ULTIMATE STRENGTH OF SINGLE BAY PRESTRESSED CONCRETE PORTAL FRAMES

Abstract

The object of this investigation was to stL ultimate strength of single-bay prestressed portal frC the moment redistribution beyond the elastic limit. The controversial opinions about the extent of redistribution moments in statically indeterminate structures at their ultimate failure. For example, Guyon is of the opinion that the distribution of moments in statically indeterminate structures, say portal frames, under service loads will not be the one deduced from the elastic theories. Some redistri-bution, Guyon says, is bound to take place and cracking2 will be delayed beyond the point indicated by the elastic theory. In contrast to this, professor R. H. Evans and J. S. Raftery found from their test on a three dimensional prestressed concrete frame that the failure occurred without the frame kit K 2xiinxN z$zxxxm& becoming a mechanism by forming a sufficient number of plastic hinges i.e., without the full redistribution of moments. P. B. T:iorice and H.B. Lewis, by performing a number of tests on prestressed concrete continuous beams and portal frames, came to the conclusion that there was full redistribution of bending moment at failure. But the degree of moment redistribution, or adaptation, obtained by them demands special examination on account of the contrary evidence produced by Macchi. An attempt has been made to find the discrepancy between the actual and the calculated ultimate loads and the degree of redistribution of bending; moments, or adaptation, that takes place. The relation between the curvature and the moment of resistance is also studied