By: Mason M. Harris

Today's industrial warehousing market is turning to the implementation of high rack storage.  High rack storage is the system of storing manufactured goods on complex systems of shelves and conveyors and often is completely automated.  High racking has proven to be a very efficient storage method but often is not implemented because of a mere lack of available space.  This is the problem Albertson's, Inc. faced when they decided to convert 620,000 square feet of an existing facility into a high capacity distribution center.  The existing facility however had a clear height of 18 feet, which for high racking is simply too low to be utilized effectively.  The owners were given the options of demolishing and rebuilding the roof at a new clear height or building a separate structure to meet their growth.  Their other alternative was to lift the existing roof 20 feet.

HIGH RACKING SYSTEMS
In the past decade construction of new warehouse and distribution buildings have undergone several changes.  The most prevalent being the implementation of increased ceiling heights.  The idea behind the design of these high-cube structures is to accommodate the ever-increasing needs of distribution companies.  Until recently many buildings have been built with 14 to 18 foot ceilings, some up to 24 feet.

One of the underlying reasons for this increased ceiling height is the continuing increase in the height of racking systems.  Extended pallet racking is now reaching up to 40 feet and often reduces the retrieval time and storage of products.  This advancement enables companies to take full advantage of the cubic feet within a warehouse.

ADDITIONAL INFLUENCES
In addition to end users, owners/landlords are also a driving force behind higher clear heights.  Many structures are considered undesirable if they are below 24 feet, making them difficult to sell or lease.  This gives owners incentive to modify their existing building to suit the needs of today's distribution and warehouse market.  Advancements in flexible high intensity lighting and highly effective ESFR sprinkler systems also allow clear heights to be safely higher than they have been in the past.

WHY BUILD UP
In general it is less expensive to build upward than outward in commercial and industrial buildings.  Using the existing roof and lifting it offers several advantages:

• No need to acquire additional land.

• Considerably less new construction.

• Significantly earlier completion.

ALBERTSON'S AT MELROSE PARK
After determining that high racking would triple the usable storage capacity of the facility, a decision was made to raise the existing 620,000 square foot roof of the building.  Liftplate International, Inc., a Florida based company specializing structural lifting, was contacted by A. Epstein & Sons, International, Inc. to provide a scenario that would allow Albertson's to gain the much needed space and yet allow Albertson's to maintain operations within the facility.  What they proposed turned out to be not only more cost effective but also considerably faster that any other feasible option.

THE STRUCTURE
The distribution center is located in the Chicago suburb of Melrose Park.  For the purpose of continuing storage and retrieving operations with the least amount of interruption, the 620,000 square foot area will be divided in five sections with each section being lifted after a previous section is at a new elevation and fitted with new high storage racks.  A temporary tunnel that passes through the area under construction maintains traffic for continued operations.  The largest roof section measures 154,000 square feet and will be lifted 20 feet with 138 lifting posts to achieve a final elevation under the trusses of 38 feet.  The entire five-section project is scheduled to be completed within fourteen months.

THE PROCESS
The process to lift the roof incorporates proprietary equipment designed and utilized by Liftplate.  This equipment, called CribPost, is essentially a "modular hydraulic post shore".  Each lifting point consists of an individual CribPost that is powered a 25-ton hydraulic jack.  For the first section, 87 CribPosts were set up in a 95,000 square foot section of the building.  The CribPosts operate by pushing post sections, or cribs, up through a loading frame at the base of the CribPost.  The loading frame contains the hydraulic jack and allows for the addition of individual crib sections.  Each of these sections is twenty-four inches high and weighs only 43 pounds.  As the jack pushes up the cribs through the frame, a gap is created allowing a new crib section to be inserted.  The hydraulics' are reset every twelve inches while new cribs are added every two feet.  This unique feature enables workers to conduct all aspects of the lift from floor level and eliminates the need for work potentially dangerous hydraulic work at the top of the columns.  In addition, this system allows the load to be held at any point mechanically.  This is essential not only to allow transfer of the load off the hydraulic jack but is an absolute necessity for safety as it operates as a device to prevent any fall-back in the event of a leak or hydraulic failure.

Another unique feature of the CribPost system is that the posts operate in a telescoping fashion.  This allows for guy cables to be attached to the posts.  Four 3/8-inch steel cables are attached from the post to the floor.  A clevis allows each cable to be tensioned after installation.  In order to continue lateral support at higher levels the “guy-sleeves” on the posts are extended in key locations and new cables are added at higher levels.  A tension meter is used to ensure that all cables pull with the same force.  During lifting, lateral positioning is monitored by lasers targeted on the roof in all four corners and at the control board.

To relieve the differential loads caused by internal stresses in the structure before lifting, Liftplate combined or “manifolded” lifting points carrying approximately the same load, thereby bringing the number of lifting points down from 87 to 40.  Most columns had two lifting points others had only one.  “Manifolding” accomplishes two things, one is that it reduces the number of points to be controlled, and the other—and most important—is that the differential loads become equal loads.  Each manifolded zone had one electric/hydraulic pump.  These pumps were then controlled by Liftplate's synchronization and monitoring system.

On this project each column was cut about six feet from the floor before lifting.  As the roof was lifted, a twenty-foot gap was created between the top and bottom sections of the column.  This technique allowed the pre-fabricated splice-sections to be quickly welded into place after the intended clear height was reached.  In other methods the lifting process relies on  "wrapping" the existing column with a steel sleeve and allowing the severed column to slide up through the sleeve as the roof is lifted.  Although this is a viable method, it is also very time consuming and considerably more expensive than adding splice-sections.  The splice-sections also afford the opportunity to have the new column section match the dimensions of the old while the "wrapping method" will substantially increase the overall dimensions of the new column.  Once the roof is lifted and all splice-sections welded in place the CribPosts are quickly dismantled and palletized for transport.  This system allows other contractors to start their work immediately after the lift. 

THE RESULT
Liftplate International, together with A. Epstein & Sons International, successfully completed lifting of the first section on January 16.  With the completion of only one section of the facility Albertson's is already taking advantage the "revived" 87,000 square foot high capacity area and effectively meeting the demand for growth their company requires.

Mason M. Harris,  is the general manager of Liftplate International Inc., 18571 SW 104 AVE, Miami, FL 33157

Copyright © 2002 Liftplate International, Inc.