About the possibility of strain hardening of steel pipe-concrete shells elements

Abstract

Formulation of the problem. Every year the need to improve the state of the housing stock, increasing the number of people in need of housing. Modern construction is, as a rule, in an already built-up downtown area, where the land value is very large, and the small area for development, thereby increasing the number of storeys. Today in Ukraine the construction industry is going through hard times. This has less to do with the current financial crisis, but with the lack of technical modernization in all areas of construction. Even the beginning of the construction boom of the 2000-th was not able to provide a certain momentum to move the industry to a new level. In science and technology and development institutes is no proper renovation building materials, construction technology and existing buildings and design go back to the middle of the last century. Methods. The tests of mechanical properties of steel, namely tensile strength, the samples of steel grades: 10G2FB; 09G2; St3. Bursting test pieces cut from plates of thickness 18 mm steel mechanical properties, production Mariupol. Ilyich. These sheets obtain dual hot rolling of continuously cast slabs to the final 250 mm of thickness. Results. Comparative studies of stretching diagrams of three construction steels. It was found that the most stable tension diagram is 10G2FB steel. Using 10G2FB steels with work hardening within the plastic deformation of 4 % to reduce the cross-section of steel pipe-concrete structures by 39 % in comparison with non-deformed during concrete hardening in the pipes of the same steel, and 110 % as compared to St3. Scientific novelty lies in justifying the choice of the grade of steel pipes for use in pipe-concrete structures. The practical significance. Increased efficiency of pipe-concrete structures is largely explained by the fact that the concrete in the pipe-concrete structures increases its volume during solidification in the middle of the steel pipe. This feature offers the ability to pipe-concrete constructions of plastic deformation of the steel pipe-concrete shell structures with concrete, which is expanding. Such plastic deformation within no more than ten percent is already used in industry, namely in the factories that produce the elements of precast concrete. Fittings and reinforcing wire is often subjected to a small plastic deformation, which increases the yield strength of the reinforcing bars, achieves a significant saving of metal, by increasing the yield stress. Also, increasing the yield strength due to low strain achieved in the distribution of a pair of steel pipes of medium and large diameter. However, this effect is to strengthen the steel liner pipe-concrete constructions purposefully unused.