Gewalt in der Schule

Vortrag auf der Tagung Bindung, Trauma und soziale Gewalt , 3.-5.12.2004 in Frankfurt am Main

Mechanical potential of eco-OSB produced from durable and nondurable species and natural resins

Oriented strand board (OSB) panels were manufactured with different mixtures of pine and cypress heartwood and resins based on lignin or tannin to develop an eco-friendly wood composite with a natural durability against termite and fungi. Some physical properties and the major elastic moduli of bulk wood as well as of the manufactured panels were determined using different measurement techniques. In addition, a micromechanical model was adapted and validated with the experimental results. The good agreement obtained between the experimental data and model predictions indicates the proper assessment of the most influential parameters, such as raw material and adhesive properties, strand orientation, layer assembly and density profile. A parameter study, enlightening the effect of strand orientation on several elastic constants, enlarges the scope of experiments. We conclude with an optimal combination of resin and wood species mixture resulting in the best performance from a biological and mechanical standpoint

Evaluation of the mechanical properties of cross laminated timber with elementary beam theories

This paper presents a study on the assessment of the mechanical properties of cross laminated timber (CLT) panels based on four-point bending tests. The most recent or well-established analytical theories have been implemented to estimate stiffness and strength properties under loads perpendicular or parallel to the principal plane of CLT panels from laboratory tests. The main objectives were to evaluate each proposed theory in predicting the associated deformation and failure mechanisms and to assess the reliability of the estimated properties with respect to the expected values and in terms of consistency among specimens with different layer configurations. The results indicate that the bending response is on average well represented in the implemented theories for the two cases of loading and in terms of both elastic and strength properties. For loads perpendicular to plane the characteristic rolling shear strength appears to have a significant variability among the different layups for all three applied methods, while for loads in plane the consideration of a combined rolling and torsional shear failure criterion provides more consistent results with respect to a less rigorous approach