Statična analiza lesenega mostu preko reke Save v kraju Sava.

Tomažič, Miha (author), Saje, Drago (mentor), Lopatič, Jože (comentor)

V magistrskem delu smo predstavili postopek kontrole nosilnosti obstoječega lesenega mostu preko reke Save v kraju Sava. Najprej smo pridobili načrte mostu, ki so bili izdelani leta 1934. S pomočjo teh, smo na terenu premerili celotno mostno konstrukcijo in izdelali posnetek obstoječega stanja mostu. Pregledali smo tudi sestavo spojev, ocenili poškodovanost nosilne konstrukcije ter podali oceno kvalitete lesa. Pridobili smo tudi oceno natezne trdnosti jekla, ki se je uporabljalo v času gradnje mostu. Ker je most zaščiten kot kulturna dediščina, na mostu nismo smeli uporabiti nobenih porušnih preiskav, da bi ugotovili dejanske karakteristike lesa in jekla. Izračunali smo lastno težo in stalno obtežbo na konstrukcijo, določili obtežbo vetra in obtežbo snega ter določili število voznih pasov ter širino pasov. V programu Excel smo izdelali algoritme za izračun posameznih obtežb in izračun nosilnosti spojev. Oceno nosilnosti mostu smo izvedli v treh zaporednih korakh. Najprej smo ocenili nosilnosti obstoječih spojev. Za tem smo izračunali osnovne nosilnosti posameznih elementov, z upoštevanjem uklonskih dolžin pri tlačenih elementih in tako dobili nosilnost elementov. Za tem smo v programu Scia Engineer modelirali glavne konstrukcijske sklope mostu. Prva dva, glavni palični nosilec in horizontalno povezje pod paličnim nosilcem, sta statično nedoločeni paličji, kjer prekrižane diagonale prenašajo samo tlačno silo, tretji sistem pa je trapezno vešalo. Na računski model smo nanesli stalno obtežbo, koristno obtežbo in karakteristično koncentrirano silo obtežne sheme LM2, kjer pa smo vpeljali faktor kLM in tako reducirali karakteristično vrednost navpične koncentrirane sile Qak. Obremenitve v elementih smo izračunali za vsak obtežni primer posebej, nato pa še merodajne obtežne kombinacije, ter preverili nosilnost elementov mostne konstrukcije v skladu s standardi Evrokod. Vse analize smo naredili na ravninskih modelih. Izračun notranjih sil v paličnih nosilcih smo v celoti izvedli z nelinearnimi analizami, medtem ko smo ostale izračune opravili z linearnimi analizami.

• Language: Slovenian
• Keywords: lesena konstrukcija, most, statični izračun, prometna obtežba
• Work type: Master's thesis/paper
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Year: 2018
• PID: 20.500.12556/RUL-101349
• Publication date in RUL: 30.05.2018

Secondary language

• Language: English
• Title: Static analysis of a wooden bridge across the Sava river in Sava.

Abstract

The objective of the Master’s thesis is to assess the load bearing capacity of an existing wooden bridge. In order to do so, we first had to obtain the bridge plans developed in 1934, which have helped us to measure in detail the bridge structure and get a comprehensive picture of the current bridge state. Furthermore, we assessed the composition of joints, damage of the supporting structure and the wood quality, and acquired data on tensile strength of steel that was used during the construction. Since the bridge is protected as a cultural heritage, we were not allowed to perform destructing testing to determine the actual wood and steel characteristics. Self weight and dead load of the construction were evaluated, while also determining the wind and snow load as well as the number of traffic lanes and their width. We used Excel to develop algorithms and thus calculate individual loads and the joints’ resistance. We assessed the load capacity of the bridge by three successive steps. First, we determined the design resistance of the existing joints. For this purpose we calculated the design resistance of individual elements, taking into account the effective length in the elements in compression, thus obtaining the load capacity of the elements. For this purpose, in the Scia Engineer program we developed computational models of the main bridge construction, which were modeled with three different load systems along the bridge and in the transverse direction. The first two, the main truss system and horizontal truss under the carriageway, are statically indeterminate trusses, where the diagonals transmit only the compressive force, while the third system is trapezoidal. The calculation model applied constant load, useful load and characteristic concentrated force for the LM2 schematic scheme, where we introduced the kLM factor, thus reducing the characteristic value of the vertically concentrated Qak force. Forces in elements were calculated for each load case separately and then we made adequate load combinations where we checked the resistance of bridge by the Eurocode standards. All the analysis were made on planar models. The calculation of the internal forces in the truss beam was carried out completely with nonlinear analysis, while the remaining calculations were carried out with linear analysis.

• Keywords: timber structure, bridge, static calculation, traffic load