The Stress Correction Factor

The stress level is an important variable that influences the response of rPET polymer concrete. However, at relatively low design stress levels, stress is likely to have little influence because the material behaviour is almost linear viscoelastic that is, the average creep modulus is essentially the same at any stress level, as detailed in the previous chapter. The response of rPET polymer concrete under design loads is always likely to be linear viscoelastic. 

Stress factor for stress f fy Strain at stress f and time i b, Strain at reference stress and time i n Number of readings 

Because of the similarity in the shape of the response curves, the stress factor is almost constant for a given stress. The COV is very low for a given stress f, which shows the time independence of the stress factors. 

Reference stress (MPa) Stress (MPa) Stress factor SD of stress factor COV (%) of stress factor 

For the stress factor, Pf, different equations can be proposed but the power law gives the best fit to the test data the power law can be expressed as  

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Once the time function, the temperature correction factor and the stress correction factor are obtained the creep model can be expressed as ... 

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