• 한국건축시공학회지
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• 제9권1호
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• pp.49-55
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• 2009

In this study, reduction methods of surface air void were examined for high performance concrete having high viscosity. The effects of assumed influencing factors such as form types, form-coating materials, tamping equipments and methods were examined based on the tests on mock-up specimens made of high performance concrete. The test results can be summarized as follows: As for form types, the most favorable results were obtained when coated plywood form was used with panel-shape tamping equipments at the contact region with concrete, the second and the third being the water/air-permeable sheets and steel with coated plywood, respectively. As for tamping equipments, a vibrator with 6.5cm diameter was most effective. Finally, the shorter the tamping intervals, the better the reduction effect of surface air void. As a conclusion, an improved method was proposed to reduce surface air void and it was verified with the test result that only four air voids as large as $5{\sim}10mm$ are found in the are of $1m^2$.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.501-509
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• 2020

건설공사 토공사는 건설의 핵심공정으로 거의 모든 공정에서 사용되며 구조물의 안전과 직결된다. 이에 평판재하시험 및 들밀도 시험을 통하여 다짐의 정도를 분석하고 확인은 필수이다. 하지만 현재 다짐측정은 아날로그 방식으로 시행되기 때문에 현장에서 실시간 확인과 정확한 위치정보, 시간정보 및 작업자의 이력관리가 어려운 실정이다. 이에 본 연구에서는 이러한 아날로그 방식의 다짐정보 구축의 문제를 해결하기 위하여 스마트건설 환경에 적합한 IoT (Internet of Things) 기반의 DCPT (Dynamic Cone Penetration Test) 기술을 개발하였다. 개발한 DCPT 기술은 국내외 개발현황을 바탕으로 개선사항을 도출하였으며, 디지털 환경에 적합한 IoT 기반의 DCPT를 개발하였다. 스마트폰 환경에서 운영되는 Smart DCPT 체계는 다양한 어플리케이션을 적용할 수 있는 유연성과 저비용, 고효율의 장점을 가지고 있다. IoT 기반의 DCPT는 디지털 다짐정보, 측정 횟수당 다짐정보, 위치정보, 시간정보, 작업자 인적관리 등을 종합적으로 기록하여 현장에서 분석하고 가사회한다. 또한 구축된 다양한 정보는 스마트폰을 통해 관리센터로 실시간 전송되기 때문에 건설공정 관리에 많은 기여가 예상된다.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.435-455
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• 2012

An impact on the ground surface may represent several phenomena, such as a crash of an airplane or an explosion or the passage of a train. In order to analyze and design structures and equipment to resist such a type of shocks, the response spectra for an impact on the ground must be given. We investigated the half-space motions due to impact using the finite element method. We performed extensive parametric analyses to define a suitable finite element model and arrive at displacement time histories and response spectra at varying distances from the impact point. The principal scope of our study has been to derive response spectra which: (a) provide insight and illustrate in detail the half-space response to an impact load, (b) can be readily used for the analysis of structures resting on a ground subjected to an impact and (c) are a new family of results for the impact problem and can serve as reference for future research.