For the rational analysis and safe design of reinforced concrete pile caps by using the three-dimensional (3D) strut-and-tie model method, the effective strength of concrete struts must be determined accurately. In this study, an equation of the effective strength of concrete strut for a typical and most appropriate 3D strut-and-tie model for four-pile caps is proposed. In the development of the equation, the effects of 3D stresses associated with tensile strains in reinforcing bars crossing a strut, deviation angle between strut orientation and compressive principal stress flow, the degree of confinement provided by the flexural reinforcement, and shape ratios defining the geometry of a four-pile cap, are considered. 3D strut-and-tie model analyses of 115 reinforced concrete four-pile caps were carried out to evaluate the proposed equation and to compare the proposed equation with those equations in several design specifications. The ultimate strengths predicted by using the proposed strut strength equation were most consistent and agreed reasonably well with experimental results.
스트럿-타이 모델 방법을 이용한 철근콘크리트 파일캡의 합리적 해석과 설계를 위해서는 3차원 파일캡 스트럿-타이 모델의 스트럿 유효강도를 스트럿이 위치한 곳의 응력 및 변형률 상태, 스트럿과 압축주응력 흐름과의 불일치의 영향, 그리고 철근에 의한 스트럿의 구속 정도 등의 주요 인자를 고려하여 정확하게 결정하여야 한다. 이 연구에서는 다양한 기하학적 설계조건과 기둥의 축하중을 지배적으로 받는 Four-pile Cap의 3차원 스트럿-타이 모델 해석/설계를 위한 스트럿의 유효강도 식을 개발, 제안하였다. 제안한 유효강도 식의 적합성을 검증하기 위하여 세계 주요설계기준 및 이 연구에서 제안한 스트럿 유효강도 식을 이용하여 파괴실험이 수행된 115개 파일캡 시험체의 파괴강도를 예측하고, 그 결과를 비교분석하였다. 이 연구에서 제안한 스트럿의 유효강도 식은 파일캡의 모든 설계변수 및 스트럿-타이 모델의 형상 변화와 무관하게 파일캡의 파괴강도를 세계 주요설계기준의 것에 비해 가장 정확하고 일관성 있게 예측하였다.
ACI-ASCE Committee 445 (2002) Examples for the Design of Structural Concrete with Strut-and-Tie Models; SP-208. American Concrete Institute, Farmington Hills, Michigan, USA.
ACI-ASCE Committee 445 (2010) Further Examples for the Design of Structural Concrete with Strut-and-Tie Models; SP-273. American Concrete Institute, Farmington Hills, Michigan, USA.
Alshegeir, A. (1992) Analysis and Design of Disturbed Regions with Strut-Tie Models. Ph.D Dissertation, School of Civil Engineering, Purdue University, Indiana, USA.
American Association of State Highway and Transportation Officials (2018) AASHTO LRFD Bridge Design Specifications. 8th Edition, Washington D.C., USA.
American Concrete Institute (2014) Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary. Farmington Hills, Michigan, USA.
Bergmeister, K., Breen, J. E., and Jirsa, J. O. (1991) Dimensioning of the Nodes and Development of Reinforcement. IABSE Colloquium, Report, International Association for Bridge and Structural Engineering, Zurich, Switzerland, 551-556.
Bergmeister, K., Breen, J. E., Jirsa, J. O., and Kreger, M. E. (1993) Detailing in Structural Concrete. Research Report 1127-3F, Center for Transportation Research, University of Texas at Austin, Texas, USA.
Canadian Standards Association (2014) Design of Concrete Structures, A23.3-14. 6th Edition, Rexdale, Ontario, Canada.
Chae, H. S., Kim, B. H., and Yun, Y. M. (2011) Indeterminate Strut-Tie Model and Load Distribution Ratio of Continuous RC Deep Beams – (II) Validity Evaluation. Journal of Korean Concrete Institute KCI, 23, 13-22. (in Korean)
Clarke, J. L. (1973) Behavior and Design of Pile Caps with Four Piles. Report No. 42.489, Cement and Concrete Association, London, UK.
Comite Euro-International du Beton (2010) CEP-FIP Model Code 2010. International Federation for Structural Concrete (fib), Lausanne, Switzerland.
European Committee for Standardization (2004) Eurocode 2: Design of Concrete Structures. Brussels, Belgium.
Ha, T. H. and Hong, S. G. (2005) Effect of Diagonal Cracking on the Strength of Concrete Strut in RC Members. KCI Spring Conference, 383-386.
Kim, B. H., Chae, H. S., and Yun, Y. M. (2011) Indeterminate Strut-Tie Model and Load Distribution Ratio of Continuous RC Deep Beams – (I) Proposal of Model & Load Distribution Ratio. Journal of Korean Concrete Institute KCI, 23, 3-12. (in Korean)
Kim, B. H., Chae, H. S., and Yun, Y. M. (2013) Refined 3-Dimensional Strut-Tie Models for Analysis and Design of Reinforced Concrete Pile Caps. Journal of the Korean Society of Civil Engineers 33(1), 1-16. (In Korean)
MacGregor, J. G. (1988) Reinforced Concrete - Mechanics and Design. Prentice Hall, Englewood Cliffs, New Jersey, USA.
MacGregor, J. G. (1997) Reinforced Concrete - Mechanics and Design. 4th Edition, Prentice Hall, Englewood Cliffs, New Jersey, USA.
Marti, P. (1985) Basic Tools of Reinforced Concrete Beam Design. Journal of American Concrete Institute 82(1), 46-56.
Nielsen, M. P., Braestrup, M. W., Jensen, B. C., and Bach, F. (1978) Concrete Plasticity, Beam Shear - Shear in Joints - Punching Shear. Special Publication, Danish Society for Structural Science and Engineering, Lyngby, Denmark.
Portland Cement Association (2004) AASHTO LRFD Strut-Tie Model Design Examples. Skokie, Illinois, USA.
Ramirez, J. A. and Breen, J. E. (1983) Proposed Design Procedure for Shear and Torsion in Reinforced and Prestressed Concrete. Research Report 248-4F, Center for Transportation Research, University of Texas at Austin, Texas, USA.
Sabnis, G. M. and Gogate, A. B. (1984) Investigation of Thick Slab (Pile Cap) Behavior. Proc., ACI Journal, Farmington Hills, Michigan, 81, 35-39.
Schlaich, J., Schaefer, K., and Jennewein, M. (1987) Towards a Consistent Design of Structural Concrete. Journal of the Prestressed Concrete Institute 32(3), 74-151.
Suzuki, K. and Otsuki, K. (2002) Experimental Study on Corner Shear Failure of Pile Caps. Transactions of the Japan Concrete Institute 23, 303-310.
Suzuki, K., Otsuki, K., and Tsubata, T. (1998) Influence of Bar Arrangement on Ultimate Strength of Four-Pile Caps. Transactions of the Japan Concrete Institute 20, 195-202.
Suzuki, K., Otsuki, K., and Tsubata, T. (1999) Experimental Study on Four-pile Caps with Taper. Transactions of the Japan Concrete Institute 21, 361-368.
Suzuki, K., Otsuki, K., and Tsuchiya, T. (2000) Influence of Edge Distance on Failure Mechanism of Pile Caps. Transactions of the Japan Concrete Institute 22, 361-368.
Thurlimann, B. (1976) Shear Strength of Reinforced and Prestressed Concrete - CEB Approach. Special Publication 59-6, American Concrete Institute, Detroit, USA.
Vecchio, F. J. and Collins, M. P. (1982) The Response of Reinforced Concrete to In-plane Shear and Normal Stresses. Publication No. 82-03, Department of Civil Engineering, University of Toronto, Canada.
Willam, K. J. and Warnke, E. P. (1975) Constitutive Model for the Triaxial Behavior of Concrete. IABSE Proceedings 19, 1-30.
Yun, Y. M. and Ramirez, J. A. (2016) Strength of Concrete Struts in Three-dimensional Strut-Tie Models. Journal of Structural Engineering, ASCE 142(11).
- Publisher :Korea Concrete Institute
- Publisher(Ko) :한국콘크리트학회
- Journal Title :Journal of the Korea Concrete Institute
- Journal Title(Ko) :콘크리트학회 논문집
- Volume : 31
- No :1
- Pages :49-59