Experimental data of strength, deformability, and crack resistance of 2,000×200×100 mm reinforced concrete and basalt-concrete beams are given. Longitudinal reinforcement consisted of 2 Ø14 A500C for reinforced concrete beams and 2 Ø14 BFRP (AKB800) for basalt-concrete beams. Transverse reinforcement consisted of 2 Ø3, 4, 5 ВрI for reinforced concrete beams and 2 Ø4, 6, 8 BFRP (АКБ800) for basalt-concrete beams. Beams were made of heavy concrete of C16/20, C30/35, and C40/50 classes. The experimental beam specimens were tested according to a four-point scheme as loosely supported beams loaded with two concentrated forces. Loading in the series of tests was stepwise increasing, static and low-cycle repeated at high levels of 0.50, 0.65, and 0.80F ult. Distance from supports to concentrated forces (shear span), a/h 0 , varied within 1, 2, 3. Experimental beam specimens were made and tested according to the theory of experimental design according to the Box B4, optimal plan D. Comparative analysis of main performance parameters of reinforced concrete and basalt-concrete beams under the action of abovementioned loads was performed. The necessity of these studies was determined by the unsatisfactory convergence of experimental and calculated values of bearing capacity of oblique sections of basalt-concrete beams determined according to existing standard methods. The studies have established the influence of design factors and loading nature on basic parameters of the working capacity of basalt-concrete beam elements in a form of experimental-statistical dependences. These results will form a basis for a physical model of resistance of oblique sections in such structures to external loads. The presented results will significantly supplement the existing database of the operation of beam basalt-concrete structures and will be used in the development of an analytical method for calculating strength, deformability, and crack resistance
In order to study the cracking of prestressed reinforced concrete T-shaped beam structures, the authors planned and carried out a full-scale experiment with five variable factors. The following factors were chosen as variable factors: the relative span of the shear, the ratio of the table overhang width to the thickness of the beam rib, the ratio of the table overhang thickness to the working height of the beam section, the coefficient of transverse reinforcement, the level of prestressing in the working reinforcement. The article describes the cracking process and the destruction of test beams. It was found that the loading level of an opening of inclined cracks is 53% larger than the loading level of a normal crack opening. Mathematical models of bending moments and transverse forces of cracking were built using the “COMPEX” software. Also, the mathematical models of the crack opening width and the projection length of a dangerous inclined crack were obtained. These models are based on the experimental data. Analysing the obtained models, the complex influence of variable factors on the main parameters of crack formation and crack resistance was established. In particular, it was found that the prestress level in the working reinforcement has the greatest effect on the bending moment of cracking. In this case, the value of the shear force of cracking significantly depends on both the prestressing level in the reinforcement and the relative span of the shear. On the basis of the experimental data, the empirical expression is obtained for determining the projection of a dangerous inclined crack for prestressed reinforced concrete T-shaped beams. The resulting equation can be used to calculate a shear reinforcement.
Abstract. Non-metal composite reinforcement is increasingly being used in modern construction. Composite reinforcement is a great step forward over steel, due to its higher strength and corrosion resistance. An analysis of the use of these fittings was performed, which showed that the United States, Japan and China are leading countries in the use of composite fittings. The more active pace of implementation of composite reinforcement is limited by the fact that composite reinforcement does not have a common method for calculating their bearing capacity. That is why the article discusses regulatory documents on the calculation and design of structures reinforced with composite reinforcement from around the world. The article provides a comparative analysis of the calculations of the bearing capacity of prototypes – beams, reinforced with basalt-plastic reinforcement, according to the available design standards of foreign countries, which were among the first to use non-metallic composite reinforcement for reinforcing span concrete structures. The methods of calculating the bearing capacity of beam elements for concrete and non-metallic composite reinforcement according to regulatory documents are examined in detail. A comparative analysis of the actual bearing capacity of inclined sections of basalt concrete beams and its calculated values calculated according to the recommendations of the existing design standards of foreign countries is carried out. The analysis showed that the actual bearing capacity of the inclined sections of basalt concrete beams and its calculated value showed their unsatisfactory convergence. A common feature of all considered foreign design standards is the underestimation, up to several times, of the bearing capacity of inclined sections of prototypes ‒ beams reinforced with both steel and basalt-plastic reinforcement. It has been established that the methods for calculating the bearing capacity of supporting sections of spans of reinforced concrete and basalt concrete structures, presented in national design standards, are based not on the new general method, but on partially improved methods that were used in previously existing standards.
This work presents a proposed engineering method for calculating the bearing capacity of the supporting sections of continuous monolithic reinforced concrete tape beams, which combine pressed or driven reinforced concrete piles into a single foundation design. According to the mechanics of reinforced concrete, it is recommended to consider the grillage to be a continuous reinforced concrete beam, which, as a rule, collapses according to the punching scheme above the middle support (pile caps), with the possible formation of a plastic hinge above it. The justification for the proposed method included the results of experimental studies, comparisons of the experimental tensile shear force with the results of calculations according to the design standards of developed countries, and modeling of the stress-strain state of the continuous beam grillage in the extreme span and above the middle support-pile adverse transverse load in the form of concentrated forces. The work is important, as it reveals the physical essence of the phenomenon and significantly clarifies the physical model of the operation of inclined sections over the middle support. The authors assessed the influence of design factors in continuous research elements, and on the basis of this, the work of the investigated elements under a transverse load was simulated in the Lira-Sapr PC to clarify the stress-strain state and confirm the scheme of their destruction adopted in the physical model by the finite element method in nonlinear formulation. Based on the analysis and comparison of the experimental and simulation results, a design model was proposed for bearing capacity near the supporting sections of continuous reinforced concrete beams and high grillages that is capable of adequately determining their strength.
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