Experiments and Simulations of an Innovative Performance Enhancement Technique for Steel Building Beam-Column Connections Machel Morrison Doug Schweizer Tasnim Hassan (PI)
Post Northridge Research AISC 341 Performance Criteria θ d =0.04 Radians Bolted Extended Endplate Bolted Flange Plate Kaiser Bolted BracketReduced Beam SectionWUF-W Figures from Hamburger et. al 2009
Heat Treated Beam Section (HBS) M f ∝ M RBS M f ∝ M HBS
Heat Treated Beam Section (HBS) Figure from :
Induction Heating - Eddy currents “induced” by alternating magnetic field Advantages: Lower energy Input than traditional heating sources Easy to localize heat input Induction heating provided by Ameritherm Inc.
Induction Heating Challenges: - Difficult to control temperature uniformity - Prescribed slow cooling rate was not achieved
Experimental Program -4 Full Scale WUF-W -3 HBS and 1 Unconditioned -Sub assemblage similar to Engelhardt et al DB5
Experiment Results 0
HBS Experiment Results WUF-W HBS
Experiment Results WUF-W
Challenges -Significant yielding spread beyond HBS region and higher moments than expected
FE Simulations -Finite Strain, Large Displacement Formulation -Initial Geometric Imperfections (Flange thickness variation, out of straightness) - Quadratic Shell Elements ANSYS 12.1 Mechanical ADPL
FE Simulation- Constitutive Model -Non Linear Kinematic Hardening Model (Chaboche 1986) Chaboche Kinematic Hardening Rule Yield Surface Flow Rule
Validation of FE Simulation
WUF-W
FE Simulation Results
Expt Results- Flange Buckling HBSWUF-W
Validation of FE Simulation
FE Results- Flange Buckling
Shear tab w/Supplemental Weld No Shear tab/Supplement weld
FE Results- Flange Buckling
FE Results –Flange Buckling WUF-W Ricles et. al 2002
Summary -Heat treatment of beam flanges reduces strength of steel and initiates yielding in the heat treated regions - Future experiments are being planned with new heat treatment technique -Uniform heat pattern difficult to achieve with Induction heating, σ-ε response varied from furnace heat treatment -Heavy shear w/supplemental fillet weld to beam web influences local flange buckling
Acknowledgments -National Science Foundation (NSF) -Network for Earthquake Engineering Simulation (NEES) -MAST U of Minnesota -Lejune Steel Company -Ameritherm Inc.
New Heat treatment Technique
COMPARISON WUF-W, HBS & RBS WUF-W No Shear tab/Supplemental weld HBS No Shear tab/Supplemental weld RBS No Shear tab/Supplemental weld
COMPARISON WUF-W, HBS & RBS WUF-W From Hassan and Syed 2009
Moment Response