Behavior of Prestressed Concrete Composite Beams


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Title: Behavior of Prestressed Concrete Composite Beams

Author(s): R. H. Evans and A. S. Parker

Publication: Journal Proceedings

Volume: 51

Issue: 5

Appears on pages(s): 861-878

Keywords: no keywords

Date: 5/1/1955

The principal object of the investigation was to determine whether a composite section consisting of in-situ and prestressed concrete acts mono-lithically with a straight line distribution of strain. Different types of prestressed elements were tested and the quality of bond for varying degrees of roughness of surface was observed. At the same time one set of beams was made specially to investigate the way in which cracks progress across the joint of the two qualities of concrete. Microscopic observations showed that although there is a certain degree of restraint between in-situ and pre-st ressed concrete, the extensibility is unaffected. In much the same way as shrinkage of concrete in reinforced concrete members produces stresses, differential shrinkage and creep of the two concretes in composite work also have an effect. This was investigated theo-rctically and the results checked against the observed cracking loads of the beams. In discussing the significance of the experimental and theoretical results the commercial possibilities of composite construction are considered and various suggestions made with regard to the best type of surface bond, the best relative concrete mixes and times of casting the concrete. The results show that the straight line theory is applicable and stress distributions based on this have been plotted to give examples of good and bad types of combined sections.