This study presents code-compliant seismic details by addressing dry mechanical splices for precast concrete (PC) beam-column connections in the ACI 318-19 code. To this end, critical observations of previous test results on precast beam-column connection specimens with the proposed seismic detail are briefly reported in this study, along with a typical reinforced concrete (RC) monolithic connection. On this basis, nonlinear dynamic models were developed to verify seismic responses of the PC emulative moment-resisting frame systems. As the current design code allows only the emulative design approach, this study aims at identifying the seismic performances of PC moment frame systems depending on their emulative levels, for which two extreme cases were intentionally chosen as the non-emulative (unbonded self-centering with marginal energy dissipation) and fully-emulative connection details. Their corresponding hysteresis models were set by using commercial finite element analysis software. According to the current seismic design provisions, a typical five-story building was designed as a target PC building. Subsequently, nonlinear dynamic time history analyses were performed with seven ground motions to investigate the impact of emulation level or hysteresis models (i.e., energy dissipation performance) on system responses between the emulative and non-emulative PC moment frames. The analytical results showed that both the base shear and story drift ratio were substantially reduced in the emulative system compared to that of the non-emulative one, and it indicates the importance of the code-compliant (i.e., emulative) connection details on the seismic performance of the precast building.

In recent automobile development, vehicle weight reduction has become a very important goal. Seat weight reduction is a large portion of vehicle weight reduction. In this study, a specimen tensile tests were conducted on the Almag material, which is an alloy of aluminum and magnesium, and also conducted on SAFH440, SAFH 590, SAFC780, and SAFH980, which are mild steel materials used in the seat frame. The tensile specimen tests were carried out in two speed; 2mm/s and 4mm/s, and the obtained stress to strain curve was converted to the analysis material card of true stress to true strain curve to be used in the seat structural analysis. The constructed analysis material card was used in the specimen tensile finite element analysis, and the analysis result was able to obtain the stress to strain curve similar to the test result.

Recently, the occurrence frequency of earthquake has increased in Korea, and the interests for seismic reinforcement of existing school buildings have been raised. To this end, the seismic performance evaluations for school buildings that did not accomplish the seismic design are required. In particular, this study checks the eigenvalue analysis, pushover curves, maximum base shears, performance points and story drift ratios, and then analyzes the seismic performance characteristics according to bracing configuration of steel frame system reinforcement. Also, this study presents the practical field application methods through the comparison of analysis results for the seismic performance characteristics.

Existing reinforced concrete buildings with seismically deficient details have premature failure under earthquake loads. The fiber-reinforced polymer column jacket enhances the lateral resisting capacities with additional confining pressures. This paper aims to quantify the retrofit effect varying the confinement and stiffness-related parameters under three earthquake scenarios and establish the retrofit strategy. The retrofit effects were estimated by comparing energy demands between non-retrofitted and retrofitted conditions. The retrofit design parameters are determined considering seismic hazard levels to maximize the retrofit effects. The critical parameters of the retrofit system were determined by the confinement-related parameters at moderate and high seismic levels and the stiffness-related parameters at low seismic levels.

목적 : 본 연구의 목표는 서울지역 20대 MZ세대 집단이 인식하는 해외 안경테 브랜드 국가의 감성의미를 도출 하는 것이다. 방법 : 먼저 연구 대상으로 이탈리아, 프랑스, 미국, 일본 4개국을 선정하였다. 의미분별법을 이용하여 감성어 휘 8개를 추출한 다음, 설문조사와 통계처리를 통하여 각각의 국가별로 해당되는 감성어휘를 결정하였고, 해외 안 경테 브랜드 국가에 대한 선호도 조사를 추가로 실시하였다. 결과 : 이탈리아, 프랑스, 미국, 일본의 4가지 해외 안경테 브랜드 국가들에 대하여 각각 고급스러움, 매력적 임, 실용적임, 동양적임이라는 감성어휘를 가장 많이 선택하였다. 안경테에 대한 선호도 순위는 이탈리아, 프랑스, 미국, 일본 순으로 나타났다. 결론 : 도출된 감성어휘들과 응답자들의 선호도를 분석했을 때, 고급스러움과 디자인적 측면을 중시하는 MZ세 대의 플렉스 소비 성향에는 이탈리아와 프랑스 브랜드의 안경테가 가정 적합한 것으로 여겨진다.

For fast-built and safe precast concrete (PC) construction, the dry mechanical splicing method is a critical technique that enables a self-sustaining system (SSS) during construction with no temporary support and minimizes onsite jobs. However, due to limited experimental evidence, traditional wet splicing methods are still dominantly adopted in the domestic precast industry. For PC beam-column connections, the current design code requires achieving emulative connection performances and corresponding structural integrity to be comparable with typical reinforced concrete (RC) systems with monolithic connections. To this end, this study conducted the standard material tests on mechanical splices to check their satisfactory performance as the Type 2 mechanical splice specified in the ACI 318 code. Two PC beam-column connection specimens with dry mechanical splices and an RC control specimen as the special moment frame were subsequently fabricated and tested under lateral reversed cyclic loadings. Test results showed that the seismic performances of all the PC specimens were fully comparable to the RC specimen in terms of strength, stiffness, energy dissipation, drift capacity, and failure mode, and their hysteresis responses showed a mitigated pinching effect compared to the control RC specimen. The seismic performances of the PC and RC specimens were evaluated quantitatively based on the ACI 374 report, and it appeared that all the test specimens fully satisfied the seismic performance criteria as a code-compliant special moment frame system.

This study presents a dry precast concrete (PC) beam-column connection, and its target seismic performance level is set to be emulative to the reinforced concrete (RC) intermediate moment resisting frame system specified in ACI 318 and ASCE 7. The key features include self-sustaining ability during construction with the dry mechanical splicing method, enabling emulative connection performances and better constructability. Test specimens with code-compliant seismic details were fabricated and tested under reversed cyclic loading, which included a PC beam-column connection specimen with dry connections and an RC control specimen. The test results showed that all the specimens failed in a similar failure mode due to plastic deformations in beam members, while the hysteretic response curve of the PC specimen showed comparable and emulative performances compared to the RC specimen. Seismic performance evaluation was quantitatively addressed, and on this basis, it confirmed that the presented system can fully satisfy all the required performance for the intermediate RC moment resisting frame.

In this study, the performance evaluation of the RC frame specimen (RV2) which was strengthened by a steel frame and a steel damper with the lateral deformation prevention details proceeded. The comparison objects are bare frame specimen (BF), RV2 and AWD, where AWD is a specimen reinforced with steel damper and aramid fiber sheets. In the evaluation of envelope curve, stiffness degradation, and energy dissipation capacity, RV2 was evaluated to have excellent capacity as a whole. To evaluate the strengthening effect of the steel frame based on the maximum strength and energy dissipation capacity, it was evaluated to have a 38% of the RV2’s capacity.

강진은 적절한 내진 설계 기술이 적용되지 않으면 건물 붕괴로 인하여 극심한 피해가 발생할 수 있다. 이를 해결할 수 있는 면진 기술은 구조물과 지반 사이에 베어링 장치를 적용하여 지진 에너지를 흡수하고 건물에 전달되는 진동을 감쇠한 다. 본 연구는 고무 마찰 베어링 장치의 구조물 적용성을 검증하고 지진으로부터 안전성을 확보하기 위하여 고무 마찰 베어링 프레임 구조물에 대한 수치해석을 수행하였다. 수치해석 결과로써 최대 지붕 가속도와 총 밑면 전단력이 감소되어 내진 성능을 확인하였다. 또한, 최대 층간 변위 및 최대 잔류 층간 변위에 대한 분석 결과로 프레임 구조물을 경제적 복구 수준의 결과를 도 출하여 고무 마찰 베어링 장치의 우수한 내진 성능을 확인하였다.

The reliable information on the hydraulic characteristics of rock mass is one of the key site factors for design and construction of deep subsurface structures such as geological radioactive nuclear waste disposal repository, underground energy storage facility, underground research laboratory, etc. In order to avoid relying on foreign field test technology in future projects, we have independently designed and made integrated type main frame, 120 bar waterproof downhole sonde, and 1,200 m wireline cable winch through a series of R&D activities. They are core apparatuses of the Deep borehole Hydraulic Test System (DHTS). Integration of individual test equipment into a single main frame allows safe and efficient work in the harsh field condition. The DHTS was developed aiming primarily for constant pressure (head) injection test and pulse test in deep impermeable rock mass. The maximum testing depth of the DHTS is about 1,050 m from the surface. Using this system, it is possible to make precise stepwise control of downhole net injection pressure in less than 2.0 kgf/cm2 with dual hydraulic volume controller and also to inject and measure the very low flow rate below 0.01 l/min with micro flow rate injection/control module. Over the past two years, we have successfully completed more than 50 in situ hydraulic tests at 5 deep boreholes located in the Mesozoic granite and sedimentary rock regions in Korea. Among them, the deepest testing depth was more than 920 m. In this paper, the major characteristics of the DHTS are introduced and also some results obtained from the high precision field tests in the deep and low permeable rock mass environment are briefly discussed.

The sub-frame is located on the lower body of a monocoque type vehicle and serves as an engine and suspension, and is an important object part that receives a lot of load. The existing press-type sub-frame has a large number of parts for assembling, which causes an increase in cost. Changing the machining form of this part from the existing press-type machining method to the hydro-forming machining method has the advantage of reducing the cost and weight at the same time due to the reduction of the process. Therefore, in this study, the purpose of this study is to change the design so that the sub-frame of the existing press type can be changed to the hydro-forming process method. To this end, we intend to present a design method by analyzing the effect on the rigidity of the sub-frame using the existing machining method through shape optimization analysis.

Hydro-forming technology is a technology that will replace the existing press-forming technology and is used in various industry range from automotive parts to electronic products. The advantage of this technology is that it has dramatically changed the existing processing method, and it can be said that the process reduction due to the reduction of parts, cost reduction, and high precision are mentioned. In this study, it is intended to present a design process using computer simulation by changing the sub-frame for automotive parts produced with the existing press forming technology to the hide-forming method. To this end, it is intended to use it as part design data by comparatively analyzing the cross-sectional shape and thickness reduction, which are the major factors necessary to determine the successful development of the developed parts.

In this study, stiffness evaluation was conducted on the main member, front cross member, and rear cross member, which are three components of sub-frame for SUVs (sports utility vehicles), through mode analysis. As for the design variables used in the analysis, the maximum frequency was examined by varying the width and height of each of the three parts into four types. Of course, the weight at this time is minimized, and the mode is set as a constraint that only bending occurs and no distortion occurs. As a result of the analysis, the member affecting the 1st mode was the rear cross member, and the member having the greatest influence on the 2nd mode was the front cross member. In addition, the member with the greatest influence on the 3rd mode appeared as the rear cross member, indicating that this part had the greatest effect on the bending stiffness.

목적 : 본 연구는 한국과 중국 성인 남녀의 안면 크기와 동공 간 거리를 조사하고, 현재 착용하고 있는 안경테의 크기 및 디자인 형상에 대해 비교를 하고자 하였다. 방법 : 경북 경산에 위치한 안경원을 방문한 20~30대 성인 남녀 각각 100명, 중국 지린성에 위치한 안경원을 방문한 20~30대 성인 남녀 각각 100명, 총 400명에 자료를 전향적 방법으로 수집하였다. 대상자들의 안면 크기 는 모바일 애플리케이션(Eye measure 1.21, Dotty Digital 2018, USA)을 이용하여 측정하였으며, 동공 간 거 리는 수동식 동공 간 거리계(PD-5, TOPCON, Japan)를 이용하여 원용과 근용 각각의 동공간 거리를 측정하였 다. 착용하고 있는 안경테에 대한 크기는 boxing system에 준하여 측정하였고, 안경테의 종류는 모양(원형, 타원 형, 직사각형), 림의 형태(온테, 반무테, 무테), 재질(플라스틱, 금속, 콤비)로 구분하여 분류하였다. 결과 : 안면 크기 측정범위는 149.73±6.28 mm(중국 여성)~152.29±14.71 mm(한국 남성)이었으나, 그룹 간 통계적 유의성은 없었다(p=0.147). 원용 및 근용 동공 간 거리 측정에서는 모두 그룹 간 통계적 유의성이 있었 다(p<0.001). 안경테의 크기 측정인 렌즈 삽입부의 크기(eye size), 연결부의 길이(bridge size) 그리고 수직 길이 (vertical height)에서 모두 그룹 간 통계적 유의성이 있었다(p<0.001). 한국과 중국의 남녀 대상자들의 착용 중 인 안경테에서 콤비 재질을 제외하고(p=0.790), 모든 항목에서 통계적 유의성이 있었다. 결론 : 본 연구는 한국과 중국 성인 남녀 간의 안면 크기는 차이는 없었지만, 동공 간 거리는 차이가 있었다. 착용 중인 안경테의 크기는 한국과 중국 착용자 간의 차이가 뚜렷하게 나타났으며, 한국 성인은 상대적으로 원형 테를 많이 착용하고 있지만, 중국은 직사각형의 안경테를 더 많이 착용하고 있었다. 따라서 나라 간 선호도가 다 름을 이해하고, 기호에 맞는 제품을 추천할 수 있어야 하고, 수출을 위한 안경 디자인을 할 때 안면의 형상 및 현 지인의 기호를 고려해야 할 것이다.

한글 글꼴의 눈에 띄는 특성에는 세리프 및 네모틀 여부가 있다. 꺾임 또는 삐침으로 장식된 글꼴은 세리프(serif)로 분류되 며, 이러한 장식이 없는 글꼴은 산세리프(san-serif)로 분류된다. 반면 네모틀은 알파벳 글꼴에는 없는 특징 범주이며, 가상의 사각형 안에 자, 모음, 그리고 받침이 조화를 이루는 특징을 의미한다. 본 연구는 오랫동안 광범위하게 사용되어 온 세리프와 네모틀 글꼴 특성을 보유한 글꼴이 그렇지 않은 글꼴보다 친숙성과 선호도가 높을 것을 가정했다. 이 가설을 검증하기 위해 한글 팬그램을 사용한 네모틀 및 탈네모틀 글꼴 그리고 세리프 및 산세리프 글꼴을 제시해 해당 네모틀 및 세리프 유무에 따른 친숙성과 선호도를 조사했다. 그 결과 참가자들은 탈네모틀 글꼴에 비해 네모틀 글꼴에 대해 친숙성과 선호도를 모두 높게 평가했으나 세리프와 산세리프 사이에 이러한 차이는 발견되지 않았다. 더 나아가 친숙성과 선호도 사이의 정적 상관은 탈네모틀 세리프 글꼴에 대해서만 관찰되었다. 이 결과는 네모틀의 특징을 보유한 한글 글꼴이 그렇지 않은 글꼴에 비해 더 친숙하고 선호될 가능성을 의미한다. 특히 본 연구는 한글 글꼴 사용자들에 있어서 익숙하고 편안한 글꼴로 네모틀 글꼴이 권장되며, 더 나아가 세리프를 동반한 네모틀 글꼴이 사용될 경우 이러한 긍정적 감성이 향상될 가능성을 시사한다.