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Določitev nastavitev naprav za razvrščanje lesa v trdnostne razrede : magistrsko delo
Fortuna, Barbara (Author), Turk, Goran (Mentor) More about this mentor... This link opens in a new window, Plos, Mitja (Co-mentor), Logar, Janko (Thesis defence commission member), Zupan, Dejan (Thesis defence commission member)

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Abstract
Z optimalnim razvrščanjem konstrukcijskega lesa pravokotnega prečnega prereza lahko element uvrstimo v najboljši možni trdnostni razred v izbrani kombinaciji. V magistrskem delu smo primerjali različne postopke optimalnega razvrščanja in sicer po trenutno veljavnem standardu, po neparametričnem in parametričnem postopku. Slednja sta oba predstavljena v predstandardu. Bistvene razlike med različnimi postopki so predvsem v računu karakteristične vrednosti vzorca. Neparametrični pristop, ravno tako kot standard, pri računu upošteva poenostavitve, parametrični pristop pa temelji na teoretičnih enačbah. Za osem različnih kombinacij trdnostnih razredov smo primerjali rezultate optimalnega razvrščanja po različnih postopkih. S simulacijami v programu Mathematica smo preverili ustreznost enačb za račun karakterističnih vrednosti, s poudarkom na enačbah, ki so podane za neparametrični pristop v predstandardu. Enačba za korekcijski faktor se, glede na predpostavke predstandarda, ni izkazala za primerno, zato smo poiskali novo enačbo, s katero dobimo primernejše rezultate. Predstavljena je nova naprava za strojno razvrščanje lesa in nastavitve zanjo. Naprava še ni certificirana, zato njena uporaba za dodeljevanje trdnostnih razredov in uradno označevanje še ni dovoljena. Nastavitve so bile izpeljane na osnovi zahtev za začetne nastavitve, ki so podane v standardu. Za indikativno količino je najbolj primeren dinamični elastični modul, saj je v najboljši povezanosti s trdnostnimi karakteristikami preizkušancev. Preverili smo tudi možnost razvrščanja lesa s poenostavljenim postopkom, brez merjenja gostote. S frekvenčnimi in cenovnimi matrikami smo za izbrane kombinacije trdnostnih razredov ocenili uspešnost naprave in preverili ostale zahteve, ki jih mora naprava izpolnjevati za certifikacijo in uvrstitev na seznam naprav za strojno razvrščanje lesa, ki je podan v standardu. Izkazalo se je, da s predpostavljeno konstantno gostoto preizkušanca dobimo precej slabše rezultate. Z merjenjem gostote pa naprava daje dobre rezultate in je zato primerna za postopek certificiranja.

Language:Slovenian
Keywords:gradbeništvo, magistrska dela, razvrščanje lesa, trdnostni razred, karakteristična vrednost, optimalni trdnostni razred, dodeljeni trdnostni razred, nastavitve naprave, odločilne lastnosti, indikativne lastnosti, frekvenčne in cenovne matrike
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:FGG - Faculty of Civil and Geodetic Engineering
Year:2015
Publisher:[B. Fortuna]
Number of pages:XII, 123 str., 1 pril.
Place:Ljubljana
COBISS.SI-ID:7155553 Link is opened in a new window
Views:1236
Downloads:440
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Secondary language

Language:English
Title:Settings derivation for strength grading machines
Abstract:
A timber specimens highest strength grade for a selected strength grade combination can be determined by optimal grading. This can be achieved by different approaches that are represented in the current standard and pre-standard. The pre-standard defines a parametric and non-parametric calculation of characteristic properties from test results, which is the essential difference between various approaches. In both the non-parametric approach and the standard procedure, some simplifications and adjustment factors are used while in the parametric calculation only equations from a theoretical background are used. Procedures are derived for eight different strength grade combination and for all results comparisons are made. With the Mathematica software we used simulations to test given equations for the calculation of characteristic properties. Special consideration was taken on the non-parametrical calculation. The correction factor equation has not proved to be suitable, at least not for the assumptions that are made in the pre-standard. Therefore, we produced a new equation, which gives better results. A new strength grading machine is under development, which is not yet standardized and cannot formally be used for strength grading and CE marking yet. The requirements for the derivation of machine settings for initial type testing were met and we established new settings. We tried different properties as the indicative property. Due to its good correlation to specimens strength properties, dynamic modulus of elasticity was chosen. Grading procedure could be simplified by avoiding density measuring. Using size matrix and global cost matrix, we evaluated grading machine performance for data with measured density and data with constant density for each of the strength grade combination. The results using the measured density were significantly better than those with a constant density. The strength grading machine gave good results and is therefore suitable for the certification process.

Keywords:civil engineering, master of science thesis, strength grading, strength class, characteristic value, optimum grade, assigned grade, strength grading machine settings, grade determining property, indicating property, size matrix, global cost matrix

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