had two stages. The first stage was between 0 and 0.9 kips load and the initial stiffness

degraded in a nonlinear way (see Fig 6-26). The second stage was linear up to peak load.

The initial non linear portion of the curve was due to the carbon wrap effect. The carbon

wrap for specimen SCG3 extended to the load points but not for specimen SCG1. That

was the reason the initial nonlinear portion was not observed for specimen SCG1. The

carbon wrap also increased the stiffness of specimen SCG3. The data from pile SCG2

were lost due to a problem with the data acquisition system and that is the reason the

load-displacement curve for specimen SCG2 is not shown in Fig. 6-26.

 15



 9

 S6

 3 -8-SCG3


 0 3 6 9 12 15 18
 Displacement (in)

Figure 6-26. Load-displacement curves for piles SCG1 and SCG3

 Pile SCG1 had higher stiffness and capacity than pile SCC1 (see Fig. 6-27). After

examining pile SCC1 it was found that the two bottom carbon reinforcing bars had been

displaced during the spinning process, reducing the effective depth by 2 in. This explains

the reduction in both stiffness and capacity shown by SCC1.

 Pile SCC1 failed in flexural compression in the constant moment region. When the

load reached the flexural capacity of the section, the compression zone exploded and the

specimen collapsed under it's own weight (see Fig. 6-28(a)). Pile SCG1 also failed rather

suddenly in flexural compression, but was not explosive like SCC1 and collapsed under