The presented test method reflects how a quality assuring measure can be applied for finger jointed structural timber by integrating a tensile proof loading device in the production process. Thereby every produced rod or beam is clamped on both ends over profiled steel plates and subjected to a defined tensile loading in terms of duration and stress level. With this method, depending on the set proof level, greatly strength reducing timber features such as the global and local grain deviation, faulty finger joints, compression failures or reaction-wood are recognised by failure and can be rejected. The results of experimental research work on a high number of specimens (4,886 #) show clearly, that there is no appreciable damage to surviving timber due to tensile proof loading at low load levels. Within a double proof loading procedure 99,96 % of all specimens could sustain higher stresses than at the first time, indicating not being damaged. Tests and simulations based on the weakest link theory to determine the length effect regarding the tensile strength distribution of sawn timber resulted in klength = 0.17, which is valuable for design purposes.
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