구조물 보수 부위의 손상, 재 박리 등의 2차 피해가 이어지며, 보수 부위의 새로운 거동 평가 기법 에 대한 연구의 필요성이 대두되고 있다. 현재 구조물 보수 부위의 거동을 알기 위해서 주로 인력 중 심의 구조물 외관 검사를 진행하고 있으나, 단편적인 검사 결과를 얻게 되어 지속적이고 세밀한 점검 이 어려운 실정이다. 따라서, 본 연구에서는 탄소나노튜브 기반 폴리머 콘크리트를 활용해 압축과 같 은 외부 응력에 대한 탄소나노튜브 함량별 전기적 변화를 분석하였으며, 균열이 발생한 콘크리트 구조 물을 보수 후 응력을 가해 거동에 따른 전기적 변화를 평가하였다. 압축 시험 결과, 응력에 따른 탄소 나노튜브 기반 폴리머 콘크리트의 전기 저항이 감소하며, 탄소나노튜브 함량이 낮을수록 응력에 대한 저항 감소 폭이 넓게 나타나며 민감도가 증가하였다. 균열 보수 시험 결과, 보수 부위에 응력이 가해 졌을 때 전기 저항이 감소해 앞서 진행된 실험 결과와 동일한 경향을 보였으며, 또한 응력이 가해지지 않을 때 초기 저항으로 회복하는 경향을 보여 구조물 보수 부위 거동에 대한 평가가 가능한 것으로 검 증되었다. 이를 통해, 탄소나노튜브 기반 폴리머 콘크리트는 구조물에 적용이 가능하며, 구조물 보수 후에도 가해지는 응력에 대한 지속적인 감지가 가능해 보수 부위 거동 평가가 가능할 것으로 판단된다.

In the contemporary era, 3D printing technology has become widely utilized across diverse fields, including biomedicine, industrial design, manufacturing, food processing, aerospace, and construction engineering. The inherent advantages of automation, precision, and speed associated with 3D printing have progressively led to its incorporation into road engineering. Asphalt, a temperature-responsive material that softens at high temperatures and solidifies as it cools, presents distinctive challenges and opportunities in this context. For the effective implementation of 3D printing technology in road engineering, 3D printed asphalt (3DPA) must exhibit favorable performance and printability. This requires attributes such as good fluidity, extrudability, and buildability. Furthermore, materials utilizing 3DPA for crack repair should possess high viscosity, elasticity, toughness, superior high-temperature stability, and resistance to low-temperature cracking. These characteristics ultimately contribute to enhancing pavement longevity and ensuring worker safety.

PURPOSES : This study aimed to develop high-performance concrete repair materials for the cross-sectional repair of deteriorated bridge concrete. METHODS : To derive the optimal mix using the dry shotcrete method, experiments were conducted to develop an appropriate performance in terms of durability and watertightness based on basic experiments on materials. By mixing silica fume, GGBFS, and natural fibers, this study compared the differences in each variable. Each variable was compared using compressive strength, flexural strength, plastic shrinkage, chlorine ion penetration resistance, and freeze-thaw tests. RESULTS : By mixing silica fume and natural fibers, watertightness and durability were secured, and by adding an expansion material and polymer powder, a material that exhibited suitable performance as a repair material was developed. The material demonstrated suitable performance in terms of compressive strength, freeze–thaw resistance, plastic shrinkage crack resistance, and chlorine ion penetration resistance. CONCLUSIONS : The repair material developed in this study has a higher performance than repair mortar, and because it uses a dry shotcrete method, the process and post-processing are simpler than the wet shotcrete method; therefore, it is believed to be more efficient for repair work.

PURPOSES : Experimental findings pertaining to the mechanical properties and microstructures of calcium sulfo-aluminate (CSA) cement and amorphous calcium aluminate (ACA) cement based-repair mortars incorporated with anhydrite gypsum (AG) are described herein. METHODS : To prepare the mortars, the CSA or ACA as binders were adopted and the ratio of water–binder was fixed at 0.57. For comparison, mortar made of Type I ordinary Portland cement (OPC) was prepared. The fluidity, setting time, compressive and bond strengths and absorption of the mortars were measured at predetermined periods. In addition, the microstructures of paste samples using OPC, CSA or ACA were visually examined through SEM observation. RESULTS : The ACA-based mortars showed the increases in the fluidity, and the acceleration of the setting time. Furthermore, the ACAbased binder effectively enhanced the compressive and bond strengths of the mortars owing to amount of formation of C2AH8 hydrates. Meanwhile, the mortar with ACA showed an excellence absorption. CONCLUSIONS : Comparing with those of CSA-based mortars, the mechanical properties of ACA based-mortars were more remarkable. However, further studies regarding the durability of repair mortars using aluminate-based binders must be conducted to obtain the optimal mixture.

Safe management of spent nuclear fuel (SNF) is a key issue to determine sustainability of current light water reactor (LWR) fleet. However, none of the countries are actually conducting permanent disposal of SNFs yet. Instead, most countries are pursuing interim storage of spent nuclear fuels in dry cask storage system (DCSS). These dry casks are usually made of stainlesssteels for resistibility against cracking and corrosion, which can be occurred over a long-term storage period. Nevertheless, some corrosion called Chloride-Induced Stress Corrosion Cracking (CISCC) can arise in certain conditions, exacerbating the lifetime of dry casks. CISCC can occur if the three conditions are satisfied simultaneously: (i) residual tensile stress, (ii) material sensitization, and (iii) chloride-rich environment. A residual tensile stress is developed by the two processes. One is the bending process of stainless-steel plates into a cylindrical shape, and the other is the welding process, which can incur solidification-induced stress. These stresses provide a driving force of pit-to-crack transition. Around the fusion weld areas, chromium is precipitated at the grain boundary as a carbide form while it depletes chromium around it, leading to material susceptible to pitting corrosion. It is called sensitization. Finally, coastal regions, where nuclear power plants usually operate, tend to have a higher relative humidity and more chloride concentration compared to inland areas. This high humidity and chloride ion concentration initiate pitting corrosion on the surface of stainless-steels. To prevent initiation of CISCC, at least one of the three conditions should be removed. For this, several surface engineering techniques are under investigation. One of the most promising approaches is surface peening method, which is the process that impacts the surface of materials with media (e.g., small pins, balls, laser pulse). By this impact, plastic deformation on the surface occurs with compressive stress that counteracts with pre-existing residual tensile stress, so this approach can prevent pit-to-crack transition of stainless-steels. Also, cold spray deposition can prevent CISCC. Cold spray deposition is a method of spraying fine metal powder to a substrate by accelerating them to supersonic velocity with propellant gas. As a result, a thin coating composed of the feedstock powders can protect the substrate from outer corrosive environments. In addition, the impact of the feedstock powder on the substrate during the process provides compressive stress, similar to the peening method.

This paper proposes a standardized vehicle body repair manual for vehicles with major damage to the rear side members caused by rear-end collisions. The manual is used to refine the vehicles. Typical work involves replacing large traffic accident modes with new members or modifying and aligning existing members. If repairs are made for various reasons, the members should be attached based on the body of a new vehicle. Unlike new vehicle members, the accident vehicle repair process depends heavily on the operator's skilled skills (i.e., the performance, purpose, level, and quality of the body replacement work due to the nature of the vehicle body replacement work). When repairing or replacing a rear side member of a body repair, three methods of operation are applied because the damage and deformation vary depending on the object of the other party, although the degree of damage varies. There is no standardized manual for side member over-hole replacement, partial replacement, or partial modification, since these repair methods vary depending on the operator's thoughts and angle of view. Therefore, customers should use standardized vehicle repair manuals to ensure that their vehicle receives the same repair when damaged. This study is expected to develop a standardized vehicle repair manual to reduce the drop in used market prices after replacement or repair of rear side members at vehicle repair plants.

Ondol is a traditional underfloor heating system designated as a national intangible cultural heritage of Korea. The Cultural Heritage Administration (CHA) publishes a standard specification for the repair of cultural properties, including ondol. This standard specification is used as a guide for contractors who repair ondol in the field. However, the standard specification for ondol repair has some errors and is difficult to understand in the field. This paper proposes a revision of the standard specification for ondol repair. This study found that the standard specification for ondol repair has some problems in terms of the terminology and structure of ondol. These problems were sufficient to confuse ondol repairers in the field. Therefore, this study proposes to revise the standard specification to correct these errors and make it easier for ondol repairers in the field to understand. This study is expected to help recognize and preserve ondol as a cultural property and not just as a building.

Cars serve as vehicles for the conveyance of both passengers and cargo. Inevitably, traffic accidents constitute a significant facet of vehicular operation. These accidents manifest in various forms, including frontal, rear-end, and lateral collisions. While the resultant vehicular damages may exhibit similarities, they remain inherently distinct. Owing to the intricate nature of automotive body repairs, simplistic adherence to textbook doctrines proves inadequate. The rectification of damaged vehicle bodies hinges upon the practitioner's experiential acumen. Consequently, discourse pertaining to body repair technology necessitates grounding in empirical data encompassing prevailing industry norms and attendant financial implications. Variability in individualized methodologies can engender substantial temporal and monetary outlays within the domain of automotive bodywork. Moreover, the integration of novel material technologies within vehicular structures mandates a perpetual pursuit of knowledge and empirical inquiry into the domain of vehicle body repair procedures, particularly as applied to emerging materials. Compounding this imperative is the unwavering commitment to preserving the safety paradigm from the vehicle owner's perspective, ensuring that restorative interventions subsequent to accidents do not compromise safety benchmarks.

Car accidents require continuous access to new technologies in the field of maintenance that cannot be achieved by textbook theory alone due to the nature of body repair without the same damage and repair conditions. In the case of vehicle repairs due to unexpected accidents, it is difficult to satisfy the needs of the vehicle owner, so in this study, it is possible to restore them to their original state with improved technology like the vehicle owner. Better maintenance technologies have been explored: complete replacement of side quarter panels, partial replacement and partial modification of side quarter panels, as well as tangible and intangible effects such as not applying depreciation rates due to traffic accidents, preventing environmental pollution and maximizing owner satisfaction.

Existing reinforced concrete (RC) frame buildings have seismic vulnerabilities because of seismically deficient details. In particular, since cumulative damage caused by successive earthquakes causes serious damage, repair/retrofit rehabilitation studies for successive earthquakes are needed. This study investigates the repair effect of fiber-reinforced polymer jacketing system for the seismically-vulnerable building structures under successive earthquakes. The repair modeling method developed and validated from the previous study was implemented to the building models. Additionally, the main parameters of the FRP jacketing system were selected as the number of FRP layers associated with the confinement effects and the installation location. To define the repair effects of the FRP jacketing system with the main parameters, this study conducted nonlinear time-history analyses for the building structural models with the various repairing scenarios. Based on this investigation, the repair effects of the damaged building structures were significantly affected by the damage levels induced from the mainshocks regardless of the retrofit scenarios.

A literature study was conducted on the management of the pavilion of the royal tomb in the late Joseon Dynasty, focusing on “Gakneung Suri Deungnok(Records relating to the repair of royal tombs)”. This study analyzed the royal tomb management system, organized the types of damage identified in the building, and examined how the damage status was recorded by type. In the above, the records related to the 1675∼1713 repair of three JeongJaGak(Geonwonneung, Sungneung, and Mokneung), which are registered as state-designated cultural properties, are summarized in three aspects: management system, damage status, and expression words. The results of the study are as follows. First, the royal tomb pavilion was regularly inspected by Observator(觀察使) in spring and autumn, and Surunggwan(守陵官) every 5th, and Servant(守僕) regularly inspected every day and night, and also inspected and reported emergency cases of natural disasters or unexpected damage. Second, the damage status of each building was continuously observed and reported for the continuous maintenance of the buildings in the royal tomb. A total of 75 records of damage to the three royal tombs' pavilion were found to have been most frequently inspected, including 19 cases (25.3%), 14 cases (18.7%), 23 cases (30.7%) of the roof, and 19 cases (25.3%) of the roof. Third, the expression of the damage status is confirmed in various ways, such as separation, separation, burst, damage, excitation, moisture, leakage, and exfoliation. Among them, the main damage records were confirmed due to the separation of the base from the peeling, the furniture, cracks, leaks, leaks in the roof, and the collapse of the roof was able to check the damage records.

This article focuses on the Namdaemum repair and the Seokguram restoration, which had begun in 1961, as an important repair conducted during the time of seeking the conservation principle of architectural heritage after liberation in Korea. Through the analysis of the principles described in the repair report issued after the two repairs, meeting records, and related expert announcements, it is shown that the principle of 'preservation of the historic state' had been established at Namdaemun repair and later have changed to the principle of 'restoration of the historic form' which means reconstruction in Seokguram restoration. By analyzing the minutes of the Cultural Heritage Committee's meeting on the repair of other cultural properties during this period, it is revealed that the key terms related to the preservation principle, 'historic form' and 'restoration', were given meaning as 'object' and 'method' of preservation, and then 'restoration of the historic form' has been gradually used as a conservation principle.

Background: Scapular dyskinesis may cause not only rotator cuff (RC) tear but also weakness of the upper extremity, studies on scapular dyskinesis that may occur after RC repair is still lacking. Objects: To determine whether scapular dsykinesis was present in patients after arthroscopic RC repair and to investigate the influence of passive scapular stabilization on upper extremity strength. Methods: A total of 30 patients after RC repair participated in this study. To compare the scapula of the arthroscopic RC repair shoulder and the contralateral shoulder, the winged scapula (WS) was measured using a scapulometer and scapular dyskinesis was also classified by type. Fixed instruments for muscle strength measurements were used to measure upper extremity muscle strength differences depending on passive scapular stabilization position or natural scapular position. A chi-square test, an independent t-test and a 2-way mixed measures analysis of variance (ANOVA) was used as statistical analysis. In analyses, p < 0.05 was deemed to be statistically significant. Results: Postoperative shoulder had a significant association with scapular dyskinesis and the WS compared to the contralateral shoulder (F = 0.052, p < 0.01). Postoperative shoulder, muscle strength in the shoulder abduction (p < 0.01), elbow flexion (p < 0.01) and forearm supination (p < 0.05) were significantly greater in the scapular stabilization position than in the scapular natural position. Conclusion: Patients underwent arthroscopic RC repair had a significant association with scapular dyskinesis and muscle strength was improved by a passive scapular stabilization position, therefore scapular stabilization is important in rehabilitation program.

Traffic accidents that occur while driving a car are inevitable, and the characteristics of the body repair field are that each vehicle accident has the same damage and no same repair conditions. Therefore, it is difficult to acquire know-how in vehicle body repair simply by theoretical method of textbook, and the repair method must be changed as new materials and new technologies are applied to it. In particular, roof panels are not frequently damaged by traffic accidents, but they are damaged by falling objects from the roof of a building or the opposite lane, resulting in roof bending and vehicle repair using dent repair to minimize VOC and reduce costs. In this study, the optimal maintenance method is proposed by analyzing the time, cost, and waste generation according to the work method when the degree of damage is large and replacement is required

As the time and cost of body repair can be greatly incurred due to differences in individual technologies, body repair technology should be discussed based on data on general working standards and costs, and as new material technology is applied to the body, continuous learning and experiment on vehicle body repair technology is essential. Since the left and right apron and side members with SPR bonding technology are made of different materials, aluminum and high-strength steel, the restoration of the left and right apron side members should be considered technically, as well as safety and environmental pollution. In this study, we experiment with heterogeneous apron and side members applied with SPR bonding and analyze the results.