• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.227-238
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• 2003

Due to deterioration of bridge, usually be using the external prestressing method among repair reinforcement method. But, there is much to be desired about a detailed account, almost it has analysed by cambers of girders, deflections of middle span and upper, bottom stresses of girders. Also, it is not examined closely that effect of internal prestress by external prestressing. The purpose of this study is confirmed the effect of internal tendons by external prestressing, estimation of additional external prestressing force and look for exact external prestressing force.

• 한국구조물진단유지관리공학회 논문집
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• 제5권2호
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• pp.103-109
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• 2001

In this paper, the prestressing order of tendons is studied to minimize a bursting force of an anchorage. The bursting forces is a primary factor of anchorage failures. The forces of the anchorage depend on the prestressing order and size of the tendons, if a lot of tendons are introduced to the anchorage. Many studies have been made to analyze the bursting force of the anchorage. However, the studies have been limited to the bursting forces of the anchorage having one or two tendons. PSC box girder bridges usually have a lot of tendons. And the difference of the bursting forces lies in the prestressing order of the tendons. As a result of the lack of studies on the prestressing order for the bridges, the order depends on the designer's intuition and experiences. It may be stated that this study should be useful for determining the reasonable prestressing order of tendons for the PSC box girder bridges.

• Computers and Concrete
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• 제5권2호
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• pp.135-154
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• 2008

This paper presents a nonlinear finite element analysis procedure for the seismic performance assessment of reinforced concrete bridge piers with unbonded reinforcing or prestressing bars. A computer program named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) is used to analyze reinforced concrete structures; this program was also used in our study. Tensile, compressive and shear models of cracked concrete and models of reinforcing and prestressing steel were used account for material nonlinearity of reinforced concrete. The smeared crack approach was incorporated. To represent the interaction between unbonded reinforcing or prestressing bar and concrete, an unbonded reinforcing or prestressing bar element based on the finite element method was developed in this study. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge piers with unbonded reinforcing or prestressing bars is verified by comparison of its results with reliable experimental results.

• 한국구조물진단유지관리공학회 논문집
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• 제5권4호
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• pp.147-153
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• 2001

The major objectives of this study are to investigate experimental and analytical behavior of composite steel plate strengthened by external post prestressing method and to study the increasing magnitude of load carrying capacity by the external post prestressing method. With installed strain gauges and LVDT, the change of structural behaviors according to the amount of prestressing force is measured and the effects of shear strengthening according to the degree of angle in tendon are studied. The analytical structural behavior according to the amount of prestressing force is also investigated using finite element method. The effectiveness of strengthening of external post prestressing method is proved and an efficient FEM model is suggested by comparing the test results and analyzing results.

• 한국구조물진단유지관리공학회 논문집
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• 제25권4호
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• pp.75-82
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• 2021

이 연구의 목적은 강관과 강봉을 이용하여 프리스트레스력의 도입이 가능하도록 개발된 프리스트레싱(prestressing reinforcing units using steel bar and pipe, 이하 SP) 보강재의 응력손실을 확인하는데에 있다. 주요변수는 SP 보강재의 종류, 프리스트레스력의 크기 및 도입방법이다. 실험결과 SP 보강재의 응력손실은 프리스트레스력이 직접 도입하는 초기단계에서 가장 크게 있었는데, 그 크기는 압축도입형 보다 인장도입형에서 더 크게 있었다. SP 보강재의 응력손실은 프리스트레스력이 항복강도의 80%로 도입된 P800 강종인 압축도입형 실험체에서 1.6%로 가장 낮았다. 한편 시간경과에 따른 SP 보강재의 릴랙세이션은 압축도입형의 경우 SP 보강재의 종류, 프리스트레스력의 크기에 관계없이 0.4~1.9%로 평가되었는데, 이는 설계기준들에서 제시하고 있는 릴랙세이션 2.5% 이하를 만족하는 수준이었다. 결과적으로 프리스트레스력 도입 즉시 발생하는 응력손실을 감안할 때에 개발된 SP 보강재의 재질과 프리스트레스력 도입방식 및 크기는 각각 P800, 압축도입형 및 항복강도의 80%로 추천된다.

• 한국재난정보학회 논문집
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• 제5권2호
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• pp.124-137
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• 2009

The research on the effect of the prestressing force on the frequency of PSC(Prestressed Concrete beam) has been conducted theoretically and experimentally, and a few theory has been presented. However, the presented theories show no agreement in predicting the effect of the prestressing force. In this paper, the theories on the effect of the prestressing force on the frequency of PSC beam are presented and evaluated using the experimental result. To obtain the experimental result, two PSC beam specimens were manufactured, and the modal test and analysis were performed. The modal analysis results revealed that the prestressing force increased the natural frequency of the PSC beam. Comparing predicted results using existing theories show that Kim's model, which substitutes the prestressing tendon with the equivalent beam, gives the best prediction result.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.955-960
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• 2003

For box girders in which the longitudinal tendon is profiled in the inclined webs. longitudinal prestressing force will induce transverse effects as well as longitudinal ones. In this paper. the method estimating transverse effects induced by longitudinal prestressing is proposed. The transverse effects in the slabs of box girders due to longitudinal prestressing are investigated. Numerical analyses are carried out depending on the parameters such as web inclination and ratio of girder length to tendon eccentricity. Analysis results show that when only prestressing are considered the magnitude of stresses in the slabs of box grder is not so large. However. if the other stresses due to dead and live load et al. are superposed on these stresses. it may be that the longitudinal prestressing effects are significant.

• 건설안전기술
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• 통권49호
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• pp.84-91
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• 2009

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 가을 학술발표회 논문집
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• pp.171-178
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• 1997

This paper describes the application of discretized continuum-type optimality criteria (DCOC) for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency fo the DCOC-based technique.

• 한국안전학회지
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• 제23권6호
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• pp.115-121
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• 2008

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.