George. V. Hadjisophocleous

Literature Review of Performance-Based Fire Codes and Design Environment

Building codes in many countries around the world are shifting from prescriptive-based to performance-based, a move that is due, in part, to the negative aspects of the prescrip tive codes, to econ...

Wind-driven rain distributions on two buildings

Abstract Wind-driven rain is an important consideration in the hygrothermal performance of building envelope parts. Wind-driven rain (in liquid form) can increase the amount of moisture present in the structure by more than 100 times that due to vapor diffusion. To date, very little work that provides field or laboratory wind driven rain data to moisture transport models is available. This information is a definite requirement as a boundary condition by the more sophisticated hygrothermal models such as LATENITE and WUFIZ which consider both vapor and liquid moisture flows. In this paper, the wind driven rain striking the exterior facade of two buildings (one twice the size of the other) is generated using a three-dimensional computational fluid dynamics (CFD) model that solves the air flow and particle tracking of the rain droplets around these two buildings. These simulations were carried out for a city center region. Four factors which govern wind-driven rain are investigated in this work: (a) upstream unobstructed wind conditions, (b) the rainfall intensity, (c) the probability distribution of raindrop sizes, and (d) the local flow patterns around the building. All four of these governing factors make wind-driven rain on a building facade very distinct. Simulations were carried out for three wind speeds of 5, 10 and 25 m/s, three rainfall intensities of 10, 25 and 50 mm/h and three wind directions 0°, 30° and 45° from the west face of the buildings. In this paper, only the results of the 0° wind direction are discussed. The results show distinct wetting patterns on the top of the building of both the two buildings which is most concentrated at the corners when the wind was normal to the facade surface. For the tallest building a distinct wetting pattern is displayed in the mid-height of the building. This information from wind engineering is directly employed for the design of building envelope moisture control. Results on a series of simulations are presented to demonstrate the effect of wind conditions, rain intensities, the interaction between the two buildings, and the droplet sizes on the wetting patterns on the faces of the short and tall building.

Performance criteria used in fire safety design

Abstract In many countries around the world, building codes are shifting from prescriptive- to performance-based for technical, economic, and social reasons. This move is made possible by progress in fire safety technologies, including the development of engineering tools that are required to implement performance codes. The development of performance-based codes follows a transparent, hierarchical structure in which there are usually three levels of objectives. The top level objectives usually state the functional requirements and the lowest level the performance criteria. Usually, one middle level exists, however, more levels can be used in this hierarchical structure depending on the complexity of the requirements. The success of performance-based codes depends on the ability to establish performance criteria that will be verifiable and enforceable. The performance criteria should be such that designers can easily demonstrate, using engineering tools, that their designs meet them and that the code authority can enforce them. This paper presents the performance criteria that are currently used by fire protection engineers in designing fire safety systems in buildings. These include deterministic and probabilistic design criteria as well as safety factors. The deterministic criteria relate mainly to life safety levels, fire growth and spread levels, fire exposure and structural performance. The probabilistic criteria focus on the incident severity and incident likelihood. Finally, the inclusion of safety factors permits a conservative design and allows for a smaller margin of error due to uncertainty in the models and the input data.

A two-zone fire growth and smoke movement model for multi-compartment buildings

A fire growth and smoke movement model for a multi-compartment building has been developed at the National Research Council of Canada. This development is primarily intended to help evaluate the risk from fires in buildings. This paper presents the related physical models, numerical methods, and some verification examples. The 2-zone ordinary differential equations (ODEs) are derived for the compartments with fire or smoke. The four independent variables for one compartment are selected as pressure, enthalpy of upper layer, and mass of upper and lower layers. The implemented fire sub-models are introduced, including combustion, fluid flow and heat transfer models. For each compartment without smoke or fire, a non-linear algebraic equation based on mass conservation is used instead of the ODEs. The numerical solution of the governing equations is obtained using a room by room iteration method. In this algorithm, an existing ODE solver, LSODA, has been modified and used to solve the stiff ODEs, and the Steffensen Acceleration Method is used to solve the algebraic equations. Experimental data for single- and two-compartment fire tests are compared to the predictions of the model. The comparison shows favourable results, especially for the upper layer gas temperature, interface height, and vent flow rate.

A Model for Calculating the Probabilities of Smoke Hazard From Fires in Multi-Storey Buildings

This paper presents a simplified model for calculating the probabilities of smoke hazard in multi-storey buildings. This model first establishes the fire development in a compartment on any floor, using the results from a one zone fire growth model1, and then computes the smoke movement in the building, yielding the temperature and concentration of toxic gases at any location in the building. At a critical time, which is defined as the time when the conditions in the stairs leading to an exit are lethal, such that occupants are trapped and cannot evacuate, the smoke movement calculations are terminated and the probabili ties of smoke hazard are computed based on the temperature and concentration of toxic gases in the building. The procedure used for the calculation of smoke movement, the criti cal time and the smoke hazard probabilities is described in this paper. Results are pre sented, as an example, for a twenty-five storey apartment building.

Computer Modeling of Compartment Fires

A three dimensional computational fluid dynamics model for the simulation of fire is presented. The model solves the governing partial differential equations for continuity, momentum, and energy using the control volume formulation. Turbulence is modeled using the k-emodel and fire is described as a heat source.The above model has been used to simulate fire inside an enclosure. The results of studies on the fire location, size of the compartment opening and existence of internal objects are presented. The predictions obtained are compared with experimental data and found to be in reasonable agreement.

Estimating Water Requirements for Firefighting Operations Using FIERAsystem

A new computer model for estimating water requirements for firefighting purposes has been developed by the Fire Risk Management Program of the National Research Council of Canada. This work was done in partnership with the Canadian Department of National Defence, as part of the development of a computer model to evaluate fire protection systems in light industrial buildings (FIERAsystem). The new model considers the geometry of the building, possible fire scenarios that may occur in the building, fire detector locations and characteristics, the effect of automatic suppression systems on the fire, the locations of adjacent buildings and the response and effectiveness of the fire department. The program calculates the required flow rates of water at the time of fire department intervention for suppression of the fire and for exposure protection for each side of the building. These flow rates can then be compared to the total capacity of the fire engines available to determine if existing resources are sufficient. The program has been designed to be interactive, so that the user can immediately see the effects of various parameters on the required water flow rate. Descriptions of case studies are also included to demonstrate the use of this model.