Wouter Botte

Influence of Design Parameters on Tensile Membrane Action in Reinforced Concrete Slabs

Abstract Reinforced concrete slabs are traditionally designed to carry a specified design load for adequate capacity at ultimate limit state (ULS). In case of an accidental event, however, tensile membrane action can be activated to establish an alternative load path, which will delay or prevent the collapse of the structure. As such, this tensile action increases the bearing capacity, safety and, hence, the robustness of structures. However, research on this important strength reserve is scarce and the residual capacity is commonly not taken into account during the design. In previous contributions of the authors, a unique test set-up was developed and described to investigate the tensile behaviour of slabs under large deformations because of the accidental removal of a support. A set of three real-scale reinforced concrete slabs of a total length of 14 m was tested. The experiments provided a unique set of data that was subsequently used to develop and validate a numerical model. In this study, this numerical model was used to perform a parameter study to identify the influence of the most important design parameters: span length, slab thickness and reinforcement (ultimate strain and geometric ratio); the results of the analysis are presented in this article. Further, the boundary conditions were shown to have an important influence on the development of tensile membrane action and this effect was investigated considering different restraint conditions as well as using the finite element model analysis of a frame.

Structural robustness assessment of concrete frames considering membrane action effects

One way to increase the structural robustness is to take into account membrane action effects in beams and slabs. This membrane action generates an additional load transfer to neighbouring supports, which can considerably increase the load-carrying capacity of the member under consideration. However, the effect of membrane action on commonly used robustness indicators is still unknown. In previous contributions of the authors, a numerical model for reinforced concrete slabs and beams under large deformations was developed and validated. In this contribution, a framework is developed in order to incorporate this numerical model in the analysis of a simple concrete frame in case of column loss, in order to assess the influence of membrane action on commonly used robustness indicators.

Redundancy-based service life assessment of corroded reinforced concrete elements considering parameter uncertainties

Abstract In order to assess the structural reliability and redundancy with respect to deterioration, appropriate models have to be selected which adequately describe the deterioration process. The parameters associated with these models have to be estimated based on statistical inference. In general, the uncertainties that arise from the estimation of parameters are not accounted for in reliability assessment and the obtained structural reliability indices are assumed to be constant values. When parameter uncertainties are considered, the structural reliability index can, however, be considered as a random variable which inevitably influences the full-probabilistic decision-making process. Furthermore, the structural reliability indices which are used in a reliability-based redundancy factor can be considered as random variables. Hence, this redundancy factor itself is a random variable as well. In this paper, a full-probabilistic framework is developed which allows for the service life assessment of reinforced concrete elements subjected to corrosion based on a probability-based redundancy factor and taking into account parameter uncertainties. It is proven that these parameter uncertainties have a significant influence on the lifetime estimates of concrete elements subjected to corrosion. Finally, a simplified method is proposed which allows to incorporate parameter uncertainties in the redundancy assessment.

Tensile membrane action in RC slabs: a parametric study

Reinforced concrete slabs are traditionally designed to carry a specified design load for adequate capacity at ULS. In case of an accidental situation, however, tensile membrane action can be activated in order to establish an alternate load path, which delays or prevents the collapse of the structure. As such, this tensile action increases the bearing capacity, safety and hence the robustness of structures. In this contribution, a validated numerical model is used to perform a parameter study in order to identify the influence of the most important design parameters, e.g. span length, slab thickness and reinforcement properties (ultimate strain). Further, the boundary conditions show to have an important influence on the development of tensile membrane action and this effect is investigated both considering different restraint conditions as well as using a FEM analysis of a frame.

Bayesian updated time-dependent chloride-induced corrosion assessment using redundancy factors

In order to assess the structural reliability and redundancy with respect to deterioration, it is required to select appropriate models which describe the deterioration process. The parameters associated with these models have to be estimated through statistical interference, which introduces uncertainties in parameter estimates. As the structural reliability indices which are incorporated in the reliability-based redundancy factor can be considered as random variable, this redundancy factor itself is a random variable as well. In case additional information becomes available, the distribution function can be updated by taking into account this extra information. In this contribution, a framework is developed, which allows for the incorporation of additional information in the uncertain reliability index and the associated redundancy factor through Bayesian updating. It is shown that in case additional information on a main variable is gathered, this has a significant effect on the (mean) value and uncertainty of the reliability index and the associated redundancy factor.