• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.49-61
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• 2022

This paper presents an experimental investigation into the effectiveness of using carbon fibre reinforced polymer (CFRP) and steel plates to repair damaged reinforced concrete (RC) beams with circular web openings at shear zones. It highlights the effectiveness of externally bonded CFRP and steel plates in repairing damaged RC beams by analysing the repaired beams'load capacity, deflection, strain, and failure mode. For the experiment, a total of five beams were used, with one solid beam as a control beam and the other four beams having an opening near the shear zone. Two beams with openings were repaired using inclined and vertical configuration CFRP plates, and the other two were repaired using inclined and vertical configuration steel plates. The results confirm the effectiveness of CFRP and steel plates for repairing damaged RC beams with circular openings. The CFRP and steel plates significantly increase ultimate capacity and reduce deflection under the openings. The inclined configuration of both CFRP and steel plates was more effective than the vertical configuration. Using an inclined configuration not only increases the ultimate capacity of the beams but also changes the mode of failure from shear to flexural.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.444-452
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• 2019

To assess the availability of a nuclear power plant's dynamic systems, it is necessary to consider the impact of dynamic interactions, such as components, software, and operating processes. However, there is currently no simple, easy-to-use tool for assessing the availability of these dynamic systems. The existing method, such as Markov chains, derives an accurate solution but has difficulty in modeling the system. When using conventional fault trees, the reliability of a system with dynamic characteristics cannot be evaluated accurately because the fault trees consider reliability of a specific operating configuration of the system. The dynamic reliability graph with general gates (DRGGG) allows an intuitive modeling similar to the actual system configuration, which can reduce the human errors that can occur during modeling of the target system. However, because the current DRGGG is able to evaluate the dynamic system in terms of only reliability without repair, a new evaluation method that can calculate the availability of the dynamic system with repair is proposed through this study. The proposed method extends the DRGGG by adding the repair condition to the dynamic gates. As a result of comparing the proposed method with Markov chains regarding a simple verification model, it is confirmed that the quantified value converges to the solution.

• Journal of Korean Institute of Industrial Engineers
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• v.8 no.1
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• pp.3-12
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• 1982

Three types of repair-ordering polices for the production facility with r-out-of-n configuration are considered. Policies are characterized by states of the system and two types of lead times ; regular lead time and expedited lead time. Optimum repair-ordering policy is determined by minimizing the cost rate for the system. Optimum policy consists of the type of policies and repair-ordering time. Variations of the optimum policies are observed with respect to variations of lead times and associated ordering costs and downtime cost, respectively.

• International Journal of Reliability and Applications
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• v.12 no.1
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• pp.15-39
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• 2011

This paper deals with the reliability analysis of a complex system with three possibilities at the time of repair. The considered system consists of two subsystems A and Bin series configuration (1-out-of-2: F). Subsystem A has n units which are connected in series whereas subsystem B consists of n units in parallel configuration. The configuration of subsystem A is of 1-out-of-n: F whereas subsystem B is of k-out-of-n: D and k+1-out-of-n: F nature. System has three states: Good, degraded and failed. Supplementary variable technique has been used for mathematical formulation of the model. Laplace transform is being utilized to solve the mathematical equation. Reliability, Availability, M.T.T.F., Busy Period and Cost effectiveness of the system have been computed. The repairs from state $S_7$ to $S_0$, $S_8$ to $S_0$, $S_9$ to $S_0$ and $S_{11}$ to $S_0$ have two types namely exponential and general. Joint probability distribution of repair rate from $S_7$ to $S_0$, $S_8$ to $S_0$, $S_9$ to $S_0$ and $S_{11}$ to $S_0$ is computed by Gumbel-Hougaard family of copula. Some particular cases of the system have also been derived to see the practical importance of the model.

• Computers and Concrete
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• v.33 no.4
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• pp.361-372
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• 2024

Reinforced concrete (RC) bridge columns are typically designated as the primary source of energy dissipation for a bridge structure during an earthquake. Therefore, seismic repair of RC bridge columns has been studied extensively during the past several decades. On the other hand, few studies have been conducted to evaluate how repaired column members influence the system-level response of an RC bridge structure in subsequent earthquakes. In this study, a numerical model was established to simulate the response of two large-scale RC columns, repaired using different techniques, reported in the literature. The columns were implemented into a prototype bridge model that was subjected to earthquake loading. Incremental dynamic analysis (IDA) and fragility analysis were conducted on numerical bridge models to evaluate the efficacy of the repairs and the post-repair seismic performance of the prototype bridge that included one or more repaired columns in various locations. For the prototype bridge herein modeled, the results showed that a confinement-enhanced oriented repair would not affect the seismic behavior of the prototype bridge. Increasing the strength of the longitudinal reinforcement could effectively reduce the drift of the prototype bridge in subsequent earthquakes. A full repair configuration for the columns was the most effective method for enhancing the seismic performance of the prototype bridge. To obtain a positive effect on seismic performance, a minimum of two repaired columns was required.

• Clinics in Shoulder and Elbow
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• v.18 no.4
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• pp.197-205
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• 2015

Background: The purpose of this study was to evaluate the postoperative magnetic resonance imaging (MRI) results of minimal-tying (one medial-row tie among 4 medial-row sutures) on the medial-row in double-row suture-bridge configuration ($2{\times}2$ anchor with $4{\times}4$ suture stands). Methods: From 2011 March to 2012 July, 79 patients underwent arthroscopic rotator cuff repair using $2{\times}2$ anchor double-row configuration. The mean age was 61.3 years (range, 31-81 years). Two double-loaded suture anchors were used for medial-row. Four medial-row stitches were made with only one medial-row knot-tying (the most anterior suture). Lateral-row was secured using the conventional suture-bridge anchor technique; all 4 strands were used for each anchor. Repair integrity was evaluated with MRI at mean 6.2 months postoperatively. Retear and the pattern of retear, change of fatty infiltration, and muscle atrophy of supraspinatus were evaluated using pre- and postoperative MRI. Results: Repaired tendon integrity was 38 for type I, 30 for type II, 6 for type III, 4 for type IV, and 1 for type V, according to Sugaya classification. Considering type IV/V as retear, the rate was 6.3% (5 out of 79 patients). Medial cuff failure was observed in 4 patients. Fatty atrophy of supraspinatus was significantly improved postoperatively according to Goutallier grading (p=0.01). The level of muscle atrophy of supraspinatus was not changed significantly after surgery. Conclusions: Minimal tying technique with suture configuration of four-by-four strand double-row suture-bridge yielded a lower retear rate (6.3%) in medium to large rotator cuff tears.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.51-54
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• 1996

We deal with a design problem of assembly/disassembly (AD) systems with finite buffer capacities where the times between failures, the times to repair, and the processing times are exponentially distributed with different parameter values. We present a solution procedure for finding the minimum cost configuration which achieves a desired throughput rate for an AD system. The configuration is defined by the types of machines to be used and capacities of buffers in the AD system. Results of computational experiments on randomly generated test problems show that the proposed heuristics give relatively good configurations in a reasonable amount of time.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.614-621
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• 1999

In this paper, the analytical appproaches are presented for jointly determining the profit-miximizing configuration of the fault-tolerance real time modular cell manufacturing system. The transient(time-dependent) analysis of Markovian models is firstly applied to modular cell manufacturing system from a performability viewpoint whose modeling advantage lies in its ability to express the performance that truly matters - the user's perception of it - as well as various performance measures compositely in the context of application. The modular cells are modeled with hybrid decomposition method and then availability measures such as instantaneous availability, interval availability, expected cumulative operational time are evaluated as special cases of performability. In addition to this evaluation, sensitivity analysis of the entire manufacturing system as well as each machining cell is performed, from which the time of a major repair policy and the optimal configuration among the alternative configurations of the system can be determined. Secondly, the recovery policies from the machine failures by computing the minimal number of redundant machines and also from the task failures by computing the minimum number of tasks equipped with detection schemes of task failure and reworked upon failure detection, to meet the timing requirements are optimized. Some numerical examples are presented to demonstrate the effectiveness of the work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.718-724
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• 2007

Some of gas turbine model of 7F-Class has constructed and is operating with units domestically. Non-destructive testing (NDT) is one of the methods being used to inspect damage $1^{st}$ stage bucket and review damage trends. We also analyze damage configuration and microstructure according to material and compare with pape of electric power research institute (EPRI). The damaged mode could be determined by leveraging failure analysis. Especially, configuration uprate of bucket is not only to prevent damage during operation but also avoid domestic manufacturing by the competitors. Modifications were mainly concentrated on surfaces such as cooling hole and bucket tips. Analyzing of bucket damage, the earlier model of 7F-Class used with one cycle with equivalent operation hour (EOH), has various cracking of the bucket surface. Bucket damage of new model is centered on tip area (54%) as analyzed by EPRI research. We conclude that improving bucket configuration would increase repair rate on the bucket tip.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.281-286
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• 2019

To repair the underside of the car, a repairman has to enter under the car body. But this work can make it difficult for him to fix it and the injuries can occur. To solve these difficult problems, the developed equipment is the automotive lift. In this study, three kinds of lift models 1, 2 and 3 were designed and the material properties of the structural steel were applied. As the same load were applied under the same conditions on all models, the structural analyses were conducted. Models 2 and 3 were shown to have the structural deformation less than model 1. Also, models 2 and 3 were shown to be more stable than model 1 structurally. By utilizing the design data on a convergence research through durability analysis according to the configuration of automotive lift obtained on the basis of this result, the esthetic feeling can be shown by being converged onto the automotive repair equipment parts at actual life.