Structural Design of Rigid and Flexible Pipe www
Structural Design of Rigid and Flexible Pipe www. concrete-pipe. org
2 Pipe Info RCP • Pipe ID = 48 inches § OD – B Wall = 58 in. = 4. 83 ft. www. concrete-pipe. org HDPE • Pipe ID = 48 inches • Manufacture = 54. 26 in. = 4. 52 ft.
3 Soil Parameters • What is the insitu soil? § Firm silt • What is the embedment material? § Silt § 90% proctor compaction • How wide is the trench? § Positive projecting embankment - NA • How deep is the installation? § 8 feet www. concrete-pipe. org
4 Indirect Design Process 1. Determine pipe installation method 2. Select bedding / standard installation 3. Calculate earth load 4. Calculate live load 5. Determine bedding factors 6. Factor of safety 7. Select pipe strength www. concrete-pipe. org
2. Select Standard Installation Type 3 – 90% Sandy Silt www. concrete-pipe. org 5
7 3. Calculate Earth Load • WE = Few. Bc. H (12. 10. 2. 1 -1) § WE = unfactored earth load (lbs/ft) § Fe = soil-structure interaction factor (VAF) § w = unit weight of soil (pcf) § Bc = outside horizontal dimension (ft) § H = height of fill over pipe (ft) w. Bc. H = Soil Prism Load - PL www. concrete-pipe. org
3. Calculate Earth Load Fe = VAF = 1. 40 www. concrete-pipe. org 8
9 3. Calculate Earth Load • Soil Prism Load § PL = w H Do § PL = (120 lbs/ft 3)(8 ft. )(4. 83 ft. ) § PL = 4, 637 lbs/ft www. concrete-pipe. org
10 3. Calculate Earth Load • WE = Few. Bc. H (12. 10. 2. 1 -1) WE = Fe PL WE = 1. 40 x 4, 637 lbs/ft WE = 6, 492 lbs/ft www. concrete-pipe. org
11 Calculate Fluid Load • www. concrete-pipe. org
12 4. Calculate Live Load • Total Live Load is negligible at H ≥ 8 • WL = 0 www. concrete-pipe. org
5. Determine Bedding Factors Bf = MTEST MFIELD Where: Bf = Bedding factors MFIELD = Maximum load in pipe under field loads before failure, N/m (inch-pounds) MTEST = Maximum load in pipe under three-edge bearing test before failure, N/m (inch-pounds) www. concrete-pipe. org 13
15 5. Determine Bedding Factors Bf = 2. 26 www. concrete-pipe. org
17 6. Determine the factor of safety • A factor of safety of 1. 0 based on the service limit state using a 0. 01 inch crack will be applied. www. concrete-pipe. org
7. Select Pipe Strength • Solve for the D-Load • • • D-Load = (WE + WF) + WL * FS Bfe Bf. LL D Where: WE = Earth load, (lbs/ft) WF = Fluid load, (lbs, ft) WL = Live load, (lbs/ft) Bfe = Earth load bedding factor Bf. LL = Live load bedding factor D = Pipe diameter, (ft) FS = Factor of safety www. concrete-pipe. org 18
7. Select Pipe Strength • Solve for the D-Load • D-Load = 6492 + 780. 5 * 1. 0 2. 26 4 D-Load = 804. 5 lb/ft/ft ASTM C 76 Class II RCP www. concrete-pipe. org 19
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