• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• KOMUNHWA
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• no.70
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• pp.133-161
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• 2007

It is judged that celadons with '○' pattern and '⊙' pattern have the indication of manufacturer by engraving mark at the internal center of the bottom. These celadons were produced at No.8.23.27 kiln sites located at Sadang-ri(사당리), Daegu-myon(대구면), Gangjin-gun(강진군), Jeollanamdo(전라남도), Korea and '⊙’ patterned celadon porcelain was found only at No. 23 and 27 kiln sites, so it is assumed that its production sites were limited. Kinds of celadons included bowl, dish, cup, bottle, case and vessel for emptied wine and there were a lot of dishes with a variety of patterns. These celadons were engraved by molded design technique using the same ceramic design as the pattern of celadons in the period of their prosperity and it was appropriate method to produce celadons of a good quality with production method to keep decorative design like pattern or size uniformly. It was also found that inlay method was not universalized in this period and similar celadons were produced with molded design in large quantities. These celadons had partially fire clay temper, but most of them were burnt by supporting the inner bottom of U-type base with quartzite after whole glazing. It was known through relics excavated at Seokreung(석릉) royal tomb of King Heejong(희종) at Ganghwa(강화) and Hyeeumwon(혜음원) temple site at Paju(파주) and military house at Wakamiyaoji(약궁대로) avenue Kamakura(겸창)-city, Japan(일본) that these celadons were manufactured at two quarters of the 13th century centering around 1230s. Therefore, these celadons will be significant materials to fill the gap of the celadons in the 13th century resulted from the record chronologically that green celadons were manufactured in the 12th century. And this period was invaded by Mongolia(몽고), but central control was achieved and green celadons were continuously produced. It was also considered that these celadons were excavated at Gabgot-ri(갑곶리) and Gwanchung-ri(관청리), Ganghwa(강화), Hyeeumwon temple, Paju which played the role of temporary palace, Bu1guksa(불국사) temple at Gyeongju(경주), Silsangsa(실상사) temple at Namwon(남원) and relics of Jangheung(장흥) adjacent to Daeguso(대구소) and these were produced for high class.