Development of a full probabilistic QRA method for quantifying the life safety risk in complex building designs

The present paper describes part of a framework for the development of a risk assessment methodology to quantify the life safety risk for people present in buildings in the context of the creation of a fire safety design. Complex building designs and regulations drive engineers towards quantitative risk analysis (QRA). One of the key aspects in quantitative risk analysis is finding the proper balance between simplification of the scope by using different models and taking important case specific features into account. In other words, a proper balance needs to be found between modelling cost versus accuracy. Increasing the accuracy by means of sophisticated models will increase the computational cost or might force to reduce the amount of representative scenarios to be analysed. In this paper, a method is discussed which quantifies the safety level with regard to building configuration detailing. Attention is given to the accuracy of the deterministic models, and at the same time approaches are analysed which reduce the computational cost. The output for the quantification of the life safety level of the building is determined by means of a procedure in which several steps are taken to obtain the risk outcome. The final risk value is calculated with regard to a failure probability in analogy with structural engineering

Simplified modelling of the performance of concrete tunnels during fire and post-fire damage classification

The performance of concrete tunnel structures during and after fire is not well understood. This is an obstacle to the adoption of risk-based approaches for fire safety design of tunnel structures. Upon the request of the Belgian fire safety consultancy FESG, a simplified assessment of the collapse probability and post-fire damages for a reference tunnel structure has been made. The structural system is modelled through 2D beam finite elements, where spalling rates have been assumed based on available literature data. Structural stability is verified for both the heating and cooling phases of the fire. In those cases where the structure survives up to burnout, the residual deformations and thermal damage to the tunnel structure are assessed

Our soil map as cultural heritage: what of the Belgium soil survey project should be preserved and what is being lost?

Between 1947 and 1991, soils of Belgium were mapped to establish a systematic inventory of the country soil resources. Field observations were done by soil auger to a standard depth of 1.25 m and at a mean density of 2 points per hectare. Cadastral plans at scale 1:5,000 where used for georeferencing field observations and for delimiting map units, subsequently generalized on the 1:10,000 topographic base map. The final map was published on sheets at scale 1:20,000 along with descriptive texts. Besides, data on about 15,000 described and analyzed soil profiles were reported in technical annexes. With the advent of computers, data on soil profiles have been transfered into relational databases and soil sheets have been digitized. Coding of the data rendered them more accessible, but inevitably implied a standardization and hence a reduction of some information. Still most of the soil surveyors have already passed away, besides their intangible expert knowledge, a wealth of information is also being lost when their field notes, unpublished reports, minutes of meetings and draft maps are being disregarded. The map legend was developed during the first decade of the survey, reflecting state of knowledge on soil formation and their relative importance for agricultural land-use in the 1950s. To guarantee that future generations will be able to appreciate the value and concepts underpinning the soil information, it is important that at least a minimum set of such historical documents would be preserved, analyzed and documented.Projet de Cartographie Numérique des Sols de Wallonie (PCNSW

Development of a risk assessment method for fire in rail tunnels

In the field of rail tunnel fire safety the concept of risk analysis plays an important part in the creation of a fire safety design that meets the objectives of the different stakeholders. For rail tunnels, there is very little information available about how to perform a quantitative risk assessment. Therefore, research on this topic has been conducted in order to develop a risk assessment methodology able to quantify the risk for people present in a tunnel. The problem is approached by means of an extensive literature study in which the deterministic cause of fires in tunnels is investigated. From this, the major contributing factors leading to disastrous events are determined. Next, a bow-tie structure was chosen for representing the risk assessment model. For the construction of the event tree part of the bow-tie, a closer look is taken at past accidents. From these experiences, the most important factors are determined to be: Human behaviour, fire growth curve, ventilation conditions, safety systems and population distribution. These factors are incorporated into the event tree by using pathway factors. After determining these factors, the frequencies are calculated for each branch outcome. The data obtained for these frequencies is based on European research projects, fault tree analysis and engineering judgement. For the determination of the consequences, the method is assisted by three integrated models: The Smoke spread, Evacuation and Consequence model. The models can take all types of geometry and materials, human behaviour and different susceptibilities of people for smoke into account. Together, they determine the possible number of fatalities, by means of a FID value, in case of a fire in a rail tunnel. The final risk is presented by the expected number of fatalities, the individual risk and the societal risk. The societal risk is demonstrated through visualisation of an FN-curve

CFD study of relation between ventilation velocity and smoke backlayering distance in large closed car parks

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Classification de sols, légende de cartes et logique SIG : expérience suite aux travaux de conversion de la légende de la Carte des Sols de la Belgique dans le système international WRB

A systematic soil survey of Belgium was conducted from 1948 to 1991. The purpose was to have a soil information base adequate for boosting agricultural production after the Second World War. Field surveys were done at the detailed scale of 1:5000, while the maps were published at a 1:20,000 scale. To enable soil surveyors to identify soils in the field, an original soil classification was developed based on readily observable physical and morphogenetic characteristics. Within the European Union, the World Reference Base (WRB) for Soil Resources (IUSS Working Group WRB, 2007), has been adopted as the common classification system. As soil surveys in most European countries were conducted independently, the challenge now is to convert the national legends into a common WRB legend. In Belgium, such a conversion is being implemented and we present some lessons learned in relation to classification and map legends. The legend of the soil map of Belgium is based primarily on soil texture, drainage status and profile development. “Soil series” are defined in an open and non-hierarchical structure by combining these three categorical variables, and to which modifiers can be added such as parent material, stoniness or depth to a substratum. The WRB-2007 classification is based on diagnostic features defined by morphological, physical and chemical properties. The conversion of the legend of the soil map of Belgium to WRB is based on insights gained from classifying, so far, more than 360 legacy soil profiles in combination with field observations. From these insights, heuristic rules have been deduced regrouping soil series into Reference Soil Groups (RSG) and for which some qualifiers could also be identified. Other qualifiers were determined by relying on databases of the legacy soil profiles. To take regional variability into account, the conversion is done by physiographic zone. Converting the legend of the soil map of Belgium to WRB actually leads to a regrouping of soil series into broader WRB categories and which can neatly be represented on 1:50,000 scale maps. Hence, it does not imply substituting one classification with another one. Users, who would need the detailed information, can still refer to the detailed symbols of the soil series. The regrouping of soil series has been made possible thanks to the flexibility of WRB for combining various qualifiers. However, as the WRB-2007 classification leads to a varying number of qualifiers it is less practical for constructing map legends. Therefore, the WRB-2010 guidelines (IUSS Working Group WRB, 2010) propose to organise qualifiers in main and optional ones with priority rules for the main qualifiers. As illustrated in Table 1, this approach may highlight, or hide, some qualifiers inconsistently. When for example only two qualifiers are retained in a map legend, the qualifier Endogleyic of stony, poorly drained Albic Podzols will not be indicated, while it will be indicated when such soils are not stony (Table 1). Moreover, the proposed hierarchy is sometimes also inconsistent when compared across Reference Soil Groups (RSG) as illustrated for the Arenosols and Regosols (Table 1). These drawbacks could be avoided if qualifiers would be organised into thematic groups ― such as profile development, texture, drainage, depth of substratum and fertility ― rather than by ranking them. Grouping qualifiers thematically would have the advantage to give more flexibility to the map user working with GIS, and indeed, it would render WRB a more “GIS logic” classification system.Omzetten van de legende van de Belgische bodemkaart naar het internationale World Reference Base systee

Quantifying the influencing parameters for egress in rail tunnels: an attempt to bridge the gap between research and FSE

The paper will describe the importance of taking into account the influencing parameters for egress in rail tunnels, such as the effect of smoke on the walking speed. More in particular the gap between research and fire safety engineering will be identified. The available data from research will be listed for the influence factor of visibility on the walking speed and the influence factor from possible mitigating measures. The practical application of the quantification of the available data for FSE in rail tunnels will be analysed. A proposition will be made to fill the gap between the research and FSE for this topic. The remainder of the paper will elaborate more on the proposition of rules of good practice for taking into account the influencing factors in egress calculations. These will describe how the influence factors can be integrated in a Quantitative Risk Assessment model that was developed specifically for evaluating life safety in rail tunnels