Tension field action for cold-formed sections in shear

For shear, the design of sections for strength is usually governed by the web plate subjected to shear force and undergoing shear buckling, or yielding in shear or a combination of the two. For webs with relatively high depth-to-thickness ratios, the shear stress distribution in the web after buckling changes and significant post-buckling strength may occur as a result of the development of a diagonal tension which is called “Tension Field Action” (TFA). Recently, the full set of shear test results for the plain lipped C- and SupaCee® sections performed at the University of Sydney shows that the post-buckling strength was attributed to TFA which was provided by the increased transverse restraints created by bolted connections attached to loading stiffeners over the full depth of the web panel at the supports and loading point. This improved the post-buckling strengths of the web in shear. Firstly, the results of finite element nonlinear simulations are compared with tests where bolted connections not over the full depth of the web panel were used to validate the FE method. Then the range of test data described previously is extended using finite element models, by reducing the bolting at support and loading points in the test data to provide further guidance on the availability of TFA in particular. Design equations are provided for Tension Field Action.

► Shear tests of cold-formed channel sections develop Tension Field Action (TFA). ► A Finite Element Model (FEM) is used to simulate nonlinear behaviour including TFA. ► The FEM is validated against tests where bolting connections develop TFA. ► Removing bolts at the connections using the FEM shows a large effect on the TFA. ► A design equation is calibrated for reduced bolting using a reduction factor.