EXPERIMENTAL INVESTIGATION OF WHITMORE SECTION AND BLOCK SHEAR FAILURES IN STEEL GUSSET PLATES USING DIGITAL IMAGE CORRELATION

Gusset plates are necessary for transferring loads from one structural member to another. During load transfer gussets can undergo shear, net section rupture and gross section yielding. Gusset design is a complex process and there is still a lack of knowledge regarding the stress and strain distribution in gusset plates. Current design practices which use Whitmore method, may not be sufficient to accurately predict the capacity of a gusset plate. An experimental study was conducted at The University of Texas at Tyler to understand the failure mechanism of gusset plates under uniaxial tensile loading. Variables considered for the experiment are pitch distance, number of bolts used and dimensions of the gusset plate. A 3/16 inch thick gusset plate was used for each test in the experiment. A WT3*8 section was used as the tension member for the experimental analysis. Limit state checks of gross section yielding, net section fracture, block shear rupture and bearing strength at holes were performed to calculate the design strength of the connection using the Load and Resistance Factor Design (LRFD) method. Digital Image Correlation (DIC) was used for analyzing major strains in the gusset plate around the bolted connection of the WT and gusset plate. All of the plates failed in block shear at loads significantly higher than those predicted by Whitmore effective width fracture mode. Furthermore, the variability of the error in prediction was significantly lower for predictions using block shear (coefficient of variance 0.05) versus those using Whitmore fracture (coefficient of variance 0.192). DIC results clearly showed evidence of strains associated with block shear including measurement of necking and clear evidence that Whitmore fracture did not occur- relatively high strains in the areas associated with a Whitmore fracture were not seen. The study ultimately shows that Whitmore fracture was not a realistic failure mode for these uniaxially loaded gusset plates