"Вестник МГСУ"

For the purposes of experimental validation of application of external reinforcement of carbon fiber to reinforce reinforced concrete structures of hydraulic structures the experimental models of typical structures of hydraulic structures with inter-block construction joints were tested. At the same time, beam-type models of concrete of class B15 with a reinforcement percentage of 0.39 % and concrete of class B25 with a reinforcement percentage of 0.83 % were tested for the effect of bending moment. The models of fragments of reinforced concrete structures of hydraulic structures of concrete class B15 with a reinforcement percentage of 0.445 % and concrete B25 with a reinforcement percentage of 0.7 % were tested for сentral extension. Reinforced concrete beam-type models were reinforced with external reinforcement of carbon tapes of the type FibArm 530/300. Models of hydraulic structures fragments were reinforced by external reinforcement from carbon tapes of the type FibArm Tape 530/300 and from carbon composite lamellae of the type FibArm Lamel 12/50. The reinforced concrete beam-type models were reinforced with carbon strips (longitudinal bands on the lower stretched face and transverse belts in the span and supporting zones). The models of fragments of reinforced concrete structures of hydraulic structures were reinforced with carbon strips and carbon composite slats directed along the action of longitudinal tensile force. The results of experimental studies showed a significant increase in the strength of reinforced concrete structures of hydraulic structures due to their reinforcement by external reinforcement of carbon fiber, and also revealed a special character of the crack formation due to the presence of inter-block construction joints. Subject of the research: the subject of the study: reinforced concrete structures of hydraulic structures (with interblock construction joints), reinforced with external reinforcement of carbon fiber. Materials and methods: reinforced concrete models were made from ordinary heavy-weight concrete of classes B15 and B25 and reinforcement of A500C class. The outer reinforcement was made of carbon tapes of the type FibArm Tape 530/300 and FibArm Lamel12 / 50. Experimental studies were carried out on the basis of physical modeling of characteristic reinforced concrete structures of hydraulic structures with interblock building joints. In this model, the beam type of concrete class B15 with a percentage of reinforcement of 0.39 % and of concrete class B25 with a percentage of reinforcement 0.83 % were tested for the action of bending moment. Models of fragments of reinforced concrete structures of hydraulic structures from concrete class B15 with a reinforcement percentage of 0.445 % and of concrete B25 with a reinforcement percentage of 0.7 % were tested for the effect of central stretching. Experimental models were equipped with control and measuring equipment for determining the values of deflections, deformations of concrete and reinforcement elements of models, crack opening width and interblock joints. Results: in the course of experimental studies, a significant increase in the strength of reinforced concrete structures of the hydraulic structures (in 1.47-2.34 times) was obtained under the action of the bending moment and the central extension due to their reinforcement by external reinforcement from the carbon fiber. Conclusions: based on the obtained experimental data on the significant increase in the strength of reinforced concrete structures of hydraulic structures (by 1.47-2.34 times) due to reinforcement by carbon composite tapes and carbon composite lamella, the substantiation of the use of external reinforcement from carbon bands and lamellas under the action of a bending moment and central extension. Also, a special type of cracking was observed, due to the presence of interblock joints, the study of which allows controlling the implementation of technical solutions for reinforcing, repairing, reconstructing reinforced concrete structures of hydraulic structures.

Composite steel and concrete slabs are often used in the reconstruction of architectural monuments to replace timber elements. Insufficient awareness of the nature of the stress-strain state of
steel-concrete slabs limits their use in the construction of residential housing. This article describes the composition, geometry, reinforcement, and anchors to enable the use of concrete slabs and steel beams. The article contains photographs that illustrate the load distribution model. Methods of testing of fiber strains of concrete slabs and steel profiles, deflections of beams, shear stresses in the layers of the "steel-to-concrete" contact area that may involve slab cracking are analyzed. Dynamics of fiber deformations of concrete slabs, steel beams, and layers of the "steel-to-concrete" contact areas, deflection development patterns, initial cracking and crack development to destruction are analyzed. The author also describes the fracture behavior of the floor model. Results of experimental studies of the three-dimensional overlapping of structural elements are compared to the test data of individual composite beams. Peculiarities of the stress-strain state of composite steel and concrete slabs, graphs of strains and stresses developing in sections of middle and external steel-and-concrete beams, deflection graphs depending on the loading intensity are provided. The findings of the experimental studies of the three-dimensional performance of composite steel-and-concrete slabs are provided, as well.