• Journal of Veterinary Clinics
• /
• v.39 no.4
• /
• pp.149-155
• /
• 2022

The aim of this study was to compare the mechanical properties of 0.6 and 0.8 mm cerclage wires with the 1.0 mm cerclage wire in the twist, single-loop, double-loop, double-wrap, and loop/twist knot methods. Six stainless steel cerclage wires of various diameters in different knot methods were tied round a customized jig mounted on a load testing machine. The initial tension, initial stiffness, and yield load were evaluated. The failure mode of each cerclage was observed. For each wire size, the double-loop, double-wrap, and loop/twist knots showed significantly greater initial stiffness, and yield load than those seen with twist and single-loop knots. The single-loop knot showed the least initial stiffness regardless of the diameter. As the cerclage wire diameter increased, the cerclage tended to show significantly greater initial stiffness, and yield load. Failure modes varied depending on the knot configurations. Single-loop knots of smaller-diameter wires less than 1 mm had similar or lower initial tension, initial stiffness, and yield load than a twist knot. Owing to the variance in mechanical properties, the clinical application of the knot type should depend on the diameter of the cerclage wire.

• Geomechanics and Engineering
• /
• v.19 no.6
• /
• pp.513-522
• /
• 2019

This study presents an elasto-plastic (EP) solution for drained cavity expansion on the basis of unified strength failure criterion and considers the influence of initial stress state. Because of the influence of initial consolidation of soil mass, the initial stress may be anisotropic in the natural soil mass. In addition, the undrained hypothesis is usually used in the calculation of cavity expansion problem, but most of the cases are in the drained situation in practical engineering. Eventually, the published solution and the presented solution are compared to verify the suitability of the study.

• Steel and Composite Structures
• /
• v.33 no.2
• /
• pp.245-259
• /
• 2019

The present study aims to investigate the ultimate strength and geometric nonlinear behavior of composite plates containing initial imperfection subjected to combined end-shortening strain and lateral pressure loading by using a semi-analytical method. In this study, the first order shear deformation plate theory is considered with the assumption of large deflections. Regarding in-plane boundary conditions, two adjacent edges of the laminates are completely held while the two others can move straightly. The formulations are based on the concept of the principle of minimum potential energy and Newton-Raphson technique is employed to solve the nonlinear set of algebraic equations. In addition, Hashin failure criteria are selected to predict the failures. Further, two distinct models are assumed to reduce the mechanical properties of the failure location, complete ply degradation model, and ply region degradation model. Degrading the material properties is assumed to be instantaneous. Finally, laminates having a wide range of thicknesses and initial geometric imperfections with different intensities of pressure load are analyzed and discuss how the ultimate strength of the plates changes.

• Geomechanics and Engineering
• /
• v.14 no.6
• /
• pp.571-580
• /
• 2018

The failure mechanism of tunnel roof is investigated with upper bound theorem of limit analysis. The stochastic settlement and nonlinear failure criterion are considered in the present analysis. For the collapse of tunnel roof, the surface settlement is estimated by the simplified stochastic medium theory. The failure curve expressions of collapse blocks in homogeneous and in layered soils are derived, and the effects of material parameters on the potential range of failure mechanisms are discussed. The results show that the material parameters of initial cohesion, nonlinear coefficient and unit weight have significant influences on the potential range of collapse block in homogeneous media. The proportion of collapse block increases as the initial cohesion increases, while decreases as the nonlinear coefficient and the unit weight increase. The ground surface settlement increases with the tunnel radius increasing, while the possible collapse proportion decreases with increase of the tunnel radius. In layered stratum, the study is investigated to analyze the effects of material parameters of different layered media on the proportion of possible collapse block.

• Geomechanics and Engineering
• /
• v.24 no.5
• /
• pp.457-470
• /
• 2021

In this study, the pull-out behavior of a tunnel-type anchorage for suspension bridges was investigated using experimental tests and image processing analyses. The study focused on evaluating the initial failure behavior and failure mode of the tunnel-type anchorage. In order to evaluate the failure mode of tunnel-type anchorage, a series of scaled model tests were conducted based on the prototype anchorage of the Ulsan Grand Bridge. In the model tests, the anchorage body and surrounding rocks were fabricated using a gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests demonstrate that the tunnel-type anchorage underwent a wedge-shaped failure. In addition, the failure mode changed according to the differences in the physical properties of the surrounding rock and the anchorage body and the size of the anchor plate. The size of the anchor plate was found to be an important parameter that determines the failure mode. However, the difference in physical properties between the surrounding rock and the anchorage body did not affect its size. In addition, this study analyzed the initial failure behavior of the tunnel-type anchorage through image analysis and confirmed that the failure was sequentially transferred from the inside of the tunnel to the surrounding rock according to the image analysis. The reasonable failure mode for the design of the tunnel-type anchorage should be wedge-type rather than pull-out type.

• Journal of Korean Society for Quality Management
• /
• v.21 no.2
• /
• pp.109-120
• /
• 1993

Most systems are composed of components which have different failure chracteristics. Since the failure characteristics of components is different, it is rational and reasonable to establish a maintenance model to be considered repair and replacement policies which are proper to failure characteristics of these components. This paper proposes the age replacement time for a system composed of components which have different failure characteristics. In this model, it is assumed that a system is composed of a critical failure component, a major failure component, minor failure component. If any failure occurs to critical component before its age replacement time, the system should be replaced. If any failure does not occur until its age replacement time, preventive replacement should be performed at age replacement time T. Major component is minimal repaired if any failure occurs during operation. Minor component should be replaced as soon as failure is found. This paper determines the optimal replacement time of the system which minimize, total maintenance cost and initial stock Quantity of minor component within this optimal replacement time. Numerical example illustrates these results.

• Journal of Periodontal and Implant Science
• /
• v.52 no.3
• /
• pp.230-241
• /
• 2022

Purpose: The purpose of this study was to evaluate failed implants and reimplantation survival and to identify the relative risk factors for implant re-failure. Methods: Ninety-one dental implants were extracted between 2006 and 2020 at the National Health Insurance Service Ilsan Hospital, including 56 implants in the maxilla and 35 implants in the mandible that were removed from 77 patients. Patient information (e.g., age, sex, and systemic diseases) and surgical information (e.g., the date of surgery and location of the implants and bone grafts) were recorded. If an implant prosthesis was used, prosthesis information was also recorded. Results: In total, 91 first-time failed dental implants in 77 patients were analyzed. Of them, 69 implants in 61 patients received reimplantation after failure. Sixteen patients (22 implants) refused reimplantation or received reimplantation at a different site. Eight of the 69 reimplants failed again. The 1-year survival rate of the 69 reimplants was 89.4%. Age at reimplantation and smoking significantly increased the risk of reimplantation failure. However, a history of taking anti-thrombotic agents showed a statistically significant negative association with reimplantation failure. Of the failed implants, 66% showed early failure and 34% showed late failure of the initial implantation. All 8 re-failed implants showed early failure. Only 3 of these 8 failed reimplants were re-tried and the second reimplants all survived. Conclusions: The total survival rate of implants, which included reimplants and second reimplants was 99.2%, although the survival rate of the initial implantations was 96.3%. Previous failure did not affect the success of the next trial. Reimplantation failure was more strongly affected by patient factors than by implant factors. Therefore, each patient's specific factors need to be meticulously controlled to achieve successful reimplantation.

• Geomechanics and Engineering
• /
• v.16 no.2
• /
• pp.205-215
• /
• 2018

Strain-based criteria are known as a direct method in determining the stability of the geomechanical structures. In spite of the widely use of Sakurai critical strain criterion, it is so conservative to make use of them in rocks with initial plastic deformation on account of the considerable difference between the failure and critical strains. In this study, a new criterion has been developed on the basis of the failure strain to attain more reasonable results in determining the stability status of the tunnels excavated in the rocks mostly characterized by plastic-elastic/plastic behavior. Firstly, the stress-strain curve was obtained having conducted uniaxial compression strength tests on 91 samples of eight rock types. Then, the initial plastic deformation was omitted making use of axis translation technique and the criterion was presented allowing for the modified secant modulus and by use of the failure strain. The results depicted that the use of failure strain criterion in such rocks not only decreases the conservativeness of the critical strain criterion up to 42%, but also it determines the stability status of the tunnel more accurately.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.59-66
• /
• 2020

Two octagonal RC bridge columns of small scale model were tested under cyclic lateral load with constant axial load. One in two specimens was solid cross section, the other was hollow cross section. The volumetric ratio of transverse spiral hoop of all specimens is 0.00206. The columns showed flexure-shear failure. Failure behavior and seismic performance were investigated. The test results showed that the structural performance of the hollow specimen such as initial crack pattern, initial stiffness, and energy dissipation performance was comparable to that of the solid specimen, but the lateral strength, ultimate displacement, energy dissipation performance of hollow specimen noticeably decreased after drift ratio of 3%.

• Journal of the Korean Institute of Gas
• /
• v.16 no.3
• /
• pp.29-34
• /
• 2012

Investigating safer ways to design and use to prevent a loss of life and property by failure of the structures are necessary and assessing total fatigue life with initiation and propagation of fatigue crack accurately through fatigue analysis is very important. The object of this study is to examine the initial life and propagation life when the fatigue crack is introduced from the root which is likely to appear in LOP(Lack of Penetration) cruciform fillet welded structure including bridges, ships and gas storage facilities which are impossible to be fully penetrated and to measure the rate of fatigue life until the final cleavage failure. As the result, each rate of fatigue life for fatigue failure is somewhat different in the range of 5% according to the thickness of material, however, the overall rate of initial life is in the range of 34~39% and propagation life showed the range of 61~66%.