Process of cracking in reinforced concrete beams (simulation and experiment)

Abstract

The paper presents the results of experimental and theoretical investigations of the mechanisms of crack formation in reinforced concrete beams subjected to quasi-static bending. The boundary-value problem has been formulated in the framework of brittle fracture mechanics and solved using the finite-element method. Numerical simulation of the vibrations of an uncracked beam and a beam with cracks of different size serves to determine the pattern of changes in the spectrum of eigenfrequencies observed during crack evolution. A series of sequential quasi-static 4-point bend tests leading to the formation of cracks in a reinforced concrete beam were performed. At each loading step, the beam was subjected to an impulse load to induce vibrations. Two stages of cracking were detected. During the first stage the nonconservative process of deformation begins to develope, but has not visible signs. The second stage is an active cracking, which is marked by a sharp change in eingenfrequencies. The boundary of a transition from one stage to another is well registered. The vibration behavior was examined for the ordinary concrete beams and the beams strengthened with a carbon-fiber polymer. The obtained results show that the vibrodiagnostic approach is an effective tool for monitoring crack formation and assessing the quality of measures aimed at strengthening concrete structures.

Calculation of the crack resistance of reinforced concrete elements with allowance for the levels of normal crack formation

“…It should be noted that the vast majority of calculation methods based on the results of the above studies were developed for the stage of stabilized cracking of reinforced concrete elements. As for the methods of calculating the crack resistance of elements, taking into account the multilevel formation of cracks, then, despite the accumulation of experimental research results of [2][3][4][5][6][7][8][9], they are very limited and practically are only beginning to form. By their orientation, these techniques can be classified as based on: • models of a "two-console" element in a section with a crack [4];…”

“…• solutions strictly within the framework of brittle fracture mechanics [9]; • models of stretched concrete resistance to reinforcement displacement in sections between adjacent cracks [7,10,11].…”

“…Solutions proposed strictly within the fracture mechanics framework [9] are so complex, that today they can be implemented only software, in particular, using the finite element method. At the same time, the physical essence of the actual deformation process of reinforced concrete elements is often lost or lowed.…”

Calculation of the Crack Resistance of Reinforced Concrete Elements With Allowance for the Levels of Normal Cracks Formation

“…При цьому варто вказати, що переважна більшість методів розрахунку за результатами згаданих досліджень розроблювалася для стадії стабілізованого тріщиноутворення залізобетонних елементів. Що ж до наявних методик розрахунку тріщиностійкості елементів з урахуванням багаторівневого утворення тріщин, то, не дивлячись на певне накопичення результатів експериментальних досліджень [2][3][4][5][6][7][8], вони є дуже обмеженими та знаходяться лише на стадії формування. За своєю спрямованістю ці методики можна класифікувати як такі, що ґрунтуються:…”

Dynamic Deformation Interaction of Elements of the “Drummer–gasket–reinforced Concrete Beam” System

“…Механика 4 (2018) 119-126 121 Результаты, представленные в данной статье, относятся к ударно-волновой вибродиагностике железобетонных конструкций. Речь идет о вибрационной диагностике в «щадящем режиме», который предполагает, что воздействие на конструкцию в процессе диагностики не вызывает неупругого деформирования в элементах инспектируемой конструкции [31][32][33].…”