Experimental Investigation of Externally Post Tension Composite Ultra High Performance Concrete-Steel Girder

Abstract

An experimental investigation was carried out to find the beneficial effect of using external prestressing technique in strengthening of an existing composite steel I-girder bridge and ultra-high performance concrete. The experimental work consists of fabricated five composite steel-concrete, non prestressed beam and four externally post- tensioned girders, classified in two groups. All girders were constructed by scaling down an existing prototype composite girder by 1/4 scale factor, were designed according to AASHTO LRFD 2012 standard specification. Each girder was tested as a simply sup-ported beam with span of 3.90m and loaded incrementally up to failure under the action of two point loads. The prestressing force in the girders of group one was (9) Ton applied after the RC deck slab was constructed, while group two was (7) Ton. The variables in-clude values of the eccentricity, with or without deviator and the magnitude of the ap-plied prestressing force. Results show appreciable enhancement in load carrying capacity of the externally prestressed girders comparing with that of the unprestressed girder (ref-erence). Group one girders showed a percentage increase in ultimate load of 36.36% and 45.45% for prestressing force of (9) Ton with eccentricity which mean that (location of prestress below bottom face are equal to 80mm and 160mm, respectively) while group two show that this percentage increase are 38.63% and 47.72% for prestress force of (7) Ton with eccentricity of (120mm and 200mm, respectively).