Generation of irregular long and short crested waves in a numerical model for wave propagation

MildWAVE (Troch, 1998) is a numerical mild-slope wave propagation model which is able to generate linear water waves over a mildly varying bathymetry and to calculate instantaneous surface elevations throughout the domain. Wave transformation processes such as refraction, shoaling, reflection, transmission and diffraction are simulated intrinsically. Characterising the wave climate in coastal regions using regular waves is mostly unsatisfactory. Irregular long crested waves are most often used to represent the real sea state. In reality the sea state is however short crested and the waves propagate in multiple directions. So, short crested wave generation is the best approach to model real waves. Both irregular long and short crested wave generation has been implemented in MildWAVE. In order to validate the numerical wave generation module, tests were run in a numerical wave flume and wave tank. The use of the so-called energy velocity appears to be a necessity when using the mild-slope equations. The result of the thesis is a multifunctional numerical model that can be used for different applications, for example to estimate the risk of flooding in a harbour due to wave penetration and overtopping or to predict the influence of coastal engineering structures on the wave propagation. The possibilities of the new MildWAVE model were demonstrated with an extensive application for the Harbour of Ostend. The present situation and two future designs with breakwaters have been compared for both long and short crested waves and for different storm scenarios

Addressing the need for standardization of test methods for self-healing concrete: an inter-laboratory study on concrete with macrocapsules.

Development and commercialization of self-healing concrete is hampered due to a lack of standardized test methods. Six inter-laboratory testing programs are being executed by the EU COST action SARCOS, each focusing on test methods for a specific self-healing technique. This paper reports on the comparison of tests for mortar and concrete specimens with polyurethane encapsulated in glass macrocapsules. First, the pre-cracking method was analysed: mortar specimens were cracked in a three-point bending test followed by an active crack width control technique to restrain the crack width up to a predefined value, while the concrete specimens were cracked in a three-point bending setup with a displacement-controlled loading system. Microscopic measurements showed that with the application of the active control technique almost all crack widths were within a narrow predefined range. Conversely, for the concrete specimens the variation on the crack width was higher. After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack. The quality of the waterproofing was found to be important, as different results were obtained in each absorption test. For the permeability test, 4 out of 6 labs obtained a comparable flow rate for the reference specimens, yet all 6 labs obtained comparable sealing efficiencies, highlighting the potential for further standardization

Influence of prior information on the assessment of concrete strength from a limited number of samples

Annex D of the European Standard EN 1990 "Basis of structural design" allows to determine the characteristic in-situ compressive strength fck from n test results, using a prediction method which is referred to as a "Bayesian procedure with vague prior distributions". The assumption of a vague or uniform prior results in a conservative approach in cases where only a limited number of test results are available. However, in case of concrete, prior information is available in literature based on the investigation of an extensive number of test results

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.Non UBCUnreviewedThis collection contains the proceedings of ICASP12, the 12th International Conference on Applications of Statistics and Probability in Civil Engineering held in Vancouver, Canada on July 12-15, 2015. Abstracts were peer-reviewed and authors of accepted abstracts were invited to submit full papers. Also full papers were peer reviewed. The editor for this collection is Professor Terje Haukaas, Department of Civil Engineering, UBC Vancouver.Facult

The Design Value Method and Adjusted Partial Factor Approach for Existing Structures

In contrast to the design of new structures, the assessment of existing structures often relies on the subjective judgement of the investigating engineer. An objective verification format for existing structures based on alternative partial factors is however feasible, enabling a rather simple and straightforward, but objective and coherent safety evaluation of existing concrete structures by practitioners. The proposed framework is compatible with the current Eurocodes fol the design of new structures, but additionally enables incorporation of alternative values for the target reliability level, alternative values for the remaining working life and also updated information based on, for example, on-site inspection data and data from testing, as all these considerably influence the partial factors in the structural reliability assessment of existing structures. After introducing the framework for the derivation of partial factors, two suitable methods for developing alternative partial factors for existing structures are described and explained, i.e. the Design Value Method (DVM) and the Adjusted Partial Factor Method (APFM). The performance of both methods is investigated by first order reliability method (FORM) based reliability analyses

The extraordinary in decision-making : myth, apology or opportunity?

Robustness, resilience and anticipation are essential aspects of a system’s first line of defence against exceptional hazards and high-impact unexpected events. This paper questions both the principles and the need of digging too deep into the often intangible world of high-consequence low-probability events that have the potential to impact systems and society as a whole. The engineering community has recently taken to referring to certain events as black swans, perfect storms or events caused by a priori unknowable unknowns, as if such appellation would constitute an apology for their sudden occurrence. We show that many of these metaphoric notions are either conceptually inappropriate, mostly from an epistemic point of view; or else, that they have little operational bearing on our knowledge base and on best practice rational decision-making. The case studies illustrate their conceptual and metaphorical role in a world of interconnected networks of everything

Towards a practical probabilistic post-fire assessment for concrete slabs

When a concrete structure has been exposed to fire, a decision has to be made whether the structure should be demolished, can be repaired, or may be used in its current state. However, many uncertainties are associated with both the fire duration and the effect of elevated temperatures on the mechanical properties of the materials. Consequently, the maximum allowable load after fire exposure should be assessed based on reliability considerations. As full-probabilistic calculations are too complex and time-consuming for normal use by practitioners, a reliability-based assessment tool has been developed which determines the maximum allowable imposed load after fire