DESIGN AND METHODOLOGY OF RESOURCE-SAVING CONTINUOUS STEEL-CONCRETE SAMPLES SLABS EXPERIMENTAL TESTS FOR THE CONSTRUCTION OF CIVIL DEFENSE STRUCTURES

Abstract

The problem of ensuring a uniform distribution of stresses in continuous steel-reinforced concrete slabs is relevant for modern construction. The use of self-stressing technologies can reduce the uneven distribution, but the issue of effective self-stressing in experimental samples of such slabs has not yet been sufficiently investigated. The paper presents design solutions and methods for the manufacture of experimentally tested samples of resource-saving non-cut three-span steel-reinforced concrete slabs that can be used for the construction of floors of civil defense structures. A two-stage technology for the manufacture of continuous steel-reinforced concrete slabs has been developed. It is proposed to create preliminary bends of the more deformed extreme spans by the slabs' own weight. The middle span should be concreted at the first stage, and the outer spans at the second. The paper describes the design features of manufacturing two samples of continuous three-span slabs 6 m long, made on fixed formwork from profiled flooring. The specimens differed in the lengths of the concreting grips, which made it possible to study the development of deflections in the extreme and middle spans due to changes in the stiffness of the section at the supports. The length of the concreting section is determined by the points of zero bending moments. During the first stage of concreting, the middle span of the steel structure bends downward due to the concrete mix's own weight, which causes the extreme sections that are not under load to bend upward. After the concrete of the first stage reaches the design strength, the concrete of the outer spans is concreted. At the same time, the extreme spans bend downward due to the weight of the concrete mixture, forcing the middle span, which already has a steel-reinforced concrete section, to bend upward. The paper presents the results of determining the physical and mechanical properties of the slab materials: concrete, steel rods of longitudinal reinforcement, and steel sheets of corrugated board of external reinforcement.