VistaFire is a thermomechanical analysis module for predicting fire effects on structures, including their residual capacity. It focuses on the responses of large-scale structures to transient dynamic loading conditions, providing a unified computational approach to evaluating the operational capacity of structures during and after fires.
VistaFire was developed on the basis of a comprehensive viscoplasticity model, which is embedded in the shell mechanics framework. It is unique in its ability to represent both creep deformation and fast dynamic response to impulsive loads. This is in contrast to empirical creep models, which are formulated to represent specific phases of creep (primary, secondary, and tertiary) and are effectively fluid models with near-extreme sensitivity to loading rates. By employing the advanced viscoplastic formulation, VistaFire delivers a consistent approach to assessing structural response to extreme thermomechanical loads with widely varying stresses, temperatures, and strain rates.
As with VistaDam, a consistent calibration and validation framework has been developed for VistaFire, significantly reducing the experimental effort necessary to calibrate the model.
High Temperature Failure Prediction – Examples
World Trade Center collapse:
While the World Trade Center collapse forensic analyses predated the formulation of VistaMat Suite, the investigation validated the initial theoretical foundation of the VistaFire module. The study of structural failure and collapse, unprecedented in both scope and depth, entailed fluid-structure interaction analyses of such phenomena as impact damage, fire dynamics, thermal softening of structural members, material failure, and progressive collapse, as well as many other effects. Key elements of the thermal softening formulation contained in VistaFire were proposed and validated during the WTC investigation.
N. Abboud, M. Levy, D. Tennant, J. Mould, H. Levine, S. King, C. Ekwueme, A. Jain, G. Hart, “Anatomy of a Disaster: A Structural Investigation of the World Trade Center Collapses,” Proceedings of the Third Congress on Forensic Engineering, San Diego, California, 2003
VistaFire has been extensively validated against data from a variety of experimental tests, including a series of tensile creep tests, buckling tests conducted for both coupon and sub component levels with varying temperatures, and burn-through tests. Burn-through failure is particularly important for prediction of fire effects on structures, since it allows for fire propagation and spread. Excellent correlation between the simulation and test data was achieved, validating the underlying fundamental theory and the constitutive model implementation.
Experiment: C. Rippe, B. Lattimer, “Burn-Through of Aluminum,” Virginia Tech Report – Office of Naval Research Program Review, January 23, 2013