than higher concrete strengths (more than 5000 psi) that tend to be more brittle and have

lower crushing strains.

 The strength of the concrete used in these beams was approximately 6100 psi

which was relatively high. Based on the crushing strain values it can be concluded that

the concrete used in this beams was brittle as expected based on its high strength.

 The compressive strains were reduced due to the presence of the CFRP grid. This

was attributed to the fact that the CFRP grid restrains concrete movement which is

manifested in the reduction of the strains. As the concrete in the compression zone is

compressed it also expands laterally. That lateral expansion of the tube beam however

was restrained by the CFRP grid which also reduced the longitudinal shortening of the

compression zone hence the reduction in the measured strain.

 Assuming that plane sections remain plane the strains at each steel layer can be

determined using similar triangles (see Fig. 4-18). Strains for both steel layers using this

procedure are presented in Table 4-4.




 c

 C


 d N.A.




 d c




Figure 4-18. Assumed strain distribution