CLIENT: Bulk Material Storage and Transload Facility
PROJECT: Tubular Conveyor Gallery consisting of thin wall steel shell
BACKGROUND: The client approached ADF Engineering to design a bulk material storage and transloading facility in the Chicago Area. As part of the project, our Structural engineers were tasked to design a conveyor bridge to transfer the product from the receiving tower to the dome type storage silo. The conveyor support bridge had several challenges.
- Had to be free spanning (134’) because intermediate supports would have interfered with emergency vehicle traffic.
- Despite being in Chicago area, it needed to be completely sealed weather-tight due to the product being extremely sensitive to moisture.
- Need to provide both personnel access to the dome headhouse as well as a trolley system to replace conveyor screws.
- Needed to support conveyor’s heavy gravity and dynamic loads, resist high wind loads, and to be cost efficient to construct and maintain.
This project was designed as a portion of a new facility design on an accelerated timeframe in order to complete construction to harvest the Fall crop. The design of the Tubular Conveyor Gallery included:
- Comparing options between an open box truss-type bridge with additional architectural panel attachments for weatherproofing vs a continuous tube steel shell structure. The Tube shell structure was selected based on the following considerations:
- Fabrication & shipping costs – Tube was fabricated off site, on site assembly was limited to (2) bolted flange splices.
- Installation costs – Tube was designed to be installed as a single lift.
- Maintenance and durability – solid thin wall shell structure eliminates possible leaks due to flashing failure.
- Sizing of Tube diameter and thickness.
- 12’-6” diameter selected based on required vertical clearance for trolley system as well as limiting overall deflection criteria for deflection sensitive screw conveyors.
- Tube plate thickness selected for required bending strength. Thickness was reduced at the ends of the span to help reduce weight and material cost
- Grade of steel was selected A36
- Design of ring stiffeners to resist shear stress, both during operation as well as while being lifted during installation.
- Connection design for both tower and silo end supports. Including additional stiffener rings & saddles, pinned type connections to resist lateral movement, and roller type connections with Teflon slide plates to allow for thermal expansion/contraction of the tube throughout the year.
Thin wall steel shell structures are an excellent alternative to a traditional box truss-type bridge. Their excellent watertight ability and strength can be a designer choice for long span conveyor bridges.
For additional information on design and application of large diameter ducts, shells, and stacks, please contact firstname.lastname@example.org
Derek Jacobs, P.E., S.E.
Structural Department Manager
937-847-2700 ext. 128