Trdnostna analiza in preizkušanje sestavljenega lesenega nosilca s sistemom poševnega moznika

Oražem, Anže (author), Halilovič, Miroslav (mentor), Koc, Pino (comentor)

Eden od načinov za premoščanje velikih razponov so leseni nosilci s sistemom poševnega moznika. Nosilec je sestavljen iz dveh nosilcev pravokotnega prereza, ki sta eden na drugem. Oba nosilca imata vdelane zareze za moznike in izvrtine za vijake. Nosilca se upogibno obremeni v smeri nasprotni od poznejše koristne obtežbe in se ju v tem stanju poveže z vijaki, na več mest vzdolž nosilca pa se v izreze vstavi moznike. Z mozniki in vijaki torej zadržimo upogibno prednapetje, kar nam pripomore k zmanjšanju povesa in povečanju nosilnosti v primerjavi z monolitnim nosilcem enakih dimenzij. S prednapetjem in dodano koristno obtežbo v nosilcu zagotovimo enakomerno porazdelitev napetosti po vsem prerezu posameznega nosilca, kar je v primerjavi z upogibom monolitnega nosilca boljše, saj ni konic napetosti, ki se pojavijo zaradi upogibnih napetosti. Prav tako posledično nosilcu zmanjšamo poves, kar je ugodno, saj se pri velikih razponih pojavi poves, ki je vizualno moteč. Omenjeno napetostno stanje, ki se pojavi v nosilcu je pridobljeno preko numeričnega modela iz programa Abaqus. Validacija numeričnega modela je izvedena z eksperimentalnim tri točkovnim upogibnim preizkušanjem enakega nosilca v realnosti.

• Language: Slovenian
• Keywords: trdnostna analiza - MKE, preizkušanje, mozničen leseni nosilec, sestavljeni nosilec, poševni moznik, prednapetje, les.
• Work type: Bachelor thesis/paper
• Organization: FS - Faculty of Mechanical Engineering
• Year: 2017
• PID: 20.500.12556/RUL-92571
• Publication date in RUL: 15.06.2017

Secondary language

• Language: English
• Title: Stress analysis and testing of keyed timber beam using sloped shear keys

Abstract

One of the way to bridge large spans are timber beam using sloped shear keys. The beam is composed of two beams with rectangular cross – section, which are located one on the other. Both beams have made notches for keys and holes for screws. Beams are bending loaded in the direction opposite from useful load. In this state are beams connected with keys and screws, which hold preload bending. With keys and screws we keep preload bending, which help to bending reduction and increase load capacity. With preloading and added useful load, we providing uniform distribution of tension according to section, which is better in comparison with monolithic beam because, there is not tension peaks. Also in beam we reduce bending deflection, which is good because in large spans occur big bending deflection, which is visually annoying. Mentioned stress state which occur in beam, we gain from numerical model in program Abaqus. Validation of numerical model is performed with experimetal three point bending test, which includes the same beam in reality.

• Keywords: stress analysis - FEM, testing, keyed timber beam, laminated, sloped shear keys, prestressed, timber.