Connection capacity of pultruded GFRP channels in multidirectional loading

Fiber Reinforced Polymer (FRP) composites is a relatively new material that offers unique advantages for many different engineering applications. While there has been plenty of research performed to understand composite fiber failure mechanisms numerically and experimentally, the exact nature of failure based on fiber orientation is unknown. Due to the complex nature of FRP composites, fiber failure mechanisms are not clearly understood and the goal of this study is to gain further knowledge regarding FRP failure, particularly with bolted connections.;The primary objective of this research is to investigate the behavior of bolted Glass Fiber Reinforced Polymer (GFRP) structural channel members subject to cyclic loading. The investigation consisted of testing various channel specimens with different flange geometric configurations. Monotonic loading is performed to determine ultimate strength of the connection in the axial and transverse directions for the first phase. The second phase comprises of how unidirectional cyclic loading effects stiffness and the overall ultimate strength of the connection in the axial and transverse direction. The last phase studies the behavior and the residual connection capacity of the GFRP specimens subject to multidirectional cyclic loading. Various load levels for cyclic loading were established as a fraction of the ultimate strengths obtained from testing.;The testing showed that the absence of the flange did not have a significant impact with respect to the ultimate strengths in the axial and transverse directions. Failure modes observed consisted of initial bearing failure followed by shear-out failure for axial specimens and net tension splitting for the transverse specimens. The GFRP channel specimens undergo a period of nonlinear progressive damage after initial failure. Furthermore, it was found that the residual behavior and strength was affected by unidirectional and multidirectional load cycles.;A probability-based design was adopted to provide design recommendations and guidelines. Resistance factors are determined using the Monte-Carlo simulation for the Load and Resistance Factor Design (LRFD) design method.