LaFarge Minot Distribution Terminal
The Lafarge Minot Distribution Terminal was planned as a 200 TPH loading and unloading terminal for cement and fly ash from rail and truck cars. It went into service in September 2009 and has met or exceeded the design discharge goal. It features steel storage silos, pneumatic conveyors, (a.k.a air slides), a high-capacity bucket elevator, rail and truck loading and unloading features, and unique concrete framing assemblies. There are ancillary office and support facilities within the terminal. The project was constructed with 5 silos, with provisions for a 6th silo to be installed at a later date.
The signature feature of this project, and the basis for submitting the nomination, is the cast-in-place reinforced concrete moment frame that supports up to six (6) 500 Metric Ton (550 Ton) cement product storage silos.
The cast in place silo support frame consisted of a 2x3 bay system that utilized 12~36” sq columns, with 30”x36” or 36”x36” concrete beams. A total of 345 CY of concrete was used to construct the frame.
Several options for the silo support structure were contemplated – steel moment frames, steel concentrically braced frames, and precast concrete and beam framing. Cast-in-place concrete was selected due to several of its relative benefits:
• Flexibility for geometry of the cast shapes
• Ability to resist column torsion and bi-axial bending while simultaneously resisting very high axial loads
• Quick and easily coordinated delivery schedules
• Optimization of the contractors labor force
• High strength capacities coupled with high stiffness from a relatively compact and easily formed shape
• Ease of creating moment frame connections using traditional reinforcing steel
• Use of the Lafarge materials and their customers for the materials
• Mass shapes that facilitated cold weather construction and curing
The cast in place concrete silo support frame was topped with a cast-in-pace floor plate bounded on all sides with monolithically cast beams. The deck was the support point for each of the silos, and topped out at an elevation 34’-0” above the finished floor. An intermediate level of beams at 17’-0” above the floor was used to support material handling equipment, the control room, but most importantly provided a level to provide bracing for the 36” square concrete columns. The frame resisted a total of 4250 Tons of axial load, a 132 kip wind shear applied at the 34’-0” framing elevation, and a total overturning moment of 3,600 k-ft. The project also utilized reinforced concrete floor slabs on grade, footings, piers, perimeter foundation walls, and a rail pit. The total volume of concrete used on the project was 1,400 CY. Total quantity of reinforcing steel was 110 tons.
The total cost of the project was $5.2 million, of which $1.8 million was for equipment, silos, and related material handling equipment. The General Construction costs of the Project were $2.75 million, and the cost of the CIP concrete and reinforcing steel was $650,000.
The primary challenges for the project included a late authorization to start the design, a compressed design schedule, a winter construction start date, high work (the highest point tops out over 170’ above grade), and tight reinforcing steel clearances and workspace. The project was drafted entirely in a BIM drafting system, and key reinforcing clearances and detailing were worked out in real scale using BIM methods. Using BIM allowed the designers to accurately pre-plan all of the rebar layouts using actual bend geometries.
The design and function of the CIP support frame was a unique challenge due to the high structural demand of the project. CIP was the only reasonable choice. Because of the structural unique design challenges, and because of extensive use of reinforced concrete, we believe the Lafarge NA Minot Cement Distribution Terminal is worthy of a NDRMCPA Award.
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