Mechanical Properties Of Steel Pipe Initial Stress Of Concrete Filled Steel Tube Bending Components

Concrete-filled steel tubular (CFST) columns have better structural performance than that of bare steel or reinforce concrete. The use of CFST structure has become widespread in the past few decades .In practice, firstly hollow steel tubes are fixed commonly , concrete in steel tubes is casted secondly. So, the actual state of concrete filled steel tube on load is always that there is pre-stress in steel tube .These members are susceptible to the effects of pre-stress in the steel tube due to construction load. The influence of pre-stress has became one of hotspot problems cared in engineering circles .In this paper:1. A mechanics model for the load-deformation relationship curves considered pre-stress in the steel tube of the CFST columns and beam-columns was established.2. An experimental study on 14 square CFST members with and without pre-stress in steel tube was carried out. A comparison of results calculated using this model shows good agreement with test results.3. Based on the theoretical model, effects of influence of slenderness ratio, the changing steel ratio, strength of the steel and the concrete, load eccentricity ratio as well as pre-stress coefficient on the bearing capacity of the members considering influence of pre-stress in steel tube was discussed.4. A kind of simplified model on the bearing capacity calculations of circular and square CFST beam-columns with pre-stress effects considered was suggested.