Coherent Laser Ranging of Deforming Objects in Fires at Sub-Millimeter Precision.

Light Detection and Ranging (LiDAR) is a powerful tool to characterize and track the surface geometry of solid objects. In a fire, however, no method has excelled at measuring three-dimensional shapes at millimeter precision while offering some immunity to the effects of flames. This paper applies coherent Frequency Modulated Continuous Wave Light Detection and Ranging to capture three-dimensional measurements of objects in fire at meters of stand-off distance. We demonstrate that despite the presence of natural gas flame depths up to 1.5 m obscuring the target, measurements with millimeter precision can be obtained. This is a significant improvement over previous work making the technique useful for many fire research applications. An approach to achieve sub-millimeter precision using spatial and temporal averaging during post-processing is presented. The technology is demonstrated in case studies of structural connection and vegetation response in fires.

Communication framework for Hybrid Fire Testing: developments and applications in virtual and real environments.

The response of structural systems to fire loads is typically assessed through performing 'standard' fire tests on individual members under constant mechanical boundary conditions. Full scale tests showed different behavior compared to the standard tests, but remain impractical. A promising approach to predict the behavior of full scale tests through testing individual structural members is Hybrid Fire Testing technique, where a subset of the structural system (Physical Substructure PS), is physically tested, while the remaining structure (Numerical Substructure NS), is simultaneously numerically analyzed. During the test, the mechanical boundary conditions on the PS and NS are continuously updated, and the updates are enabled by the communication framework. The communication framework is a key element for a successful hybrid fire testing and this paper will present the development of such communication in MATLAB. To validate the communication framework, first, a single degree of freedom linear system was analyzed, followed by a ten-story steel frame structure exposed to design fire. The analysis of the latter underlined the importance of considering the effect of the cold surrounding in assessing the fire behavior of structures under design fires. Sensitivity analysis showed the importance of several parameters (time step and substructures stiffness) in hybrid fire testing.