LAUSR

Abstract The objective of the present work is improving compressed concrete filled steel tube elements of square section by means of helical reinforcement of a concrete core. Conducted experimental studies of centrically and eccentrically compressed laboratory samples of such elements have shown that in comparison with similar samples without helical reinforcement their durability ha increased by 31÷42%. Values of longitudinal sample deformation fixed at maximum with helical reinforcement made of C25 concrete class have increased almost 3 times. Maximum longitudinal sample deformation made of C50 concrete class were inferior by 20%. Increase in durability and deformability of improved samples is explained by increase in performance of placing of shear reinforcement that is ensured by helical reinforcement. Confining element ration at central compression was equal to 1.36÷1.9, at eccentrical compression with eccentricity ratio of 0.107 it was 1.28÷1.35, and at eccentricity ratio of 0.214 -1.15÷1.26. High durability and deformability ensure greater tenacity of such structure that makes them attractive for usage in buildings and constructions in areas with increased seismic activity. The revealed features of strength resistance of concrete filled steel tube elements with square section will be used when developing an algorithm and a computer program for the automated calculation of their bearing capacity.