Prefabrication of shell units has been discussed in Chapter 9. Concrete shell elements, viz., doubly curved shells, cylindrical shells, etc. which are resting on load bearing structures of buildings are erected using cranes. Figures 25.18(a), (b) and 25.19 show the erection of short and long cylindrical shells and double curvature shells. Re-course is made to a ground level pre-assembly and load-gripping arrangement which eliminates erection stresses. Elements are pre-assembled in panels of 3 m × 6 m size or special mobile jig beds on the ground which are within the reach of an erection crane. After welding cover plates, two erection tie bars are fitted in each element.
Figure 25.18 Erection of short and long cylindrical shells
Figure 25.19 Erection of double curvature shell assembly
Following are the steps of operation (Atalev, 1985), in general:
- Pre-assembly of units of shells.
- Trueing and securing of edge trusses within the reach of an erecting crane.
- Welding of insets of elements of shells and of trusses.
- Removal of temporary erection fastening devices and grouting with rich concrete in places where the elements adjoin trusses and shell joints.
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