Initial crack effect on the strength of oblique cross sections of reinforced concrete beams strengthened with carbon fiber

Abstract

In the theory of reinforced concrete, the issue on strength of the oblique beam sections is more complicated than that on the standard sections, since it depends on many factors. The change of at least one of them leads to a significant change in the carrying capacity and in the structural damage pattern. This is due to the fact that at the operating level of the load, all conventional reinforced concrete structures work with cracks, which must be considered in the calculation. However, in the existing regulatory documents and public sources, this issue is not specified. This paper considers the effect of initial cracks on the strength of oblique cross sections of the reinforced concrete beams strengthened with carbon fiber. The experimental studies results obtained through the transverse force testing of forty-two prototypes made of heavy concrete of B30 design grade are presented. The test samples had initial oblique cracks of 0.6-0.9 mm width and were reinforced with three composite U stirrups from the fabric based on unidirectional carbon fibers in the shear span. Initial cracks in the beams were formed at three values of the shear span – 1.5h0, 2h0 and 2.5h0. The test data show the impact of initial cracks on the efficiency of composite reinforcement of oblique cross sections of the prototypes at various values of shear spans.

Nanomodification of Lightweight Fiber Reinforced Concrete with Micro Silica and Its Influence on the Constructive Quality Coefficient

“…To assess the effectiveness of the developed proposals, it is important to conduct a comparative analysis with the results previously obtained by other authors. As already noted in the Introduction section, various authors [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] considered the issues of nanomodification of heavy concrete with various additives. We, for the first time, carried out a study of the possibility of using a nano-modifying additive, namely micro silica for dispersed reinforced concretes, among other things, having a light weight.…”

“…Analysis of literature data [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] shows that dispersed mineral additives are widely used in the manufacture of cement building materials and products. Thus, both tasks of improving the properties of building materials and the disposal of industrial waste are being solved.…”

Optimization of Composition and Technological Factors for the Lightweight Fiber-Reinforced Concrete Production on a Combined Aggregate with an Increased Coefficient of Structural Quality

“…The main aim of the research presented in this article was to develop a dispersedreinforced lightweight concrete [24][25][26][27][28] that includes both heavy and light aggregate [29]. Thus, a part of the traditional heavy aggregate from dense rocks was replaced by an analogue of lightweight porous filler with equal volume but that was significantly lighter in weight.…”

“…Additionally, the aim of this work is to identify and develop proposals for a rational formulation and technology for new materials with an increased coefficient of constructive quality (CCQ). In the scientific and technical literature, CCQ means the ratio of the strength and density characteristics [24][25][26][27][28].…”

Stress-deformed state of proof areas of reinforced concrete beams

“…Дослідження з цієї тематики активно тривають, зокрема в статті [7] запропонована нова розрахункова модель для визначення міцності похилих перетинів вигнутих залізобетонних елементів і наведені розрахункові залежності для визначення складових сил, що діють у похилій ділянці. У роботі [8] аналізується вплив початкових тріщин на міцність похилих перетинів залізобетонних балок, посилених вуглецевим волокном. Поведінка похилих перетинів залізобетонних балок у процесі поперечного динамічного навантаження досліджується в [9], зокрема наголошується на перевагах використання податливих опор, поданих як вставні елементи з кільцевим поперечним перерізом.…”