19. Characterization of Cover-Plate Bolted Steel Joints with Full-Field Measurements

The combination of cover-plate bolted joints commonly used in steel structures allows the transfer of various internal loads such as bending, shear or axial forces. The mechanical behavior of these joints is complex because it depends on both the contact evolution due to load transfer between bolts and holes, and the elastoplastic response of the constitutive material of the plates. The interaction between the holes in the plates is also of great importance regarding the various configurations of joint and hole positions. The different failure modes such as net section fracture, gross section plastic yielding, shear out and bearing, are difficult to predict because they combine local compression under bolt and shear at loaded end distance of the plate. Many studies analyze the behavior of cover-plate joints by combining finite element approaches and/or experiments, but for obvious practical or economic reasons, only limited numbers of strain gages are employed to estimate the strain distribution in the components of the joints. Here the grid method is used to analyze in details the strain distribution on the plates with various configurations of bolts and holes positions. This approach enables us to observe the strain fields in the plate around the bolts during both the elastic and plastic phases of the material response. The obtained results help understanding the evolution of the failure zones regarding mainly the bearing mode. They can also be used as a reference to calibrate sophisticated finite element models.