Utbyte av rullager i höghållfast stål : En jämförande studie av metod och problematik

Sammanfattning: Different kinds of bridges require different kinds of bearings. The Swedish Traffic Agency (Trafikverket) maintains 53 bridges in Sweden with high strength steel roller bearings. These kinds of bearings may cause failure due to fatigue and corrosion and therefore they need to be replaced as a safety reason. Swedish Traffic Agency has been working on the replacement since 2011 and this study is aimed at four different bridges maintained by the Swedish Traffic Agency where bearing replacement is completed or planned. Bridges with high strength steel roller bearings are dimensioned according to old norms which didn’t require dimensioning for bearing replacement. This creates problems when the superstructure needs to be lifted with hydraulic jacks to unload the bearings during the replacement. These problems are repetitive and consist for example of lack of space and construction parts that aren’t dimensioned to handle the loads that occur during the lift of the superstructure. Therefor some kind of temporary construction is arranged to solve the problems. The purpose of the study is to compare methods and cost for bearing replacement, safety solutions and the use of temporary bearings for three types of supports. This study has dealt with three different kinds of supports: circular column, abutment and wall pier, where four different methods of bearing replacement have been compared. Through interviews, observation of blueprints and literature studies a comparison between methods has been made.  The temporary constructions are made of steel or concrete. Results of the study shows that a temporary construction made of steel is more adaptable but more expensive than a temporary construction made of concrete. A temporary construction made of concrete requires a greater encroachment of the structure. Bridge structures are complex constructions whom may differ from each other. The individual bridge’s unique location, shape and type are factors that affect the choice of method. This had led to difficulties to define the best bridge bearing replacement method. Constructions of steel are expensive and should, if possible, be reused. When using of the method of temporary concrete construction the structure should be dimensioned for permanent use.