부산 배산성 북쪽 성벽구간 발굴 결과, 삼국시대 초축 성벽과 통일신라시대 개축 성벽이 함께 조사되었다. 삼국시대 초축 성벽은 수직식성벽으로 하부에 기단석축과 기단보축이 함 께 설치된 구조이다. 수직식성벽은 내부에서 발생하는 측력으로 인해 붕괴 위험이 높다. 이 를 보완하기 위하여 계단식내벽을 쌓아 측력을 일부 흡수하기도 하나 장기간에 걸쳐 누적된 압력으로 인해 결국 수직식성벽은 붕괴되고 만다. 수직식성벽은 적들이 등성하기 어렵다는 장점은 있으나 붕괴 위험이 높아 통일신라시대에는 층단식성벽 축조기법이 등장한다. 외벽 의 성돌 크기는 더욱 커지고 가공 수법은 판상형 할석에서 장방형 또는 방형 할석으로 바뀐 다. 바른층쌓기 수법은 더욱 정교하게 적용되고 기단보축은 소멸한다. 두 가지 축조수법이 확인된 배산성 초축 시기는 6세기 중엽경, 개축 시기는 8세기 중엽경으로 약 2세기의 시간 차가 있다. 신라 경덕왕 16년(757) 12월 삼국사기 지리지에는 거칠산군을 동래군으로 고쳤다는 기 록이 있는데, 배산성 개축 시점과 거의 일치한다. 그 동안 동래군 치소성(행정 읍치)으로 동 래고읍성을 지목하여 왔으나 고읍성 축성은 배산성 개축 시점보다 후행하는 것으로 판단된 다. 따라서 배산성은 고대 부산의 행정 치소로 오랫동안 기능하여 왔으며, 고읍성이 축성된 이후에는 행정 기능은 자연히 이양되지만, 배산성은 여전히 방어적 배후산성으로 활용되었 던 것으로 여겨진다.

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.

PURPOSES : This study describes the experimental findings on the mechanical properties of calcium aluminate cement (CAC)-based repair mortars with or without natural cellulose fiber (NCF). Additionally, the effect of adding NCF to the reduction of fugitive dust in the CAC powder was examined. METHODS : To produce mortar, four different levels of NCF (0.0.5, 1.0, and 2.0% by binder weight) were adopted, and the water-binder ratio was fixed at 0.485. The flow, strength characteristics, absorption, and surface electrical resistivity of the mortars were measured at predetermined periods. Additionally, SEM observations were performed to examine the microstructural changes and hydrates formed on the 28 day-mortar samples. RESULTS : The addition of NCF led to a decrease in fugitive dust. Regarding the mechanical properties of the mortars, that with 0.5% NCF exhibited a better performance in terms of strength development and surface electric resistivity compared to those of other mortars. However, the addition of NCF was less effective in the enhancement of the absorption of mortars. Further, we discovered that the microstructures of the mortars with additional NCF were comparatively dense compared to those without NCF. CONCLUSIONS : The appropriate addition of NCF can enhance the performance of CAC-based repair materials. However, further studies on the durability of CAC with the addition of NCF are needed to determine the optimal mixture.

In this study, as the proportion of aged pipelines increases rapidly, in the event of an accident caused by corrosion and structural deterioration of metal pipes, appropriate overlay welding is applied in the field to partially repair it. The size of the base steel plate and the selection of a stable welding method were evaluated, and possible problems caused by the overlay welding were identified, and improvement measures were proposed. For the test, a new steel pipe coated with epoxy lining on the inner surface and polyethylene on the outer surface was subjected to a tensile test by processing the repaired specimen through overlay welding with a steel plate after artificial cracking, and structural safety was evaluated after repair. Furthermore, the influences of the size of the throat and the size of the steel plate were analyzed. As a result of the tensile test by dividing the repaired steel plate overlay into a constraint and non-constraint conditions, the tensile load was concentrated in the welded part and damage occurred in the welded part. It was found that the maximum load leading to breakage increases as the size of the welding throat increases. In addition, it was found that the resistance to load increased slightly as the size of the overlaid steel plate increased, but the effect was not significant, confirming the need for repair in consideration of the site conditions. As a result of evaluating the damage to the coating material on the back side of the welding, it was confirmed that the coating material on the opposite side of the welding burned black(epoxy) or was greatly deformed by heat(polyethylene). Therefore, it is necessary to secure structural stability through repainting, etc. in order to prevent damage to the coating material on the opposite side during overlay welding.

PURPOSES : Experimental findings pertaining to the mechanical properties of calcium aluminate cement (CAC)-based repair mortars incorporated with anhydrite gypsum (AG) are described herein. METHODS : To prepare the mortars, three different levels of AG were adopted and the ratio of water–cementitious materials was fixed at 0.50. For comparison, mortar composed of ordinary Portland cement was prepared. The fluidity, setting time, compressive and bond strengths, absorption and surface electric resistivity of the mortars were measured at predetermined periods. RESULTS : The incorporation of AG increases the fluidity but decreases the setting time of the CAC-based repair material system. However, the AG in the CAC mixes does not effectively enhance the compressive strength of the mortars owing to the decreased formation of CA hydrates, such as CAH10 and C2AH8. Meanwhile, the mortar with 10% AG shows excellence absorption. CONCLUSIONS : The mechanical properties of CAC based-mortars rely significantly on the amount of AG incorporated. However, further studies regarding the microstructure and durability of CAC-AG repair mortars must be conducted to obtain the optimal mixture.

PURPOSES : In this study, a method to use magnesium phosphate ceramic (MPC) concrete for the surface maintenance of airport pavements with jointed concrete is developed. METHODS : To investigate the application of a material incorporated with MPC for the surface maintenance of airport pavements with jointed concrete, structures with various cross-sections and thicknesses were constructed. The cross-section of the structure was modeled for the surface maintenance of four types of pavements and typical pavement construction processes, such as cutting, cleaning, production and casting, finishing, hardening, and joint reinstallation. Subsequently, the hours required for each process was determined. RESULTS : The MPC concrete used for the surface maintenance of airport pavements with jointed concrete demonstrate excellent performance. The MPC concrete indicates a compressive strength exceeding 25 MPa for 2 h, and its hydration heat is 52.9 ℃~61.2 ℃. Meanwhile, the crushing and cleaning performed during the production and casting of the MPC require a significant amount of time. Specifically, for a partial repair process, a total of 6 h is sufficient under traffic control, although this duration is inadequate for a complete repair process. CONCLUSIONS : MPC concrete is advantageous for the surface maintenance of airport pavements with jointed concrete. In fact, MPC concrete can be sufficiently constructed using existing concrete maintenance equipment, and partial repair works spanning a cross-sectional area of 11 m2 can be completed in 1 d. In addition, if the crushing and cleaning are performed separately from production and construction, then repair work using MPC concrete can be performed at a larger scale.

PURPOSES : The objective of this study is to analyze the significance of binder aging in a hot-mix asphalt (HMA) mixture in an insulated camber for a long duration for repair works, where the absolute viscosity level and service life reduction (SLR) are assessed based on the haul time, as well as to suggest a methodology for reducing the aging level. METHODS : Because the HMA mixture is stored in an insulated box carriage at high temperature for repair works, if the binder in the mix is severely oxidized, then the repaired pavement will not exhibit a long service life. Therefore, the 13-mm dense-graded HMA mix with PG64-22 was aged in an oven at 160 °C for 1, 2, 4 and 8 h to evaluate its aging level. Gel-permeation chromatography was performed on the mixture particle without binder recovery to measure the large-molecular size ratio, from which the estimated absolute viscosity (EAV) was computed using a best-fit regression model. The SLR values of aged and repaired mixes were estimated to determine the amount of deterioration in the mixes caused by severe aging. Hydrated lime (HL) was introduced into the mix at a ratio of 1.5 wt% of the total mix. The aging level and SLR were compared with those of the repaired mix without HL. RESULTS : The binder EAV of the HMA mix increases significantly with the mixture aging duration. In particular, the binder EAV level of a 4-h aged mix is similar to the asphalt viscosity level of a pavement with approximately 7 years of service life. The service life expressed based on the aging level is interpreted as the reduced service life of the aged mix, which is already oxidized before it is used. Meanwhile, the binder of an 8-h aged mix without HL aged significantly and its SLR is approximately 11 years. However, its aging level and SLR reduced significantly when HL. is incorporated. CONCLUSIONS : The binder aging level of the repaired mix increases significantly with its storage duration in a hot chamber for carriage. However, since the aging level decreases significantly by the incorporation of HL, the use of HL is highly recommended when preparing new mix for repair works to be performed in a hot-chamber for a long duration.

본 연구는 부·울·경의 전국동시지방선거 중 시·도지사 선거결과를 통해 보수정당으로의 회귀 가능성과 향후 선거 결과에 대한 전망을 하는 것이 주요한 목적이다. 실제로 전국동시지방선거에서 부산은 국민의힘이 더불 어민주당을 7:1로 이겼고, 울산에서는 국민의힘이 6:1로 우세했다. 그리 고 경남에서는 국민의힘과 더불어민주당의 전적은 6:2의 결과를 보였다. 이것은 지역주의와 지연주의가 부·울·경에서 강하게 작용하고 있다는 것 을 보여준다. 제8회 전국동시지방선거에서 국민의힘이 전국에서 승리하 였고, 특히 부·울·경 지역에서는 양당 후보 간 20%~35%p의 큰 격차를 보였다. 그리고 부·울·경의 역대선거 결과를 비교분석해 볼 때, “유권자 의 선택이 중요하며, 그 점에서 부·울·경은 보수정당 지지로 선회했고, 이 흐름은 당분간 지속할 것으로 전망된다. 하지만, 박근혜 대통령의 탄 핵이라는 큰 변수는 제7회 전국동시지방선거에서 더불어민주당의 전국적 인 승리를 안겨주었다는 점에서 정치적 이슈에 따라 유권자의 선택이 언 제든 변화할 수 있다.

연구대상판결은 크게 두 부분으로 구성되어 있다. 첫째, 민법 제663조 제2항과 제3항에 의해 도급인의 ‘하자보수청구권’과 ‘하자 보수에 갈음하는 손해배상채권’은 특별한 사정이 없는 한 수급인의 도급인에 대한 ‘공사대금채권’과 동시이행의 관계에 있고, 이로 인해 도급인이 하자보수나 이에 갈음하는 손해배상청구권을 보유하고 이를 행사하는 한 도급인의 공사비 지급채무는 이행지체에 빠지지 않는다. 둘째, 수급인의 공사비채권의 변제기는 건물의 준공, 인도일이고, 도급인의 하자 보수에 갈음하는 손해배상채권의 변제기는 도급인이 그 권리를 행사한 때인데, 도급인이 하자보수에 갈음하는 손해배상채권을 자동채권으로 하고, 수급인의 공사비잔대금채권을 수동채권으로 하여 상계의 의사표시를 한 경우, 상계적상일 다음날이 아니라 “상계의 의사표시를 한 다음날”부터 이행지체에 빠진다. 연구대상판결은 동시이행의 범위에서 전부거절설에 기초하고 있다. 그러나 전부 거절설을 취한 이유에 대해서는 밝히지 않고 있다. 그러나 연구대상판결에서 동시이행의 항변권에 기해 전부거절설을 취한 것은 i) 하자보수에 갈음한 손해배상채권과 보수채권 사이의 동시이행의 항변권은 비쌍무계약상 동시이행의 항변권에 해당하므로, ii) 제667조 제3항에서 제536조 를 준용한 취지를 살펴 그 동시이행의 항변권에 기한 이행거절의 범위를 결정할 필요가 있는데, iii) 그 준용의 취지가 하자보수에 갈음하는 손해배상채권에 기한 상계권을 대금감액적으로 행사할 수 있도록 특별히 동시이행관계를 설정한 것 이라고 보는 것이 가장 적절한 설명이 될 수 있을 것으로 보인다. 또한 상계적상일 다음날이 아니라 상계의 의사표시 다음날부터 잔여보수채무의 이행지체책임을 지도록 한 것은 i) 하자보수에 갈음한 손해배상청구에서 하자 보수비용의 확정이 현실적으로 용이하지 않다는 현실적인 문제를 고려하여 그 하자보수비용 확정 전에 보수채무의 변제기가 도래하는 상황에서 도급인이 하자보수에 갈음하는 손해배상채권에 기한 상계권을 대금감액을 위해 행사할 수 있도록 제667조 제3항에서 제536조를 준용하여 하자보수에 갈음하는 손해 배상채권에 기한 동시이행의 항변권의 행사로 보수채무 전부를 거절할 수 있다는 현실적 관점과 ii) 상계의 소급효가 전부거절설에 의한 이행지체책임의 면제이익을 뒤집을 수 없다는 이론적 관점에서 정당화될 수 있다고 본다.

PURPOSES : Recently, the generation of industrial by-products has been increased owing to the increase in electrical power consumption. This experimental study investigated a special mortar development using outstanding benefits of porous structures in heavy oil fly ash (HOFA) and bottom ash (BA) to reduce heat transfer and weight of tunnel repair mortar. METHODS : Based on the concept of materials usable for this objective being porous and light, the physical and chemical properties of heavy oil fly ash and bottom ash were analyzed to determine the application possibility for tunnel repair mortar. In addition to satisfying this primary requirement, the research aimed at determining the relationships between the characteristics of porous structures and effectiveness of reducing weight and thermal conductivity. This study was undertaken on the use of bottom ash as fine aggregate and heavy oil ash as filler in mortar mix proportion. Four different levels of bottom ash (25%, 50%, 75%, 100%, and 5%), and 10%, 15%, and 20% of heavy oil fly ash were investigated to determine the proper replacement amount within the designed specification. According to the analytic results on the effectiveness of both by-products and chemical additives, the repair mortar with optimum mixture proportion was investigated using various tests including thermal conductivity and porosity. RESULTS : The use of porous by-products increased the demand for mixing water in obtaining the required flowability, but the compressive strength did not decrease significantly in proportion by adding an amount of bottom ash. Based on the results, bottom ash can be replaced with aggregate as much as 50%, but adding an amount of heavy oil ash is suggested as below 10% in formulation. CONCLUSIONS : The optimized repair mortar, which was produced by conclusive formulation, was evaluated as a high-performance material to repair tunnels with the effectiveness of porous and remarkable physical properties.

Asphalt concrete(Ascon) is used to repair potholes and cracks. Special truck-mounted cargo boxes transport 200℃ asphalt concrete to repair potholes and cracks. However, long working and transportation hours to repair wide roads decrease the temperature of the asphalt concrete inside the cargo boxes. If the asphalt concrete temperature drops below 170℃, the adhesion with roads that need repair decreases. Therefore, the temperature of the asphalt concrete needs to be maintained for a long time. Conventional asphalt concrete cargo boxes are mostly burner-type models using hot air to prevent the temperature of the asphalt concrete from dropping. However, there are significant temperature differences between the asphalt concrete near and far away from the hot air, so the temperature decreases over time and leads to the disposal of large amounts of asphalt concrete. This causes waste of resources and environmental pollution. Therefore, this study proposed a heat dissipation cut-off type cargo box model to solve this problem and demonstrated its performance over conventional burner-type models through tests and analysis.