This example for lifting Steel Roof Tank
In the vicinity of St. Nazaire at the mouth of the Loire, a transit plant for liquefied natural gas was built from 1977 to 1979. This plant contains also two LNG tanks, each of 120 000 m3 capacity. A further LNG tank of the same size was added in 1980
Details of the structures
The tanks are of concrete, which is internally insulated with PVC panels and sealed with steel. Each tank has an external diameter of 64.90 m and a height (from the base slab to the highest point of the dome) of 51.93 m. The 1000 mm thick bottom slab rests 2 m above the ground, so that it can be well ventilated below. It stands on 113 square columns, which are carried on piles of elongated
Cross-section, 35 to 40 m in length. The thickness of the wall is 900 mm, that of the dome (radius 60 m) is 600 mm. The bottom slab has external hoop post-tensioning, the wall contains post-tensioning cables in the horizontal and vertical directions. The connections between wall and bottom slab and wall and dome are monolithic ).
After completion of the foundation and the bottom slab, the wall was constructed by slip forming. This method was preferred to climbing formwork, on account of its better guarantee of tightness. In addition, it was possible to use the formwork
twice, which offered economic advantages. The concrete dome was erected on the steel dome which served as seal and formwork skin.
After the wall had been built, the steel dome was assembled on the base slab. This dome contains stiffeners, some of which were of a temporary nature. After the dome had been completed it was lifted as a unit into its final position. In the lifting state its weight was 600 tones. For the lift, 12 lifting frames of steel were erected on the upper edge of the tank wall. Each of these brackets was fitted with a VSL motive unit SLU-70, cable comprising 7 strands Ø 15 mm ran. The lifting distance was 32 m. The dome was raised to 100 mm above the bearing plane, and was then fitted with the ends of the beams, which came to rest on the bearings when the dome was set down.
The first dome was lifted in June and the second in July 1978
م. رزق حجاوي