Construction of steel-reinforced concrete arches from high-strength concrete with ensuring of thermal crack resistance of the structure

Abstract

Listen

Translate article

Introduction. The design and technology of continuous concreting of two massive steel-reinforced concrete arches inclined to each other (height 19 m, span 47 and 81 m) with a volume of 184 and 283 m3 in a fixed formwork, the function of which was performed by a steel shell with a diameter of 2 and 2.5 m, with a design class of concrete B70 are presented. The aim of the complex of design and technological works was the calculation and design of arches, including the calculation of the thermally stressed state of massive structures in the initial period after concreting, and the determination of prescription and temperature-time parameters of concrete production technology and concrete quality control. Materials and methods. The rigidity of the structure is ensured due to the steel-reinforced concrete section of the arches, which, in comparison with the metal structure, has increased bending stiffness up to 5.5 times and axial stiffness – up to 3.5 times. The features of the technology for the construction and quality control of concrete arches were as follows: a self-compacting concrete mixture with additives of an organomineral modifier of the MB 2-30C brand, a superplasticizer and a hardening retarder was used; unhindered heat exchange of structures with the environment at the air temperature of 28–33 °C was ensured; the strength of concrete in the structure was monitored according to control samples made from samples of the mixture taken during concreting of structures. Results. The actual values of concrete strength and temperature parameters of arch structures fully correspond to the design requirements and values determined by the calculation of the thermally stressed state of structures, including: the compressive strength of concrete in structures at the design age is 108.1 and 111.3 MPa, corresponds to the actual classes of compressive strength Bf94 and Bf97 and exceeds the requirements of the project; the maximum temperature of concrete in the core of structures was 57–68 °C; the average cooling rate of structures did not exceed 5 °C/day; the temperature difference along the length of the structures was 0.6–0.8 °C/m; the temperature difference between the core and the surface of the steel shell, as well as the surface of the shell and the environment did not exceed 20 °C. Conclusions. The proposed approaches, taking into account the specifics of calculation, design, technology of construction and quality control of concrete, can be used in the construction of technically complex steelreinforced concrete structures in fixed formwork.