Michael Spearpoint

Predicting the burning of wood using an integral model

This paper experimentally and theoretically examines the horizontal burning of four species of wood exposed to incident heat fluxes of 25–75 kW/m2 with their grain oriented either parallel or perpendicular to the incident heat flux. Mass loss, temperatures, and char fractions were measured. A one-dimensional integral model that describes the transient pyrolysis of a semi-infinite charring solid subject to a constant radiant heat flux was developed. The solutions to the integral model for the burning rate were compared with data using analytical short-time and long-time solutions. Reasonable comparative results are shown for mass loss rate, surface temperature, char depth, and effective thermal penetration.

Implementing a glass fracture module in the BRANZFIRE zone model

A glass fracture routine has been successfully implemented in the BRANZFIRE zone model, based largely on the heat transfer model developed by Sincaglia and Barnett and the fracture criterion of Pagni and Joshi. A second implementation of the model has been successfully created as a spreadsheet. The zone model implementation has been compared against an existing glass fracture model, BREAK1 and against a series of experiments. This model has been found to predict fracture times consistent with BREAK1 over a range of simulations. Fracture time predictions have also compared well with experimental results. A Monte Carlo based sensitivity analysis found that fracture strength was the most important input variable, though this is largely attributable to the large standard deviation of the probability distribution used for this input.

Calibrating an FDS Simulation of Goods-vehicle Fire Growth in a Tunnel Using the Runehamar Experiment

As with any complex fuel assembly configuration, modeling a goods-vehicle fire using fire dynamics simulator (FDS) to estimate the heat release rate in a tunnel is a challenging task. The present study involves the use of heat release rate curves taken from the Runehamar tunnel fire experiment T1 to ‘calibrate’ the heat release rate curve predicted using FDS 4.0.7. The article presents a simplified geometric representation of burning wood and plastic pallets and then illustrates that an FDS simulation of this representation is able to reproduce a reasonable estimate of the fire growth characteristics in the tunnel. The effects of the assumptions made in simplifying the fuel array are considered in order to calibrate these simulations. Finally, the article shows how the fire growth might change if conditions in the tunnel were varied.

Determination of kinetic properties of polyurethane foam decomposition for pyrolysis modelling

A non-fire-retardant and a fire retardant polyurethane foam are tested under a nitrogen environment using thermogravimetry at different heating rates of 1, 5, 20 and 60 °C min−1 to obtain the foams’ decomposition behaviours. During decomposition, both foams experience two major mass loss reactions with the second reaction consuming most of the fuel. Three graphical techniques applied to calculate the kinetic properties governing each reaction are kinetic analysis, the Arrhenius plot method and the inflection point methods. In general, these methods are compatible with the pyrolysis model within Fire Dynamics Simulator Version 5 and Gpyro. A normalised version of the inflection point methods is also developed to improve the suitability of the kinetic properties with the simplest decomposition scheme of the pyrolysis model. A consistent trend is noted in the calculated kinetic properties of both foams regardless of the calculation techniques applied.

Modeling Lifted Methane Jet Fires Using the Boundary-Layer Equations

ABSTRACT The focus of this article is turbulent lifted jet fires. The main objective is to present a lifted jet fire methodology using the boundary-layer equations as a basis. The advantages of this are that finite-volume, mesh-independent predictions of the mean flow fields can be calculated on readily available computer resources, which leads to rigorous model calibration. A number of lift-off models are evaluated. The model of choice is one based on the laminar flamelet quenching concept combined with a model for the large-scale strain rate.

The Effect of Pre-evacuation on Evacuation Times in the Simulex Model:

The evacuation time of a building in an emergency can be broken down into a number of constituent times including the pre-evacuation time and the travel time. This paper examines how distributions of pre-evacuation times affect the occupant travel time and hence their effect on the evacuation time in the Simulex model. A simple scenario is assessed mathematically and compared with the results from Simulex with further simulations carried out on a somewhat more complex scenario. Because we expect the pre-evacuation time to be characterized by a distribution of values, simply adding the maximum pre-evacuation time and the movement time over-estimates the evacuation time. Furthermore, when the preevacuation distribution is small the travelling and queuing effects dominate the simulated evacuation time. When the pre-evacuation distribution is large, then travel and queuing effects are not so important and it is the pre-evacuation time that dominates. Finally, the paper examines some aspects of the Simulex model in situations where there is a high occupant density in a space.

Movement on Stairs During Building Evacuations

The time that it takes an occupant population to reach safety when descending a stair during building evacuations is typically estimated by measureable engineering variables such as stair geometry, speed, stair density, and pre-observation delay. In turn, engineering models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. As part of a program to better understand occupant movement and behavior during building emergencies, the Engineering Laboratory at the National Institute of Standards and Technology (NIST) has been collecting stair movement data during fire drill evacuations of office and residential buildings. These data collections are intended to provide a better understanding of this principal building egress feature and develop a technical foundation for future codes and standards requirements. NIST has collected fire drill evacuation data in 14 buildings (11 office buildings and 3 residential buildings) ranging from six to 62 stories in height that have included a range of stair widths and occupant densities. A total of more than 22000 individual measurements are included in the data set. This report provides details of the data collected, an analysis of the data, and examples of the use of the data. The intention is to better understand movement during stair evacuations and provide data to test the predictive capability of building egress models. While mean movement speeds in the current study of 0.44 m/s ± 0.19 m/s are observed to be quite similar to the range of values in previous studies, mean local movement speeds as occupants traverse down the stairs are seen to vary widely within a given stair, ranging from 0.10 m/s ± 0.008 m/s to 1.7 m/s ± 0.13 m/s. These data provide confirmation of the adequacy of existing literature values typically used for occupant movement speeds and provide updated data for use in egress modeling or other engineering calculations. (Less)

Regulatory Knowledge Encoding Guidelines for Automated Compliance Audit of Building Engineering Design

The main challenges in automating the regulatory compliance checking of building engineering designs are the availability of computable representations of the building and the regulatory knowledge, as well as a system that can process and manage these representations effectively. The emergence of Building Information Modelling (BIM) and Industry Foundation Classes (IFC) at the start of the millennium has sparked useful research in the area of sharing building information effectively, but challenges remain with producing a practical and manageable regulatory knowledge representation that can be processed effectively by a compliance checking system. Research is being conducted to develop a two-part regulatory knowledge representation, which can be maintained independently by designers and regulators. One part is a set of compliant design procedures modelled as Business Process Diagrams (BPD) using an open standard Business Process Model and Notation (BPMN), and the other is the associated regulatory constraints and rules encoded in a computable format suitable for execution with the BPMN. This paper reports on a set of guidelines developed for the purposes of encoding regulatory knowledge into the proposed computable representation. A verification method (C/VM2) prescribed by the New Zealand Building Code (NZBC) for the performance-based design of buildings related to fire safety has been selected as a case study to illustrate the encoding process. These guidelines are adaptable for encoding the entire NZBC. BACKGROUND

COMPARATIVE VERIFICATION EXERCISES ON A PROBABILISTIC NETWORK MODEL FOR BUILDING EVACUATION

Functional testing of any model is a vital step in demonstrating that its predictive capabilities are working appropriately; correspond as expected to the circumstances being modeled and where further work should be directed. This article presents a series of exercises used to substantiate the movement prediction capability of a probabilistic network-based evacuation model that is currently under development. Two simple component configurations and two previously available worked examples are used to demonstrate that the model performs adequately. Movement times from model predictions, hand calculations, alternative empirical methods, and other computer models were compared for a range of typical occupant densities.

Transfer of Architectural Data from the IFC Building Product Model to a Fire Simulation Software Tool

A standardized, object-oriented building product model for buildings is introduced that can be used as a means of electronic exchange between various software tools. The ability to transfer architectural data between a commercially available computer-aided design (CAD) program and a widely available zone fire simulation tool illustrates the applicability of this model in fire engineering. This article describes the software developed to interpret the building product model and the test buildings used to verify the exchange process. In general the building geometry, topology, and other properties can be transferred satisfactorily but some inconsistencies exist due to the structure of the building product model, the CAD implementation of the model, and the simplifications required by the zone modeling approach.