The large horizontal load transferred to the caissons at the bottom of the tower structure and the center core required 20 of the caissons to be designed with enlarged diameters at the top.
The cage fabricated to fit the smaller diameter excavation and centered within the excavation. In some cases, the length of the smaller diameter excavation required the reinforcing cage to be fabricated in two sections. These cages were spliced over the hole. The cage was suspended, from the casing , by using bars that are threaded through the horizontal reinforcement and span through the diameter of the casing.
Once the lower cage is set and secure, the larger diameter cage was lowered over the smaller diameter cage and spliced to the lower section using a combination of Z-bars, lap splices and clips. The spliced cage was then lowered to the design elevation and set on the casing or frame. The cage was suspended on angle iron or channels, which are tack welded to the casing or frame to prevent uplift during concrete pouring.
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