Computational and experimental assessment of load bearing capacity of glued laminated beams made of beech wood

Study of the mechanical properties of glued laminated beech beams is presented in this doctoral thesis. The high strength and stiffness properties of beech wood require that special attention be paid to the tensile strength of different finger joint profiles with different adhesives used for longitudinal gluing of beech boards. The results of experimental testing of finger joints in tension have shown that longer and slimmer finger joints are required to increase the load bearing capacity of finger joints. The influence of the type of adhesive used decreases with the length of the finger joints, so that existing structural adhesives are suitable for use with glued laminated beech beams. Fourteen glued laminated beech beams were produced. The beams were then tested and the strength and stiffness properties were measured. In addition to flexural strength and flexural elastic modulus, shear modulus and contact stiffness between layers were measured. Analytical and numerical models for the analysis of glued laminated beech beams were established. The models are based on Reissner’s planar beam theory and take into account the slip between laminations and the influence of finger joints. The analytical solution for Euler-Bernoulli and Timoshenko-Ehrenfest glued laminated beech beams is presented. The numerical model can be used for modelling glued laminated beams with an arbitrary number of laminations and an arbitrary number of finger joints. The model has been validated with the experimental results and the results agree well. Stochastic analysis of glued laminated beech beams is also performed using analytical and numerical model and the results showed a good agreement with the experimental results and that numerical model can simulate the mechanical behaviour of the glued laminated beech beams. V doktorski disertaciji je predstavljena analiza mehanskih lastnosti lameliranih lepljenih nosilcev iz bukovega lesa. Zaradi visokih mehanskih lastnosti bukovega lesa je potrebno posebno pozornost posvetiti zobatim spojem ter njihovi natezni nosilnosti. Pri tem sta geometrija zobatih spojev in lepilo, ki se uporablja za dolžinsko spajanje bukovih desk, bistvenega pomena. Rezultati eksperimentalnih testov so pokazali, da z daljšimi in ožjimi zobatimi spoji nosilnost zobatega spoja narašča pri tem pa se vpliv lepila zmanjšuje. Obstoječa konstrukcijska lepila so se izkazala kot ustrezna za uporabo v lepljenih lameliranih nosilcih iz bukovega lesa. Štirinajst lameliranih lepljenih nosilcev iz bukovega lesa je bilo testiranih v upogibu. Poleg upogibne trdnosti in upogibnega elastičnega modula lepljenih lameliranih nosilcev iz bukovega lesa, smo izmerili tudi strižni modul nosilcev in togost stika med lamelami. Za analizo lameliranih lepljenih nosilcev iz bukovega lesa sta pripravljena analitični in numerični model. Oba temeljita na Reissnerjevi teoriji ravninskih nosilcev. Pri analizi je upoštevan zdrs med sloji in vpliv zobatih spojev. Analitična rešitev je prikazana za Euler-Bernoullijev in Timoshenko-Ehrenfestov nosilec. Z numeričnim modelom je mogoče modelirati lamelirane lepljene nosilce s poljubnim številom lamel ter poljubnim številom zobatih spojev. Model je validiran z rezultati eksperimentalnih testov in pokazalo se je dobro ujemanje med izracunanimi in izmerjenimi vrednostmi. Za ovrednotenje rezultatov je bila opravljena tudi stohastična analiza, tako z analitičnim, kot tudi numeričnim modelom lameliranega lepljenega nosilca.