VOLUME 54, ISSUE 6/2013

For using bamboo as a construction material, the behaviour under static and cyclic load is of interest. Whereas studies on cyclic loading of bamboo do not exist, in the present study fatigue tests were performed on the bamboo species Phyllostachys pubescens and Guadua angustifolia. In order to determine the fatigue strength test, specimens were made of the outer tube wall region with and without nodes. On the basis of SN curves (SN – stress amplitude (S) and number of cycles to failure (N)) numbers of cycles were determined on different load steps at constant stress amplitude. Using the arcsine√P-transformation the statistical analysis and visualization was performed in SN diagrams. The results are presented in part 2 of this publication.

Determine the age of wooden objects is a classic application of dendrochronology. The procedure, especially sampling and measurement of annual ring widths, depends on the nature of the object to be examined. The most important prerequisite for a successful age determination represents the quality of the used standard chronology. Through years of work in the field of dendrochronology and the related analysis of several thousands of samples, such chronologies are available at the Chair of Forest Utilization for all important construction timbers in the regions of Saxony, Thuringia and Brandenburg.

An established technique to obtain dark colour tones, in particular of tannin-rich wood species such as oak wood, is their smoking. This technique consists in the wood treatment with ammonia. It is connected with the formation of acidic acid and acetamide. In addition, considerable amount of ammonia remain within the treated wood. These compounds are subsequently emitted from the wood any may cause problems particularly with products requiring registration. The treatment duration decreases remarkably when the treatment temperature is raised. In addition, the subsequent emission of ammonia was reduced by 66 % at a treatment temperature of 50 °C. The emission of acetamide remarkably decreased even at a treatment temperature of 35 °C. No explanation could be found for the irregular fluctuations of the acetic acid emission.

In this study, laminated lumber of pine (Pinus sylvestris L.), oak (Quercus petrea L.) and beech (Fagus orientalis L.) was investigated. For gluing one 2K-PVAc (D4) were used. The effect of the number of wood layers (three, five and seven-layer) and the influence of the change of the relative humidity were investigated. The sample preparation was carried out at 20 °C and 65 % relative humidity. The tests were taken with the conditioned samples at 20 °C and 35 %, 65 % and 95 % relative humidity. Examined parameters were the dimensional stability, the bending strength and modulus of elasticity (bending). As expected, the dimensions of the samples were reduced as a result of the lower humidity. In case of the increased humidity, the dimensions of the samples were increased. The highest detected dimensional changes were at the five-layer laminated wood samples with about 6 %, in contrast the smallest dimensional changes had the three-layer samples with only 1 %. The bending strength was increased in climate 20/35 compared with the values from the climate 20/65. Depending on the species, the increases amounted between 13 and 27 %. The modulus of elasticity increases by approximately 13 % for hardwoods and only 1 % in the case of pine. The bending strength decreases of about 18 % due to the increased relative humidity of 95 %. The modulus of elasticity was decreased with about 3 to 7 %.

Algae and wood staining fungi on wood based materials in outdoor exposure affect not only the optic but also the performance, as for example the safety-related slip property at deckings. A prediction of an infestation risk by microorganisms and the change of the slip properties of deckings during the usage are complicated because of the lack of suited test standards. By means of natural weathering and laboratory tests with deckings from wood and WPC, algae and fungus species were determined and a lab test for the determination of the algae resistance was refined. During the two years of weathering it was found a slight infestation by algae but a heavy infestation with wood stain fungi in dependence of the specific material. Furthermore the ability of pendulum test and ramp test (each with wetted surface) for the estimation of slip properties during the weathering was checked and test methods were developed. Both tests were suited for wood and WPC. Different slip resistances of the new materials equalled during the weathering time in the most cases.

Small and medium-sized enterprises are challenged by fulfilling market demands for environmentally benign products, proven by transparent and reliable evaluation such as assessments based on a life cycle approach. In the assessment two different types of woodpolymer composites (WPC), differing in composition and geometry are compared. Functional unit is 1 m² covered terrace. Data sources are industry and the database ecoinvent (including transports). The impact assessment is done with CML 2001. The impact categories assessed are global warming potential, acidification potential, ozone depletion potential, photochemical ozone creation potential, and eutrophication potential. Inventory shown is cumulated energy demand. Results show that in all impact categories materials provision and manufacturing are the key driver.

The chemical changes of the wood matrix which are caused by the thermal treatment can be explained by spectroscopic and chemical analysis. From the results, predicates can be derived about the quality of heat-treated wood. However, the methods have in common that they require long test times, high cost and/or the interpretation or evaluation of the results on a high skill level of the employees. Therefore only the IR spectroscopy appears to be a suitable method for rapid, operational and online quality control of the TMT material. The direct testing of biological resistance also cannot be used for internal quality control due to the very long test times.

Building services installations are normally also led through components forming fire compartments. The penetrations required for that must be sealed off in terms of fire protection. Examples of incorrect penetrations are given in Mayr und Battran (2007). Due to the increase in multi-storey timber houses the issue is getting more relevant. However the testing standards have only defined concrete constructions. In the framework of a research project funded by innovative companies the influence on the fixing and the charring of the timber structure has been analysed. The results and solutions for penetrations of water-bearing lines, air-ducts and electrical lines in timber elements as well as connection details of shafts to timber walls and ceilings are shown in Teibinger und Matzinger (2012).