Full Session with Abstracts
This presentation gives an overview of Chapter 5 of the new Alternative Load Path Analysis Guidelines, developed by the Disproportionate Collapse Technical Committee. This chapter, entitled Advanced Computational Methods, presents modeling approaches that can directly account for key nonlinear effects in alternative load path analysis, including the interaction of bending moment and axial force associated with arching action or catenary action and the development of membrane forces in floor slabs under large deflections. Because the focus is on faithfully modeling such nonlinear effects, linear analysis procedures are not considered in this chapter, nor are plastic-hinge models that neglect the influence of axial forces on connection behavior.
The primary focus of this chapter is on modeling and analysis using the finite element method (FEM), although alternative methods are also described, including the applied element method (AEM) and a two-scale cohesive modeling approach. Micro-modeling approaches using continuum elements are described, with the highest level of fidelity including models in which individual bolts and plates are modeled using solid elements, accounting for contact, material damage, and fracture. Such a high-fidelity approach is feasible only for relatively small subsystems. Recognizing this, macro-modeling approaches are also described, which can capture the same mechanics as the micro-modeling approaches, but through a reduced-order approach in which discrete elements represent the nonlinear load-displacement behavior and failure of individual connection components. Key aspects of the various modeling approaches are described, and example analysis problems are presented, including both subsystem and full-building analyses. Example analysis problems include a steel frame building, a reinforced concrete frame building, and a concrete shear wall building with a flat-plate floor system.