Earticle

Risk level for each construction work can be very important factors to establish advanced prevention measures. But it is important how to produce it. There are three different methods to set it up for construction situation. They are as follows; 1) occurrence frequency = the number of accident workers of each work kind / yearly accident workers 2) occurrence frequency = the number of accident workers of each work kind / yearly workers 3) occurrence frequency = the number of accident workers of each work kind / the total workers All these three concepts(=averaged concept)are analyzed. Additionally frequency based on discrete curve, and severity based on continuous curve are also combined for producing risk level with more scientific approach. This risk level can be very useful to make prevention plan or take measures at construction sites. This is study result can change existing risk level concept to new concept of it, namely rail way work and in-water work showed be high risk level and RC work be low risk level, different from the situation which we have thought commonly, so far.

Risk level for each construction work can be very important factors to establish advanced preventionmeasures. But it is important how to produce it. There are three different methods to set it up for consturuction situation. They are as follows; 1) occurrence frequency = the number of accident workers of each work kind / yearly accident workers 2) occurrence frequency = the number of accident workers of each work kind / yearly workers 3) occurrence frequency = the number of accident workers of each work kind / the total workers All these three concepts(=averaged concept)are analyzed. Additionally frequency based on discrete curve, and severity based on continuous curve are also combined for producing risk level with more scientific approach. This risk level can be very useful to make prevention plan or take measures at construction sites. This is study result can change existing risk level concept to new concept of it, namely rail way work and in-water work showed be high risk level and RC work be low risk level, different from the situation which we have thought commonly, so far.

최근 RC 슬래브의 붕괴사고가 발생하였으며, 거푸집 동바리의 조기 철거시 압축강도가 충분히 발현되지 못해 슬래브에 과도한 처짐 혹은 균열이 발생할 수 있으며, 구조물 시공 중 거푸집 동바리의 존치기간을 결정하는 것은 중요하다. 본 연구에서는 단층 및 다층 RC 플랫 플레이트 구조물을 대상으로 거푸집 동바리의 존치기간을 검토하기 위하여 구조물을 설계하고 시공단계별 하중을 산정하여 유한요소해석을 수행하였다. 본 연구의 주요 결론은 다음과 같다. (1) 구조물의 층수와 층당 시공주기에 따라 최소 거푸집 동바리 존치기간이 달라지며, 단층과 다층으로 단순히 구분하는 것은 불합리하다고 판단된다. (2) 유한요소해석을 통해 파악된 처짐 혹은 균열을 바탕으로 거푸집 동바리 존치기간을 검토하였으며, 현행 기준은 2층과 3층 구조물에 대해 큰 안전율이 적용되고 있다. (3) 고강도 콘크리트일수록 거푸집 동바리 존치기간이 단축될 수 있다. (4) 슬래브 두께가 두꺼울수록 초기에 큰 하중이 작용하여 거푸집 동바리의 존치기간이 증가하므로, 슬래브의 두께에 따른 영향을 고려할 필요가 있다.

Recently, collapses of RC slab occurred, and when the form-work shoring is removed early, compressive strength of concrete is not sufficiently developed, which can cause large deflection and/or crack in the slab. Therefore, it is important to determine form-work shoring period during construction of structure. In this study, it was designed the RC structure and analyzed using finite element method, to evaluate the form-work shoring period. The results of this study are as follows; (1) The form-work shoring period was showed different according to story and floor construction cycle, so it is unreasonable to classify simply into single and multi-structure. (2) Based on the deflection and/or crack shown in the finite element analysis result, the form-work shoring period was reviewed, and revealing that a high safety margin was applied to the structures of 2 and 3-story. (3) According to the effect of specified compressive strength of concrete, the form-work shoring period can be shortened, in the case of the high strength of concrete. (4) As the thickness of slab increased, the form-work shoring period increased due to initial weight. Therefore, the standards are needed considering the influence of slab thickness.