Stabiliteit van een dragende-leuning brug uitgevoerd in beton. Stability of a concrete pedestrain bridge with load bearing railings

Abstract

Usually, concrete bridges contain a ‘thick’ bridge deck. For various reasons, bridges are constructed with railings. This thesis discusses the stability problem of concrete bridges, which are designed with integrated railings into the carrying construction. The most important advantage, using load bearing railings, is a thinner bridge deck. This was also one of the requests of Public Works Rotterdam. The load bearing railings have to endure buckling. This phenomena is not very common in massive concrete bridges. Since the request for to alternative bridges with a thinner bridge deck, like this one, is becoming larger and larger, there is need for a simple rule of thumb. This indication is necessary for estimating the dimensions of this kind of bridge without a complicated calculation. For this thesis, the stability of a concrete pedestrian bridge with load bearing railings, has been checked in three ways. There has been focussed at the compression zone of the bridge, the handrails. 1. First the buckling force is calculated. Using the buckling force and the actual normal force in the handrails, it is possible to calculate the second order effects. 2. The total resisting moment in the handrails must be large enough to withstand the external first and second order moments. The resisting moment is based on uncracked concrete, therefore no tension stresses in the handrails are aloud. 3. If stability isn’t the problem, strength is. Hence the external normal force in the handrails most be lower than the normal force resisted. The problem has been analysed. The three checking’s are visualized in graphs over various dimensions. These graphs were used as a starting point of a parameter study to get a rule of thumb, which can be used for concrete pedestrian bridges with load bearing railings. There is also concluded that bridges with load bearing railings are more sensitive to local forces (on bridge deck and railings), than plate bridges are. The rule of thumb is applicable for bridges larger than 14 meter and smaller than 23 meter, depending on the applied concrete strength. Using this indications gives a correct estimation of the dimensions of a concrete pedestrian bridge with load bearing railings.