Behavior of RHS X-joints having high brace to chord width ratio under axial compression

Abstract

In this study, the behavior of Rectangular Hollow Section (RHS) X-joints having a brace to chord width ratio (BCWR) higher than 0.85, or the behavior as affected by the chord sidewall buckling was investigated experimentally and analytically. The experimental program tested a total of six full-scale RHS X-joints fabricated from both ordinary and high strength steel under axial compression. All high strength steel specimens with a measured yield stress as high as 700 MPa exceeded the Eurocode nominal strength with sufficient margin. Significantly different joint behavior was observed depending upon BCWR; the joints with high BCWR exceeding 0.85 was very brittle or they initially showed very stiff, almost elastic behavior and buckled with subsequent rapid strength degradation irrespective of steel grades. According to the test results, brittle behavior of RHS X-joints as affected by the chord sidewall buckling seemed probable at a BCWR less than 0.85. The sidewall buckling strength in Eurocode was again shown to be very conservative, more for high strength steel joints. A new strength formula for RHS X-joints prone to chord sidewall buckling was proposed. The effect of chord stress was also numerically investigated based on test-validated FE nonlinear analysis.