1. History of Design Methodology1
History of Design Methodology
Joseph P. Zicaro, P.E.

2. What is indirect design What is direct design What is SPIDA
What is SIDD

3. History 1910 Marston Theory 1911-1916 Laboratory Tests Sand bearing
2 edge bearing
3 edge bearing
Iowa exp. Station
Strength comparisons
Mechanical gage

4. 1920-1930’s Spangler Supporting strength in culvert embankments
’s Spangler Supporting strength in culvert embankments James M. Paris – Stress coef Schlick Loads – Wide trenches Spangler & Schlick Negative projection conduits 1950 H. Olander (USBR) Stress analysis of conc. pipe

5. Structural behavior of concrete pipe 1970 ACPA European study mission
F.J. Heger
Structural behavior of
concrete pipe
1970 ACPA European study mission
Non-circular shapes
Non-reinforced concrete pipe
Research program
Soil-pipe interaction design &
analysis ( SPIDA )

6. Northwestern University Dr. R. Parmalee Simpson, Gumpertz & Heger
Dr. F. Heger
University of Mass.
Dr. E. Selig
1980’s Caltrans Research
Dimension ratio
CP Info 12 Lateral pressure
& Bedding factors

7. 1992 Design Data 40 Standard Installations & Bedding Factors 1994 ASCE Direct Design of Concrete Pipe (Standard Installations)

8. Research Confirmed 1. Marston, Spangler and Schlick research was very good. 2. Loosely placed soil directly under the invert significantly reduces stressed in the pipe. 3. Compaction level of the soil from the pipe springline to the top of the pipe grade, has negligible effect on the pipe stresses. Compaction is not necessary unless required for pavement structures. 4. Typical compaction in the haunch area is difficult to achieve and can not be depended on. ( voids are included in SPIDA designs.))

9. D-Load Test (Indirect Design)
A test procedure that applies a concentrated load to the pipe to cause the same service load moment (established by the bedding factor) as would occur in the installed pipe without exceeding a crack width of 0.01 inch. The test load is then increased beyond the service load to a minimum ultimate load.

10. Bedding Factor
Ratio of the supporting strength of a buried pipe to the strength determined in the three-edge bearing test. The better the installation the greater the bedding factor.

11. 3 Edge Bearing Loading
The most severe loading that pipe will be subject to.
No lateral support
Applied forces virtually point loads

12. Vertical Load

13. Marston/Spangler Theory of External Loads on Closed Conduits - Iowa State College, 1930 -
EFFECTS OF LATERAL PRESSURES IGNORED when bedding factors were established in 1930

14. Fig. 1a - Trench Beddings, Circular Pipe

15. Fig. 1b - Trench Beddings, Circular Pipe

16. Class B bedding No lateral force
Bedding angle = 75 degrees Mom. Field = We Dm Mom 3eb = Q Dm B.F. = / B.F. = 1.85

17. M 75 deg = We Dm 75
We = (0.159 / 0.086)Q =1.85 Q

18. Bedding Factors – Vertical Load

19. Standard Installation & Bedding Factors for the Indirect Design Method - 1992 -
EFFECTS OF LATERAL PRESSURES INCLUDED as per conclusions of 20 year research program. Dr. Frank J. Heger Simpson, Gumpertz & Heger Cambridge, Mass.

20. Lateral Pressure Active pressure Passive pressure
Decreases bending moments in the pipe wall.
Increases pipe supporting strength

21. Lateral forces acting in the field
Lateral forces acting in the field. Cause bending in the opposite direction. M lat. = We Dm, for k =0.33 B.F. = 0.159/ ( ) =2.49

22. Bedding Factors – Lateral Load
We also have lateral forces acting in the field,
which cause bending in the opposite direction.
For Rankin k = 0.33
MLAT = We Dm

23. Bedding factors Uniform lateral pressure
Mfield = Mom vertical + Mom lateral = 0.085WeDm – 0.021WeDm = We Dm M3eb = 0.159Q Dm B.F. = 0.159/0.064 B.F = 2.49

24. Direct Design
Design based on the loads applied and the earth pressure distribution of the design bedding. ( installed condition). Such design considers all forces, vertical, horizontal and internal pressure. Flexural strength Shear strength Radial tension strength Concrete compression service load crack control.

25. Spangler Research

26. Paris Design Method

27. Paris Radial Forces

28. Olander Force Distribution

29. Caltrans Reasearch

30. Caltrans Lateral Force Ratio

31. SPIDA
A finite element design method that specifically considers the type of soils and compaction, as incrementally applied in the actual construction of the installation. An exacting procedure as a function of the soil factors and the pipe response to those loads.

32. SPIDA

33. SIDD
A direct design procedure based on SPIDA, but using the lower range values of the soil information in determining the design factors and therefore a more conservative application of SPIDA. Voids and soft inclusions are assumed to exist from 15 to 40 degrees each side of the invert.

34. SIDD

35. Figure 4: Arching Coefficients and Heger Earth Pressure Distributions

36. SIDD

37. SIDD

38. SIDD

39. Bedding factors
Old Method New Method Class A Type 1 Class B Type 2 Class C Type 3 Class D Type 4

40. SIDD Bedding Factors
M 3eb = Nfs (D + t) Mfield = Mfi – 0.38 Nfi Nfi C Nfs = thrust at springline Mfi = mom at invert Nfi = thrust at invert D = diameter t = wall thickness C = cover over steel B.F. = M3eb / Ffield

41. Bedding Factors
Old Factors Embankment Trench Class A 3.6 – Class B 2.5 – Class C 1.7 – Class D New Factors Embankment Trench Type – Type – Type Type

42. Embankment Installation Bedding Factors
Dia. Type 1 Type 2 Type 3 Type

43. Variable Trench Bedding Factor
Bfv = (Bfe–Bfo)(Bd–Bc)/(Bdt-Bc) –Bfo
Bc = Outside horizontal span of pipe, ft.
Bd = Trench width at top of pipe, ft.
Bdt = Transition width at top of pipe, ft.
Bfe = Bedding factor , embankment.
Bfo minimum bedding factor , trench.
Bfv = Variable bedding factor , trench.

44. Bedding Factors Comparison

45. What is SPIDA and SIDD
Results of 25 years Research Covering a Range of Installations

46. Standard installations ( SIDD ) Provide
1. Improved load modeling
2. Embankment ( Max ) Loads
3. Safety factors maintained
4. Quantifiable installations
5. Established by independent experts
6. Conservative design
(Based on hard sub-base and voids )