Abstract
Due to the insufficient radial stiffness of the steel tube, the cracking of the weld and the plastic deformation of the string often occur under the cyclic loading of the hollow section pipe joint. In order to avoid such a failure, the overlapped K-joints were strengthened by pouring different concrete into the chords. Furthermore, to explore the detailed effect of filling different concrete in a chord on the hysteretic behavior of the overlapped K-joints, six full-scale specimens were fabricated by two forms, which included the circular chord and braces, the square chord and circular braces, and the low cyclic loading tests, which were carried out. The failure modes, hysteretic curves and skeleton curves of the joints were obtained, and the bearing capacity, ductility and energy dissipation of the joints were evaluated quantitatively. The results showed that plastic failure occurs on the surface of the chord of the joints without filling concrete, while the failure mode of the joints filled with concrete in the chords was the tensile failure of the chords at the weld of the brace toe, and the compressive braces had a certain buckling deformation; The strengthening measures of concrete filled with chord can effectively improve the mechanical properties of the K-joints, the delay of the plastic deformation of the chord, and improve the bearing capacity of the K-joints. Contrarily, the ductility coefficient and the energy dissipation ratio of K-joints decreased with the concrete filled in the chord. The hysteretic behavior of the K-joints with a circular chord and brace was slightly better than that of the K-joints with a square chord and circular brace, and the hysteretic behavior of the K-joints strengthened with fly ash concrete, which was better than that of the K-joints strengthened with ordinary concrete. The results of ANSYS (a large general finite element analysis software developed by ANSYS Company in the United States) analysis agreed well with the experimental results.
Highlights
Steel tube truss structure has become one of the most common building structures in large public buildings at home and abroad due to its large torsional stiffness, excellent seismic performance [1,2,3,4,5,6], easy installation and meets the requirements of modern buildings for the sense of view
Only concrete is grouted into the chords of CFST truss structures, while no concrete was added to the braces [13]
The results showed that the influence of hidden welds on the static strength of overlapped K-joints was not obvious, while it may have influenced the failure mode
Summary
Steel tube truss structure has become one of the most common building structures in large public buildings at home and abroad due to its large torsional stiffness, excellent seismic performance [1,2,3,4,5,6], easy installation and meets the requirements of modern buildings for the sense of view. Only concrete is grouted into the chords of CFST truss structures, while no concrete was added to the braces [13]. Compared with the unstrengthened steel tube truss structure or concrete counter parts, the mechanical properties of steel tubular members grouting concrete have been effectively improved, such as the stiffness, the bearing capacity, buckling resistance [14,15,16,17,18,19], and impact resistance [20,21,22]. Welded steel tubular joints are usually used to connect the brace and chord of the Circular Hollow Section (CHS) structures and CFST structures, which includes K-joints, KK-joints, KT-joints, T-joints, N-joints, Y-joints, X-joints and so on
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
