Utmattning av järnvägsbroar av armerad betong: Jämförande beräkning för två befintliga plattrambroar
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Many existing railway bridges in Sweden are approaching their estimated life span. There is also a desire to increase their loads, the number of passages and the speed limit in order to meet current and future demands. To avoid demolishing fully functional bridges, the fatigue investigations on existing structures should give results that are close to reality. The regulations of today may condemn fully functioning bridges, even though only few of them show signs of fatigue.This thesis compares three fatigue models by assessing two slab frame railway bridges, one from 1972 and one from 1995. The fatigue models are based on the Swedish Code BBK04, the Eurocode and the Fib Model Code 2010. The concrete and reinforcement in the bridges are assessed for bending and shear. The methods used are simplified models and cumulative damage analysis method. In most of the calculated cases, it is indicated that the bridges do not have enough fatigue capacity, even though there were no signs of fatigue registered during the latest inspection. The factors that give the highest impact on the fatigue capacity are the stress range, the number of load cycles, the diameter of the reinforcement and the diameter of the mandrel used for bending reinforcement. All the investigated fatigue models are affected by these factors. It is not possible to single out one model that in all cases give the lowest capacity, except in the cumulative damage analysis where the Fib Model Code 2010 give the highest capacity.For more accurate calculations the cumulative damage method is applied, where the actual number of load cycles is used. The calculations show that the analysis was in this case not the most favorable method to use on these short, slab frame bridges. Further research is needed to be able to make more accurate assessment of existing structures are investigated. The norms of today give too conservative results that do not reflect reality. Either improvement can be made by reducing the impact on the fatigue capacity of the above mentioned factors or by inventing completely new methods. Other questions to study are e.g the size of the stress ranges (calculation models, dynamic factor, monitoring) and number of load cycles for different stress ranges.
Place, publisher, year, edition, pages
2015. , 206 p.
Teknik, Plattrambro, järnvägsbro, utmattning, armerad betong, BBK04, eurokod, Fib model code 2010, TRV bärjvg
IdentifiersURN: urn:nbn:se:ltu:diva-46131Local ID: 3c5e06e6-95d1-44e2-b318-6ec5948109dcOAI: oai:DiVA.org:ltu-46131DiVA: diva2:1019443
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20150611 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved