Assessment of Resistance Factors for LRFD of Steel Bolted Connections in Pultruded FRP Frames

Resistance factors (ϕ-factors) are reliability-based factors of safety used in load and resistance factor design (LRFD) of structural systems. The ϕ-factors specified in the consensus standard for the structural design of pultruded fiber-reinforced polymer (FRP) structural members and connections are generally lower than the ϕ-factors used for more conventional materials (e.g., structural steel, reinforced concrete, and wood) for comparable limit states, consequently potentially limiting the application of pultruded FRP as a structural material. This work describes a review of 350 published experimental tests of bolted connections in pultruded FRP and compares these test results with the nominal strengths from equations in the consensus standard. Subsequently, a first-order reliability method analysis—following the methodology proposed by Ellingwood for pultruded FRP composites—was performed to re-examine ϕ-factors for the most common limit states of bolted connections in pultruded FRP. All relevant limit states for bearing-type connections as defined by the consensus standard were considered in the study and the derived ϕ-factors were compared with the ϕ-factors prescribed in the consensus standard with the goal of highlighting the need for additional research.