Structural behaviour of high strength concrete beams

Tests are reported on the flexural behaviour of high strength reinforced and prestressed concrete beams in terms of strength, cracking and deformation. The beams were made from concrete having a cube strength of 85–110 N/mm². The working stress in concrete varied between 27·7 N/mm² and 34·5 n/mm², and that in steel between 230 N/mm² and 345 N/mm². The results show that high strength concrete beams possess adequate load factors, and show ample warning and ductility prior to failure. The crack widths under design loads are within acceptable limits, although steel working stresses of 345 N/mm² may result in excessive long-term deflection. The strength and deflection can be satisfactorily predicted by existing methods.