EXPERIMENTAL STUDY ON BENDING CAPACITY OF MULTIPLANAR RHS-TO-CHS TT-JOINTS IN SPACE TRUSSES

摘要

The space tubular trusses made of rectangular or square hollow section (RHS or SHS) braces and circular hollow section (CHS) chords are new application in civil engineering. There is no idea and design guideline for the bending capacity of the multiplanar tubular joint. The behavior of multiplanar welded TT-joins with two RHS braces and a CHS chord under bending moments on the braces in the plane and out of plane was investigated experimentally in the paper. The detained experimental setup is presented. Three test specimens with different geometric parameters were organized. Special self-balanced equipment was design in order to apply bending moment to the braces of the TTjoints. During the tests, a lot of strain gauges were installed at both the CHS chord and the RHS brace close to the circumference of the weld connecting the brace to the chord. The failure modes and ultimate bending capacity of these joints were observed and analyzed. It is concluded from the current experiments that the joints underwent CHS chord plastification, RHS brace local buckling and RHS weld failure under in-plane bending, whereas CHS chord plastification under outof-plane bending. The in-plane bending capacity of the joints was within a range of the elastic bending moment and plastic moment of the RHS brace, but the out-of-plane bending capacity of the joints was less than the elastic bending moment of the RHS brace. So the in-plane bending capacity was higher than the out-of plane bending capacity.