The Influence of Freezing and Thawing Process on the Bending Moment Capacity of L-Shaped Heat-Treated Wood Dowel Joints

In this work, the influence of the freezing and thawing process on the bending moment capacity of L-shaped heat-treated wood dowel joints is analysed. The parts of the joints were made of heat-treated ash (Fraxinus excelsior) wood. Half of the analysed joints were randomly divided in two groups. One group was frozen and thawed in a climatic chamber and the other group was kept in laboratory environmental conditions. The bending moment capacity was calculated by means of ultimate failure load, which was experimentally obtained. One-way analysis of variance (One-way ANOVA) was applied to figure out if there is a significant difference between the analysed groups. Based on the obtained results, it was concluded that the freezing and thawing process did not significantly affect the strength of the L-shaped heat-treated wood dowel joints.

THE INFLUENCE OF THE NUMBER AND POSITION OF DOWELS ON THE BENDING MOMENT CAPACITY OF HEAT-TREATED WOOD DOWEL JOINTS

In this work, the influence of the number of dowels and the option to place the dowels in the cross section of part on the bending moment capacity of heat-treated wood dowel joints was analysed. The joints, which were made of heat-treated ash, were tested by means of a universal testing machine.The ultimate failure load and the moment arms were used to figure out the bending moment capacity of the joints loaded in compression or in tension. The number of dowels affected the tensile strength of the L-shaped heat-treated wood joints. The modality to place the dowels in the cross section of rail, namely, in collinearity or in a triangular shape, did not significantly affect the strength of the heat-treated wood dowel joints.

Comparison between artificial neural networks and response surface methodology to predict the bending moment capacity of heat-treated wood dowel joints

The bending moment capacity of heat-treated wood dowel joints loaded in compression or tension was predicted via two artificial neural network (ANN) models. Additionally, a comparative study between similar models that were developed through response surface methodology (RSM) was performed. The joints were made of heat-treated ash (Fraxinus excelsior). The values of the ultimate failure load and the moment arms were recorded for each run via a universal testing machine. To develop the ANN models, the experimental data were randomly divided into three subsets, which were needed for the training, testing, and validation phases. The RSM models were obtained from the literature. The performances of the models were analyzed in terms of the correlation coefficient, coefficient of determination, root mean square error, mean square error, and mean absolute prediction error. A sensitivity analysis was also performed to observe potential changes in the results due to the uncertainty in the input variables. The ANN model better predicted the bending moment capacity of heat-treated wood dowel joints loaded in compression than the RSM model. In contrast, the RSM model predicted the bending moment capacity of joints loaded in tension more accurately than the ANN model.

Experimental Study on the Effect of Moisture on Bolt Embedment and Connection Loaded Parallel to Grain for Timber Structures

Connections are critical parts of timber structures, transmitting static and dynamic forces between structural elements. The ultimate behaviour of a building depends strongly on the structural configuration and the capacity of its connections. The complete collapse of a building or other less extensive accidents that may occur usually start as a local failure inside or in the vicinity of a joint. The main aim of this study has been to investigate if the short-term capacity of steel-wood dowel joints loaded parallel to the grain is affected by variations in moisture content associated with post fabrication drying or wetting of the timber. Extensive experiments were conducted. The experimental results showed that the stiffness and load-bearing capacity of the joints is reduced by post-fabrication wetting and is increased by post-fabrication drying. It was clear from those test results that changes in mechanical properties were greater than could be explained by effects moisture content changes have on material properties, implying that simple adjustments of properties in that way for purposes of structural design are unreliable Currently in the design of timber connection in code of practise is the effect of variation of moisture is not considered. The results revealed that there is a great effect on timber performance which is due to an increase of moisture content.