Recently, machine learning is widely used to solve optimization problems in various engineering fields. In this study, machine learning is applied to development of a control algorithm for a smart control device for reduction of seismic responses. For this purpose, Deep Q-network (DQN) out of reinforcement learning algorithms was employed to develop control algorithm. A single degree of freedom (SDOF) structure with a smart tuned mass damper (TMD) was used as an example structure. A smart TMD system was composed of MR (magnetorheological) damper instead of passive damper. Reward design of reinforcement learning mainly affects the control performance of the smart TMD. Various hyperparameters were investigated to optimize the control performance of DQN-based control algorithm. Usually, decrease of the time step for numerical simulation is desirable to increase the accuracy of simulation results. However, the numerical simulation results presented that decrease of the time step for reward calculation might decrease the control performance of DQN-based control algorithm. Therefore, a proper time step for reward calculation should be selected in a DQN training process.

본 연구에서는 모듈러 DSCT 풍력 타워의 볼트접합방법을 택하여 해석하고 성능을 검토하였다. 기존방식은 용접을 활용한 접합방법이 많이 사용되어 왔다. 하지만 현장에서 시공하기에는 용접접합방법보다 볼트접합방법이 더 간편하고 효율적이라고 판단하였다. 볼트접합방법을 사용한 모듈러는 총 2가지 방법으로 Case1은 상단부의 10mm만을 강재판으로 용접하고 하단부 125mm는 볼트접합한 상태이며, Case2는 상단부 60mm을 H의 형태의 링에 용접하고 하단부 125mm는 볼트접합을 한 형태이다. 이를 범용 유한요소해석프로그램인 ABAQUS 6.12로 재료비선형해석을 수행하였다. 수행 전에 간단한 Mesh검증과 모델검증을 통하여 모델의 타당성을 증명하였다. 재료비선형해석을 수행한 결과 연결부를 사용하여 조립한 모듈러 DSCT 풍력타워와 일체형 DSCT 풍력타워의 전체거동은 거의 차이가 없었음을 확인하였다. 또한 2가지 형식 모두 연결부에서 국부적인 응력이 발생하지만 그 응력 값이 지점부에서 발생하는 응력보다 작기 때문에 모듈러 DSCT 풍력타워의 성능을 지배하는 요인은 단면이 갖고 있는 성능에 의해 지배된다는 것을 의미한다. 그러므로 현재 사용하고자 하는 볼트접합방법이 안전함을 보여주었다.

서해안을 방문하는 관광객 수가 꾸준히 증가하면서 항만시설이 아닌 여가 시설로 관광용 보도 잔교가 많이 설치되고 있다. 하지만 현재 국내 보도교 설계는 서울시 시설물 설계 및 시공편람의 소규모 강교 및 보도 육교에 대한 설계기준 또는 도로교설계기준을 적용하고 있다. 이에 해안에 설치되는 보도용 잔교설계는 특별한 기준이 없어 항만 및 어항설계기준을 준용하고 있으나 이 기준은 선박 및 작업기계를 고려한 부두시설로써 잔교를 대상으로 하여 보도용 잔교에 적용하면 과다한 설계를 유발하고 있는 실정이다. 이에 연안역 조립식 경골잔교(Fish-bone Girder Bridge)를 개발하게 되었다. 하지만 연안역 조립식 경골잔교는 단일거더시스템이므로 비틀림에 큰 영향을 받는 구조물이다. 본 연구에서는 잔교를 보다 합리적으로 해석하기 위한 모델을 제시하고, 사용하중에 대한 안전성을 검토하고, 볼트연결부 설계를 위한 단면력을 산정하고자 한다.

This experiments was conducted to investigate the influence on growth of rye, triticale with legume and investigated their productivity, feed value and stock carrying capacity in order to select the appropriate forage species in the central region of Korea. In the results, Rye+Red clover showed 5.2ton/ha of dry matter yield. But there was no significant difference with Triticale+Red clover and Rye in upland field. In paddy field, Rye+Hairy vetch showed 5.2ton/ha, but there was no significant difference with Triticale+Hairy vetch and Rye. Mixture effects with Rye, Triticale and Red clover, Hairy vetch by relative yield were more than 1.00 compared to monoculture, and their mixture effect was recognized in upland and paddy field. Relative feed value was highest in the applications of Triticale mixture in upland and paddy field. The average value of KCP and KTDN showed the highest one as 2.75head/ha/yr in Rye+Red clover in upland field and 2.84head/ha/yr in Triticale+Hairy vetch in paddy field. According to the results, Rye+Red clover in upland field and Triticale+Hairy vetch in paddy field were considered to be the most appropriate winter forage crops for the central region of Korea in terms of productivity, feed value and stock carrying capacity.

This experiments was conducted to investigate the influence on the growth of Sorghum × Sudangrass hybrid by use of various organic fertilizer and investigated their productivity, feed value and stock carrying capacity. In the results, the application of fermented poultry manure showed 93.6ton/ha, 19.6ton/ha, 1.12ton/ha, 11.31ton/ha of fresh yield, dry matter yield, crude protein (CP) yield and total digestible nutrients (TDN) yield but there were no significant differences with the application of poultry by-product compost (poultry manure with sawdust) and swine by-product compost (swine manure with sawdust). And the average value of Kcp and Ktdn showed the highest one as 9.45head/ha/yr in the application of fermented poultry manure. However, organic matter content of fermented poultry manure to the lower portion of 32.1% compared to other organic fertilizers could imagine that mineralization of fermented poultry manure was fairly advanced and plant used most of nitrogen in fermented poultry manure, so productivity of Sorghum × Sudangrass hybrid was shown more than other organic fertilizers. If other organic fertilizers use continuous, this difference can be considered to be reduced further. As a result, fermented poultry manure is better than other organic fertilizers in productivity, feed value and stock carrying capacity due to the higher content of mineralizable matters. In addition, mixing poultry manure with cow and swine manure is better choice because cow and swine manure will meet a low organic matter in poultry manure.

본 연구에서는 기존의 연안역 특성을 고려한 말뚝지지형 조립식 잔교의 하부 구조 모델의 부족한 점을 보완하고 관광용 특성을 살린 디자인과 연안에서의 시공의 단순함을 조립식으로 계량화 시킨 Fish Bone Bridge를 제시하였다. 이에 기존 모델과의 거동 차이와 Fish Bone Bridge의 문제점인 온도하중에 의한 경간수 그리고 말뚝과 거더의 연결 조건이 고정-힌지와의 차이를 알아보기 위해 범용유한요소해석 프로그램인 MIDAS Civil 2009을 사용하여 비교-분석하였다.

본 연구에서는 기존에 개발된 말뚝지지형 조립식 잔교는 하나의 말뚝을 사용하여 단순하고 조립이 간단한 형태로 개발된 조립식 잔교지만, 하나의 말뚝으로 인한 해상 항타 시 수직도 문제 및 파력이 작용하였을 경우 수평문제가 야기되었으며, 상부구조물의 편측제어에 따른 불안전성이라는 문제가 노출되었다. 이에 상·하부 구조의 불안전성을 해결하기 위하여 상·하부 구조의 거동이 같이 될 수 있는 라멘구조의 역할이 가능한 지그재그 형태의 ‘Fish Bone Bridge’를 개발하게 되었다. 하지만 지그재그 형태로 개발을 하다보니, 비대칭적인 구조로 인하여 상부구조의 Main girder에 과도한 비틀림 하중을 유발하게 되었다. 본 논문에서는 ‘Fish Bone Bridge’ 상부구조에 작용하는 적절한 설계하중을 결정하고, 상부구조의 주요부재인 Main girder에 대한 적절한 설계 단면 및 Main girder에 작용하는 하중에 대한 유한요소해석 프로그램을 통한 해석모델의 타당성을 검증하였으며, 하중조합에 따른 Main girder 단면의 안전성을 검증하였다.

This experiment was conducted to investigate the selection of regional double cropping system for production of organic forage in middle part of Korea and investigated their productivity, feed values and stock carrying capacity. The test results proved the Sorghum×Sudangrass hybrid was 10.9 ton ․ ha-1, the one of Rye + Red clover and Rye + Hairy vetch were the highest one as 3.3 ton ․ ha-1 and the relative yield about a Rye is higher in the dry matter yield in the field soil. And as for the relative forage values (RFV), Corn is the most excellent ones as 96.6 but there were no the significant difference between the Sorghum×Sudangrass hybrid of 84.4 and it. The total digestible nutrient (TDN) content in Rye + Hairy vetch is higher than others as 59.7%. As for the relative feed value, Rye + Red clover is the highest one as 83.8 but there was no significant differences between them. As for the ability to raise livestock in the field soil, the average values of KCP and KTDN are shown as 4.27 head/ha/yr in Sorghum×Sudangrass hybrid. As for the same crops, the average values of KCP and KTDN showed the highest ones as 1.74 head/ha/yr, in Rye + Red clover but there were no the significant differences. As for the dry matter yield of the rice field soil, organic rice straw was 3.3 ton ․ ha-1 and Rye + Red clover significantly showed the highest values as 4.1 ton ․ ha-1. In the rice filed soil, the crude protein content of organic rice straw was 3.1% and the TDN content of organic rice straw was 55%. The TDN content in Rye + Red clover was higher than others as 59.7%. As for the relative forage values, Rye + Red clover showed the highest one as 83.8 but there were no significant differences between them. As for the ability to raise livestock in the rice field, the average values of KCP and KTDN in the organic rice straw was 1.04 head/ha/yr and the average values of KCP and KTDNM in Rye + Red clover is the highest one as 1.84 head/ha/yr, but there were no significant differences in all of them.

In attempt to select the most appropriate forage legume species, this study was conducted on the 10 forage legume crops suitable for the central region of Korea and investigated their productivity, feed values and stock carrying capacity. In the results, red clover showed fresh matter yield 38.6 ton/ha, dry matter yield 7.8 ton/ha, crude protein yield 1.0 ton/ha, total digestible nutrients(TDN) yield 4.6 ton/ha, its fresh matter yield, dry matter yield and nutrient yield were significantly(p＜0.05) higher than other species. The value of neutral detergent fiber(NDF) and acid detergent fiber(ADF) were getting higher by the late harvest time then galega and cicer milkvetch were the highest and yellow suckling clover was the lowest value. Relative feed value(RFV) showed good feed values above 100 except cicer milkvetch and galega. In terms of feed grading, yellow suckling clover, yellow blossom sweet clover, crimson clover, hairy vetch were classified into 1st grade, above 151%. The average stock carrying capacity was yet high Kcp(2.18 head/ ha/yr), KTDN(1.25 head/ha/yr) and K(0.04 head/ha/yr). Especially, red clover had the highest stock carrying capacity, Kcp 6.84 head/ha/yr, KTDN 3.64 head/ha/yr and K 0.05 head/ha/yr. According to results, red clover is considered to be the most appropriate crops for the central region, in terms of quality, feed value and stock carrying capacity.