CALCULATION OF STRENGTH OF CONCRETE FILLED STEEL BOX COLUMNS

Abstract

The experimental - theoretical researches of concrete filled steel box columns (CFSBC) with pressed structure of concrete are executed. It is offered to make the CFSBC with preliminary pressed concrete core to improve their construction. The bearing capacity of centrally compressed samples of CFSBC has increased by 10 ÷ 15%. The received results are explained by the significant increase of the strength of concrete core in the preliminary compressed CFSBC samples due to the simultaneous display of three effects: long-term compression of concrete mix, preliminary lateral compression of concrete core and its work in the conditions of volume compression. The calculation of strength of CFSBC should be carried out on the basis of nonlinear deformation model of reinforced concrete. Three-axis tensely – deformed conditions are accepted for the analytical description of work of concrete core and external steel holder. Nonuniformity of stress state of concrete and bending of walls of external steel holder are taken into account. The basic dependences, which allow to carry out the approximate calculations of the strength of compressed CFSBC on limiting efforts, are also resulted.