• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.743-746
• /
• 2011

본 연구에서는 유한요소해석을 이용하여 차량속도 및 긴장재의 설계에 따른 CFTA 거더의 동적거동 및 동적증폭계수를 분석하였다. 긴장재의 해석변수로서는 긴장재의 양과 긴장력을 고려하였으며 차량하중은 도로교설계기준의 DB-24 하중을 선택하였다. 차량하중은 3축-2트랙에 작용하는 등가절점하중으로 변환하여 속도에 따라 시간함수로 모델링하였다. 긴장재의 양은 외측 �� 내측 덕트의 유무에 따라 변화시켰으며 긴장력은 설계긴장력의 0%에서 100%까지 25%씩 증가시켰다. 차량속도는 40km/hr에서 100km/hr까지 20km/hr씩 증가시켰으며, 해석결과 긴장재의 긴장력 변화는 거더의 동적거동에 영향을 주지 않았으며 초기처짐에만 영향을 주었다. 긴장재의 양에 따라서는 거더의 동적거동이 다르게 나타났으며 긴장재의 양이 적을 수록 동적처짐은 증가하였다. 이를 바탕으로 거더의 동적증폭계수(DAF)를 산출하였으며, 이 결과 긴장재가 없는 경우에도 도로교표준시방서에서 정한 기준 값보다 매우 작은 거동을 보였다.

• Journal of the Society of Disaster Information
• /
• v.17 no.1
• /
• pp.128-142
• /
• 2021

Purpose: This study examines the safety management of anchors that have already been constructed and evaluates the results of lift-off tests conducted at the site. The purpose of the project is to study countermeasures if necessary. Method: Compare the residual load gained after the lift-off test at 36 points behind the site with the preemptive load, allowable load, and design load. We also analyze stability through this and evaluate the stability of anchors. Results and Conclusion: The residual tension at 26 points remained stable. However, the residual load at 10 points was analyzed to be greater than the designed load and less than the allowable load, and it was evaluated as an instability that could cause fracture problems. Therefore, anchors with unstable conditions at 10 points should be monitored and monitored through periodic measurements and quality tests, and the anchor should be observed at the surrounding points as well as the relevant points to maintain stability.

• Journal of the Korea Concrete Institute
• /
• v.16 no.3 s.81
• /
• pp.335-344
• /
• 2004

A general composite section of precast and cast-in-place concrete with prestressed and nonprestressed reinforcements was analyzed to calculate residual stresses and loss of prestressing force caused by internal constraints of concrete long-term deformation. From the analytical results, equations to design additional prestressing force and to evaluate resistant moment of the composite section were proposed. The equations shows that the additional prestressing force can be over-estimated if the loss rate of the first prestressing force is over-estimated from the lumped sum of a design code. The analytical procedure with the proposed equations has been applied to a composite section using the AASHTO Type 5 girder. The loss rates of the additional prestressing force appling to the precast concrete girder was less than those appling to the composite girder. However, the resistant moment of the additional prestressing force on the composite girder was much larger than that on the precast concrete girder. The additional prestressing force appling to the composite section was very effective for strengthening of the prestressed concrete composite girder.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.178-181
• /
• 2011

본 연구에서는 광섬유센서를 내장한 스마트강연선을 이용하여 초고성능콘트리트로 제작된 하이브리드 사장교 세그먼트의 횡방향 도입 긴장력을 계측하고 세그먼트 내부의 프리스트레스를 계측하여 즉시손실에 해당하는 정착장치 활동에 의한 손실과 마찰손실을 도로교설계기준(2005)의 설계 마찰손실과 비교하였다. 제작된 2개의 UHPC 사장교 세그먼트는 횡방향 길이 16.7m, 종방향 길이 1.75m, 높이 1.5m이며 각 시험체의 1/4, 1/2, 3/4지점에 긴장력을 계측하기 위해 3개의 FBG센서를 배치하였다. 긴장력은 유압잭을 이용하여 5개의 강연선에 동시에 순차적으로 도입되었으며, 단부에서 최대 도입 긴장력은 세그먼트 1은 734kN, 세그먼트 2는 639kN이었다. 도로교설계기준에 제시된 마찰계수의 중간값(파상마찰계수=0.00405, 곡률마찰계수=0.20)을 사용하여 FBG센서 위치에서 계산된 긴장력은 계측치와 5% 이내의 차이를 보였으며, 정착장치 활동에 의한 순간손실은 긴장단에서 최대 12.8%로 계측되었다. 이로부터 이 연구에서 제시하는 긴장력계측방법의 적용성을 입증할 수 있었으며, 향후 이 방법은 프리스트레스트 콘크리트 교량의 설계기준 마찰계수 개정을 위한 연구에 좋은 도구로 활용될 수 있을 것으로 기대된다.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.1 no.2 s.2
• /
• pp.103-114
• /
• 2001

As the results of comparison with several anchorage design methods of PSC box girder, stress superposition effect by the order of prestressing force can't be considered in the case of multi-anchorage design with existing design methods. In anchorage design by 3-D finite element analysis, estimation of stress concentration region and stress flow are correctly defined, but the estimation of sectional forces in anchorage is very complicated. In the case of anchorage design by strut-tie model method, the stress superposition effect can be considered and sectional forces in anchorage are easily calculated. Therefore, strut-tie model method is remarkably suitable to anchorage design if geometrical conditions of the truss members are carefully considered.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.19 no.2 s.72
• /
• pp.115-124
• /
• 2006

The 1st and 2nd tension forces of the PSSC(Prestressed Steel and Concrete) grider constructed with commercial rolling beams and concrete are optimally designed. The design variables are the 1st and 2nd tension forces due to multi-step prestressing and live load. The objective function is set to the maximum live load. Design conditions are allowable stresses at the top and bottom of slab, beam and infilled concrete due at the several construction stages. A Matlab based optimization program is developed. The results show that the tendon position as well as concrete compression strength have significant influence on the beam strength.

• Computational Structural Engineering
• /
• v.11 no.4
• /
• pp.177-186
• /
• 1998

PSC 연속 평판슬래브의 설계는 부정정 평판슬래브에 대한 정확한 해석의 어려움 등으로 등가보이론과 등가골조이론에 의한 근사식을 수정없이 사용하거나 컴퓨터를 이용한 해석에 의존하고 있으나 해석결과를 간단하게 정확히 평가할 수 있는 기법은 없는 실정이다. 또한 PSC 연속 평판슬래브의 부재력은 긴장재의 곡선형태에 따라 변하므로 실제 설계시 PS 긴장재의 정확한 곡선식을 찾는 것은 매우 중요하다. 본 연구에서는 비부착 PSC 연속 평판슬래브를 설계할 때 기둥과 기둥을 연결하는 PS 긴장재의 기하학적 곡선형태를 결정하는 방법과, PS 긴장력으로 인해 발생하는 평판슬래브의 기둥부 휨모멘트에 대하여 판이론을 기초로 간편하게 계산하는 방법을 제안하였다. 본 연구에서 제안된 이론으로 계산된 PSC 연속 평판슬래브에 대한 해석값과 유한요소 해석에 의한 지점 부모멘트를 비교 검토하여, 본 논문에서 제시한 기법의 타당성을 입증하였다. 따라서 본 연구는 설계자에게 컴퓨터의 해석결과를 간단하고 정확하게 검증할 수 있도록 하였다.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.549-558
• /
• 2000

In strengthening structure, the external post-tensioning method which secure clearness in the structure analysis process is adopted to bridges as well as architecture structure. In this study, to investigate the behavior of composite beam in the process of post-tensioning, the amount of prestress force loss, the amount of prestressed compression stress at the lower flange and the behavior of lower flange connected with anchorage are analyzed by comparing the results of finite element analysis with the measured results of installed strain gauges. After finishing the post-tensioning, the strengthening effect of external post-tensioning method is analyzed by static loading test. It is also investigated that the strengthening effect of shear section in the harped external post-tensioning specimens.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.181-192
• /
• 2007

In domestic case, there are no results of corresponding researches for measuring external tendon force. The purpose of the present paper is therefore to measure external tendon force by using deriving ultrasonic method. For this purpose, we designed and manufactured wedges and test system, and measured ultrasonic pulse velocity and pulse amplitude. By using measured data, we tried to analyze the characteristics of tendon force, and to derive the relationship between tendon force and ultrasonic pulse velocity, finally to develop the technic of measuring system using ultrasonic pulse velocity. So tendon force-velocity relationship was proposed by equations, and those equations of which errors were 3.92~8.77% will be possible to adapt in-site.

• Tunnel and Underground Space
• /
• v.28 no.5
• /
• pp.493-511
• /
• 2018

This paper deals with visual confirmation device for tensile force verification in order to cope with tensile force loss of ground anchor. Ground anchors are constructed to ensure the stability of social infrastructure facilities, but continuous loss of tensile force is seriously concerned about safety of the facilities. This requires the maintenance of the anchors, but the current measuring of residual tensile force is done by sampling, taking into account economic aspects, which limits precision. In this paper, conducted a conceptual design, tensile experiment, and field test for the purpose of developing an anchor tensile force visual device to check the tensile force of the anchors.