Penthouse structure at JSW cement – Case Study

Project execution: A crane has been rigged up and lifted the ring beam assembly above the silo. The ring beam was secured with stay cables at 44m. Then with the help of 2 x 250t cranes, the rafter assembly (25t each) is connected. The silo’s load is gradually released once the complete rafters have been assembled. After the ring beam is erected with a rafter, the entire penthouse set (150t) of dimensions (15m x 15m x 22m) is lifted and placed on top. As per the scope we initially lifted the 40m long conveyor in tandem with 450t and 250t cranes and erected it over the existing column and silo.

Challenges of the project:

• The main crane had to hold the ring beam above the silo for 15 days. During this day, the rafters and purlins were installed, increasing the load from 70t to 135 tons.
• The rigging arrangement of the penthouse assembly was designed to lift the load with minimal stress on the steel structure detailed load analysis was done, and counterweights were added to the structure to ensure the COG of the load remained at the centre of the structure.
• As the site was near to maintain the wind speed was high which created a tunnel effect and the load surface area is also high, we had to calculate the permissible wind speed to mitigate the tunnel effect.
• A complex rigging system