ATTACHMENT-1
RAILROAD CROSSING DESIGN CALCULATIONS
API Recommended Practice 1102
Pipe, Operational, Installation & Site Characteristics
Steel Grade
Specified Minimum Yield Strength
Values Units
Gr. X60
SMYS
60,000.00
psi
Es
2.90E+07
psi
vs
0.30
αT
6.50E-06
Design Factor for Location Class
Design Factor for Effective Stress
Outside Diameter
F1
0.72
F2
0.90
D
12 inches
Nominal Wall Thickness
Depth
tw
0.375 inches
H
67 inches
Young's Modulus
Poisson's Ratio
Coefficient of Thermal Expansion
Bored Type
per oF
Trenching
Bored Diameter
Bd
Maximum Allowable Operating Pressure
Temperature at time of Installation
P
14.70
T1
81.00
o
T2
196.00
o
T
1.00
Operating Temperature Max
Temperature Derating Factor
Spec No. & Pipe Class
12 inches
(API 1102 Para. 4.7.2.1)
psig
F
F
(B31.8 Table 841.1.8-1)
API 5L - Electric Welded
Longitudinal Joint Factor
E
Soil Type
1.00
(B31.8 Table 841.1.7-1)
Loose Sands and Gravels
Modulus of Soil Reaction
Resilient Modulus
Soil Unit Weight
Axle load per SAES-L-460 Section 4
Type of Longitudinal Weld
Fatigue Endurance Limit of Girth Weld
E'
500.00
psi
(API 1102 Table A-1)
Er
10,000.00
psi
(API 1102 Table A-2)
γ
0.069
Ib/in3
E-80
P (Ibs)
:
E-80
ERW - Electric-Resistance-Welded
F. E. L. of Longitudinal Weld
SFG
12,000.00
psi
(API 1102 Table 3)
SFL
23,000.00
psi
(API 1102 Table 3)
Check Allowable Barlow Stresses
[S Hi (Barlow) = pD ⁄ 2t w ] ≤ F × E × T × SMYS
SHi
Actual Barlow Stress
Allowable Barlow Stress
SMYS x F 1
(API 1102 Equation 8a/8b)
235.20
psi
43,200.00
psi
Actual Barlow Stress < Allowable Stress
SAFE
Stress Due to Earth Load
The circumferential stress at the pipeline invert caused by earth load, SHe, is determined as follows
S He = K He B e E e γD
KHe
Be
γ
Stiffness factor for circumferential stress from earth load
Burial factor for earth load
Excavation factor for earth load
Soil unit weight
D
Pipe outside diameter
Ee
(API 1102 Equation 1)
Earth Load stiffness Factor, KHe, accounts for the interaction between the soil and the pipe
tw/D
0.03
Modulus of Soil Reaction
Stiffness Factor
E'
KHe
500.00
psi
1,449.00
Burial Factor, Be
H/Bd
(API 1102 Figure 3)
5.58
Soil Type
A
Be
1.13
Excavation Factor (1 as Existing pipeline)
Ee
0.83
Circumferential Stress Due to Earth Load
SHe
1,125.27
Burial Factor
(API 1102 Figure 4)
Excavation Factor, Ee
Bd/D
1.00
(API 1102 Figure 5)
psi
Stresses due to Live Loads
Surface Live Loads, due to the rail load applied at the surface of the crossing.
Impact Factor
Applied Design Surface Pressure
FI
1.75
w
13.900
(API 1102 Figure 7)
psi
(API 1102 Para 4.7.2.2.1)
Railroad Cyclic Stresses
Cyclic Circumferential Stresses
The cyclic circumferential stress due to rail load, ∆SHr may be calculated from the following
∆S Hr = K Hr G Hr N H F i w
KHr
GHr
(API 1102 Equation 3)
NH
Fi
Railroad stiffness factor for cyclic circumferential stress
Railroad geometry factor for cyclic circumferential stress
Railroad single or double track factor for cyclic circumferential stress
Impact factor
w
Applied design surface pressure
Railroad stiffness factor, KHr
tw/D
Resilient Soil Modulus
Stiffness Factor
0.03
Er
KHr
10,000.00
psi
310.00
(API 1102 Figure 8)
Railroad geometry factor, GHr
Outside Diameter
Depth
Geometry Factor
D
12.000 inches
H
67.000 inches
GHr
Railroad single or double track factor, NH
NH (1.00 for single track)
Circumferential Stress Due to Rail Load
SHr
1.000
(API 1102 Figure 9)
1.09
(API 1102 Figure10)
8,219.42
psi
Cyclic Longitudinal Stresses
The cyclic longitudinal stress due to rail load, ∆SLr may be calculated from the following
∆S Lr = K Lr G Lr N L F i w
KLr
GLr
(API 1102 Equation 4)
Railroad stiffness factor for cyclic longitudinal stress
NL
Fi
Railroad geometry factor for cyclic longitudinal stress
Railroad single or double track factor for cyclic longitudinal stress
Impact factor
w
Applied design surface pressure
Railroad stiffness factor, KLr
tw/D
0.031
Resilient Modulus
Stiffness Factor
Er
10,000.000
KLr
420.00
psi
(API 1102 Figure 11)
Railroad geometry factor, GLr
Outside Diameter
Depth
Geometry Factor
D
12.00 inches
H
67 inches
GLr
1.00
(API 1102 Figure 12)
1.00
(API 1102 Figure13)
Railroad single or double track factor, NL
NL (1.00 for single track)
SLr
Longitudinal Stress Due to Rail Load
10,216.50
psi
Stresses due to Internal Load
The circumferential stress due to internal pressure, SHi may be calculated from the following;
S Hi = p(D – t w ) ⁄ 2t w
p
Internal pressure taken as MAOP or MOP
D
Tw
Pipe Outside Diameter
Wall thickness
(API 1102 Equation 7)
Circumferential stress due to internal pressure, SHi
SHi
227.850
psi
Check for allowable Stresses
S 1 = S He + ∆S H + S Hi
Maximum Circumferential Stress
S1
Maximum Circumferential Stress
9,572.53
(API 1102 Equation 9)
psi
S 2 = ∆S L – E s αT(T 2 – T 1 ) + ν s (S He + S Hi )
Maximum Longitudinal Stress
S2
Maximum Longitudinal Stress
-11,055.065
S 3 = –p = –MAOP or –MOP
Maximum Radial Stress
S3
S
= 1
-14.700
[(S
−S
(API 1102 Equation 10)
psi
(API 1102 Equation 11)
psi
)2 + (S
−S
)2 + (S
−S
)2 ]
eff
2
2
3
3
1
2 1
(API 1102 Equation 12)
Total Effective Stress
The check against the yielding of the pipeline may be accomplished by assuring that the total effective stress is less than
90% SMYS per combined stress.
Total Effective Stress
Allowable Effective Stress
Seff
17,878.79
psi
SMYS x F 2
54,000.00
psi
S eff ≤ SMYS × F
Actual Effective Stress < Allowable Stress
(API 1102 Equation 13)
SAFE
Check for fatigue
Girth Welds
The cyclic stress that must be checked for potential fatigue in a girth weld located beneath a railroad crossing is the
longitudinal stress due to live load.
Girth Welds
RF SLr / NL
4,903.92
psi
F1 x SFG
8,640.00
psi
RF
RF
0.48
(API 1102 Figure18-A/18-B)
Longitudinal stress reduction factor for fatigue.
The general form of the design check against girth weld fatigue is given by the following
R F ∆S Lr / N L ≤ S FG × F
(API 1102 Equation 15)
Longitudinal Stress < Fatigue Endurance Limit
SAFE
Longitudinal Welds
The cyclic stress that must be checked for potential fatigue in a longitudinal weld located beneath a railroad crossing is
the circumferential stress due to live load.
Longitudinal Welds
SHr / NH
7,540.75
psi
F1 x SFL
8,640.00
psi
The general form of the design check against longitudinal weld fatigue is given by the following
∆S Hr / N H ≤ S FL × F
Circumferential Stress < Fatigue Endurance Limit
(API 1102 Equation 19)
SAFE