Behavior of Q690 high-strength steel columns: Part 1: Experimental investigation

With the increasing application of high-strength steel over the past years, the urgent problem is to determine buckling curves in current codes for design of axial compression columns fabricated by high-strength steel. The current design curves cannot cover the high-strength steel columns due to that the available curves were based on research of mild carbon steels. To study the overall buckling behavior of high-strength steel columns, an experimental investigation on the ultimate bearing capacity of weld box and H columns with a nominal yield stress of 690 MPa subjected to axial compression was carried out. Twelve columns with slenderness ratios ranging from 30 to 70 were comprised in the experiment. The geometrical dimensions and initial geometrical imperfection involving initial deflection and loading eccentricity were measured. The buckling deformation and bearing capacity of the columns were studied on the basis of the test results. By comparing the experimental results with the buckling curves stipulated in GB50017-2003, Eurocode 3, and ANSI/AISC 360-10, it is found that the current design curves underestimate the ultimate strength of the axially loaded box and H columns welded by 690 MPa high-strength steel plates. The curves "a" in the corresponding codes such as GB50017-2003 and Eurocode 3 are found to be suitable for the welded 690 MPa high-strength steel box- and H-columns buckling about minor axis. The test results are intended to assess the accuracy of the numerical method presented in Part 2 of the paper.