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Influence of impact angle and real target properties on drop test results of cubic containers
(2017)
Drop test scenarios with cubic containers without impact limiters at interim storage sites or in a final repository have been investigated by numerical simulations. An ideally flat drop is impossible to conduct as a free fall of a container even under laboratory conditions. Dynamic stresses and strains inside the container structure are sensitive to the impact angle. Even very small impact angles cause remarkable changes in the experimental or numerical results when a flat bottom or wall of a container hits a flat target. For drop tests with transport packages the International Atomic Energy Agency (IAEA) regulations define an essentially unyielding target. In contrast, potential accident scenarios for storage containers are derived from site-specific safety analyses or acceptance criteria in Germany. Each interim storage site or repository has a yielding or so-called real target with individual structural and material properties. The real target acts as a kind of impact limiter. A more conservative container design is required if the impact limiting effect of the target is not considered.
Based on the state-of-the-art research and advances in dynamic testing methods in the past decades, the research project aims to develop a non-destructive methodology to determine the axial forces and real stress state in existing truss structures making use of the vibration signatures of the natural frequencies and mode shapes. Furthermore, it aims to estimate the joint rigidity of trusses as well as to design structural health monitoring schemes for the safety of existing truss-type structures.
Measurements of downburst wind loading acting on an overhead transmission line in northern Germany
(2017)
Along an overhead transmission line in Northern Germany, a unique instrumentation of anemometers and force measurements is installed. Details of this test line with wind measurements along a horizontal axis are given. A recent event of a presumable downburst wind event is analyzed by means of available data and precedent works on thunderstorm analysis. The measured response of the conductors at the suspension tower is investigated and compared with time domain simulation of a finite element model.
Suction Bucket Jackets (SBJ) are found as a suitable alternative to driven piles for the support of foundations for offshore wind energy converters. In the case of jackets or multipods, a predominant vertical load is to be expected. The effect of such a tensile loading is the generation of suction in the soil inside the bucket which leads to an increment of tensile capacity. This paper aims to study the bearing behaviour of a suction foundation by taking into account how the soil permeability and the loading rate influence the foundation behaviour. Moreover, after submitting the structure to a storm load, the bearing capacity is studied again, in order to see the effect of such a load on the bucket's bearing behaviour. This study is carried out by means of Finite Element numerical simulations based on the formulation of Biot's equations combined with a constitutive model that reproduces the key aspects of cyclic soil behaviour in the frame of Generalized Plasticity.
The paper presents a comparison between different numerical modelling approaches aiming to simulate the in-plain behaviour of three types of earthen materials, namely adobe masonry, rammed earth and cob. For this purpose, uniaxial and diagonal compression tests were carried out, which allowed determining important mechanical parameters, such as compressive strength, Young’s modulus, Poisson’s ratio, shear strength and shear modulus. Furthermore, the tests allowed assessing the level of non-linear behaviour of the respective stress strain relationships as well as the failure modes. The experimental results were then used for the calibration of numerical models (based on the finite element method) for simulating the non-linear behaviour of the earth materials under in-plane shear loading. Both macro- and micro-modelling approaches were considered for this purpose. The procedures adopted for model calibration established the reliability of various modelling strategies for the different loading conditions. The simplified Approach based on macromodelling shows a satisfactory accuracy and low computational costs. The results reproducing the uniaxial compression are in good correspondence with the post-elastic behaviour observed in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with higher computational cost, represents a suitable tool to predict the adobe masonry and rammed earth collapse mechanisms.