Ruben Van Coile

Full-Probabilistic Analysis of Concrete Beams During Fire

Asimplified full-probabilistic calculation tool is developed which is capable of calculating the bending moment capacity of simply supported beams exposed to fire. It is found that the uncertainty with respect to the reduction factors for the material properties at elevated temperatures and the uncertainty with respect to the concrete cover have a negative effect on the safety level corresponding to the design value of the bending moment capacity calculated according to the Eurocode. Furthermore, the model allows an objective comparison of different design alternatives with respect to the safety level.

A Parametric Study on Concrete Columns Exposed to Biaxial Bending at Elevated Temperatures Using a Probabilistic Analysis

Concrete columns exhibit a loss of both strength and stiffness during fire. The current contribution focusses on the fire performance of concrete columns subjected to biaxial bending in combination with axial loads, as such information is rarely available in literature. First, the second-order effects are quantified using a numerical tool. In Eurocode 2, the most important parameters which influence second-order effects of columns during fire are the slenderness ratio, fire duration as well as the magnitude of the axial loading. The influences of these parameters are investigated using a parametric study. Additionally, from the viewpoint of fire safety and structural reliability, uncertainties should be incorporated in the second-order analysis in order to achieve reliability-based design guidelines. Hence, the numerical tool is further developed in order to take into account uncertainties. Furthermore, the tool is validated using the Eurocode provisions and existing experimental data, while considering an ISO 834 standard fire. Finally, examples are given for the fire resistance design of concrete columns.

Decision support tool on investments in life safety based on sampling theory

Abstract For decisions related to investments in societal safety and health, it is often difficult to balance the discretionary competence of decision-makers with theoretical optimum levels of investment. While removing day-to-day decisions about risk from the political arena would arguably result in better decisions, a full depoliticisation is not desirable since public and private risk preferences cannot simply be neglected without negatively affecting the perception of risk and inducing a democratic deficit. Therefore, a decision-making tool has been developed which allows for narrowing the scope of possible decisions for the decision-maker, based on predetermined maximum acceptable deviations from the theoretic optimum investment level. These maximum acceptable deviations should be established upfront on a general basis and may subsequently be applied on a case-by-case basis. In this paper, the basic calculation concepts are explained and a detailed example study is presented in which limits for the target safety level of concrete slabs are determined under some specific considerations.

Probabilistic FAD and Ductile Tearing Assessment

The assessment of cracks in pipelines is one of the key elements for the integrity verification and the remaining lifetime evaluation of pipelines. This crack assessment is commonly performed through Failure Assessment Diagram (FAD) methods in which two failure criteria are combined, i.e. brittle fracture and plastic collapse. FAD assessments are, however, highly deterministic and do not take into account the various uncertainties that affect cracking. A probabilistic FAD tool is developed that accounts for these uncertainties and determines the probability of failure as a function of the crack dimensions, steel grade and pipeline characteristics. The failure probabilities are associated with a reliability index β, which is commonly used to describe structural safety. The results allow an objective comparison of different cracks across a wide range of operating characteristics, and can be used to construct a reliability-based inspection plan. Multiple parameter studies are executed in which the influence of specific variables on the reliability level is quantified.

Computationally efficient estimation of the probability density function for the load bearing capacity of concrete columns exposed to fire

Concrete columns are critical for the stability of structures in case of fire. In order to allow for a true Performance Based Design, the design should be based on considerations of risk and reliability. Consequently, the probability density function (PDF) which describes the load-bearing capacity of concrete columns during fire exposure has to be assessed. As second order effects can be very significant for columns, traditional probabilistic methods to determine the PDF become very computationally expensive. More precisely, for most current numerical calculation tools (e.g. Finite Element), the computational requirements are so high that traditional Monte Carlo simulations become infeasible for any practical application. In order to tackle this, a computationally very efficient method is presented and applied in this paper. The method combines the Maximum Entropy Principle together with the Multiplicative Dimensional Reduction Method, and Gaussian Interpolation, resulting in an estimation of the full PDF requiring only a very limited number of numerical calculations. Although the result is necessarily an approximation, it gives very good assessment of the PDF and it is a significant step forward towards true risk- and reliability-based structural fire safety.