Despite big advances in analytical modelling of the performance of structures exposed to fire, there has been difficulty in modelling the fire performance of precast prestressed concrete floor slabs in multi storey buildings. The fire resistance of these floor systems is heavily influenced by the end connections and the stiffness of the surrounding structure, both of which must be considered in any analysis. Previous “traditional” studies have modelled the floor slabs with beam or shell elements in which the end nodes share the nodes of the beam elements representing the supporting beams. This is acceptable for cast-in-situ or precast flooring systemwithout prestressing, but leads to a major problem for precast prestressed flooringsystems where the steel tendons terminate at the end of the flooring units, becausethe approach of sharing nodes of the supporting beam and floor assumes that thesetendons are anchored into the supporting beams.In order to solve this problem, a “multi-spring” connection element has beendeveloped. The multi-spring connection element consists of several parallel axialsprings sandwiched between two rigid plates. Each spring represents either a steelreinforcing layer or a segment of concrete in the floor cross-section. The concretesprings have compression-only properties. This multi-spring connection is placedbetween the end nodes of the floor and the nodes of the supporting beam. With thiselement, it is possible to terminate the prestressing tendons at the end node of thefloor elements and to anchor only the topping reinforcement into the supportingsystems predicted using the traditional approach and the newly developed multispringconnection, with applications to different forms of precast concrete floors in multi storey buildings.
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