• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.4
• /
• pp.183-193
• /
• 2006

This study deals with the response of reinforced concrete beams strengthened with carbon fiber sheets. Test beams are subjected to static loading and repeated loading. Based on the static test results of the RC beams strengthened with carbon fiber sheets, repeated loading tests are performed. The variables of repeated loading test are composed of the number of carbon fiber sheets, the existence of U-shaped band at the end for anchoring, and loading rate of repeated loading, etc. Test results show the flexural behavior, the characteristics of strength, the characteristics of ductility, the change of flexural rigidity, and the amount of energy loss of RC beams under monotonic incremental loading and repeated loading. The failure strain of carbon fiber sheets is also estimated under repeated loading. From the experimental results, this work presents a basis of the data needed to analyze and design the static and dynamic flexural response of RC beams strengthened with carbon fiber sheets.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.1 no.1
• /
• pp.64-72
• /
• 2008

Compression neuropathy around elbow and wrist are one of the common disturbing problems in the upper extremity. The understanding of normal nerve architectures and pathophysiologic changes in compression neuropathy is important to interpret the ultrasonographic images correctly. Compression neuropathies have characteristic ultrasonographic imaging features of flattened nerve at compression and hypoechoic swollen nerve with loss of fascicular patterns at proximal segments. Dynamic ultrasonographic imagings on motion can show dymanic subluxation of ulnar nerve and medial head of triceps muscle over the medial epicondyle in snapping triceps syndrome. Dynamic compression of median nerve also can be visualized in pronator teres syndrome by dynamic imaging studies. A quantitative measures of cross sectional area or compression ratio can be helpful to diagnose compression neuropathies, such as carpal tunnel syndrome or cubital tunnel syndrome. With the clinical features and electeophysiologic studies, the untrasonographic imagings are useful tool for evaluation of the compression neuropathies in the upper extremities.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.105-113
• /
• 2003

Because structural systems are becoming lighter and more flexible and have lower natural frequencies and dampings than before, coordinated rhythmic activities such as dancing, audience participation in arenas or concert halls, and aerobics result in undesirable levels of vibration. For rhythmic activities, it is resonant or near resonant behavior that result in significant dynamic amplification and hence human discomfort. The most rational design strategy is to provide enough of a gap between the natural frequency of a floor system and the dominant frequencies excited by planned human activities to assure reasonably that resonance will not occur. For the case study the vibration measurements were performed at the floor of a long-span multi-purpose hall during the rock concert of popular singer.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.1
• /
• pp.81-90
• /
• 2008

This study deals with a method to identify structural damage using the combined finite element method (FEM) and the advanced damage search technique. The novelty of this study is the application of plates with arbitrary damage shapes and their response due to the anomalies in a structure subjected to impact loading. The technique described in this paper may allow us not only to detect the stiffness distribution of the damaged areas but also to find locations and the extent of damage. To demonstrate the feasibility of the method, the algorithm is applied to a steel thin plate structures with an arbitrary damage shape. The results demonstrate the excellencies of the method from the standpoints of computation efficiency as well as its ability to investigate the arbitrary stiffness reductions.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.2
• /
• pp.1-8
• /
• 2020

In the case of power plant facilities, seismic stability of non-structural elements is important. In particular, Cabinet structures to which electrical equipment is attached, should have functional safety against earthquakes. Therefore, in this study the dynamic characteristics of non-structural elements inside existing power plant buildings were identified and the response level generated during dynamic behavior was analyzed. In addition, The steel plate dampers were adopted and adjusted to suit the size of the target equipment. In order to derive the optimal seismic reinforcement, the variables according to the attachment location were set and the responses were analyzed by the seismic movement input before and after reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.1
• /
• pp.160-165
• /
• 2014

In this study, an efficiency test was performed by fabricating MEMS (Micro Electro Mechanical Systems) based 3-axis acceleration sensor modules and an earthquake monitoring system was composed. Data acquisition device (NI-9239) with a 24bit ADC (Analog to Digital Converter) was used for improving the performance of 3-axis acceleration sensor modules and filtered data (100Hz Low Pass Filter) was used for reducing noises. Also this paper focused on detecting meaningful vibration in the building by developing the earthquake monitoring software. If vector sum of 3-axis acceleration is greater than the preset value, the value will be recorded and saved to the file.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.5
• /
• pp.1-12
• /
• 2018

This study presents the seismic response characteristics of domestic cable-supported bridges due to 3 earthquakes with magnitudes of 5.1, 5.8, and 4.5 in Richter scale, which occurred around Gyeongju region in 2016. The seismic acceleration response signals, recorded by the seismic acceleration sensors at the free field near bridge and designated positions on bridge, are utilized to characterize the seismic responses of structural elements of cable-supported bridges. The dynamic behaviors of bridges are presented through Fourier transform of acceleration time history. Using the peak accelerations normalized by those at the free fields, amplification effects on the tops of the pylons are analyzed comparatively bridge by bridge. Using aforementioned analyses, the necessity of development on the creteria of alert levels is discussed for the earthquake disaster response of cable-supported bridges.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.2 s.54
• /
• pp.189-198
• /
• 2009

In this paper, the performance of bridge health monitoring system(BHMS) installed in suspension bridge was tested and the field loading tests have been done by using BHMS to get quantitative results on the response of bridge. Before the field tests, globally structural analysis was performed to verify and estimate the test results and the static and dynamic field loading tests were carried out. Depending on comparison with results of field tests and structural analysis, field tests results were evaluated as 30%~50% less than structural analysis results, so it was confirmed that the bridge has excellent structural performance. Therefore field test results were measured within an acceptable error range, so it is verified that the BHMS in the bridge has been reliable and efficient.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.4 s.56
• /
• pp.137-147
• /
• 2009

In this study, several flexural vibration characteristics of prestressed concrete girders due to changes in prestress forces are experimentally analyzed. In order to achieve the objective, the following approaches are implemented. First, several methods to extract vibration response features from output-only signal are selected. Next, a large-scaled prestressed concrete girder model is constructed to analyze relation between the prestress forces and the vibration features in the prestressed concrete girder. Then acceleration responses are measured from the girder for several prestress force scenarios. Finally, vibration characteristics of the prestressed concrete girder due to change in prestress force are experimentally analyzed. The values of features extracted by the selected methods are reduced due to prestress-loss. Especially, the value of features are linearly reduced in the early prestress-loss.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.1
• /
• pp.59-66
• /
• 2017

In this paper, to protect the piping in nuclear power plants and various plant facilities, we have developed a damper using the friction method and carried out a study to analyze the performance. Friction typed damper means a device for attenuating vibration by generating a frictional force to the bearing and the shaft by applying a compressive force to the MER-Spring. In order to analyze the performance of the damper, the properties of MER-Spring and friction materials were analyzed, a study on the effects of friction was carried out, and the behavior of this equation was established. And, to determine whether deformation of the material and to examine the reliability of the behavior equation established, prototypes was produced and, through a performance test and finite element analysis of a damper made of specimens, they were analyzed. As a result, it is noted that the reliability of the material was confirmed, the coefficient of friction have to be adjusted according to the velocity, cyclic loading test and finite element analysis results show exhibits excellent results. In addition, a review of the dynamic loads in the future shall be performed for the usage in more broad fields.