CONCRETE PIPE Curved Alignment Change of direction in sewers is usually accomplished at manhole structures. Grade and alignment changes in concrete pipelines can be incorporated through the use of deflected straight pipe, beveled (radius) pipe, or bends. When concrete pipe is to be installed in a curved alignment, local concrete pipe manufacturers should be consulted regarding manufacturing and installation feasibility. Many manufacturers have standardized joint configurations and deflections for specific radii and economies may be realized by using standard pipe. Defected Straight Pipe When concrete pipe is installed in a straight alignment and the joints are in a home (or normal) position, the joint space or distance between the ends of adjacent pipe sections is essentially uniform around the periphery of the pipe. Starting from this home position any joint may be opened the maximum permissible amount on one side while the other side remains in the home position. The difference between the home and opened joint space is generally designated as the pull. The maximum permissible pull must be limited to that opening which will provide satisfactory joint performance. This varies for different joint configurations and is best obtained from the pipe manufacturer. The radius of curvature which may be obtained by this method is a function of the diameter of the pipe, length of the pipe sections, and the deflection angle per joint. The radius of curvature is computed by the equation below: R= L 2 tan      2N   Where R = radius of curvature L = laying length of pipe section measured along the centerline L D = total deflection angle of curve  Pull R Pull = -1 =N sin sin = number of pipe with =  -1joints 2B 2(D+2t)  pulled 2N D/N = total deflection  of each pipe c 2 tan angle 2N   One half the deflection angle, D/2N is defined as:  2N = sin-1 Pull 2(D+2t) = sin-1 Pull 2Bc Where: Pull = joint opening D = inside pipe diameter t = wall thickness Bc = outside pipe diameter PAGE 38 LAFARGE PIPE eMANUAL