Ultra high-performance or ultra high-strength concrete is a new class of cement-based materials with increased strength and durability. The widespread use of this concrete in construction practice requires theoretical and experimental studies of the stress-strain state of structures made from them. The article presents and analyzes the shear strength of I-shaped beams made of ultra-high-performance concrete tested by the authors. In the experiments, we varied the fiber content, the shear span, the shear reinforcement ratio, and the width of the compressed flange.

Keywords: shear strength, shear force, ultra high-performance steel fiber-reinforced concrete, I-shaped beams

The article presents the results of comparative analysis of the equations of Russian and foreign design codes for calculating the web strength capacity of I-beams with steel and fiber reinforced polymer (FRP) transverse reinforcement. It is known that the strength of the web is affected by the properties of the transverse FRP, in particular, its relatively low modulus of elasticity. When calculating the strength of the webl, both homeland and foreign design codes do not distinguish between structures with FRP and steel transverse reinforcement. To assess the accuracy of the equations of the codes, the calculation was performed on a sample made up of the results of our tests and the experiments of other authors. When calculating according to the method of SP 295 and Eurocode 2, overestimated values of the resistance of the web with FRP were obtained. The formulas for the strength of the webs, which give a significant margin when calculating beams with steel transverse reinforcement, also overestimate the resistance of beams for specimens with composite transverse reinforcement

Keywords: wall strength, I-beams, transverse reinforcement, design standards, basalt-composite reinforcement, steel reinforcement

The article presents the results of experimental studies of crack resistance of inclined cross sections of I-shaped beams using basalt fibre reinforced bars as a transverse reinforcement . The data of previously conducted experiments were studied and the test of own samples was carried out. The beams had the same geometric characteristics and differed from each other in the angle of inclination of the transverse reinforcement, the percentage of transverse reinforcement and the shear span to depth ratio. The influence of variable parameters on the load of formation of inclined cracks and the width of their opening is analyzed. In most cases, the width of the opening of inclined cracks does not exceed the permissible values established by the codes of different countries. The exceptions were mainly samples with the lowest percentage of transverse reinforcement.

Keywords: crack resistance, I-shaped beams, transverse reinforcement, inclined cross sections, shear span, basalt fibre reinforced bars, inclined cracks

Paper considers maximum annual values of mean wind velocity in all plain, piedmont and seaside regions of Krasnodar Krai for more than 60-year period of monitoring. Substantial areal differencies of trends of wind velocities change are revealed in north-east, seaside and central zones. Simultaneous analysis of time series of vane and anemometric measurements of mean wind velocities over 1965-2012 allowed to reveal a period of significant increase of wind velocities up to 1977 and detect a gradual decrease of velocities in 1979-2012. Significant areal differencies in wind velocity trends in north-east, seaside and central zones of region are shown. It is shown that time series of wind velocities used for SNKK 20-303-2002 allowed to develop a reliable base for wind loads which provides up to date an annual certainty level 0.98 adopted in the current version of building code SP 20.13330.2016 "Loads and actions".

Keywords: wind loads, actions, local building code, inversion criterion, trend significance, time series

Paper presents a review of scientific works investigating of effect of carbon nanotubes (CNT) concentration on electrical conductivity and pizeresistive properties of concrete. Different values of the percolation threshold for nanomodified concrete obtained by different authors are given. Recommendations for specifying the favorable concentration of nanotubes in composites are considered. As a result of review a need for additional dedicated research for the assessment of relation between favorable CNT concentration and their characteristics, method for the producing of composite and conditions of its application is stated.

Keywords: concrete, sensor, carbon nanotubes, percolation threshold, electrical conductivity, monitoring of stress-strain state

Paper considers maximum annual values of mean wind velocity in all plain and piedmont regions of Krasnodar Krai, which served as the basis for design values of wind loads on buildings in local code SNKK “Loads and Actions. Snow Loads and Wind Actions”. Time series of anemometric measurements of wind velocities are analyzed from the beginning of 1970s to 2012 extended by 13 years as compared to the time series used for developing this code. For detecting the significance of the linear trend of wind velocity maximums inversion criterion was employed. Calculations were performed for the data of anemometric wind velocity measurements on 29 meteorological stations uniformly distributed over a territory of the region. They showed that significant trend of increase of wind velocity with the high level of statistical certainty 0,95 is present only in two cases. In half of the rest cases trend is descending, in another half trend is statistically insignificant as well as mostly descending. Average decrease of wind velocity is 30%.

Keywords: wind loads, actions, local building code, inversion criterion, trend significance, time series

Paper presents results of full-scale test to failure of reinforced concrete room-sized module type "cap" by static loading. Loading process, used testing facilities, loading and measuring equipment are described. Obtained data considering module's strength, stiffness and cracking resistance are given.

Keywords: room unit, static loading test, data acquisition system, strain transducer