Developing Experimental Capabilities for a new National Fire Research Laboratory Project

This project will develop the tools, safety systems, protective measures, and design reaction frames needed to conduct real-scale experiments in the National Fire Research Laboratory (NFRL) to measure the performance of loaded structural components under fire conditions.   

What is the problem Fire costs the U.S. economy approximately $270B/year (Ref: Hall, NFPA, 2008).  Yet, current building design practice does not consider fire as a design condition for structures.  Rather, required fire ratings of building components and assemblies derived from standard fire endurance tests, such as ASTM E-119, are specified in current building codes.  Currently, there are no science-based, accepted measurement tools to evaluate the fire performance of entire structures, including connections, under realistic fire scenarios.  The state of the art in measurement science to predict structural performance to failure under extreme loading conditions such as in an uncontrollable fire is lacking. This can lead to significant safety concerns.  Thus, there is an urgent and critical need to develop and implement improved standards, methodologies, and tools that explicitly consider realistic building fire loads, both in the design of new structures and in the rehabilitation of existing structures.  A critical component of this effort is the validation of numerical models developed to predict the performance of structures in realistic fires in support of the development of performance-based design guidance

Why is it hard to solve   Analysis of structural systems under fire conditions involves the prediction of performance of the entire structural system at, or near, its limit state of collapse as an uncontrolled fire is considered an extreme (rare though not improbable) event.  Development of accurate models to predict complex structural system behavior resulting from the effects of thermal expansion and diminished mechanical properties at elevated temperatures requires the availability of robust computational models, validated against large-scale tests under real fire exposures.  At the present time, experimental data on the behavior of connections, members, and systems under realistic building fire conditions are lacking.  Conducting real-scale structural/fire experiments poses significant challenges with respect to structural loading, instrumentation, protection of the facility and hydraulic components reaction frames from fire exposure, and ensuring that tests can be conducted safely and effectively to support the validation of predictive models

How is it solved today, and by whom? The problem is not solved today.  Most structural/fire experiments are conducted in furnace environments.  These experiments while useful, do not faithfully replicate real fire conditions, nor do they allow for a structure to be tested to failure.  Further, in furnace tests, most relevant data on structural behavior can be acquired outside of the heated zone, greatly simplifying data acquisition.  Limited large-scale fire tests have been conducted (e.g., Cardington) but these have been limited and have not provided the level of control expected with the nfrl. 

Why NIST? Analysis of structural systems under fire conditions involves the prediction of performance of the entire structural system at, or near, its limit state of collapse as an uncontrolled fire is considered an extreme (rare though not improbable) event.  Development of accurate models to predict complex structural system behavior resulting from the effects of thermal expansion and diminished mechanical properties at elevated temperatures requires the availability of robust computational models, validated against large-scale tests under real fire exposures.  At the present time, experimental data on the behavior of connections, members, and systems under realistic building fire conditions are lacking.  In addition, detailed modeling of a complete structural system to failure imposes large computational demands.  Reduced models of key structural components such as connections that capture the predominant behaviors and failure modes at elevated temperatures are needed for cost effective assessment of structural response to fire and resistance to collapse in an uncontrolled fire.  Development and validation of such models pose a challenge

What is the new technical idea  NIST is constructing a National Structural Fire Research Laboratory (nfrl) which is expected to be completed in April 2012 and, after commissioning, available for conducting experiments in early 2013.  Using this unique facility, NIST will develop an experimental database on the performance of large-scale structural connections, components, subassemblies and systems under applied structural loads and realistic fire conditions.  The experimental data will be used to validate predictive models and enable the development of performance-based design methodologies.  This project will address gaps not addressed by the construction or the design of the structural loading system that are critical to safe, effective operation of the facility to conduct real-scale structural tests under fire conditions

Specifically, the project will address the design of systems to:  (1) protect the reaction wall and reaction frames from fire effects and from structural overloads; (2) ensure safety of personnel during experiments; (3) monitor the building during experiments; (4) analyze heat release rate and exhaust products during experiments; (5) monitor experiments

Why can we succeed now NIST received funding to construct the nfrl and procure the hydraulic loading system through the American Recovery and Reinvestment Act.  Construction of the building is scheduled to begin in the fall of 2010.  NIST has significant experience gained through conducting large scale experiments in the existing Large Fire Laboratory and will expand on this experience to meet the objectives of this project

What is the research plan  This project will address the safety and operational aspects of the nfrl that are not addressed as part of the construction of the laboratory.  The effort envisioned under this project will focus on the design of these systems, with acquisition to be accomplished as the facility approaches completion.  Specifically, this project aims to address the following

1. Technical Description of nfrl.  This document will provide technical guidance for the design of experiments to be run in the nfrl. The technical description of the laboratory will include the structural load capacities of the laboratory, attachment points and dimensions, fire size and available fuels.    
2. Three-dimensional visualization of laboratory  A three-dimensional model of the laboratory will be developed to provide a tool for NIST to describe the facility in presentations
3. Three-dimensional finite element structural model of laboratory.  A finite element structural model of the laboratory will be developed to provide a tool to assist in the design of experiments and to ensure that experiments planned for the laboratory do not exceed the structural capacity of the strong floor, reaction wall, or other components.  
4. Reaction Frames.  Define the requirements for a system of steel reaction frames that can be used for the range of structures that are anticipated to be tested in the nfrl.  In addition to the reaction frames, a design for the protection of the frames from heat effects will be produced
5. Actuator Mounting and Structural Loading Devices.  This task will focus on designing mounts to be used for attaching the hydraulic actuators to the strong floor, strong wall and reaction frames.  The task will also focus on designing devices that will be used to apply distributed vertical load to test structures.  This design task will also include design of systems to protect these devices from the effects of fire
6. Protection of the reaction wall and strong floor from fire effects.  This task will involve the definition of requirements for a water spray system to cool the reaction wall during fire experiments and a collection system to collect water and channel it away from the strong floor.  This task will also involve the analysis of options for protection of the strong floor and selection of an appropriate protection method.  Finally, it will include the design of temperature monitoring system for the strong wall and consideration of a flow control for the water spray system
7. Design of Exhaust Hood Curtains.  This task will focus on the design of exhaust hood side curtains that can be extended or retracted as appropriate for specific tests to ensure capture of exhaust products
8. Instrumentation of exhaust gas test section.  This task will address the design and specification of instrumentation for conducting calorimetery and chemical analysis of exhaust products from fire experiments in the nfrl
9. Test Warning System and Safety Lockout.  The purpose of this task will be to develop the requirements for a system to alert staff and visitors when a test is in progress in the nfrl and to prevent unauthorized entry into the laboratory during a test
10. Control Room  Due to the scale of tests envisioned for the nfrl, a moveable control room that can be lifted and relocated using the overhead crane is envisioned.  This task will involve developing the specification for a fire-protected control room to include the controls for the hydraulic loading system.   
11. Building Temperature Monitoring System.  This task will develop the requirements for a system to monitor the temperatures of the building itself during experiments.  The purpose of the system will be to monitor the effects that large, long-duration firesplanned for the nfrl have on the building structure
12. Video Monitoring System for Tests.  The requirements will be developed for a video monitoring system  to provide full coverage of experiments conducted in the nfrl.  This task will develop the specifications for a system to be implemented in the nfrl
13. Develop Plan to Outfit Computer Room.  This task will specify the equipment needed for the computer room used for control of fires and collection of data during experiments

How will teamwork be ensured  This project is led by the Structures Group of the Materials and Construction Research Division (MCRD) in close collaboration with researchers from the Fire Research Division's Large Fire Laboratory.  This project is closely tied to and directly supports the Fire Resistance Design and Rehabilitation of Structures project