THE FRACTURE TOUGHNESS OF THIN-WALLED COVER SHELLS HYPERBOLIC PARABOLOID SHAPED OF FERROCEMENT AND STEEL FIBER CONCRETE UNDER THE ACTION OF OPERATING LOADS

Abstract

Experimental research of new materials and structures with improved parameters of strength, fracture toughness, bearing capacity and their lifetime in comparison with typical elements is an actual problem of building science.

Nowadays there is a trend to design and use for buildings covering the new design solutions as the thin shells. One of the types of thin shells are Gaussian shells with negative curvature. It’s worth to note that in the last decade, a considerable number of researches of thin-walled structures made of steel fiber reinforced concrete were conducted, which confirmed the efficiency of its use to enhance their hardness, fracture toughness and thus longer life.

The article presents the results of the authors’ experimental studies of fracture toughness of thin-walled cover structures with Gaussian negative curvature in the shape of hyperbolic paraboloid made of ferrocement and steel fiber reinforced concrete under the action of the operating load.

The load application was carried out for ten steps, after each step the pause was for 15...20 min, during which the data of the strain-gauge station VNP-8 was recorded, using a microscope were measured and recorded the width of the cracks, deflections of the structure were measured etc.

The external force was evenly-distributed to its applications and the impact was simulated according to the real conditions of construction use.

The experimental part of the research was conducted at the laboratory of building materials and structures of Lutsk National Technical University. In scientific work carried out mapping and comparison of the obtained experimental results, carried out processing and analysis, presents the conclusions.

During the researches it was found that the fracture toughness of thin-walled shell cover with Gaussian negative curvature in the shape of a hyperbolic paraboloid with dispersed reinforcement (steel fiber reinforced concrete) is higher than in the shell made of ferrocement. Accordingly, it can be argued about the increasing of the lifetime of steel fiber reinforced concrete shell covering in comparison with the ferrocement shell.