Precast Concrete Pipe Design

1. Portland, OR Precast Concrete Pipe Design Josh Beakley Director of Technical Services www.concrete-pipe.org

2. 2 Outline • Soil-Structure Interaction • Standard Concrete Pipe Design • Special Design of RCP www.concrete-pipe.org

3. Basic Soil Pressures on Pipe INSTALLED CONDITION

4. Rigid vs Flexible Pipe– Vertical Live load Live load Dead load Dead load Rigid Pipe Flexible Pipe Flexible Flexible Flexible Stiff Stiff Stiff Flexible pipe – embedment soil must carry most of the load. Rigid pipe – the pipe carries the majority of the load.

5. Rigid vs Flexible Pipe– Horizontal Live load Live load Dead load Dead load Lateral support Rigid Pipe Flexible Pipe Passive support Flexible pipe deflects until the side soil can carry the load. Lateral support has slight affect on the Bedding Factor for RCP

6. Flexible Pipe • Flexible pipe - Can deflect 2% or more without structural damage (cracking).

7. Deformation of a Concrete Pipe

8. Rigid Pipe Flexure Crack Control Radial Tension Diagonal Tension (shear) Flexible Pipe Deflection (Strain) Wall Thrust Buckling Stress Local Buckling Design Criteria

9. Pipe/Soil Structure - Concrete Pipe Pipe Class 3EB Capacity = Load / Bedding Factor Ratio of field conditions to test conditions

12. Installation Standards for Culvert, Storm, and Sewer Pipes • Concrete Pipe • ASTM C 1479 – “Standard Practice for Installation of Precast Concrete Sewer, Storm Drain, and Culvert Pipe Using Standard Installations” • AASHTO LRFD Bridge Construction Specifications, Section 27, “Concrete Culverts” • Thermoplastic Pipe • ASTM D 2321 – “Standard Practice for Underground Installation of Thermoplastic Pipe for Sewers and other Gravity Flow Applications” • AASHTO LRFD Bridge Construction Specifications, Section 30, “Thermoplastic Pipe” • Metal Pipe • ASTM A 798 – “Standard Practice for Installing Factory-Made Corrugated Steel Pipe for Sewers and Other Applications” • AASHTO LRFD Bridge Construction Specifications, Section 26, “Metal Culverts”

13. AASHTO Section 12.10.1 General • “The structural design of the types of pipes indicated above may proceed by either of two methods: • The direct design method at the strength limit state as specified in Article 12.10.4.2, or • The indirect design method at the service limit state as specified in Article 12.10.4.3.”

14. For Special Cases, use the Direct Design Method

15. Indirect Design Method

16. ASTM C 76

17. ASCEStandard 15-93 American Society of Civil Engineers Standard Practice for Direct Design of Buried Precast Concrete Pipe Using Standard Installations (SIDD)

18. Design and Installation • Standard Installations • Developed by ASCE (15-93) • Adopted by AASHTO (Sections 17 & 27) • LRFD Section 12 and Section 27 of Construction Standard

19. PIPE/INSTALLATION TERMINOLOGY H Do Crown Overfill Haunch Springline Lower Side Di Bottom Bedding Invert

20. Overfill Soil Category I, II, III Standard Embankment Installation Do / 6 (Min.) Do Do (Min.) H Haunch- See Table Springline Di Lower-Side See Table Bedding See table Do / 3 Middle Bedding loosely placed uncompacted bedding except for Type 4 Outer Bedding materials and compaction each side, same requirements as haunch Foundation

21. Standard Installation Soils and Minimum Compaction Requirements

22. EQUIVALENT USCS AND AASHTO SOIL CLASSIFICATIONS FOR SIDD SOIL DESIGNATIONS

23. INSTALLATION TYPE INCREASEDPIPE DESIGN PIPE STRENGTH INSTALLATION QUALITY INCREASED MATERIAL QUALITY 1 2 3 4

24. Calculation of Earth Load Final Grade We = prism load x VAF Where : VAF = vertical arching factor as per Heger distribution Prism Load Area O.D.

25. A B Trench Soil Load Bd F Wc load on pipe C D Bc Side fill P = weight of backfill, ABCD; F = upward shear on AC, BD W = P - 2F

26. Vertical Pressures TRENCH

27. Embankment Installation Soil Prism Frictional Forces Natural Ground

28. Vertical Pressures

29. www.concrete-pipe.org

30. ARCHING FACTORS

31. Embankment Installation Soil Prism Frictional Forces Natural Ground

35. Data Acquisition Sys DC Power Supply

36. Design Steps 1. Select Bedding 2. Determine Earth Load 3. Determine Live Load 4. Determine Bedding Factor 5. Application of Factor of Safety 6. Selection of Pipe Strength

37. AASHTO LRFD 12.10.2.1 • WE = Fe w Bc H • Fe = Soil-structure Interaction Factor • w = unit weight of soil (pcf) • Bc = outside diameter of pipe (ft) • H = height of fill over the pipe (ft) www.concrete-pipe.org

38. AASHTO LRFD 12.10.2.1 • “Standard installations for both embankments and trenches shall be designed for positive projection, embankment loading conditions where Fe shall be taken as the vertical arching factor, VAF, specified in Table 12.10.2.1-3 for each type of standard installation.” www.concrete-pipe.org

39. AASHTO LRFD 12.10.2.1

40. AASHTO LRFD 12.10.2.2 – Pipe Fluid Weight • “The unfactored weight of fluid, WF, in the pipe shall be considered in design based on a fluid weight of 62.4 lb./ft3, unless otherwise specified.” www.concrete-pipe.org

41. D-Load Equation www.concrete-pipe.org

42. Bedding Factor Vs. www.ccpa.com

43. Basic Bedding Factor Relationship

44. Bedding Factors 75o M = 0.170 We r M = 0.318 P r We /P = 1.9 = Bf

45. Earth Load Bedding Factor

46. ASTM C 76 Pipe Classes • Class I - D0.01 = 800 lbs/ft/ft • Class II - D0.01 = 1000 lbs/ft/ft • Class III - D0.01 = 1350 lbs/ft/ft • Class IV - D0.01 = 2000 lbs/ft/ft • Class V - D0.01 = 3000 lbs/ft/ft

47. AASHTO LIVE LOAD DESIGN

48. Less Than 2 Feet of Cover E = 96 + 1.44S (4.6.2.10.2-1) E = Distribution width perpendicular to span in inches S = Clear Span in feet

49. Less Than 2 Feet of Cover Espan = Distribution width parallel to span in inches Espan = LT + LLDF(H) LT = length of contact area parallel to span (in) LLDF = live load distribution factor H = depth of fill

50. Live Load Spread for Less Than 2 feet of Cover (single axle) (Perpendicular) E Espan