The international FORUM of fire research directors: A position paper on verification and validation of numerical fire models

The international FORUM of Fire research directors periodically takes positions on issues dealing with the direction and implementation of fire research with the potential for significant impact on safety and/or global practices, standards and test methods. This short communication represents the FORUM's position on the validation of numerical fire models. These models are increasingly being used on the fire protection engineering community, and have the potential for a significant impact with the increasing acceptance of performance based fire codes. The FORUM position is to require verification and validation of these models. Activities should include; code verification to identify and reduce coding errors, calculation verification to establish appropriate model usage, and model validation to provide a quantitative assessment of the predictive capabilities of a model. Peer-reviewed documentation of these activities should be published in the open literature. The importance of verification of models for fire phenomenon, and an overview of these activities, are discussed.     

Cost-effectiveness of protective measures for single-layer reticulated domes subject to impact loading

Many spatial structures, including some public buildings, were built in the last thirty years, but considerable uncertainty remains with respect to their structural performance under impact loading. This paper focuses on single-layer reticulated domes because they encounter significant safety hazards when subject to terrorist attack. Three kinds of protective measures are proposed for mitigating the probability of global structural collapse under impact loads. The risk reduction measures include Lighter Roofs, Whole Member Strengthening and Strengthening of Key Members. These measures are compared and evaluated with respect to risk reduction. A technique is then used for assessing the cost-effectiveness of these measures. An example of a single-layer reticulated dome subject to airplane impact is used to illustrate when the protective measures are cost-effective, with quantifying costs being useful in the decision-making process.     

Methodological approach of construction business failure prediction studies: a review

Performance of bankruptcy prediction models (BPM), which partly depends on the methodological approach used to develop it, has virtually stagnated over the years. The methodological positions of BPM studies were thus investigated. Systematic review was used to search and retrieve 70 journal articles and doctoral theses. Their “general methods” and “philosophical underpinnings” were investigated using summary of findings tables and meta-analysis. “General methods” results showed positive trends in terms of techniques being used, error cost consideration and model validation, with some use of skewed data being the main drawback. For “philosophical underpinnings”, positivism paradigm was discovered to be at the core of BPM studies. This is deemed inadequate because of the need to consider industries’ dynamism, financial variables flaws and social factors which actually lead to the financial status of firms. The pragmatism paradigm using mixed method is proposed. A research design framework for executing the proposed methodology is presented. This will help BPM developers go through more rigorous and robust methodology to deliver better and more valid models. Limitations of study include not reviewing studies not reported in English language and impact of different countries’ accounting practices on ratios. Limited availability of theses’ database resulted in reviewing only four theses.     

Benchmark experiments for moisture transfer modelling in air and porous materials

The presence of hygroscopic materials has a large impact on the moisture balance of buildings. Nowadays, HAM (Heat, Air and Moisture) models are widely used to investigate the role of hygroscopic materials on the performance of buildings, i.e. on the building envelope, the indoor climate and valuable objects stored within the building. Recently, these HAM models are being coupled to CFD (Computational Fluid Dynamics) models to study the moisture exchange between air and porous materials on a local scale (microclimates), or to BES (Building Energy Simulation) models which focus on the interaction between air and porous materials at building level. Validation of these numerical codes is essential to gain confidence in the codes. However, available experimental data are rather scarce.     

Comparison of theoretical and statistical models of air-conditioning-unit usage behaviour in a residential setting under Japanese climatic conditions

Occupant behaviour and its relation to energy use within the built environment have become more important in recent years. This paper first describes three statistical models based on a field survey and measurement for summer and winter respectively, which can be used to predict the percentage of air-conditioning-units used during night-time with a realistic assumption of human behaviour. The first statistical models are the results of a common approach to connect the occupant behaviour with the mean outdoor air temperature through the use of logistic regression. The present investigation extends these models to one including further external factors such as the mean outdoor air temperature the night before. The final models also include the preference and background of the individual subject. The statistical models are then compared to a theoretical model of occupant behaviour based on a comprehensive literature review. In conclusion, mean outdoor air temperature of the foregoing night(s) had a major impact on occupant behaviour during summertime, but a minor one in wintertime. The impact of the individual factors had the same magnitude as the external factors in summer, but an eight times higher impact in winter. Detailed research on the occupant behaviour is proposed to clarify further aspects of the theoretical model.     

Fire Resistance Performance of Lightweight Wood-Framed Assemblies

There are extensive efforts underway around the world, including those by the National Research Council of Canada (NRC), to develop fire resistance models. NRC is currently developing thermal and structural models for lightweight wood-framed assemblies, in collaboration with the Canadian wood industry. These models will be used in NRC's risk-cost assessment models as well as in the development of fire resistance design equations. To aid the development of fire resistance models, NRC has just completed, as a first step, a literature review on the efforts made to predict the fire resistance of lightweight wood-framed assemblies, with the objective of determining the gaps that need to be filled. This paper presents the results of this literature review, which include: standard versus real time-temperature fire curves, experimental studies, available fire resistance models and design methods and the identification of their limitations, charring of wood, and material properties of assembly components at elevated temperatures.     

Determination of accidental forklift truck impact forces on drive-in steel rack structures

The paper addresses the problem of determining the accidental forklift truck impact forces on steel storage racks. Based on first principles of mechanics, simple models of a loaded forklift truck and a drive-in racking structure are presented. Model masses, as well as stiffness and damping coefficients are calibrated against experimental results obtained from tests of a forklift truck and a drive-in racking structure. Comparisons between experimental results and solutions obtained from the simple mechanical models show that the simple models accurately reproduce the static and dynamic behaviours of their associated structures. Based on the drive-in rack impact test results presented in a companion paper (Gilbert and Rasmussen, submitted for publication) [1] and the simple mechanical models for drive-in racks, actual impact forces are calculated and presented. Finally, using the impact test results and the simple mechanical models, the actual motion of the forklift truck body is calculated. This motion, being a common characteristic to all drive-in racking impacts, allows impact forces to be obtained for various pallet loads, impact elevations and rack characteristics. Thus, the paper concludes with a general method for calculating forces generated under forklift truck impact.     

Development of the revised drinking water standard for chromium

Comprehensive regulations are being developed to limit human exposure to contamination in drinking water by the United States Environmental Protection Agency (EPA) under the authority of the Safe Drinking Water Act (SDWA). These regulations are being developed in several phases and include synthetic organic chemicals, inorganic chemicals, microbiological contaminants and radionuclides. This paper addresses the fundamental concepts and approaches used by EPA in setting drinking water regulations and how EPA is using these concepts to revise the drinking water standard for chromium.     

Simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems

This paper describes the development of a simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems. The simplified design tool is able to account for key differences between UFAD and traditional mixing overhead (OH) systems. These include: (1) difference between design day cooling load profiles, (2) impact of a thermally stratified environment for UFAD versus well-mixed for OH, and (3) impact of heat transfer (temperature gain) in underfloor air supply plenums. The new design tool allows the use of a familiar load calculation procedure for OH mixing systems as input to the UFAD design tool. Based on 87 EnergyPlus simulations, four regression models have been developed to transform the OH cooling load into the UFAD cooling load, and then to split this total load between the supply plenum, zone (room), and return plenum. The regression models mainly depend on floor level, and position (interior or perimeter) and orientation of the zone under analysis. Although considered in the analysis, supply air temperature, window-to-wall ratio, internal heat gain, plenum configuration, climate, presence of the carpet and structure type do not strongly influence the developed models. The results show that, generally, UFAD has a peak cooling load 19% higher than an overhead cooling load and 22% and 37% of the total zone UFAD cooling load goes to the supply plenum in the perimeter and interior, respectively.     

Value proposition on interoperability of BIM and collaborative working environments

Interoperability has become recognized as a problem in the AEC sector due to the many heterogeneous applications and systems typically in use by the different players, together with the dynamics and adaptability needed to operate in this sector. In spite of the availability of many proposals to represent standardized data models and services for the main business and AEC activities, the goal of seamless global interoperability is far from being realized. Instead of focusing only on the technological level, the authors suggest that seeking solution(s) to the interoperability problem should include an analysis of an interoperability value proposition in the AEC sector, i.e., at the business level. The model presented for measuring the impact of interoperability at the enterprise level considers the interaction type, breadth of the impact, and geographic range dimensions. A specific analysis of actual and potential value of interoperability in the AEC sector is also conducted.     

Regionalisation of impervious area parameters of urban drainage models

Stormwater drainage models are increasingly being used in design and analysis of urban drainage systems. If these models are to be used for ungauged drainage systems for which no storm and corresponding flow data are available, then the model parameters have to be estimated through regional equations. These regional equations define the model parameters via measurable catchment properties. In this study, regional equations of two impervious area parameters, namely directly connected impervious area percentage (DCIA) and its depression storage (DS_i ), were developed for use in urban drainage models, using 15 gauged urban catchments in Melbourne Metropolitan area (Australia). The ‘small’ storm events of these gauged catchments were first used to calibrate the impervious area parameters, since the ‘small’ storm events produce runoff only from the impervious areas. These calibrated impervious area model parameters were then analysed with several measurable catchment properties to derive the regional equations. The results of the study revealed that DCIA was depended only on household density of the catchment, while DS_i was not correlated with any of the catchment properties analysed.     

Capabilities and limitations of thermal models for use in thermal comfort standards

Thermal models of the human body and its interactions with the surrounding thermal environment are often proposed, and to some extent are used, as the basis for thermal comfort standards. These models range from simple, one-dimensional, steady-state simulations to complex, transient, finite element codes with thousands of nodes. The models are potentially very useful in that they provide a straightforward means to incorporate the numerous physical variables that affect comfort. Some models can be applied to complex situations which would be difficult, if not impossible, to reflect in simple charts or equations. Whether simple or complex, all of these models have limitations for use in standards. These limitations include the accuracy of the physical simulation and the accuracy of the inputs to the model. Perhaps, the biggest limitation is the accuracy with which comfort perceptions can be related to the physiological variables simulated in the thermal models.     

Projecting employment in a transportation planning land use model

Large scale computer-based land use simulation models are being used increasingly in the transportation planning process. This paper discusses one aspect of these models' development: the projection of employment. More specifically, it describes the process of employment projection in the Georgia Transportation Planning Land Use Model, a rural transportation corridor impact analysis model. The employment projection method chosen for use in the Phase I model is shift and share combined with regression analysis to incorporate the impact of transportation facility improvements. Further refinement is needed to better incorporate transportation and other locational factors.     

Modeling Sorption Transport In Rooms And Sorption Filtration Systems For Building Air Quality Analysis

Adsorption, desorption and chemisorption are known to impact the dispersal of volatile organic and chemically reactive compounds in buildings. These same three processes may be used to advantage to control the levels of these compounds indoors using building sorption filtration devices. To add to the understanding of these processes, to provide the means to predict the impact of these processes on human exposure and to provide the tools needed to design gaseous filtration systems to mitigate the exposure to these compounds, a general approach to modeling the dynamics of these processes is presented. Equations are presented to account for the elemental advection, diffusion, sorption, and chemical transport steps affecting single component sorption dynamics in rooms and sorption filtration systems. These element equations are based on general principles and formulated in terms of fundamental physical parameters that may be determined using standard procedures. Models to predict room and sorption filtration system dynamics are formulated using assemblages of these element equations and a series of simplified models of these systems are derived. Initial applications to model single-component sorption transport in rooms and sorption filtration systems indicate that the approach has the potential to provide accurate predictions providing the sorption and chemical characteristics of the sorbate-sorbent system being considered are well-characterized. This potential is, however, compromised by the lack (or present uncertainty) of fundamental data relating to sorption equilibrium, porous diffusion, surface chemistry, and boundary layer mass transport     

Analytical quantification of airflows from soil through building substructures

Soil gas pollutants (VOCs, radon, …) have long been known to intrude into buildings through various openings, e.g., cracks and gaps in the foundations. As yet no model has been developed which can quantify this rate of flow whilst taking into account various substructure configurations. This is due to the complex phenomena that need to be consider and particularly to the difficulty in estimating pollutant flows at soil-building interfaces. In this paper analytical models have been developed to quantify these flows. The models have been developed for some typical substructure configurations: slab-on-grade, basement and crawlspace. The inputs of these models include particularly the foundation wall depth and the slab permeability. The analytical models have been compared to existing analytical models for one of the configurations. Moreover a 2-D finite element model has been used for numerical comparison. The models are presented as pressure-flow relationships and can be integrated into risk assessment tools in order to study the impact of soil gas pollutants on indoor air quality.     

The impact of a delivery project's business model in a project-based firm

If projects are independent business organizations having goals of their own instead of being direct subordinates to the parent firm, then project-level goals might contradict those of the parent firm. This raises an empirical question on the impact of delivery projects in a project-based firm. We use the business model concept to study the mechanisms of generating revenues in five delivery projects in a case firm from the mining and metallurgical industry. Our findings suggest that although project-level business models are often derived top–down from firm-level business models, projects also create autonomous business models that have a bottom–up effect on the firm by shaping the existing business models or creating completely new ones. These results strengthen the understanding of the dynamic relations between a project-based firm and its delivery projects.     

Simulation of dynamic response for steel fibrous concrete members using new material modeling

Present investigation includes formulation of new nonlinear material constitutive mathematical models of steel fiber reinforced concrete (SFRC) material depending on many experimental data available in literature. Eight-node degenerated plate elements were used to investigate the dynamic performance of SFRC slabs and beams under blast and impact loadings. Two models are used to simulate the compressive behavior of fibrous concrete material namely the elastic perfectly plastic and strain hardening plasticity models. Dynamic yield function is assumed to be a function of strain rate. Geometrical nonlinearity in the layered approach is considered in the mathematical model, which is based on the total Lagrange approach taking into account Von Karman assumptions. Implicit Newmark with corrector–predictor algorithm was adopted for time integration solution of the equation of the motion. Concrete crack pattern has been determined according to smeared fixed crack approach. Present numerical outputs show suitable agreement with experimental results available in literature which include deflections and failure pattern.     

Quantification of climate change effects on extreme precipitation used for high resolution hydrologic design

Design of urban drainage structures should include the climatic changes anticipated over the technical lifetime of the system. In Northern Europe climate changes implies increasing occurrences of extreme rainfall. Three approaches to quantify the impact of climate changes on extreme rainfall are studied, all based on output from historical rain series of the present climate and output from Regional Climate Models. Two models are applied, one being based on an extreme value model, the Partial Duration Series Approach, and the other based on a stochastic rainfall generator model. Finally an approach is based on identification of areas, where the present climate resembles the anticipated future climate for the region in question. The results indicate that design intensities in Denmark are likely to be increased by 10–50% within the next 100 years. The increase in design intensities depend on the duration and the return period in question.     

运用虚拟现实技术辅助可持续建筑参与式设计

参与式设计方法已经被广泛应用于可持续建筑设计。虚拟现实技术创造出的多维虚拟环境能为参与式设计过程中、有着不同知识背景的参与者提供交流平台，并促进知识传递。实际案例分析基础上的比较研究显示．在建筑设计的不同阶段，运用虚拟现实技术来辅助决策的效果有所不同——在设计初期时所起的作用有限，随着模型细节的深化，其在设计后期促进交流时效果显著。     

Analysis and calibration of default steel strip pullout models used in Japan

The calibration of default pullout capacity models for smooth and ribbed steel strip reinforcement, used in reinforced soil walls in Japan, was carried out more than two decades ago and was based on a small number of physical tests available at that time. The writers have collected and organized a much larger database of more than 600 laboratory pullout box and in situ pullout tests from among the Japanese literature. The new database is a useful reference for design engineers to match project-specific soils to previous pullout tests and to check the accuracy of the current lower-bound design curves proposed in the late 70s and 80s. Today, only the ribbed-type steel reinforcement strips are used. The new data show that a three-parameter exponential function better captures the trend in pullout data for ribbed steel reinforcement than the current bi-linear models adopted from European practice. The formulations also have the advantage of being smoothly continuous with depth. Parameter values are determined for default pullout models that can be used in load and resistance factor design (LRFD) and for the current lower-bound (factor of safety) allowable stress design (ASD). The current PWRC model and a newly proposed model for ribbed steel strip reinforcement, that include the soil coefficient of uniformity (U_c) in their formulations, are shown to be no more accurate than the simpler default models without this term.