.1.6. Loading conditions 44 5.2 Parametric Study 45 5.2.1. Parameter : joint length 45 5.2.2. Assumption to find the effect of joint length 46 5.2.3. Analysis results 47 5.3 Conclusion 50 6. Conclusions 51 6.1 Summary and Conclusions 51 6.2 Prospects for Further Study 52 Reference 53 국문초록 61Maste

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