An empirical model was developed using available knowledge from research on

concrete confined using FRP sheets and prefabricated jackets or shells. The empirical

model is presented in this chapter. The model was in good agreement with the

experimental data available from the CFRP grid cylinder tests.

 Manufacturing

 Nine standard (6 in x 12 in) cylinders were cast. Table 3-1 contains the test matrix

of the cylinders. Two layers of grid, formed into concentric tubular configurations and

held with plastic ties, were cast into six of the specimens while the remaining three

cylinders were cast without reinforcement. The cylinders with the CFRP grid were

designated as grid cylinders. The grid cylinders were divided into two groups (3 cylinders

in each group) with each group having a different grid diameter. The CFRP grid for the

first group was formed into a tubular configuration that was approximately 11.4-in long

with a diameter of 5.25-in and a diameter of 5.5-in for the second grid cylinder group

(Fig. 3-1). Two layers of the grid were applied with the grid lapping the 2 layers for an

additional 7 in for development purposes. The grid openings were aligned to facilitate the

flow of concrete through the grid. The CFRP grid round tubes were placed inside plastic

cylinder molds and concrete was added (Fig. 3-2).

 A Class II standard FDOT bridge deck concrete mixture was used to make the

cylinders. The specified minimum compressive strength of this concrete at 28 days is

5000 psi. Concrete was sampled as per ASTM C172 (ASTM 2004). Both the control and

grid cylinders were cast in the field according to ASTM C31 except they were ambient

cured rather than moist cured (ASTM 2003).

 All concrete cylinders were allowed to cure in the field inside the plastic mold for

approximately one month and were then taken to the laboratory where they remained