Modified Three-Parameter Power Model to Predict Moment-Rotation Curve of Top- and Seat-Angle Connection

Abstract

This study conducted on improving three-parameter power model [1] to estimate ultimate moment of connections based on the failure mechanisms developed by more practical means and finally, to predict moment-rotation relations of top-and seat-angle connections for intrinsic replacement of experimental curves and/or finite element (FE) analysis results. Bolt stiffness, shear and bending deformation of tension angle and prying force acted on tension angle are considered to determine the ultimate moment of connections implementing two possible failure mechanisms. These failure mechanisms are developed based on the concept of T-stub model [2] and adjusted the position of plastic hinges applying advanced FE analysis method [3-6]. Then, moment-rotation (M−θ r) characteristics of top-and seat-angle connections are constructed applying proposed modified three-parameter power model. Applicability of the proposed formulation is examined by comparing M−θ r curves and ultimate moment capacities with those of Kishi-Chen power model, FE analyses [3, 4] and experiments [7, 8]. The comparison implies that proposed formulation and Kishi-Chen's method both achieved closer approximation for maximum of cases and better accuracy for the modified cases to drive M−θ r curves of the connections; but ultimate moments of the connections defined by the proposed method is more realistic than that predicted by Kishi-Chen power model.