• Steel and Composite Structures
• /
• v.13 no.4
• /
• pp.383-396
• /
• 2012

In order to develop a verification method for extremely low cycle fatigue (ELCF) of steel structures, the initiation mechanism of ductile cracks is investigated in the present study, which is the first step of brittle fracture, occurred in steel bridge piers with thick-walled sections. For this purpose, a total of six steel columns with small width-thickness ratios were tested under cyclic loading. It is found that ductile cracks occurred at the column base in all the specimens regardless of cyclic loading histories subjected. Moreover, strain history near the crack initiation location is illustrated and an index of energy dissipation amount is proposed to evaluate deformation capacity of structures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.4 no.4
• /
• pp.141-148
• /
• 2000

Recently the Carbon Fiber Sheet(CFS) is widely used for strengthening damaged RC structures. Strengthening compression members such as column can increase ductility and strength due to the confinement effect. In this experiment, the behavior of concrete cylinders confined by CFS was examined. The confinement pressure is increased linearly as axial stress is increased in low axial stress, and the confinement effect of CFS was rapidly developed after near maximum axial stress, thus axial strength and ductility was improved. As the ratio of CPS is increased, concrete cylinders failed due to local fracture of CFS. The confinement effect of circular section is more efficient than that of rectangular section. And significant improvement of axial strength, axial strain, transverse strain at failure is observed in circular section. This is because in rectangular section the local fracture of CFS near corner may be occured, thus the strain efficiency ratio must be considered for RC structures with CFS.

• Journal of Yeungnam Medical Science
• /
• v.19 no.2
• /
• pp.73-91
• /
• 2002

Method of management of the spine injury should be determined, based on the status of neurological injury as well as on the presence of traumatic instability. At the thoracic and lumbar spine, patterns of neurological injury are different from the cervical spine due to their neuro-anatomical characteristics. Especially, at the thoracolumbar junction, neurological injury patterns with their respective prognosis vary from the complete cord injury or conus medullaris syndrome to the cauda equina syndrome according to the injury level. The concept of Holdsworth's instability based on the posterior ligament complex theory has evolved into the current 3-column theory of Denis. Flexion-rotation injury and fracture-dislocation are well known to be unstable that surgical fixation is frequently needed for these injuries. However, there have been some controversies for the stability of burst fractures and their treatment, such as indirect or direct decompression and anterior or posterior approach. In this article, current concepts and management of traumatic instabilities at the thoracic and lumbar spine have been reviewed and summarized.

• Journal of Yeungnam Medical Science
• /
• v.13 no.2
• /
• pp.234-242
• /
• 1996

Ten patients with a thoracolumbar spine fractures were treated with Kaneda internal fixation device through anterolateral approach during last 1 year. In all cases, spinal decompression, internal instrument fixation and hone fusion with rib were performed. No patient showed neurological deterioration after surgery and 6(60%) patients improved postoperatively with entering the next Frankel subgroup. Follwo-up patient evaluation showed the correction of the fracture deformity with good bony fusion, but 3 patient arc remained back pain. According to above results we concluded that anterolateral internal fixation combined with hone fusion using rib was good mechanical stability and decompression of protruding ventral bone fragments above conus medullaris level.

• Steel and Composite Structures
• /
• v.15 no.5
• /
• pp.507-518
• /
• 2013

The seismic performance of six types of weak-axis steel moment connections was investigated through cyclic testing of six full-scale specimens. These weak-axis moment connections were the column-tree type, WUF-B type, FF-W type, WFP type, BFP-B type and DST type weak-axis connections. The testing results showed that each of these weak-axis connection types achieved excellent seismic performance, except the WFP and the WUF-B types. The WFP and WUF-B connections displayed poor seismic performance because a fracture appeared prematurely at the weld joint due to stress concentrations. The column-tree type connection showed the best seismic behavior such that the story drift ratio could reach 5%.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.37-41
• /
• 2004

Liquid injection in a Venturi Scrubber creates great effect on the dust-collection efficiency and operation cost of venturi scrubbers. We have developed a model that can numerically simulate atomization of the liquid jet in the Venturi Scrubber. This simulation consists of models on liquid column, jet surface breakup, column fracture and secondary droplet breakup. These models have been embedded in the KIVA3-V code. We have calculated such parameters as the jet penetration, jet trajectory, droplet size, velocity field and the volume flux distribution. The results are compared with the experimental data in this paper.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.3
• /
• pp.304-310
• /
• 2004

In this paper, cracking threshold for nanoindentation is analyzed by using 3D finited-element method. The analysis by maximum principal stress criterion can obtain the reliable results for determining to crack initiation location and load. Because the ratio of maximum principal stress to indentation depth for Victors indentation is smaller than flat-plane-column indentation and cracking for Victors indentation occurs from the inner part of specimen difficult to measure crack length, the nanoindentation facture test for flat-plane-column indentation is more effective.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.845-850
• /
• 2007

The empirical AISC panel zone thickness provision$(t_z\geq(d_z+w_z)$/90) to prevent the cyclic shear buckling of the panel zone was proposed based on the test data of Krawinkler et al. (1971) and Bertero et al. (1973) However, no published records of the equation development or any other background information appear to be available. The calibrated finite element analysis results of this study indicated that the AISC provision was not reasonable. In this study, through including the effects of the column axial force and the aspect ratio of the panel zone, a new equation for the relative strength between the beam and the panel zone was proposed such that the proposed equation can prevent the panel zone shear buckling and reduce the potential fracture associated with the kinking of the column flanges.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.182-192
• /
• 2022

Brittle feature is one of the fracture behaviors of structure s and has a great influence on the seismic performance of structure materials. The load velocity acts as one of the main causes of brittle fracture, and in particular, in situations such as earthquakes, a high load velocity acts on buildings. However, most of the seismic performance evaluation of the domestic and external steel connections is conducted through static experiments. Therefore, there is a possibility that brittle fracture due to factors such as degradation of material toughness and reduction of maximum deformation rate due to high load velocity during an earthquake was not sufficiently considered in the existing seismic performance evaluation. This study conducts a static test at a low load velocity according to the existing experimental method and a dynamic test at a high load velocity using a shaking table, respectively. It compares and analyzes the fracture shape and structural performance according to the results of each experiment, and finally analyzes the effect of the load velocity size on the seismic performance of the connection.

• Journal of the Korean Ceramic Society
• /
• v.49 no.4
• /
• pp.369-374
• /
• 2012

Based on the structure feature of a tree, a cylindrical $Ti_2AlC$/graphite layered composite has been fabricated through heat treating a graphite column and six close-matched thin wall $Ti_2AlC$ cylinders bonded with the $Ti_2AlC$ powders at $1300^{\circ}C$ and low oxygen partial pressure. SEM examination reveals that the bond interlayers between cylinders or that between cylinder and column are not fully dense without any crack formation. During the compressive test, the strain of the $Ti_2AlC$/graphite layered composite is about twice higher than that of the monolithic $Ti_2AlC$ ceramic, and the compressive strength of the layered composite is 348 MPa. The layered composite show the noncatastrophic fracture behaviors due to the debonding and shelling off of the layers, which are different from the monolithic $Ti_2AlC$ ceramic. The mechanism of the improved deformation capacity and noncatastrophic failure modes are attributed to the presence of the central soft graphite column and cracks deflection by the bond interlayers.