Simulation of load-duration effects in wood

Summary The load-duration behavior of wood floor joists was examined using the Monte Carlo method. The simulations were performed using a cumulative damage model and a stochastic floor live load model. Floor joists designed to the existing American wood design code exhibited a decreasing failure rate. Although weak members tended to be the ones to fail, a majority of the weak members in a population were still surviving after 50 years. The total number of joists to fail in 50 years is very dependent on the distributional assumption made for short term strength.     

Investigations on the influence of wood-inhabiting bacteria on the pH-value in trees

Regardless of their isolation origin, bacteria from wetwood of fir and poplar, from polluted beech and spruce trees, and from discoloured timber of Ilomba, acidified aerobically glucose-rich substrates by organic acid production and increased the pH of protein media by ammonia. The pH-changes occurred in laboratory nutrient media and also in the physiologically characterized capillary liquids and wood flours of fir, poplar and spruce.     

Zur Taxonomie und Pathogenität von Ophiostoma piceae (Münch) Syd. im Zusammenhang mit Absterbeerscheinungen in Trauben- und Stieleichenbeständen des mittel- und nordostdeutschen Diluviums

Taxonomy and pathogenicity of Ophiostoma piceae (Münch) Syd. in connection with dieback in sessile- and pedunculate oak stands of the Central German and the North Eastern German Diluvium Region. The loss of vitality resulting in the dying of oak forests is most probably caused by a complex of phytopathological factors. One part of this complex may be a vascular mycosis. In this connection Ophiostoma piceae (Münch) Syd. is one of the most discussed vascular fungi. Results of investigations on the variability of some morphological parameters, of cultural growth, of the pathogenicity and of the toxicity of metabolites are reported.     

Untersuchungen zur Abhängigkeit der Buchen-Rindennekrose von der Stärke des Befalls durch Cryptococcus fagisuga in Buchen-(Fagus sylvatica-)Wirtschaftswäldern

Investigations into the dependence of beech bark necrosis on infection with Cryptococcus fagisuga in commercial beech-(Fagus sylvatica)forests. Occurrence and sequence of attack of Fagus sylvatica by Cryptococcus fagisuga, slime flux, and necrosis were followed with four different methods of observation. Under average climatic conditions provocation and development of individual successive infection waves overlap to such a high degree that, because of the relatively short duration of the scale attack and because of the long duration and the great variation of the intensity of the necrotic reaction of the susceptible members of the beech population, individual waves of attack can hardly be discriminated in time and space.