Client: Perini Corporation
Contract Value: $2 Million
Description: Engineering of the precise geometry of large diameter pipeline
involving multiple compound deflections in three dimensions.

In preparation for mass-transit expansion in Cambridge, Massachusetts, the MBTA undertook to relocate more than 1,000 feet of 48” water main. Butt-welded steel pipe would snake through this congested urban area passing through three deep jacked “tunnels” and involving numerous valves, tees and elbows. Because butt welds in large diameter pipe are very unforgiving of even minor misalignments, it was important to resolve the exact geometry of the entire line before fabrication.

Test pits were dug to establish the location, direction, and slope at all tie in points. At several locations, 45-degree elbows were used in pairs to achieve major changes in direction, slope and elevation. Although pipe work is not usually very mathematically “glamorous”, the resolution of the exact geometry in this case was complicated by the non-orthogonal nature of all of the systems pipe runs and components. To establish centerline mathematics as well as the placement and roll of the various fittings, analytic geometry provided the required systems of equations and numerical analysis techniques were employed to solve them. The resulting plan of centerline geometry became the basis for shop drawing preparation, fabrication and layout for this unusually complex utility.

Although the original work was done with programmable calculators, subsequent work in this area has resulted in a comprehensive set of routines to solve a wide range of 3-D problems within the CAD environment.