gfrp rc beams

huangyhg

gfrp rc beams
can some one tell me the benefit of ductility in a gfrp simply supported beam.i realise that adequate warning of failure is necessary but wouldn't the development of cracks indicate possible failure and be sufficient.
thanks
davis42
frp-reinforced concrete beams do not possess any significant ductility (unless you count concrete crushing).  the reinforcing remains elastic until rupture.  unlike traditional steel-reinforced beams, the frp-reinforced beams will not exhibit the pronounced sagging and cracking that warn of impending collapse.  for this reason, higher factors of safety are warranted.  aci 440.1r-03 is a good reference.
thanks allot taro.
have you heard of ductility being achieved in a simply supported over reinforced beam, reinforced with gfrp, by placing gfrp rods in the compression zone as well as the tension zone??
thanks again for your help
davis42
no.  adding bars in the compression zone might reduce the stress on the concrete but would not enhance the beam's ductility.  the problem would remain that the tension bars would strain elastically until they reached their ultimate strength, then suddenly rupture and cause catastrophic collapse.  instead of relying on ductility for these members, the accepted design approach incorporates a larger factor of safety to ensure that the ultimate bar stress is not reached even if the   
hey taro,
sorry for the delay, have been away. thanks a lot for your input. it was very helpful.
regards davis42