Collapse Of Steel Structures Research Articles

Cyclic fracture simulation through element deletion in structural steel systems

This paper presents a finite element-based model for direct simulation of cyclic fracture in steel components and connections with application to predicting failure and collapse of steel structures. The formulation couples a plasticity model for large deformations that captures plastic work stagnation and the Bauschinger effect with a two-stage damage model to simulate fracture initiation, propagation, and failure through an element deletion strategy. The model includes the non-proportional loading and load-history effects in the fracture initiation and propagation process. Fracture initiation and propagation is controlled using new fracture initiation strain and fracture energy surfaces with stress triaxiality and Lode angle dependance that can represent different fracture behaviors. Model calibration is discussed for common grades of structural steel, weldments and bolts using typical material tests. The model capabilities are validated against experiments including ancillary material tests, components, and subassemblies of steel structures that experienced fracture subjected to monotonic and cyclic loading. A culminating validation is conducted on a four-story steel frame structure tested to collapse. The proposed model provides a robust and valuable tool for stability analysis and simulations of damage and collapse triggered by fracture in components and connections of three-dimensional steel structures subjected to extreme loads.

Collapse performance of composite steel frames under fire

Collapse of steel structures under extreme hazards has been placed at the forefront of research in recent decades. While significant number of studies has been conducted in the past on steel members and subassemblies under fire, the response of steel buildings exposed to fire loadings has not received a similar level of attention. In addition, only handful of previous studies, mainly 2D with only one study pertaining to 3D frames, encompassed the full response of the system up to and including collapse. In this study, a 3D numerical finite element model is developed for a six-story steel-frame building with moment frames, gravity frames, and center concentrically braced frame to evaluate the collapse behavior of the structure under fire loading. A standard and a parametric fire curve are selected to simulate the fire loadings and are applied independently to the building model under two different contained fire scenarios. The two scenarios include first floor corner compartment fire and whole first floor fire. This allowed for the assessment of different global system response where collapse is triggered by twist of the entire structure accompanied by lateral deformation in the case of a corner compartment fire and progressive vertical displacement of the entire system in the case of the whole first floor fire. The simulation results show that structural response of steel buildings including collapse mechanism and behavior of structural members and connections during fire events can be predicted with reasonable accuracy using advanced numerical finite element analysis.

Instability and plastic collapse of steel structures

Instability and plastic collapse of steel structures