Design and Analysis of Burried fiberglass Pipeline based on "Fiberglass Pipe Design Manual M-45 Standard"

This guidline is intended to provide the design and system engineers with the general scheme of designing and analysing the burried GRP composite pipning system. It is only a general guidline as proposed by AWWA M-45 manual.

Design Methodalogy for Buried GRP Composite Pipe lines

1. Determining the soil load acting on the pipe at minimum and maximum burial depth

2. Determining the live (trafic) load exerted on the pipe at minimum and maximum burial depth.

3. Calculate the predicted pipe deflaction. Compare the prdicted value with the maximum allowable

deflection of the Faratec GRP pipe to ensure that predicted deflection is less than the maximum

allowable deflection.

4. Verify that the working pressure is less or equal to the nominal pressure (PN).

5. Verify that the surge pressure is less than allowable limit. (1.4*PN)6. Calculate the hoop tensile strain at working pressure7. Calculate the bending strain at th8. Calculate the bending strain. 9. Verify that the combined loading conditions are satisfied for pressure as influenced by bending and

bending as influenced by pressure.10. Calculate critical buckling pressure at minmum and maximum bur11. Verify that buckling safety factor is satisfied for both normal and for trafic conditions

Equtions Used For Design and Analysis

Soil load Calculations

Where:

Wc = soil load - N / m^2

dens = soil density -

H = burial depth � m

Traffic Load Calculation

Wl = (P) * (If) / (L1 * L2)

Load width parallel to travel

L1 = 0.253 + 1.75 * H

If = 1 for H => 0.91

If = 1.1 for H < 0.91

Where:

Wl = traffic load - N / m^2

Verify that the surge pressure is less than allowable limit. (1.4*PN) Calculate the hoop tensile strain at working pressure Calculate the bending strain at the maximum allowed deflection

Verify that the combined loading conditions are satisfied for pressure as influenced by bending and bending as influenced by pressure. Calculate critical buckling pressure at minmum and maximum burial depth Verify that buckling safety factor is satisfied for both normal and for trafic conditions

Used For Design and Analysis for Buried GRP Composite Pipe lines

Wc= (dens) * H

N / m^2

- N / m^3

m

Load width parallel to travel Load width perpendicular to travel

L1 = 0.253 + 1.75 * H for H < 0.756 m L2 = 0.509 + 1.75 *H

for H => 0.756 m

If = 1 for H => 0.91

for H < 0.91

N / m^2

Typical Pipe Stiffness

Verify that the combined loading conditions are satisfied for pressure as influenced by bending and

Verify that buckling safety factor is satisfied for both normal and for trafic conditions

for Buried GRP Composite Pipe lines

Load width perpendicular to travel

L2 = 0.509 + 1.75 *H

L1 = width parallel - m

L2 = width perpend. - m

P = load - N

If = impact factor

Deflaction Calculation

kx * ( Wl + Dl * Wc)

dD/D = ----------------------------- * 100

8*SN + 0.061 * E'b * Sc

Where:

dD = deflection - %

SN = stiffness - N /m^2

E'b = backfill modulus - N / m^2

Dl = deflection lag factor ( For genereal analysis purposes a value of 1.5 is reasonable

assumption.

Sc = soil support combining factor (function of diameter and trench width)

kx = bedding coefficient

NOTE: dD/D must be greater or equal to the dDmax ( maximum allowed deflection %)

Working Pressure

Pw < = PN

Where:

Pw = working pressure - bars

PN = rated pressure � bars

Surge Pressure

Pw + Ps < = 1.4 * PN

Where:

Pw = working pressure - bars

PN = rated pressure � bars

Ps = surge pressure � bars

Pressure Strain Calculation

Pw * ( OD - t)

Ep = ------------------------- * 100

2 * Eht * tr

Where:

Pw = working pressure - bars * 100000 (Mpa)

OD = pipe outside diameter - mm

t = pipe wall thickness - mm

Eht = hoop tensile modulus - Gpa

tr = reinforced wall thickness - mm

ep = pressure strain - %

Bending Strain at max deflection Calculation

Df * t * dDmax

ebmax = -----------------------------------

(OD - t)

Where:

Df = shape factor - dimensionless

dDmax = max allowed long term deflection -%

t = wall thickness � mm

OD = pipe outside diameter - mm

ebmax = bending strain at max deflection - %

Rerounded bending strain Calculation

eb = Rc * ebmax

Where:

Rc = 1 - PN / 30 (rerounding coefficient � dimensionless)

Combined Loading Calculation

Pressure influenced by bending

1 - eb / Sb

ep / HDB < = --------------------------

1.8

Bending influenced by pressure

1 - eb / Sb

ep / HDB < = --------------------------

1.8

Where:

HDB = hydrostatic design basis - % strain

eb = rerounded bending strain - % strain

ep = pressure strain - % strain

Sb = long term ring bending strain - % strain

Note: 1.8 and 1.5 values are the maximum safety factor for pressure and for bending

Critical Buckling Pressure Calculation

qc = ( 32 * Rw * B' * SN * E' * Sc ) ^0.5

Where:

qc = critical buckling pressure - N / m^2

E'b = backfill modulus - N / m^2

Sc = soil support combining factor - dimensionless

Rw = 1 - 0.33 *( H - hw) / H (water buouancy factor � dimensionless)

H = burial depth - meters

hw = height of ground water over pipe � meters

1

B� = -------------------------- coefficient of elastic support - dimensionless

1 + 4 0.213 H

Buckling Safety Factors Calculation

q c / q = > 2.5

a. typical conditions

q = Wc + Ww + Wv

b. traffic conditions

q = Wc + Ww + Wl

Where:

q = actual pressure - N / m^2

qc = 2.5 is minimum safety factor (critical buckling pressure - N / m^2)

Wc = Soils load - N /m^2

Ww = 9800 * hw - N / m^2 (Water load - N / m^2)

Wv = vacuum load - N / m^2

Wl = traffice load - N /m^2

TABLES

NOTE: Some values preseneted in these tables are typical valuse intended for general use for exact values

contact Farassan Man. & Ind. Compnaay

Table 1: Modulus of Soil Reaction (E'n) for Native Soils (Mpa)

Native

Soil Blow E' values Non-Cohesive Soils Cohesive Soils

Group Counts

(1) (psi) (MPa) Description Friction Angle Description Unconfined Compr. Strength

(degrees) (tsf) (kPa)

6 0 - 1 50 0.34 very, very loose 28 very,very soft 0 - 0.125 0 - 12

5 1 - 2 200 1.4 very loose 28 very soft 0.125 - 0.25 12 - 24

4 2 - 4 700 4.8 very loose 28 soft 0.25 - 0.50 24 - 48

3 4 - 8 1,500 10.3 loose 29 medium 0.50 -1.0 48 - 96

2 8 - 15 3,000 20.7 slight compact 30 stiff 1.0 - 2.0 96 - 192

1 >15 5,000 34.5 compact 33 very stiff 2.0 - 4.0 192 - 384

Table 2: Modulus of Soil Reaction (E'b) For Pipe Zone Backfills (Mpa)

Table 3: Bedding Coefficent (kx):

Installation Condition kx

Inconsistent haunching support

(typical direct bury condition) 0.1

Uniform shaped bottom support 0.083

For typical installations, use kx = 0.1

Backfill

Table of non-saturated E' values (MPa) Table of saturated E' values (MPa)

Soil Type Description of backfill soils

Relative Compaction (% max. Std. Proctor Density)

Relative Compaction (% max. Std. Proctor Density)

80% 85% 90% 95%

80% 85% 90% 95%

A Crushed stone , 12% fines 16 18 20 22 12 13 14 15 B Sand, <12% fines 7 11 16 19 5 7 10 12 C Silty sand, 12 - 35% fines 6 9 14 17 2 3 4 4

D Silty, clayey sand, 35 - 50% fines 3 6 9 10 1 1.7 2.4 2.8 3.1

E Sandy, clayey silt, 50 - 70% fines, LL<40% 3 6 9 10 1 2 1.7 2.1 2.4

F Low plasticity fine grained soil, LL<40% 3 6 9 10 0.7 1.4 1.7 2.1

Table 4: Soil Support Combining Factor (Sc)

E'n/E'b B/D Value

1.5 1.75 2 2.5 3 4 5

0.01 0.015 0.04 0.10 0.15 0.30 0.50 0.80

0.02 0.030 0.05 0.12 0.20 0.35 0.56 0.84

0.03 0.045 0.07 0.14 0.25 0.40 0.62 0.87

0.04 0.060 0.09 0.16 0.30 0.45 0.66 0.90

0.05 0.075 0.11 0.18 0.35 0.50 0.70 0.93

0.06 0.090 0.13 0.20 0.40 0.55 0.74 0.96

0.07 0.105 0.15 0.22 0.45 0.60 0.78 0.98

0.08 0.120 0.17 0.20 0.50 0.65 0.82 1.00

0.09 0.135 0.19 0.25 0.55 0.75 0.86 1.00

0.10 0.15 0.21 0.30 0.60 0.80 0.90 1.00

0.20 0.30 0.36 0.45 0.70 0.85 0.92 1.00

0.40 0.50 0.54 0.60 0.80 0.90 0.95 1.00

0.60 0.70 0.74 0.80 0.90 0.95 1.00 1.00

0.80 0.85 0.87 0.90 0.95 0.98 1.00 1.00

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

1.50 1.30 1.24 1.15 1.10 1.05 1.00 1.00

2.00 1.50 1.42 1.30 1.15 1.10 1.05 1.00

3.00 1.75 1.63 1.45 1.30 1.20 1.08 1.00

5.00 2.00 1.84 1.60 1.40 1.25 1.10 1.00

7.00 2.00 1.95 1.70 1.47 1.28 1.11 1.00

10.00 2.00 2.00 1.80 1.53 1.30 1.12 1.00

15.00 2.00 2.00 1.92 1.58 1.32 1.13 1.00

20.00 2.00 2.00 2.00 1.62 1.34 1.14 1.00

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