Advanced Analysis for Three-Dimensional Semi-Rigid Steel Frames subjected to Static and Dynamic Loadings

Abstract or Introduction

This dissertation presents three various advanced analysis approaches which can capture accurately and efficiently the ultimate strength and behavior of steel framed structures with nonlinear beam-to-column connections subjected to static and dynamic loadings. Three major sources of nonlinearity are considered in the analyses as follows: (1) material nonlinearity; (2) geometric nonlinearity; and (3) connection nonlinearity. Three types of nonlinear beam-column element formulation considering both geometric and material nonlinearities are coded into two nonlinear structural analysis programs: (1) Nonlinear Structural Analysis Program (NSAP) – 2-D plastic-zone finite element; (2) Practical Advanced Analysis Program (PAAP) – 3-D refined plastic-hinge element and 3-D plastic-fiber element. Three types of steel frames analyzed by the proposed program are: (1) rigid frames – beam-to-column connections are fully rigid; (2) linear semi-rigid frames – beam-to-column connections have constant stiffness; and (3) nonlinear semi-rigid frames – beam-to-column connections have continuously variable stiffness. Three types of analysis can be performed are: (1) nonlinear inelastic static analysis; (2) nonlinear elastic and inelastic time-history analysis; and (3) free vibration analysis. Three main resources of damping are taken into account in the proposed programs are: (1) hysteretic damping due to inelastic material; (2) structural viscous damping employing Rayleigh damping; (3) hysteretic damping due to nonlinear beam-to-column connections.

Two computer programs are developed: (1) Nonlinear Structural Analysis Program (NSAP) – written in the C++ programming language; (2) Practical Advanced Analysis Program (PAAP) – written in the FORTRAN 77 programming language. They are verified for accuracy and computational efficiency by comparing predicted results with those generated by the commercial finite element analysis packages of ABAQUS and SAP2000, and other results available in the literature. Through several numerical examples, the proposed program (PAAP) proves to be a reliable and efficient tool for daily practice design in lieu of using costly and time-consuming commercial software.