• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.2
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• pp.23-34
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• 2021

Cable was targeted for cable, which is a main material of cable-stayed bridges that have high frequency of use at home and abroad and many future construction plans. First of all, experiments were conducted on temperature loads that were permanently used due to changes in temperature of cables and changes in air temperature, taking into account changes in normal fat. The dynamic characteristics of cables were compared and analyzed by applying various systems to change dynamic characteristics by applying temperature change of cables. Comparing and analyzing the dynamic characteristics of cables, the acceleration, frequency and tension of cables due to temperature rise tended to decrease, the degree of influence of displacement of cables was analyzed, and the results of the mode characteristics of cables were analyzed. In particular, the correlation of cable acceleration, natural frequency, and tension due to changes in cable temperature showed that the cable tension is highly sensitive to acceleration and natural frequency.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.102-112
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• 2020

In this study, in order to design a wedge-type anchor that can hold an wide carbon plate with a width of 100 mm or more that can be used in a bridge structure, the mechanical behaviors are evaluated based on the main design variables such as the angle of the wedge and the coefficient of friction between the guide and the wedge. The stress state of the carbon plate was calculated by numerical analysis method for each design variable, and the performance of the anchor in the critical state was evaluated according to the failure criteria for composite material, and the optimal design specifications of the anchor were determined based on numerical results. The performance of the optimally designed anchor was verified through actual experiments, and the results of this study are considered to be useful for the optimal design of the CFRP plate anchor to reinforce large structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.95-102
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• 2021

Elastometic bearings using flexible rubber materials have recently been widely applied for seismic retrofit of bridges. However, due to various factors, the aging of the rubber material progresses, which causes the shear stiffness change of the bearing, which affects the seismic performance of the bridge. For natural rubber, accelerated heat aging test was performed with variables of heating temperatures and exposure time to analyze shear characteristics. As aging progresses (i.e. increase of temperature and exposure time), the maximum shear stress and shear strain decrease. Also, the shear stiffness is greatly increased at the same shear strain. This means that the rubber material is hardened, implying that the seismic performance of the elastomeric bearing becomes poor.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.21-28
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• 2022

The TMD has a simple structure than other vibration control devices and shows excellent control performance for the simple harmonic vibration generated in the structure. However, the vibration control range is narrower than other control devices, making it vulnerable to vibration cycles caused by unexpected external loads. The ETMD developed in this study consisted of Mass with electromagnets. Therefore when supplying a current, the magnetic field is formed to increase the friction force with the friction plate, thereby instantaneously controlling the behavior of the Mass. The experiment was conducted to compare the control performance of the control device by installing the ETMD developed for control performance evaluation in the center of the model simple beam bridge to forced excitation at 3.02 Hz where the maximum bending displacement occurs. As a result of the experiment, ETMD exhibited excellent control performance with a maximum bending displacement attenuation rate of 57.51%.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.1-7
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• 2023

Durability was evaluated by performing a full-scale vertical load fatigue test and a wheel load performance test on the HRS, which reduces the replacement time of the existing expansion joint and improves serviceability to allow partial replacement by lane. As a result of the vertical load fatigue test, the maximum stress of the rail-type expansion joint is 170 MPa, which is about 47.8% of the yield strength of the HRS expansion joint rail 355 MPa. The vertical load fatigue test of the HRS expansion joint with improved serviceability set the size and load of the load plate according to the road bridge design standards, did not show any fracture behavior in the vertical load fatigue test and the wheel load performance test 2 million times, and its durability and safety were verified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.58-66
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• 2023

In this study, cable tension was measured using the vibration method, and a vision-based system was applied as a sensor to measure the displacement response of a cable in a non-contact method. In the vision-based system, the camera is installed in a location that considers the target structure and the field of view of the camera. However, it can be difficult to recognize the control points required to measure the displacement response of a structure as the target structure and other structures such as vehicles may be included in the image at the intended installation location. In this study, a distorted image including a vehicle shows inaccurate results in image analysis due to the installation position of the vision-based system. Accordingly, the image including the vehicle was eliminated by calculating the similarity between the two images. To verify the validity of the method of estimating the cable tension of cable-stayed bridges using the proposed method, the vibration method was applied to cable-stayed bridges in service to measure the tension.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.127-135
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• 2006

In this study, steel deck bridges are chosen as analytic model to show the structural behaviors generated by high temperature of pavement and to formulate the simplified approximate analysis of thermal effects. In general, the thermal effect is changed by the material property of pavements and environmental temperature as well as shape, size and boundary conditions of bridge. Specially, this effect is the representative initial stress problem dependent on time. The thermal effect, however, does not depend on time and thermal effect is regarded as initial load in this study. After these thermal loading is modelled as moving loads, influence lines of reactions of shoes are calculated and the successive pavement steps with arbitrary segments are determined to minimize the thermal effect of shoes by influence line.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.171-180
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• 2007

Reliability analysis of prestressed steel and concrete(PSSC) girders is conducted for deflection, stress and moment strength limit state. PSSC girder has strong advantages in terms of construction cost and vertical clearance for the span length of over 40 meters. In this paper, example PSSC girders with different span lengths, section dimensions and design stress levels are designed and analyzed to calculate the midspan deflection, stress and the section moment strength. Deflection limit state, stress limit state and strength limit state functions are assumed and the reliability indexes are obtained by Monte-Carlo simulation and Rackwitz-Fiessler procedure. The results show that the reliability of PSSC girder for deflection limit state is appropriately higher than the stress limit state and the reliability for moment strength is significantly conservative.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.134-144
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• 2007

In this study, a smart sensor unit is developed by using the smart sensor technology that is being rapidly developed in recent years for structural health monitoring system, and its performance is evaluated through various experiments, and also, damage detection experiment is performed on a model structure. This paper as the first half of this study contains the development and performance evaluation of the smart sensor. In the latter half of this study, structure damage detection experiment is performed for the application of verified smart sensor unit into structural health monitoring, and it is compared with a wire measurement system. The smart sensor is developed by using high-power wireless modem, MEMS Sensor and AVR microcontroller, and an embedded program is also developed for the control and operation of the sensor unit. To verify the performance of the smart sensor, many experiments are performed for sensitivity and resolution analysis tests, data acquisition by using cantilever beam and shaker, and on-site application using actual bridge. As a result, the smart sensor proves to be satisfactory in its performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.91-100
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• 2008

Multi-stepwise Thermal Prestressing Method(TPSM) is a newly proposed prestressing method, which is combined the external prestressing method and the external bonding method. Multi-stepwise thermal prestressing force is induced by cooling process of cover-plate in the multi-stepwise temperature distribution after the cover-plate being bolted to the girder. In this study, the heating capacity test of the developed heating system for applying the multi-stepwise TPSM effectively and multi-stepwise TPSM inducing test of H-beam is performed. Also, a field test of the rhamen type temporary bridge is carried out to evaluate the effect and application of the multi-stepwise TPSM. Truck load was loaded and compared with the structure analysis results.