Sustainable Land Development Today - July/August 2008 - (Page 34) GEOSYNTHETICS Ensuring Security With Careful Planning and Design Combining fencing and retaining walls may fail if not designed and implemented without careful consideration to engineering factors. By Jon Calle S Security is a top priority in the shipping industry. So when plans for DHL’s new 290,000-square-foot distribution facility in Allentown, Pennsylvania called for 3,450 linear feet of retaining wall along the perimeter of this 72-acre site, the chain link fencing above the walls quickly became a topic of concern for the wall contractor and construction manager. “It is rarely understood by clients that fencing cannot be installed on top of perimeter walls without careful design considerations,” states Andre De Carville, Vice President of Pickering Valley Landscape, Inc. “The grading plan noted a fence above every wall but did not provide a structural detail showing how to integrate our work with that of the fence contractor.” Segmental Retaining Walls (SRW) most appealing quality is how the dry stacked block face and geosynthetic reinforcement (Geogrid) combine to form a retention system capable of holding back steep slopes and handle heavy loads. A limitation, however, is that the dry stacked wall face has minimal resistance to overturning in the upper two or three courses when a point load is applied to the block. This is precisely what happens when a load is placed on a fence post in close proximity to the wall face. That, along with tearing through the embedded soil reinforcement behind the wall with an auger, can greatly affect both the integrity of the wall and fence structures. New pre-engineered product offers a solution At this point, Strata Systems, the manufacturer of an advanced, pre-engineered product called Sleeve-It™ 1224R was contacted. This fence-ready and code compliant design was created to address the very issues the construction team was concerned about. Strata provided test reports and additional calcu- lations to the project engineer explaining how the Sleeve-It approach meets or exceeds the building code requirements for railings along the sides of elevated walking surfaces. A Strata technical representative was also made available for further on-site consultation. With only 10 days from the bid award date to provide a final wall design and 120 days from ground breaking for the new facility to be fully operational there was no time to waste. “We recommended the use of the preengineered Sleeve-It system to the construction manager, Opus Corporation, for integrating the chain link fence with the SRWs.” says wall design engineer Bart Shippee PE. “The Sleeve-It product test data translates exceptionally well for a six-foot tall chain link fence with tenfoot post spacing addressing the IBC load criteria for railings in commercial applications.” A simple and effective installation process In all, over 350 Sleeve-It units were installed during wall construction. SleeveIt 1224R is typically pre-assembled at the material staging area for the wall then set 34 July/August 2008 Sustainable Land Development Today
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