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- 2015 (57) (entfernen)
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- Elastic wave propagation (2)
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Eingeladener Vortrag
- nein (16)
The determination of the blast protection level of laminated glass windows and facades is of crucial importance, and it is normally done by using experimental investigations. In recent years numerical methods have become much more powerful also with respect to this kind of application. This report attempts to give a first idea of a possible standardisation concerning such numerical simulations. Attention is drawn to the representation of the blast loading and of the behaviour of the material of the mentioned products, to the geometrical meshing, as well as to the modelling of the connections of the glass components to the main structure. The need to validate the numerical models against reliable experimental data, some of which are indicated, is underlined.
Aktueller Stand der Normung
(2015)
Amplitudes variation of GPR rebar reflection due to the influence of concrete aggregate scattering
(2015)
Dense GPR measurements of rebar reflection amplitudes Show relative variations, which can be in the order of more than 10% - 20%. Former investigations demonstrated that these variations are caused by the heterogeneity of concrete, i.e. due to the inclusion of aggregates in concrete. These amplitude variations make it difficult to analyse single reflection amplitudes in order to determine the rebar diameter or to estimate the concrete deterioration state. In a systematic study we have quantified the statistical variation of the rebar reflection amplitude for concrete covers of 6 cm, 9 cm, 12 cm, 15 cm and 18 cm, for two different grading curves and for the rebar diameters 12 mm and 28 mm. Also the influence of the wavelength has been investigated by using antennas with different centre frequencies in relation to the aggregate size. The results are discussed with regard to a quantitative amplitude evaluation of GPR measurements and also the potential of using these variations for a characterization of concrete material properties.
Combining CO2 Streams from Different Emitters – A Challenge For Transport And Storage Infrastructure
(2015)
The European Directive 2009/31/EC on the geological storage of CO2 envisages an open access of CO2 streams from different emitters to a nation- or even EUwide CO2 pipeline network if CO2 stream compositions meet “reasonable minimum composition thresholds”. As of today it is not known how such “composition thresholds” may be defined and which impurity levels may be viable in practical application.
To set up recommendations for criteria and respective threshold values for CO2 stream compositions, the project “CLUSTER” will investigate how a dynamic interplay – both in terms of mass fluxes and compositions – of CO2 streams from regionally clustered CO2 sources sharing a transport and storage infrastructure will impact corrosion, e.g., of pipelines and plant components, and geochemical alteration of cap rocks and reservoir rocks. In addition, the behaviour of such a highly dynamic CCS system will be considered for an overall optimization of system design including CO2 stream mixing schemes and facilities or interim CO2 storage.
Simulations of concrete on the mesoscale require complex geometry models that resolve single aggregates. Since they fill up to 60-80% of the virtual specimen, efficient algorithms for their placement are necessary.
Event-driven molecular dynamics (EDMD) algorithms using growing spheres are proven to create dense polydisperse sphere packings. In this paper, a modified EDMD algorithm is presented and compared to the widely used random sequential addition algorithm. It reaches denser aggregate packings and saves computation time at high volume fractions.
When meshing the geometry, a minimal distance between the aggregates ensures undistorted elements. It is obtained by increasing the aggregate size during the placement process, which makes the packing problem more challenging. For a given aggregate volume fraction, the presented algorithm maximizes this distance and meshable mesoscale geometries for concrete specimens with more than 70% aggregate content are produced.
In this work an approach for smoothing the oscillations of normal contact is presented. On the other side a higher order time discretization scheme in association with a higher order spatial discretization, like the spectral element method, is used. The contact constraints are reformulated in order to get an explicit equation for the motion.
We present the results of several machine learning (ML)- inspired data fusion algorithms applied to multi-sensory nondestructive testing (NDT) data. Our dataset consists of Impact-Echo (IE), Ultrasonic Pulse Echo (US) and Ground Penetrating Radar (GPR) data collected on large-scale concrete specimens with built–in simulated honeycombing defects. The main objective is to improve the detectability of honeycombs by fusing the information from the three different sensors. We describe normalization, feature detection and optimal feature selection. We have used unsupervised and supervised ML, i.e., classification and clustering, for data fusion. We demonstrate the advantage of data fusion in reducing the false positives up to 10% compared to the best single sensor, thus, improving the detectability of the defects. The methods were evaluated on a concrete specimen. The effectiveness of the proposed approach was demonstrated on a separate full-scale concrete specimen. The results indicate the transportability of the conclusions from one specimen to the other.
The special design of buildings, constructed for nuclear power plants is a particular challenge for the nondestructive testing in the building industry. In particular the major component thicknesses, the degree of reinforcement and surface coating systems make the application of NDT methods difficult. The studies first steps were undertaken to determine to which extent established applications of these techniques are useable in the field of infrastructure buildings. Methods have been evaluated that are already state of the art. So for example the ground penetrating radar was used for locating metallic mounting parts. Furthermore, the low-lying internal structure of the containment was investigated with the ultrasonic method.