Non‐linear Analysis of Circular Composite Columns

Abstract

AbstractComposite columns provide many advantages for the application in multi‐story and high‐rise buildings. However, EN 1994‐1‐1 does not provide rules for the design of circular concrete sections with fully encased steel profiles according to the simplified methods. Normally, the simplified method for the design of composite columns is based on a normal force‐moment interaction diagram which assumes plastic cross‐section resistance. However, the moment resistance is to be reduced by a reduction factor αM, considering among other the difference between strain‐limited and plastic moment resistance. This reduction factor is developed and calibrated for composite compression members with concrete encased sections, partially encased sections and concrete filled rectangular and circular tubes. Comparison of plastic moment resistance to results based on strain limitation show that the application for circular section with encased steel section but without a steel tube may lead to unsafe results.The paper discusses different approaches for the determination of the N‐M Interaction curve and the design on cross‐section level. The results obtained from these methods are then compared to each other for different dimensions of cross‐sections of circular columns; and for different ratios of reinforcements, various steel grades and for normal and high strength concretes. Furthermore, the investigation focuses on the validation of the reduction factor αM and shows for which section types the values according to Eurocode 4 cannot be applied.