Comparison of behavior between hollow and composite K-joints under sustained loading and corrosion

Abstract

Concrete filled steel tubular (CFST) truss structures are widely being used in bridges and transmission towers all over the world. Design of connections is one of the most critical issues in truss structures; and it becomes even more complicated when corrosion causes loss of outer steel tube section. However, behavior of composite joints is among the least understood topics in structural engineering today. Previous attempts (numerical and experimental) to study the behavior of composite joints have focused mainly on the effect of sustained loading. But the widespread use of CFST structures in harsh, marine environment necessitates observing the performance of composite joints under corrosion alongside long-term loading. The aim of this paper therefore is to study the combined effect of chloride corrosion and sustained loading on circular composite K-joints through finite element analysis (FEA). The results thus obtained have been presented and verified against experimental observations of previous researchers. For a side by side comparison with composite K-joints, FEA has also been established for circular hollow section (CHS) K-joints. In addition to these, failure modes and load-deformation characteristics of both the composite and hollow K-joints have been thoroughly investigated under various practical loading cases and different corrosion scenario. From numerical analyses, it has been observed that corrosion in infilled chord leads to only 4% loss of joint strength whereas, corrosion of equal intensity in hollow braces decreases the joint capacity by 35%. Finally, joint strength and ductility have been predicted based on the full-range numerical analyses. Concrete infills have been found to enhance the joint strength by 2.5-3.0 times.