Untersuchungen zur Homogenität von Bauwerksteilen mit Lasertechniken

Investigations concerning homogeneity of building parts by laser techniques. The subproject B1 “Diagnostics and Quality Control by Non‐Destructive, Contactless Testing Techniques” is working within the CRC 524 on the procedural and measurement technological evolutionary development of the conventional ultrasonic through‐transmission method towards an optical measuring method by application of laser technologies. The aim is the determination of the distribution of elastic characteristic parameters for the evaluation of laboratory test specimens in investigations on durability of concrete and for the actual state of construction elements in the course of revitalising buildings. In this case, a laser induced sound excitation takes place by means of an Nd:YAG‐laser. The sound waves that have been influenced by the investigation object are detected by a laser vibrometer. By applying these methods, both a high lasing rate and a high achievable data density are to be expected since the laser beams in both systems can be deflected optically by means of scanners. Furthermore, a surveying‐technological approach for sound path determination at each pair of measuring points has been developed, which can also be used for the conventional application of the ultrasonic through‐transmission method.     

Europäische Dämmstoffnormen der 2. Generation: Prüfmethoden zur Ermittlung flüchtiger organischer Komponenten (VOC)

2nd generation European Standards for insulating materials and products: test methods for the determination of emissions of volatile organic compounds (VOC) In October 2001 ten “first generation” standards (EN 13162 through EN 13171) were introduced in Europe dealing with insulating materials and products. The new standards now in effect had to be based on the European Construction Products Directive (CPD) and conceptual details had been mandated by the European Commission to the standardization body CEN. Among other properties like thermal conductivity and fire performance the mandate requested to standardize a so called “initial type test (ITT)” for the release of dangerous substances (also called “regulated substances”) to be performed by an independent testing laboratory on behalf of the manufacturer before placing the product onto the market. However, due to the lack of experience and due to a non‐existing European harmonized common method for testing and classification, this property could not be included in the standards in due time and reference was only made to national regulations. Because of this shortcoming, a research project, started in 2003, developed a cost effective and very practical test method based on the emission cell device with a subunit that proved suitable for an initial type test (ITT) for the determination of emissions from thermal insulation materials and products – in particular volatile organic compounds (VOC).     

Zur Neufassung der DIN 4178 “Glockentürme”

To the introduction of the revised German Code DIN 4178 “Bell towers“. The new German Code DIN 4178 replaces the version validated since 1978 for calculation and design of bell towers under bell ringing forces. It contains further aspects of maintenance and restoration especially of historical buildings and gives indications to measurement of oscillation.     

Tragwerke aus Textilbeton – Berechnungsmodelle,Anwendungen

Textile concrete structures – computational models and applications. Structures with reinforcement consisting of textile fabrics are innovative developments in civil engineering. The textile reinforcement embedded in finegrained concrete can be applied for new constructions or supplementary strengthenings. Computational models and applications of textile concrete structures are presented in the paper, which are produced in the Collaborative Research Centre 528. The generalized treatment of uncertain datas is especially pointed out, because data uncertainty influences the structural responses significantly.     

SEM and UV-microscopic investigation of glue lines in Parallam® PSL

? PSL were investigated using scanning electron- and UV-microscopy. In the SEM it was found that resin penetrates predominantly through cut open tracheids and rays. Bordered pits block the flow of resin from cell to cell whereas simple pits are only a minor obstacle. UV-absorbance spectra of cells from the glue line area indicated the presence of phenol-formaldehyde resin in the wood cell wall. Compared to the pattern of absorbance of pure cell wall substance, spectra of cells embedded in the glue showed significant differences which were attributed to the penetration of phenol-formaldehyde resin during the process of gluing.

---

? PSL wurden mit dem Rasterelektronenmikroskop und dem UV-Mikroskop untersucht. Im REM zeigte sich, da? Leim vor allem in angeschnittene Tracheiden und in Holzstrahlen eindringt. Ein Flie?en durch Hoftüpfel konnte nicht nachgewiesen werden, wohingegen einfache Tüpfel ein geringeres Hindernis darstellen. UV-Absorptionsspektren von Holzzellen aus dem Leimfugenbereich deuteten auf das Vorhandensein von Phenol-Formaldehydharz in der Zellwand hin. Die Spektren dieser Zellen wiesen im Vergleich zum Absorptionsverhalten der reinen Zellwandsubstanz deutliche Unterschiede auf, die auf das Eindringen von Phenol-Formaldehydharz w?hrend des Verleimvorganges schlie?en lie?en.

     

Melamine salts as hardeners for urea formaldehyde resins

Various salts derived from melamine and organic acids were prepared and used as melamine substitutes for melamine urea formaldehyde (MUF) resins. The synthesis of these melamine salts and a detailed characterization of their stoichiometry are described. All salts form 1 : 1 or 1 : 2 stoichiometries in a homogeneous reaction. They crystallize during cooling of the hot and diluted reaction mixture. Both ¹³C–NMR and ¹⁵N–NMR data are reported and point toward the formation of real ionic structures. Most salts have higher water solubility than that of pure melamine and are tested for their ability to substitute melamine in MUF resins. The mechanical and chemical properties of plywood panels made up of traditional MUF resins and mixtures of UF resins with melamine salts are investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1654–1661, 2001