Simple Modifications to a Direct Shear Device to Perform Constant Normal Stiffness (CNS) Tests

This paper describes a simple approach to modify a direct shear test device to perform interface shear tests under constant normal stiffness (CNS) conditions. There is continued interest in the use of piles and pile anchors for both fixed and floating offshore wind structures, particularly in the sandy soils along the East Coast of the United States. Design analyses and modeling may require CNS testing, which closely represents the boundary conditions near the interface of the pile during axial monotonic and cyclic loading. The simple and economical modifications allow for the testing of any pile material-sand interface by mechanically maintaining constant normal stiffness conditions on the sample during shear.