History of Design Methodology 1 History of Design Methodology Joseph P. Zicaro, P.E. www.concrete-pipe.org

What is indirect design What is direct design What is SPIDA What is SIDD www.concrete-pipe.org

History 1910 Marston Theory 1911-1916 Laboratory Tests Sand bearing 2 edge bearing 3 edge bearing 1923 Iowa exp. Station Strength comparisons Mechanical gage www.concrete-pipe.org

1920-1930’s Spangler Supporting strength in culvert embankments 1920-1930’s Spangler Supporting strength in culvert embankments. 1921 James M. Paris – Stress coef. 1930 Schlick Loads – Wide trenches 1949-1953 Spangler & Schlick Negative projection conduits 1950 H. Olander (USBR) Stress analysis of conc. pipe www.concrete-pipe.org

Structural behavior of concrete pipe 1970 ACPA European study mission 1963 F.J. Heger Structural behavior of concrete pipe 1970 ACPA European study mission Non-circular shapes Non-reinforced concrete pipe 1970-1989 Research program Soil-pipe interaction design & analysis ( SPIDA ) www.concrete-pipe.org

Northwestern University Dr. R. Parmalee Simpson, Gumpertz & Heger Dr. F. Heger University of Mass. Dr. E. Selig 1980’s Caltrans Research Dimension ratio 1991 CP Info 12 Lateral pressure & Bedding factors www.concrete-pipe.org

1992 Design Data 40 Standard Installations & Bedding Factors 1994 ASCE Direct Design of Concrete Pipe (Standard Installations) www.concrete-pipe.org

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.)) www.concrete-pipe.org

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. www.concrete-pipe.org

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. www.concrete-pipe.org

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

Vertical Load www.concrete-pipe.org

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 www.concrete-pipe.org

Fig. 1a - Trench Beddings, Circular Pipe www.concrete-pipe.org

Fig. 1b - Trench Beddings, Circular Pipe www.concrete-pipe.org

Class B bedding No lateral force Bedding angle = 75 degrees Mom. Field = 0.086 We Dm Mom 3eb = 0.159 Q Dm B.F. = 0.159 / 0.086 B.F. = 1.85 www.concrete-pipe.org

M 75 deg = 0.086 We Dm 75 We = (0.159 / 0.086)Q =1.85 Q www.concrete-pipe.org

Bedding Factors – Vertical Load www.concrete-pipe.org

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. www.concrete-pipe.org

Lateral Pressure Active pressure Passive pressure Decreases bending moments in the pipe wall. Increases pipe supporting strength www.concrete-pipe.org

Lateral forces acting in the field Lateral forces acting in the field. Cause bending in the opposite direction. M lat. = -0.021 We Dm, for k =0.33 B.F. = 0.159/ (0.085-0.021) =2.49 www.concrete-pipe.org

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 = -.021 We Dm www.concrete-pipe.org

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

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. www.concrete-pipe.org

Spangler Research www.concrete-pipe.org

Paris Design Method www.concrete-pipe.org

Paris Radial Forces www.concrete-pipe.org

Olander Force Distribution www.concrete-pipe.org

Caltrans Reasearch www.concrete-pipe.org

Caltrans Lateral Force Ratio www.concrete-pipe.org

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. www.concrete-pipe.org

SPIDA www.concrete-pipe.org

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. www.concrete-pipe.org

SIDD www.concrete-pipe.org

Figure 4: Arching Coefficients and Heger Earth Pressure Distributions www.concrete-pipe.org

SIDD www.concrete-pipe.org

SIDD www.concrete-pipe.org

SIDD www.concrete-pipe.org

Bedding factors Old Method New Method Class A Type 1 Class B Type 2 Class C Type 3 Class D Type 4 www.concrete-pipe.org

SIDD Bedding Factors M 3eb = 0.318 Nfs (D + t) Mfield = Mfi – 0.38 Nfi - 0.125 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 www.concrete-pipe.org

Bedding Factors Old Factors Embankment Trench Class A 3.6 – 4.8 2.8 Class B 2.5 – 2.9 1.9 Class C 1.7 – 2.3 1.5 Class D 1.1 1.1 New Factors Embankment Trench Type 1 3.6 – 4.4 2.3 Type 2 2.8 – 3.2 1.9 Type 3 2.2 - 2.5 1.7 Type 4 1.7 1.5 www.concrete-pipe.org

Embankment Installation Bedding Factors Dia. Type 1 Type 2 Type 3 Type 4 12 4.4 3.2 2.5 1.7 24 4.2 3.0 2.4 1.7 36 4.0 2.9 2.3 1.7 72 3.8 2.8 2.2 1.7 144 3.6 2.8 2.2 1.7 www.concrete-pipe.org

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. www.concrete-pipe.org

Bedding Factors Comparison www.concrete-pipe.org

What is SPIDA and SIDD Results of 25 years Research Covering a Range of Installations www.concrete-pipe.org

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 ) www.concrete-pipe.org