Precast Solutions - March/April 2008 - (Page 19)

The higher the level of importance of the application, the more important it is to consider long-term performance. Concrete pipelines in critical applications have a long history of high performance. assist with stormwater quality; • any portion of a storm sewer that controls runoff volume to downstream properties; and • any run of the pipeline that would be difficult to replace due to depth of bury or proximity to other critical structures or services. portion of storm drain. Fill height tables should be used only in the following scenarios: • The designer completely understands the design and trench condition assumptions made to develop the fill height table. • The fill height table is developed in such a way that the design engineer can select a conservative The higher the level of importance of the application, the more important it is to consider long-term performance, including confirmed structural strength in the decision of the pipe material to be selected. Concrete pipelines in critical applications have a history of high performance. Pipeline design must address hydraulics of the system and structural capacity to accommodate anticipated loads. The design process cannot be completed without a thorough knowledge of pipe materials and how the structure is designed. There is a fundamental difference in the structural design requirements for rigid and flexible pipelines. • The structural component of pipe design is often overlooked, taken lightly or oversimplified with fill height tables. The use of published fill heights may be sufficient in non-critical applications or installations; however, almost every project contains a critical trench installation that he or she is confident can be met or exceeded on the job site. • The project has trench backfill materials and installation requirements that meet or exceed fill height table assumptions. • The designer has the flexibility to be conservative in his or her selection of an allowable/maximum fill height. • In critical application areas, the designer should complete a full structural design or be able to use an accepted design confirmation process or tool to make sure the pipe product will accommodate the anticipated construction and lifetime loads. Full design or structural confirmation of any pipe product requires the following: • The engineer must know construction site conditions and soil properties, or specifications and installation details that clearly specify in-situ soil and MARCH/APRIL 2008 | PRECAST SOLUTIONS 19

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Precast Solutions - March/April 2008 Contents Smooth Move Riding the Waves Comparing RCP With Plastic Pipe Cost-Value Analysis of Storm Sewer Pipe Concrete Testing On a Grand Scale Building Confidence

Precast Solutions - March/April 2008

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