Reliability analysis of concrete filled steel tube for quadrilateral and circular cross sections

Concrete filled steel tube beams is a structural composition that brings the advantages of the combination of the surrounding steel with the core concrete, this structural member had been investigated under different conditions but still, there is a significant difference among the well-known design codes provisions and limitations. Assessing the limit states of the codes can be conducted based on structural reliability analysis. Bending capacity of the beams can be characterized by the reliability index in terms that can be readily understood by structural engineers with only a basic knowledge of probability theory. In this study, First-order Reliability Method was used in assessing the selected tested specimens. More than 2000 concrete filled steel tube members of different shapes cross-section had been collected from recently introduced literature (from 2000 up to 2018); moreover, the selected specimens were compared with the provisions of many codes. The judgment was based on the convergences between the calculated beams load capacity in term of bending strength according to mentioned codes and the recorded load capacity that obtained from the experimental work. Different parameters were evaluated from the selected beams, while the geometry of the beams were the main parameters, the tube thickness is ranging between, the width of the members. The material properties are also altered in order to evaluate its effect on the beam strength, where the concrete compressive strength was ranging between 10 to 154 MPa, and the steel yield strength was less than 762 MPa. The results show that both codes (EC4-2004 and AISC360-10) have percentages of error within the unsafe zone, and EC4 is less conservative than the AISC.