• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.401-404
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• 2005

Because the underwater structures are subjected to the deterioration according to use environment, it is necessary to repair and reinforce when the durable performance are considered in structures. Epoxy mortar in the underwater used to the repair and reinforcement for durability. Epoxy mortar in the underwater-harding maked epoxy and filler. Filler is divided aggregate and powder system. Because aggregate take a matter too seriously to supply that alternation material is used to rapidly chilled steel slag. As result of study, it is possible that rapidly chilled steel slag can be applied for replacement materials about aggregate in epoxy mortar because the strength is not different.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.230-231
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• 2013

A fire outbreak in a reinforcement concrete structure looses the organism by different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So, concrete reinforcement structure is damaged partial or whole structure system. Therefore accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, consider case of investigation methods and repair work in fire damaged structure concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.135-143
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• 2002

This study is to investigate its use by applying stainless steel wire mash reinforcement method of construction, which is newly developed, on the high strength concrete beam mixed with polymer-steel fiber. In this test, it is investigated and observed such as follows: the ultimate load, the initial flexure crack load, the initial diagonal tension crack load, the relation between load and deflection, load-strain relation, and also crack growth and fracture aspect by increasing load. The results of this test are; first, the stainless steel wire showed some useful reinforcement effects in multiplying the steel's resisting force of moment to the tensile force of beam or slab: second, the promoting strength and internal force was made in the process of the integration at the same reaction by using the penetrating polymer-mortar with an excellent durability and physical property. On the basis of this results, because such instances in applying stainless steel wire Mash reinforcement method of construction have been few so far, through the experimental investigation such as this test over and over again, the efficient and useful method must be developed for the practice.

• Journal of Korean Foot and Ankle Society
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• v.10 no.2
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• pp.259-263
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• 2006

The acute Achilles tendon rupture usually occurs to the people who participate in sports-related activities between 30 and 40 years of age. Recently surgical repair is the standard treatment in acute Achilles tendon rupture. After the Achilles tendon rupture in the left ankle, a 30-years old young man had been suffered from re-rupturing within three months after the primary repair. 2 years later, right-side Achilles tendon was reruptured after primary repair consequently. In the revision surgery, we performed V-Y advancement of the gastrocnemius-soleus fascia and reinforcement of the semitendinosus tendon. None of the English-literature was reported about using the semitendinosus tendon in revision surgery of the Achilles tendon retear previously. Therefore, we report this case and surgical technique because of the simple technique and the excellent results.

• Smart Structures and Systems
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• v.30 no.6
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• pp.571-582
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• 2022

Optimal life-cycle management is a challenging issue for deteriorating regional bridges. Due to the complexity of regional bridge structural conditions and a large number of inspection and maintenance actions, decision-makers generally choose traditional passive management strategies. They are less efficiency and cost-effectiveness. This paper suggests a deep reinforcement learning framework employing double-deep Q-networks (DDQNs) to improve the life-cycle management of deteriorating regional bridges to tackle these problems. It could produce optimal maintenance plans considering restrictions to maximize maintenance cost-effectiveness to the greatest extent possible. DDQNs method could handle the problem of the overestimation of Q-values in the Nature DQNs. This study also identifies regional bridge deterioration characteristics and the consequence of scheduled maintenance from years of inspection data. To validate the proposed method, a case study containing hundreds of bridges is used to develop optimal life-cycle management strategies. The optimization solutions recommend fewer replacement actions and prefer preventative repair actions when bridges are damaged or are expected to be damaged. By employing the optimal life-cycle regional maintenance strategies, the conditions of bridges can be controlled to a good level. Compared to the nature DQNs, DDQNs offer an optimized scheme containing fewer low-condition bridges and a more costeffective life-cycle management plan.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.127-135
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• 2011

In this study, the engineering characteristics of outer wall insulation panels according to type of insulation materials, their combination, and the contents of insulation materials were tested. Vermiculate, ceramic bead, perlite and expanded polystyrene were used as insulation materials. Flexural strength and thermal conductivity depending on the insulation materials used were measured. It was found that the flow of fresh mortar significantly decreased with an increase in the contents of insulation materials. In terms of the effect of insulation materials on thermal conductivity, an increase in insulation materials resulted in a decrease of thermal conductivity. In particular, PL and EPS, when used together, have lower thermal conductivity than other materials. Regarding the flexural strength of the hardened mortar, the strength showed a tendency to gradually decrease according to the increase in contents of insulation materials, compared to that of the plain mortar. In terms of the flexural strength depending on various types of insulation materials and its combination, it was found that the flexural strength of cement mortar containing 3% of vermiculate(V)+ceramic bead(CB)+perlite(PL) was the highest among the specimens tested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.181-189
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• 2001

Recently, the need for strengthening reinforced concrete(R.C.) structure has been increased, particularly when there is an increase in load requirements, a change in use, a degradation problem, or design/construction defects. The use of composite materials for structural repair presents several advantages and has been investigated all over the world. It is well known that the incorporation of carbon fiber sheet(CFS) with concrete is one of the most effective ways to strengthen the R.C. structure. In this papers, experimentally investigated the ductile behavior of the R.C. beams strengthened with CFS, and provided the basic data for design of R.C. beams strengthened with CFS. Tests were carried out with 15 beams ($20cm{\times}30cm{\times}240cm$) reinforced with CFS, and with parameters including and the ratio of tensile reinforcement to that of balanced condition and number of CFS. The results show that strengthened and non-strengthened beams exhibit different ductile behovior. Non-strengthened beams showed increase of ductility as amount of the tensile reinforcement decreased. However, bearing capacity of the CFS-strengthened beams are dictated by the strength of the CFS layers that a very high ductility is indicated for the beams with large number of CFS.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.143-144
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• 2016

The core drilling method is considered to be the most effective and common method of assessing the compressive strength of concrete in existing reinforced concrete buildings for structural repair and retrofit. In general, core specimens within reinforcing bars are not permitted in the regulations with regard to assessing concrete strength even if the core specimens can contain the bars in some cases. The purpose of this study is to investigate the effects of the reinforcement arrangement on the concrete compressive strength as a basic research to propose the quantitative criteria of strength for core specimens containing reinforcements. To complete the basic research, cylinder specimens inserted in a variety of reinforcement arrangements were prepared and tested.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.605-610
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• 1997

An experimental investigation was conducted to examine the feasibility of Carbon Fiber Sheet(CFS), a kind of high strength fiber, for a repair and reinforcement method of concrete structures. The experimental program included tests of flexural beams different in wrapping method and amount of CFS. The beams were subjected to monotonic loading. Although the flexural strength for concrete members increases with wrapping methods of CFS., the reduction factor due to the distribution, amount bond of CFS should be completely examined. This study approached the effectiveness and application of CFS, along with reinforcement effects of CFS on reinforced concrete beams through tests. Test results indicated that the increase in the number of CFS layer caused the increase in strength of beams in strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.200-201
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• 2013

This study is interested in manufacturing the concrete surface impregnants including tetra ethyl ortho silicate, alkali silicate for the repair of the exposed concrete and the color concrete requiring the advanced function in view of the concrete appearance. The surface layer change and porosity properties was tested for the review of application. The result of this study show that the effective silicate are tetra ethyl ortho silicate and alkali silicate t. The adhesion in tension is slightly increased but the reinforcement of concrete substrate is slight. So, the concrete impregnant of this study is more desirable for the improvement of durability rather than the reinforcement.