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footing to the roofline of the silo. The structure was 110 ft (34 m) to the roof and 30 ft (9 m) in diameter. This one silo that we were contracted to reline was singled out by ICI because of the blower/ventilation system that this silo was equipped with. Bringing this silo back online by early summer was critical to help meet the demand for needed storage for the beginning of the area’s wheat harvest. Additional repairs to other grain silos at this facility are being evaluated for future relining projects. For analysis and design of the strengthening for the 110 ft (34 m) structure, we brought Vance Behrens, PE, SE, Principal of Structural Design Group in Lincoln, NE, onto our team. His structural evaluation of the silo gave us guidance on the additional load capacity we could put on the structure while cutting access holes into the sides of the silo, as well as the roof’s capacity for rigging suspended scaffolding inside the structure during construction. He also provided a design for the reinforcing bar size and spacing for the shotcrete lining on the interior walls. ACI 506.2-13, “Specification for Shotcrete,” was the construction specification used for shotcreting the lining of the silo and the shotcrete mixture as well. Proper Tools and Lighting Beyond the use of a Reed B50 concrete pump, 170 Ingersoll/Rand compressor, and a few hundred feet of pipe and hose, four ACI Nozzlemen (Rich Hodtwakler, Ben Russell, Matt Russell, and Ron Stricklett) and their crew produced a game plan to place 140 yd3 (107 m3) of shotcrete on the Fig. 1: Working on the 30 ft (9 m) diameter grain silo requires special inside of the grain silo. We had a few other things equipment. McGill Restoration had to use specialized, blast-proof lights to contend with first. to generate enough light for their crews to safely complete their work Working in and around grain storage facilities can be one of the most dangerous working environments. There are strictly enforced “no- and hazardous working conditions. These types smoking” polices at these facilities. If caught of lights can be run off 120-volt AC power and smoking on the premises, it is an automatic firing stay cool to the touch. offense. Grain dust is highly combustible, so as a contractor, one is not allowed to use impact tools, Round Hole, Square Peg drills, and suspended scaffold hoist (motors) that McGill Restoration has decades of experience are electrical-driven. This posed another challenge, when it comes to constructing scaffolding or as it meant all tools used on this project had to be other aerial lift equipment on high-rise buildings, air-driven. This caused a slight reduction of bridges, water tanks, and many other types of production on the project as a whole, but safety structures. Because they do not make curved is always our first concern. suspended scaffolding systems, laying out a Because working in a grain silo is very much configuration that is conducive to a cylindrical like working in a tunnel, we had to generate our shape was challenging. You need to design the own lighting (refer to Fig. 1). The lighting had to scaffolding system to maximize your working follow strict guidelines as well. Our lighting had area to get close enough to place dowels and to be explosion-proof-rated and generate enough tie-reinforcing steel in the walls, but also have illumination for us to work. Abrasive Blast Supply enough spaced on the scaffolding deck for the Inc. proved to be a very good resource for what nozzlemen to control their placement distance. we needed. They were able to provide us with a A decagon-shaped suspended-scaffolding system directional LED light that provided 10,000 design was constructed to a 28 ft 4 in. (8.6 m) lumens, which was suitable for explosion-proof diameter for the duration of doweling and tying Shotcrete • Fall 2015 31


2015FallShotcreteEMag
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