The loss of prestress in cable supported structure is a direct cause of structural deterioration of the structure. Thus, measurement and evaluation of the tensile force acted on a strand consist of the cable system have been a significant technological factor. However, a measurement method of tension for each of strands is not proposed, as well as conservative assessment of cable system is bing adopted in industrial application. This paper proposes a new and effective method for measurement of tensile force in a strand based on ultrasound. Electromagnetic acoustic transducer(EMAT) is used for generation of ultrasound. Tensile force acting on a strand can be measured by characterization of guided waves that propagate along the boundary of geometry. Consequently, proposed method is experimentally verified by some experiments using seven-wire strand.

In this paper, an magnetic hysteresis monitoring result for various PS tendon is indtoduced to apply the EM sensing technique to measure the tensile force of PSC bridge. The tensile force of PS tendon is a very important factor in the performance evaluation of PSC bridges. To measure the tensile force of PS tendons, the EM sensing based NDT method was developed but the proposed method cannot be applied to various class of PS tendons. The permeability of specimen was gradually decreased according to increase of tensile force.

PSC girder bridges, widely applied to bridge and railroad bridge (25 ~ 50 m), are a type of bridge that introduces compressive force in advance to the part where tensile force of concrete is generated. The tension force for introducing the compressive force by inserting the tendon into the concrete is a key element of the structural performance in the PSC. At present, however, measurement and verification of this is indirectly managed through deflection and cracking. However, it has become more necessary to develop practical evaluation methods of prestress force of PSC bridges. In this experiment, a small scale PSC beam with various curvature radii was made. Tension force monitoring with FBG sensor and EM sensor was performed on test members using 3 point flexural loading test. The measured values of the FBG sensors and the EM sensors used in the experiment were analyzed and compared with the measured values of the load cell.

PSC girder bridges, widely applied to bridge and railroad bridge (25 ~ 50 m), are a type of bridge that introduces compressive force in advance to the part where tensile force of concrete is generated. The tension force for introducing the compressive force by inserting the tendon into the concrete is a key element of the structural performance in the PSC. At present, however, measurement and verification of this is indirectly managed through deflection and cracking. However, it has become more necessary to develop practical evaluation methods of prestress force of PSC bridges. In this experiment, a small scale PSC beam with various curvature radii was made. Tension force monitoring with FBG sensor and EM sensor was performed on test members using 3 point flexural loading test. The measured values of the FBG sensors and the EM sensors used in the experiment were analyzed and compared with the measured values of the load cell.

As public service life of PSC bridges is on the increase, lots of effort has been devoted to verify safety of PSC bridges. On the safety of PSC bridges, effective prestress force is one of the most important factors. At the moment, however, indirect measurements are mostly employed to evaluate the effective prestress force during and after construction. In this study, performances of FBG and EM sensors, which can directly measure the effective prestress force, are tested and investigated.

For reinforced soil slopes with anchors, additional slope reinforcement using anchors is highly difficult due to their interference with previously installed anchors. This case study presents the applicability of high pressure jet nail for the reinforcement of slopes where additional reinforcement is needed due to the loss of tensile force in the anchors.

A new electromechanical impedance-based method was proposed to estimate the remaining tensile force of post-tensioning system. It was applied to a real-scaled anchorage system which has 19 strands, wedges, and anchor head, a bearing plate, and a steel duct. Experimental results showed that the proposed scheme has great potential to evaluate the remaining tensile force quite accurately.

Simulation studies were performed to study the possibility of tensile force monitoring with piezoelectric sensors attached on anchorage devices of bonded tendon systems. The results showed that the impedance signals from piezoelectric sensors has sensitivity enough to evaluate the effective tensile force.

This study propose the embedded sensing system for tensile force estimation of PSC tendon using FBG and EM sensors. Through experimental study, it was found that the tensile force can be estimated by measuring the strain and permeability using proposed sensing system.

A PSC girder with I-typed section is one of the most common types applied to road and rail bridges in South Korea. As public service life of PSC bridges is on increase, lots of effort has been devoted to verify safety of PSC bridges. On the safety of PSC bridges, effective prestress force is one of the most important factor. At the current time, however, indirect measurements are mostly employed to measure the effective prestress force during construction. In this study, performances of FBG and EM sensors, which can directly measure the effective prestress force, are tested and investigated. The test result can be useful to develop block-out PSC girders with FBG and EM sensors monitoring effective prestress force during service life.

In this study, long term monitoring of tensile force of pre-tensioned prestressing strand embedded in UHPC ribbed deck by means of FBG sensor encapsulated into 7-wire prestressing strand. Based on the monitoring result for two years, it was confirmed that the technique proposed in this study offers efficient and robust way of monitoring the internal prestress of pre-tensioned PSC structures.

When prestressing tendons are placed with non-equal prestressing forces, restoring forces(torsional moment and bimoment) are occurred. Restoring forces was derived based on the theorem of virtual work for the purpose of controlling the torsional rotation. Numerical analysis was carried out on the existing double-T beam to clarify that the torsional rotation could be controlled by restoring forces.

To evaluate the prestressing loss of tendon caused by deflection angle, test is conducted with the variables of a deflection angle and a diameter of deviator head. Results show that the prestressing loss increases when the delfection angle increases but the diameter of deviator head gives no significant influence on the prestressing loss.

Rolling fatigue test was performed to study the behavioral characteristics of prestressed rib-type UHPC deck built-in optical fiber sensors for cable-stayed bridges. As the result, it was verified that this deck has sufficient structural integrity using optical fiber sensors

PSC거더교는 탁월한 안정성, 사용성 등의 특징으로 전세계적으로 가장 많이 사용되는 교량의 한 형식이다. 그러나, 긴장재 (강연선)의 시공오차나 곡률반경 등에 의하여 절곡되는 상황이 발생하는 경우가 생기며, 이는 국부적인 긴장력의 손실울 유발한다. 그러나, 일반적으로 설계와 시공과정에서는 긴장재의 국부적인 절곡으로 발생하는 긴장력의 손실에 대하여는 간과하고 있다. 이 연구에서는 PSC 거더 연속화 지점부에서 시공오차와 선형반경으로 인하여 발생하는 긴장력 손실량을 실험적으로 규명하였다. 또한, 국부적 긴장력 손실을 감소시킬수 있는 공법을 제안하고 이에 대한 효용을 실험으로 검증하였다. 실험결과에 따르면 국부적 절곡에 의해 최대 10%의 긴장손실이 나타났고, 블록아웃 공법을 통해 손실률을 최대 약 5% 감소시킬 수 있는 것으로 나타났으며, 이는 블록아웃 공법으로 연속화 교량의 긴장효율을 향상시킬 수 있음을 의미한다.

The FBG sensor responses simultaneously to changes in thermal strain as well as elastic strain. Thus the total strain measured from a single FBG sensor shall be corrected to obtain the elastic strain by removing the temperature effect. This paper addresses how the temperature effect can be removed when the FBG sensor is encapsulated in a 7-wire steel strand. For this purpose, fundamental properties of the FBG sensor are identified through tests using a controlled temperature chamber. Then field measurements on a UHPC pi girder with the size of 11.0 m long, 5.0 m wide, and 0.6 m high have been conducted for about one year, and the prestressing force is estimated using the raw data from the FBG sensor and by applying temperature correction technique proposed in this study. Estimated results indicate that the proposed correction technique is executable for extracting the elastic strain from monitoring data using the FBG sensor in civil infrastructures.

Theoretical modeling is presented for the prediction of prestress loss of strands during the steam curing process. The model comprises heat transfer model, bond-slip model at elevated temperature and micromechanical model for prestress loss. The model was able to predict the experimentally measured prestress loss in a reasonable accuracy.

In prestressed concrete (PSC) bridges, structural damage such as concrete cracks is related to the shift of the neutral axis due to the reduction in tendon forces. As such, monitoring the tendon force is important to maintain PSC bridges and prolong its remaining life. However, measuring the tendon force of PSC bridges in service is challenging. This study proposes a data fusion-based tendon force monitoring method using acceleration and strain responses. The proposed approach is validated using a PSC bridge model in the Pukyung National University.

현재 국내에 건설되고 있는 도심지내 고가도로 및 중소형 교량의 경우 일반적으로 교각 기둥 상부에 코핑부가 설치되며, 그 위에 거더가 놓이는 형식을 대부분 사용하고 있다. 하지만 이와 같은 형식에서의 코핑부는 큰 부피와 투박한 형상으로 인해 시각적 개방감을 저하시키는 비 친화적인 구조물로 인식되고 있다. 코핑-거더 일체형 강교량은 이와 같은 단점을 개선하고자, 코핑부를 거더의 높이 내에 위치시켜 상호 일체화함으로써 형하공간의 확보를 통한 하부차로의 공간 확대 및 미관향상의 장점을 지닌다. 본 연구에서는 코핑-거더일체형 강교량의 연결부 실물실험 결과를 토대로 유한요소 해석을 실시하여 수치해석적으로 획득한 변위 및 변형률 값을 비교, 분석하였다. 또한 코핑-거더 일체형 강교량의 구성요소 중 PC강봉에 가해지는 긴장력을 매개변수로 비선형 유한요소해석을 진행하여 코핑-거더 일체형 강교량 연결부의 구조적 성능을 분석한다.

본 연구의 목표는 PSC 거더 구조물의 긴장력 변화 조건하에 계측을 통한 잔류 긴장력을 예측하는데 있다. 이를 위해 본 연구에서는 도시형 자기부상열차 직선부 PSC 거더의 긴장력 변화에 따른 처짐, 동적임피던스, 그리고 가속도 계측을 통한 고유진동수를 계측하여 거더의 잔류긴장력 변화에 따른 계측 데이터의 변화를 분석하였다.