The primary objective of the Structure Separation Experiment project is to assess structure-to-st... more The primary objective of the Structure Separation Experiment project is to assess structure-to-structure fire spread for structures located in the Wildland Urban Interface (WUI). As part of this project, full scale fire experiments will be conducted in which various types of structures (sources of fire) will be used to generate typical radiative and convective heat exposures on target structures (residential dwellings). The spacing between the source and target structures will be varied to identify safe structure separation distance (SSD). Most experiments will be conducted with construction materials currently listed in State of California building codes and using code compliant structural assemblies. A limited number of experiments will be conducted with enhanced, ignition resistant, materials that may not currently be listed by the State of California. The project is divided into three phases. Phase 1 will test sheds as fire sources, Phase 2 will test in-law buildings and Phase 3...
Journal of Applied Meteorology and Climatology, 2020
Accurate simulation of planetary boundary layer height (PBLH) is key to greenhouse gas emission e... more Accurate simulation of planetary boundary layer height (PBLH) is key to greenhouse gas emission estimation, air quality prediction, and weather forecasting. This paper describes an extensive performance assessment of several Weather Research and Forecasting (WRF) Model configurations in which novel observations from ceilometers, surface stations, and a flux tower were used to study their ability to reproduce the PBLH and the impact that the urban heat island (UHI) has on the modeled PBLHs in the greater Washington, D.C., area. In addition, CO2 measurements at two urban towers were compared with tracer transport simulations. The ensemble of models used four PBL parameterizations, two sources of initial and boundary conditions, and one configuration including the building energy parameterization urban canopy model. Results have shown low biases over the whole domain and period for wind speed, wind direction, and temperature, with no drastic differences between meteorological drivers. ...
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
• Evaluation of modeled urban carbon dioxide using multiple emissions inventories • Modeled carbo... more • Evaluation of modeled urban carbon dioxide using multiple emissions inventories • Modeled carbon dioxide mole fractions agree with observations on average within 1% • Spread in emissions inventories secondary to error resulting from model meteorology • Synoptic meteorology as important as time of day for simulating observations
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
There has been a resurgence of interest in the response of building structures to fires over the ... more There has been a resurgence of interest in the response of building structures to fires over the past several years. Typically, simulations of thermally induced structural response are de-coupled from fire dynamics. The thermal environment in such simulations is specified by a time temperature curve and attention is confined to the structural response (stress analysis) to spatially uniform enclosure temperatures. As a result the structural response of the building to spatially and temporally varying fires can not be studied. Simulation of the effects of severe fires on the structural integrity of building requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling the Fire Dynamics Simulator [1] with finite element methods for predicting the coupled thermal – structural response of structural components and assemblies [2]. A simple radiative transport model...
There has been a resurgence of interest in the response of building structures to fires over the ... more There has been a resurgence of interest in the response of building structures to fires over the past several years. Typically, simulations of thermally induced structural response are de-coupled from fire dynamics. The thermal environment in such simulations is specified by a time temperature curve and attention is confined to the structural response (stress analysis) to spatially uniform enclosure temperatures. As a result the structural response of the building to spatially and temporally varying fires can not be studied. Simulation of the effects of severe fires on the structural integrity of building requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling the Fire Dynamics Simulator [1] with finite element methods for predicting the coupled thermal-structural response of structural components and assemblies [2]. A simple radiative transport model that assumes the compartment is divided into a hot, soot laden upper layer and a cool relatively clear lower layer is employed to account for sub-grid structural members. Finite element models are developed for the critical structural components and the role of imperfection in fireproofing is demonstrated. An interface is constructed for mapping the results of the thermal analysis on the structural components to predict the spatially varying body loads. The methodology is employed to predict the thermo-structural response of complex building assemblies.
Map of the long-term observing network over Indianapolis, Indiana. CH4 concentration enhancement ... more Map of the long-term observing network over Indianapolis, Indiana. CH4 concentration enhancement observed during a drive-around campaign (21 Jan 2013) near the SouthSide Landfill CO2 mole fractions observed from the air (
Over the past several years, there has been a resurgence of interest in studying the response of ... more Over the past several years, there has been a resurgence of interest in studying the response of building structures to fires. Simulations of the effects of severe fires on the structural integrity of buildings requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling CFD simulations of fire growth with finite element models for thermal analysis and for using the thermal data to compute the demand-to-capacity ratio in a multi-story structure. A simple radiative transport model that assumes the compartment is divided locally into a hot, soot laden upper layer and a cool, relatively clear lower layer is employed to predict radiative fluxes incident on sub-grid scale structural members. Thermal response coupled with realistic fire simulations of various steel structural components on floors of World Trade Center Tower 1 that were subjected to aircraft impact damage and fires are presented. The thermal response was used to compute the reduction in load carrying capacity of the structural components as a function of time, which ultimately results in global collapse of the towers.
One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysi... more One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysis and calibration by error minimization. Analysis of an existing heat and mass transfer model indicates that mass transfer and condensation of water vapor are not of primary importance in predicting board temperatures. A computationally efficient and robust heat transfer model is developed for predicting temperatures in gypsum wallboard partitions. Kinetic parameters are calibrated by error minimization with respect to literature thermogravimetric analysis (TGA) data. Additional thermophysical parameters are calibrated by error minimization with respect to literature ASTM E119 furnace test data. It is found that the calibrated heat transfer model is capable of predicting board temperatures given large thermal conductivities and specific heats at high temperatures. It is hypothesized that these observations imply the need to account for porous media radiation, temperature varying specific heats, and calcium carbonate decomposition in future models. Local sensitivity analysis reveals that board temperatures are most sensitive to initial density, thermal conductivity at moderately high temperatures (∼ 800 • C), and the activation energy of the dehydration reactions. Conversely, model predictions are relatively insensitive to dehydration reaction pre-exponentials and low-temperature heat capacities.
Recent development of accurate instruments for measuring greenhouse gas concentrations and the ab... more Recent development of accurate instruments for measuring greenhouse gas concentrations and the ability to mount them in ground-based vehicles has provided an opportunity to make temporally and spatially resolved measurements in the vicinity of suspected source locations, and for subsequently estimating the source location and strength. The basic approach of us ing downwind atmospheric measurements in an inversion methodology to predict the source strength and location is an ill-posed problem and results in large uncertainty. In this report, we present a new measurement methodology for reducing the uncertainty in predicting source strength from downwind measurements associated with inverse modeling. In order to demon strate the approach, an inversion methodology built around a plume dispersion model is de veloped. Synthetic data derived from an assumed source distribution is used to compare and contrast the predicted source strength and location. The effect of introducing various levels of noise in the synthetic data or uncertainty in meteorological variables on the inversion method ology is studied. Results indicate that the use of noisy measurement data had a small effect on the total predicted source strength, but gave rise to several spurious sources (in many cases 8-10 sources were detected, while the assumed source distribution only consisted of 2 sources). Use of noisy measurement data for inversion also introduced large uncertainty in the location of the predicted sources. A mathematical model for estimating an upper bound on the un certainty, and a bootstrap statistical approach for determining the variability in the predicted source distribution is demonstrated. The new measurement methodology, which involves using measurement data from two or more wind directions, combined together as part of a single inversion process is presented. Results of the bootstrap process indicated that the uncertainty in locating sources reduced significantly when measurements are made using the new proposed measurement approach. The proposed measurement system can be significant in determining emission inventories in urban domains at a high level of reliability, and for studying the role of remediation measures.
The Indianapolis Flux Experiment (INFLUX) was designed to develop top-down methods for measuremen... more The Indianapolis Flux Experiment (INFLUX) was designed to develop top-down methods for measurement and modeling of urban fluxes of greenhouse gases (GHG) to the atmosphere with spatial and temporal scale of one km. and one hour respectively. A small bias in the observation data relative to the background can introduce significantly large bias in the computed fluxes if it is relatively high to the emission enhancement. Hence, it is important to maintain accuracy of in situ GHG data for unbiased estimation of urban fluxes. Accuracy of GHG observation data can be influenced by quality control (QC) process used for error detection, instrument calibration and error correction. Currently different organizations employ different QC processes on the same raw data resulting in significantly different QC'ed data. This report introduces a standardized approach integrating all present techniques. It consists of four major sequential steps: data screening, gas source based data separation, calibration and time-lag correction, and data averaging. QC'ed data for a set of twelve towers are compared with that from other organization for a period of two months. The influences of different methodologies in the QC process were analyzed, and the important parameters were optimized to reconcile the differences. Finally, recommendations in different phases of QC process are presented to provide guidelines for tower observation.
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of .Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
Localized ignition is initiated by an external radiant source at the middle of a thin solid sheet... more Localized ignition is initiated by an external radiant source at the middle of a thin solid sheet under external slow flow, simulating fire initiation in a spacecraft with a slow ventilation flow. Ignition behavior, subsequent transition simultaneously to upstream and downstream flame spread, and flame growth behavior are studied theoretically and experimentally. There are two transition stages in this study; one is the first transition from the onset of the ignition to form an initial anchored flame close to the sample surface, near the ignited area. The second transition is the flame growth stage from the anchored flame to a steady fire spread state (i.e. no change in flame size or in heat release rate) or a quasi-steady state, if either exists. Observations of experimental spot ignition characteristics and of the second transition over a thermally thin paper were made to determine the effects of external flow velocity. Both transitions have been studied theoretically to determine...
While ASTM E119-07a is commonly employed to establish a fire rating for a fire resistive material... more While ASTM E119-07a is commonly employed to establish a fire rating for a fire resistive material (FRM)/steel assembly, the test method provides little quantitative information on either the thermophysical or adhesion properties of the FRM, beyond indicating that they are sufficient to achieve the measured rating. As part of the Building and Fire Research Laboratory (BFRL) Structural Performance Under Multi-hazards program, a materials science-based approach is being applied to develop new methodologies and test methods for characterizing these complex dynamic materials. These quantitative characterizations can then be used as inputs to thermal/mechanical performance models and also for obtaining a better understanding of how these materials perform their intended role and how they could be improved. Thermophysical properties that must be characterized as a function of temperature include density, heat capacity, thermal conductivity, and heats of reactions and phase changes. For example, for high temperature thermal conductivity, a new measurement technique based on the use of a slug calorimeter has been developed and standardized in the ASTM E37 Thermal Measurements committee. In addition to adequate thermophysical properties, adhesion properties are critical to ensure that the FRM continues to protect its substrate during a fire exposure. Research on developing new test methods for both laboratory and field evaluations of adhesion will be presented. Like thermal properties, adhesion has also been observed to be strongly influenced by exposure to elevated temperatures. Finally, capabilities developed at NIST to obtain quantitative descriptions of the three-dimensional microstructures of FRMs and relate them to thermal properties such as thermal conductivity will be demonstrated. Much of this research has been completed as part of the ongoing NIST/industry consortium on "Performance Assessment and Optimization of Fire Resistive Materials.
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
The primary objective of the Structure Separation Experiment project is to assess structure-to-st... more The primary objective of the Structure Separation Experiment project is to assess structure-to-structure fire spread for structures located in the Wildland Urban Interface (WUI). As part of this project, full scale fire experiments will be conducted in which various types of structures (sources of fire) will be used to generate typical radiative and convective heat exposures on target structures (residential dwellings). The spacing between the source and target structures will be varied to identify safe structure separation distance (SSD). Most experiments will be conducted with construction materials currently listed in State of California building codes and using code compliant structural assemblies. A limited number of experiments will be conducted with enhanced, ignition resistant, materials that may not currently be listed by the State of California. The project is divided into three phases. Phase 1 will test sheds as fire sources, Phase 2 will test in-law buildings and Phase 3...
Journal of Applied Meteorology and Climatology, 2020
Accurate simulation of planetary boundary layer height (PBLH) is key to greenhouse gas emission e... more Accurate simulation of planetary boundary layer height (PBLH) is key to greenhouse gas emission estimation, air quality prediction, and weather forecasting. This paper describes an extensive performance assessment of several Weather Research and Forecasting (WRF) Model configurations in which novel observations from ceilometers, surface stations, and a flux tower were used to study their ability to reproduce the PBLH and the impact that the urban heat island (UHI) has on the modeled PBLHs in the greater Washington, D.C., area. In addition, CO2 measurements at two urban towers were compared with tracer transport simulations. The ensemble of models used four PBL parameterizations, two sources of initial and boundary conditions, and one configuration including the building energy parameterization urban canopy model. Results have shown low biases over the whole domain and period for wind speed, wind direction, and temperature, with no drastic differences between meteorological drivers. ...
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
• Evaluation of modeled urban carbon dioxide using multiple emissions inventories • Modeled carbo... more • Evaluation of modeled urban carbon dioxide using multiple emissions inventories • Modeled carbon dioxide mole fractions agree with observations on average within 1% • Spread in emissions inventories secondary to error resulting from model meteorology • Synoptic meteorology as important as time of day for simulating observations
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
There has been a resurgence of interest in the response of building structures to fires over the ... more There has been a resurgence of interest in the response of building structures to fires over the past several years. Typically, simulations of thermally induced structural response are de-coupled from fire dynamics. The thermal environment in such simulations is specified by a time temperature curve and attention is confined to the structural response (stress analysis) to spatially uniform enclosure temperatures. As a result the structural response of the building to spatially and temporally varying fires can not be studied. Simulation of the effects of severe fires on the structural integrity of building requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling the Fire Dynamics Simulator [1] with finite element methods for predicting the coupled thermal – structural response of structural components and assemblies [2]. A simple radiative transport model...
There has been a resurgence of interest in the response of building structures to fires over the ... more There has been a resurgence of interest in the response of building structures to fires over the past several years. Typically, simulations of thermally induced structural response are de-coupled from fire dynamics. The thermal environment in such simulations is specified by a time temperature curve and attention is confined to the structural response (stress analysis) to spatially uniform enclosure temperatures. As a result the structural response of the building to spatially and temporally varying fires can not be studied. Simulation of the effects of severe fires on the structural integrity of building requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling the Fire Dynamics Simulator [1] with finite element methods for predicting the coupled thermal-structural response of structural components and assemblies [2]. A simple radiative transport model that assumes the compartment is divided into a hot, soot laden upper layer and a cool relatively clear lower layer is employed to account for sub-grid structural members. Finite element models are developed for the critical structural components and the role of imperfection in fireproofing is demonstrated. An interface is constructed for mapping the results of the thermal analysis on the structural components to predict the spatially varying body loads. The methodology is employed to predict the thermo-structural response of complex building assemblies.
Map of the long-term observing network over Indianapolis, Indiana. CH4 concentration enhancement ... more Map of the long-term observing network over Indianapolis, Indiana. CH4 concentration enhancement observed during a drive-around campaign (21 Jan 2013) near the SouthSide Landfill CO2 mole fractions observed from the air (
Over the past several years, there has been a resurgence of interest in studying the response of ... more Over the past several years, there has been a resurgence of interest in studying the response of building structures to fires. Simulations of the effects of severe fires on the structural integrity of buildings requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. A methodology has been developed for coupling CFD simulations of fire growth with finite element models for thermal analysis and for using the thermal data to compute the demand-to-capacity ratio in a multi-story structure. A simple radiative transport model that assumes the compartment is divided locally into a hot, soot laden upper layer and a cool, relatively clear lower layer is employed to predict radiative fluxes incident on sub-grid scale structural members. Thermal response coupled with realistic fire simulations of various steel structural components on floors of World Trade Center Tower 1 that were subjected to aircraft impact damage and fires are presented. The thermal response was used to compute the reduction in load carrying capacity of the structural components as a function of time, which ultimately results in global collapse of the towers.
One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysi... more One-dimensional heat transfer in gypsum wallboard partitions is studied using sensitivity analysis and calibration by error minimization. Analysis of an existing heat and mass transfer model indicates that mass transfer and condensation of water vapor are not of primary importance in predicting board temperatures. A computationally efficient and robust heat transfer model is developed for predicting temperatures in gypsum wallboard partitions. Kinetic parameters are calibrated by error minimization with respect to literature thermogravimetric analysis (TGA) data. Additional thermophysical parameters are calibrated by error minimization with respect to literature ASTM E119 furnace test data. It is found that the calibrated heat transfer model is capable of predicting board temperatures given large thermal conductivities and specific heats at high temperatures. It is hypothesized that these observations imply the need to account for porous media radiation, temperature varying specific heats, and calcium carbonate decomposition in future models. Local sensitivity analysis reveals that board temperatures are most sensitive to initial density, thermal conductivity at moderately high temperatures (∼ 800 • C), and the activation energy of the dehydration reactions. Conversely, model predictions are relatively insensitive to dehydration reaction pre-exponentials and low-temperature heat capacities.
Recent development of accurate instruments for measuring greenhouse gas concentrations and the ab... more Recent development of accurate instruments for measuring greenhouse gas concentrations and the ability to mount them in ground-based vehicles has provided an opportunity to make temporally and spatially resolved measurements in the vicinity of suspected source locations, and for subsequently estimating the source location and strength. The basic approach of us ing downwind atmospheric measurements in an inversion methodology to predict the source strength and location is an ill-posed problem and results in large uncertainty. In this report, we present a new measurement methodology for reducing the uncertainty in predicting source strength from downwind measurements associated with inverse modeling. In order to demon strate the approach, an inversion methodology built around a plume dispersion model is de veloped. Synthetic data derived from an assumed source distribution is used to compare and contrast the predicted source strength and location. The effect of introducing various levels of noise in the synthetic data or uncertainty in meteorological variables on the inversion method ology is studied. Results indicate that the use of noisy measurement data had a small effect on the total predicted source strength, but gave rise to several spurious sources (in many cases 8-10 sources were detected, while the assumed source distribution only consisted of 2 sources). Use of noisy measurement data for inversion also introduced large uncertainty in the location of the predicted sources. A mathematical model for estimating an upper bound on the un certainty, and a bootstrap statistical approach for determining the variability in the predicted source distribution is demonstrated. The new measurement methodology, which involves using measurement data from two or more wind directions, combined together as part of a single inversion process is presented. Results of the bootstrap process indicated that the uncertainty in locating sources reduced significantly when measurements are made using the new proposed measurement approach. The proposed measurement system can be significant in determining emission inventories in urban domains at a high level of reliability, and for studying the role of remediation measures.
The Indianapolis Flux Experiment (INFLUX) was designed to develop top-down methods for measuremen... more The Indianapolis Flux Experiment (INFLUX) was designed to develop top-down methods for measurement and modeling of urban fluxes of greenhouse gases (GHG) to the atmosphere with spatial and temporal scale of one km. and one hour respectively. A small bias in the observation data relative to the background can introduce significantly large bias in the computed fluxes if it is relatively high to the emission enhancement. Hence, it is important to maintain accuracy of in situ GHG data for unbiased estimation of urban fluxes. Accuracy of GHG observation data can be influenced by quality control (QC) process used for error detection, instrument calibration and error correction. Currently different organizations employ different QC processes on the same raw data resulting in significantly different QC'ed data. This report introduces a standardized approach integrating all present techniques. It consists of four major sequential steps: data screening, gas source based data separation, calibration and time-lag correction, and data averaging. QC'ed data for a set of twelve towers are compared with that from other organization for a period of two months. The influences of different methodologies in the QC process were analyzed, and the important parameters were optimized to reconcile the differences. Finally, recommendations in different phases of QC process are presented to provide guidelines for tower observation.
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of .Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
Localized ignition is initiated by an external radiant source at the middle of a thin solid sheet... more Localized ignition is initiated by an external radiant source at the middle of a thin solid sheet under external slow flow, simulating fire initiation in a spacecraft with a slow ventilation flow. Ignition behavior, subsequent transition simultaneously to upstream and downstream flame spread, and flame growth behavior are studied theoretically and experimentally. There are two transition stages in this study; one is the first transition from the onset of the ignition to form an initial anchored flame close to the sample surface, near the ignited area. The second transition is the flame growth stage from the anchored flame to a steady fire spread state (i.e. no change in flame size or in heat release rate) or a quasi-steady state, if either exists. Observations of experimental spot ignition characteristics and of the second transition over a thermally thin paper were made to determine the effects of external flow velocity. Both transitions have been studied theoretically to determine...
While ASTM E119-07a is commonly employed to establish a fire rating for a fire resistive material... more While ASTM E119-07a is commonly employed to establish a fire rating for a fire resistive material (FRM)/steel assembly, the test method provides little quantitative information on either the thermophysical or adhesion properties of the FRM, beyond indicating that they are sufficient to achieve the measured rating. As part of the Building and Fire Research Laboratory (BFRL) Structural Performance Under Multi-hazards program, a materials science-based approach is being applied to develop new methodologies and test methods for characterizing these complex dynamic materials. These quantitative characterizations can then be used as inputs to thermal/mechanical performance models and also for obtaining a better understanding of how these materials perform their intended role and how they could be improved. Thermophysical properties that must be characterized as a function of temperature include density, heat capacity, thermal conductivity, and heats of reactions and phase changes. For example, for high temperature thermal conductivity, a new measurement technique based on the use of a slug calorimeter has been developed and standardized in the ASTM E37 Thermal Measurements committee. In addition to adequate thermophysical properties, adhesion properties are critical to ensure that the FRM continues to protect its substrate during a fire exposure. Research on developing new test methods for both laboratory and field evaluations of adhesion will be presented. Like thermal properties, adhesion has also been observed to be strongly influenced by exposure to elevated temperatures. Finally, capabilities developed at NIST to obtain quantitative descriptions of the three-dimensional microstructures of FRMs and relate them to thermal properties such as thermal conductivity will be demonstrated. Much of this research has been completed as part of the ongoing NIST/industry consortium on "Performance Assessment and Optimization of Fire Resistive Materials.
Certain commercial entities, equipment, products, or materials are identified in this document in... more Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology. Disclaimer No. 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document, however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline. Disclaimer No. 3 Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the voluntary provision of that type of information" (15 USC 7306c). In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been provided to NIST under nondisclosure agreements. Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining compliance when implementing building codes. Where an Investigation report states whether a system was designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met. Use in Legal Proceedings No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
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