Q690 high strength steel T-stub tensile behavior: Experimental and numerical analysis

To evaluate the tension behavior of welded high strength steel (HSS) T-stub joint accurately, an experimental study on the mechanical properties of welded T-stub joints with nominal yield strength of 690 MPa under tensile load was conducted. This experimental program includes twelve welded T-stub joints varying with bolt diameter, bolt strength grade, and flange size. Plastic bearing capacity and initial stiffness were obtained from the test and compared with the EC3 Part 1-8 predicted ones. A simplified finite element model considering the nonlinearity of material, geometry and contact was developed and verified in order to perform an extensively parametric study. The effects of flange thickness, bolt pretension and stiffener on the mechanical properties of joints were investigated and discussed. The test results show that the methods proposed in EC3 Part 1-8 for plastic bearing capacity calculation and identifying the failure mode can be applicable to HSS T-stub joints, but the methods evaluated with initial stiffness overestimate the initial stiffness of the joint. The parameter analysis results show that when the flange boundary condition close to simply supported or fixedly supported, the effect of which on the initial stiffness of the joint should be taken into account. The initial stiffness of joint increases linearly as the bolt pretension increases. However, when the pretension exceeds the standard value, an increase in pretension exerts a weak influence on the initial stiffness. When the length-height ratio of stiffener is lower than 1.0, the post-limit stiffness degenerates remarkably, and thus the ductility gets worse.