Shear and Local Effects in All-FRP Bolted Built-Up Columns

The study analyzes the performances of built-up columns made of FRP (fiber reinforced polymer) profiles connected by steel bolts. The research aims specifically at verifying the influence of the shear deformability as well as the local effect after collapse at the bolted connections. The analyzed case regards a built-up column made of four pultruded FRP channel. The investigation involves two different types of built-up columns, the first one with smaller pultruded FRP channels and less intermediate bolted connection with respect to the second one, which is generally stiffer. The study proposes a numerical analysis and comparison to experimental results. The research highlights that shear effect generates a reduction of the Eulerian critical load that came from to 10% to 20%; this phenomenon is less for single channel in which case the Eulerian critical load prevails. The investigation shows also a good agreement between the non linear analysis and the experimental results because it well captures the interaction between global buckling and the local one that appears in a single channel of the built-up column between bolts.