KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
권호 표지

Identification of Relaxation Function in Early-Age Concrete Using Differential-Type Viscoelastic Constitutive Law

미분형 크리프 구성방정식을 이용한 초기재령 콘크리트의 응력이완함수 추정

Oh, Byung-Hwan;Choi, Seong-Cheol;Cha, Soo-Won
오병환;최성철;차수원

  • Published : 2005.01.31

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Abstract

The hydration heat generally induces thermal stresses and this in turn may cause the cracking problem in concrete at early ages. Therefore, it is necessary to accurately evaluate the actual stresses that occur in early-age concrete. However, the behavior of concrete at early ages is too complicated to accurately to predict because the development of viscoelastic properties is so rapid due to the fast hydration process during early stages. The purpose of the present study, therefore, is to identify the relaxation function from the measured strains and stresses which reflect the viscoelastic properties for early-age concrete. Furthermore, the compliance function which is necessary in predicting the stress in early-age concrete, was proposed based on the identified relaxation function. To this end, several series of full-scale test members were fabricated, from which temperature, total strains, stress-independent strains, and stresses have been directly measured. The calculated stresses based on the proposed model agree very well with measured stresses. Thus, the proposed model allows more realistic evaluation of actual stresses occurring in early-age concrete.

본 연구는 구속된 변형률에 의해 초기재령 콘크리트에서 발생하는 응력을 합리적으로 평가하기 위하여 실제 구조물의 초기거동 및 응력 특성을 나타낼 수 있는 실구조물 크기의 시험체를 제작하여 타설과 동시에 시간에 따라 온도, 변형률 및 응력을 계측하였다. 시간에 따른 변형률 및 응력 변화량 사이의 구성방정식과 계측된 자료를 이용하여 초기재령 콘크리트의 응력이완함수를 추정하였다. 추정한 응력이완함수를 컴플라이언스 함수로 변환하여 실제 초기재령 콘크리트의 점탄성 거동의 특성을 나타낼 수 있는 컴플라이언스 함수를 제안하였다. 제안한 컴플라이언스 함수와 기존의 모델들을 이용한 응력 해석 결과를 계측 결과와 비교함으로써 제안한 모델의 타당성을 검토하였다. 따라서 본 연구에서 추정한 응력이완함수 및 제안한 컴플라이언스함수는 초기재령 콘크리트의 시간에 따른 응력을 합리적으로 평가하는데 유용하게 활용될 수 있을 것으로 사료된다.

Keywords

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