Computational Model for the Evaluation of the Service Life Of Fiber-Reinforced Concrete Structures Under Long-Term Stati
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COMPUTATIONAL MODEL FOR THE EVALUATION OF THE SERVICE LIFE OF FIBER-REINFORCED CONCRETE STRUCTURES UNDER LONG-TERM STATIC LOADING О. E. Andreikiv,1,2 I. Ya. Dolinska,3 and O. К. Raiter3
UDC: 539.375
We propose a computational model for the evaluation of the service life of fiber-reinforced concrete structural elements subjected to long-term tension. The model is based on the first law of thermodynamics and a proposed idealized tensile stress-strain diagram of fibrous concrete. This model is used for the evaluation of the service life of a fiber-reinforced concrete plate containing a circular hole under the conditions of long-term bilateral tension. Keywords: service life, computational model, fiber-reinforced concrete structural elements, idealized tensile strain-strain diagram for fibrous concrete.
Introduction Numerous results of investigations of the long-term strength of fiber-reinforced-concrete structural elements under static loading have been accumulated for the last 20–40 yr [1, 2]. At the same time, the researchers undertake new attempts to construct the theory of retarded fracture of fibrous concretes under long-term static loading when the mechanism of creep begins to act and fibrous concrete is slowly damaged, which finally leads to the destruction of a structural element. The aim of the present work is to develop a theory of this kind on the basis of the existing physical regularities and, in particular, to propose a computational model for the evaluation of the period of growth of the volume defect in fibrous concrete up to the critical size under the corresponding conditions. This model is based on the first law of thermodynamics [3, 4] specifying both the energy balance and the balance of the rates of energy variations in structural elements made of fiber-reinforced concrete with volume defects and subjected to long-term static tensile loading. Formulation of the Model Consider a structural element made of fiber-reinforced concrete, containing an initial defect (or stress concentrator) of volume q0 , and subjected to the action of long-term static tension p applied far from the defect (Fig. 1). It is necessary to determine the time t = t* for which, as a result of creep, the volume q increases to the critical value q∗ and the fiber-reinforced concrete element is destroyed. Here, q is the volume of the material deformed in the second stage of tension under the stress σ > σ bc . 1 2 3
I. Franko Lviv National University, Lviv, Ukraine.
Corresponding author; e-mail: [email protected].
Karpenko Physicomechanical Institute, Ukrainian National Academy of Sciences, Lviv, Ukraine.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 3, pp. 7–14, May–June, 2020. Original article submitted May 22, 2019. 1068-820X/20/5603–0291
© 2020
Springer Science+Business Media, LLC
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O. К. RAITER
Fig. 1. Schematic diagram of loading of a body containing a defect. For the solution of this problem, we first construct a mathematical model, i.e., the
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