Modified stiffness model for thick flange in built-up T-stub connections

The results of the finite element simulations are used to develop a modified stiffness model to predict the behavior of thick-flange in built-up T-stub connections with Complete Joint Penetration (CJP) and fillet welds. Using ABAQUS, three-dimensional finite element (FE) models are developed for the selected cases. The performance of the FE model results is compared to experimental results for validation. The FE model results are used to develop the modified stiffness model that characterizes the behavior of thick-flange in built-up T-stub connections. The model is based on a combination of finite element and a stiffness modeling approach that incorporates the overall flange deformations of key component elements, and it includes nonlinear material behavior of both tension bolts and base material, accounts for pretension of fasteners, and contact interactions. The modified stiffness model consists of linear and nonlinear springs which model deformations from tension bolt elongation, T-stub flange, and prying force. The model predicts the force-deformation curve of the whole T-stub flange taking into account flange-partial-yielding and accounting for the contact force encountered. A new failure limit state is highlighted, which is partial-yielding at the K-zone followed by bolt fracture, with or without prying. The behavioral characteristics of the flange in T-stub connections are examined including strength, stiffness, and deformation capacity. Comparisons of model predictions with FE and experimental data show that the modified stiffness model accurately predicts the response of thick-flange built-up T-stub connections with CJP or fillet welds and accounts for flange-partial-yielding followed by tension-bolt-fracture, with and without prying.

► The model is based on an incremental approach and predicts the force–deformation.
► The model takes into account bolt pretensioning, partial yielding and contact.
► The proposed model predicts partial-yielding of the flange followed by bolt fracture.
► A new failure limit state is highlighted.
► The model presents a simple tool in predicting the behavior.