Article analyzes the state of technical regulation of construction in Russia. It is noted that a number of problems have not been solved in this area to date. One of them is the contradiction of obligatory and voluntary application of regulations in design and production practice. The list of mandatory application regulations approved on July 4, 2020 by The Government’s Resolution No. 985, as well as the previous one, contains conceptual errors when the regulatory document is divided into parts for voluntary and binding application. Article 6, paragraph 7, documents applied on a voluntary basis also ensure compliance with the mandatory requirements of the Regulation, is also in line with the technical regulations on building and construction safety. There are uncertainties with mandatory compliance as the Building and Construction Safety Regulations contain provisions on the possibility of compliance with mandatory requirements on an alternative basis.

Corrosion of reinforcement of marine and coastal hydrotechnical structures due to chloride aggression and carbonation of concrete leads to a sharp decrease in the safety of the structure. The reinforcement is subjected to a depassivation process as soon as the chloride content on its surface exceeds the threshold concentration, or the pH value in the protective layer of concrete decreases to the threshold value as a result of carbonation. When oxygen penetrates to the surface of the reinforcement, electrochemical reactions are realized with the formation of corrosion products. This leads to cracking the protective layer of concrete, reducing the cross-sectional area of the reinforcement. The paper proposes a method for predicting the complex degradation of reinforced concrete structures of coastal structures, taking into account various mechanisms of corrosion wear, which makes it possible to develop effective ways to increase the durability and maintainability of structures operated in the marine environment.

The general characteristics of the structural system of a fully assembled frame made of “H”elements are described. The “H” element is a frame of two racks, each one floor high, connected monolithically with a crossbar. Structural cells with a longitudinal, transverse or cross arrangement of bearing frames are assembled from these elements. The joints of the racks with crossbars are rigid and are located in the middle of the floor height. The overall spatial stability of the frame is provided by the arrangement of frame elements, as well as the use of various kinds of connections. Floor slabs are prefabricated. The joints of the frame racks are prefabricated-monolithic with the use of combined couplings. Connections of “H” elements on screeds with the use of strands made of smooth reinforcement or screw reinforcement rolled products.

Nano-fiber concrete is a building material for which a distinctive feature is an increase in the crack resistance characteristic. Determination of the stress intensity coefficient of nano-fiber concrete makes it possible to correctly assess the resistance of the material during the formation and development of cracks. The paper presents a multi-parametric method for evaluating the quality indicators of nano-fiber concrete. The proposed method makes it possible to evaluate the quality of the nano-fiber concrete structure in the laboratory and during construction work. Modern and well-known methods of non-destructive testing, such as ultrasonic sounding, ultrasound tomography, elastic rebound, separation with chipping, are used to carry out control at the construction site. For laboratory studies, the method provides for the production of samples-prisms. Test samples can be molded or cut out of the body of the structure. This technique makes it possible to study in laboratory conditions such parameters of the material as the tensile strength during bending, tensile strength at splitting, the critical coefficient of stress intensity at normal pull-off, the critical coefficient of stress intensity during transverse shear, energy consumption for individual stages of deformation and destruction of the sample. Moreover, it is provided to obtain all the parameters on one sample from the series, which eliminates errors and inaccuracies in the quality indicators of the material associated with different conditions of hardening, molding, inaccuracies in the duplication of the composition.

The main regularities of the formation of the optimum grain structure of construction composite materials on a cement basis with mineral fillers are considered and generalized. A complex method of 3D computer reconstruction of the grain structure and calculation of optimal compositions of raw materials mixtures is proposed, which makes it possible to vary a wide range of parameters and evaluate the derived properties of dispersed systems, as well as select optimal granulometric compositions of mixtures. Experimental data of studies on achieving the optimal structure of a building composite material are presented.

The article presents the research work aimed at developing a methodology for calculating strength of reinforced concrete slab-columns joints made of different strength grade of concrete in monolithic frame of high-rise buildings. The results of Russian and foreign regulatory documents analysis and technical literature on this issue are briefly presented. On the basis of review and generalization of laboratory tests of slab-columns joints the factors influencing their compressive strength were formulated. Numerical analysis of “slab-column” type units’ behavior was carried out with preliminary verification calculations, which showed good accuracy with experimental data on fracture pattern and ultimate breaking loads. Based on results of calculations of finite element models of middle, extreme and corner slab-columns joints, which had a variation of ratios of column dimensions and slab thicknesses, strength grade of concrete, stress acting on the slab and its maximum value, the formulas for compressive strength analysis were derived.