Tubular Joint API RP 2A Design
Tubular Joint API RP 2A Design
Tubular Joint API RP 2A Design
Contents
Tubular Joints
Behaviour of Tubular connections
Failure
Fail e modes
API RP 2A Design Method
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
distrib tion
distribution
depends
on
the
relati e
relative
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Gl b l Stress
Global
St
A l i
Analysis
Global stress analysis to find the nominal axial and
bending stresses in the members
Typical 20ksi (140 N/mm2) in a jacket bracing for a
one-time extreme wave load
What are the stresses in the tubular connection?
The local stress distributions are extremely complex
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Punching Shear
To formulate design criteria, the complex stress
distribution in chord is represented by a simple
punching
p
g shear
The average punching shear stress V p acting at the
perimeter of the brace-to-chord
brace to chord intersection is defined
as
acting
g Vp = sin( fa + fb )
Punching component normal to the chord wall
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
= t /T
l b
between
t
members
b
= angle
f a + f = nominal axial and bending
Stress in brace
16 July 2007
11
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Elastic Stresses in
C li d
Cylinders
S
Subjected
bj
d to
Punching Shear
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Three-Dimensional
Elements
Iso-parametric
Finite
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
P
Parametric
t i Equations
E
ti
Ro
Routine
tine design of simple joints can use
se empirical
formulas obtained from prior stress analyses of
similar configurations
The general form is based on static strength
consideration
Specific coefficients are derived from the
detailed finite element or experimental stress
analysis
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Behaviour
of
Tubular Connections
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Reserve Strength
The theoretical and experimental stress analyses are
useful in understanding the behavior of tubular
and indispensable in fatigue analysis
joints
Th
They do
d not provide
id a practical
i l measure off ultimate
li
strength
Most tubular joints have a tremendous reserve
strength beyond first yield
Considerable
reserve
strength
beyond
theoretical
yielding due to triaxiality, plasticity, large deflection
effects, and load redistribution
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
The
The difference between elastic and plastic bending section moduli
plastic load redistribution
restraint
i to plastic
l i flflow d
due to tri-axial
i i l stresses
strain hardening
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
F il
Failure
M
Modes
d
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Failure Criteria
Reaching the elastic limit of the material
Reaching the material yield strength
Detection of first cracking in a tension joints
Maximum load a joint will sustain in compression
b f
before
gross d
deformation
f
ti occurs
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
General Collapse
p
of the Chord
Involves more of collapse with
a) Ovalisation
b) Beam bending
c) Beam shear
d) Sidewall web bucking
e) Longitudinal distress
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Unzipping
pp g or Progress
g
Failure
Uneven distribution of load
across the weld
Peak load can be a factor of
two higher than the nominal
load
Local
L
l yielding
i ldi
may occur for
f
load distribution
If the weld is a weak, it may
unzip before redistribution
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Material Problems
Need plastic deformation to reach design
capacity
p
y
Fracture and fatigue
Lamellar tearing
Weldability (HAZ)
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Static Strength
g Design
g
of Tubular Connections
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Definitions
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
53
Validity Range
The validity range for application of the practice defined is as follows:
0.2
1.0
10
50
30
90
Fy
72 kksii (500 MP
MPa))
g/D
>
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Simplified condition
Fyb ( sin )
1 .0
1 .5
Fyc (11 +
)
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Design Criteria
Based on punching shear
Although failure mechanisms and strength properties may be
different when approaching 1.0
At present, insufficient experimental evidence exists to precisely
quantify
tif the
th degree
d
off increased
i
d strength
t
th
Nominal loads
Equivalent results
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
63
Axial
T
Tension
i
Axial
Compress
C
ion
Out-of- Plane
B di
Bending
(1.10-0.20/ ) Qg
TT & Y
X
3.72-0.67/
(1.10-0.20/
(1.100.20/
0 .3
for > 0 . 6
(1 0 . 833 )
= 1 . 0 for 0 . 6
16 July 2007
(1.37-0.67/ )Q
(0.750.20/ )Q
Q =
Q
In-plane
B di
Bending
64
Q g = 1 .8 0 .1g / Tfor 20
Q g = 1 .8 4 g / Dfor > 20
Q g 1 .0
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
2
2 + 2
f AX
f IPB + f OPB
65
0.6 FYC
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Interaction Equations
2
Vp
V pa
Vp
1.0
+
V
IPB pa OPB
Vp
V
2
+ arcsin p
V
pa
V pa
16 July 2007
AX
66
Vp
+
1.0
10
IPB V pa OPB
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Allowable Moment
(Inplane or Out-of plane)
FT
P =QQ
FS sin
yc
FT d
M =QQ
FS sin
yc
Where
Pa = allowable capacity for brace axial load
Ma = allowable capacity for brace bending moment,
Fy = the yield stress of the chord member at the joint for 0
0.8
8 of the
tensile strength, if less), ksi (MPa)
FS = safety factor = 1.60
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
FSPc
FSM c
2
Q f = 1 + C1
C
A
2
3
P
M
p
y
Py M p
Wh
Where
Pc and
d Mc are the
h nominal
i l axial
i l lload
d and
db
bending
di resultant
l
(i.e. M2c = M2ipb + M2opb
Py is the yield axial capacity of the chord
Mp is the plastic moment capacity of the chord, and
C1, C2 and C3 are coefficients depending on joint and load type
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Interaction Equations
P
P
a
AX
M
+
M
M
+
1.0
IPB
OPB
Where
P and M are applied axial load and
moment in brace member
Pa and Ma are allowable axial load and
bending moment in brace member
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
71
Joint Data
Brace 1 Data
d 1 := 508 mm
t 1 := 15.88 mm
1 := 45 deg
Brace 2 Data
d 2 := 406 mm
t 2 := 12.7 mm
2 := 30 deg
g
D := 762 mm
T c := 15.88 mm
Chord Data
Yield Strength
F y := 345 MPa
Loads on brace 1
P 1 := 900 kN
M 1IP := 275 kN m
M 1OP := 125 kN m
Loads on brace 2
P 2 := 1275 kN
M 2IP := 225 kN m
M 2OP := 145 kN m
Q f := 1
16 July 2007
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
gap := 50 mm
Geometric parameters
1 :=
:=
gap
D
1 = 0.667
2 :=
d2
D
2 = 0.533
D
= 23.992
2 Tc
= 0.066
gap
Qg := 1 + 0.2 1 2.8
D
Qg for K joint
16 July 2007
d1
Qg = 1.109
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
73
Q uax1 := ( 16 + 1.2 ) 1
Q ulim1 := 40 1
1.2
1.2
Qg
Q uax1 = 30.53
Qg
Q ulim1 = 27.264
2
Fy T c
P a1 := Q uax1 Q f
1.6 sin
( 1)
Q uip1 := ( 5 + 0.7 ) 1
P a1 = 2347.7 kN
12
1.2
Q uip1 = 13.398
2.6
Q uop1 = 5.74
Fy T c d 1
M a1IP := Q uip1 Q f
1.6 sin 1
Allowable out-off
out off plane bending
moment
Fy T c d 1
M a1OP
1OP := Q uop1
1 Q f 1.6 sin
1
UC1 :=
( )
M a1IP = 523.4 m kN
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( )
74
P1
P a1
2
2
M 1IP
M 1OP
M a1IP
M a1OP
M a1OP = 224.2 m kN
UC1 = 0.97
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Q uax2 := ( 16 + 1.2 ) 2
Q ulim2 := 40 2
1.2
1.2
Qg
Q uax2 = 23.33
Qg
Q ulim2 = 20.835
2
Fy T c
P a2 := Q uax2 Q f
1.6 sin
( 2)
Q uip2 :=
: ( 5 + 0.7
0 7 ) 2
P a2 = 2537.2 kN
1.2
Q uip2 = 10.239
10 239
1.2
Q uop2 = 6.868
Fy T c d 2
M a2IP := Q uip2 Q f
1.6 sin 2
Fy T c d 2
M a2OP := Q uop2
p Qf 1
1.66 sin 2
( )
M a2IP = 452.1 m kN
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( )
UC2 :=
P2
P a2
M a2OP
303 2 m kN
2OP = 303.2
M 2IP
M 2OP
M
+M
a2IP
a2OP
UC2 = 0.979
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
75
Q uax1 := ( 16 + 1.2 ) 1
1.2
Q uax1 = 27.535
Q ulim1 := 30 1
Q ulim1 = 20
P a1 := Q uax1 Q f
Fy T c
( )
P a1 = 2117.4 kN
1.6 sin 1
Q uip1 := ( 5 + 0.7
0 7 ) 1
1.2
Q uip1 = 13.398
2.6
Q uop1 = 5.74
Fy T c d 1
M a1IP := Q uip1 Q f
1.6 sin 1
Fy T c d 1
M a1OP := Q uop1 Q f
1.6 sin 1
UC1 :=
( )
M a1IP = 523.4 m kN
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( )
76
P1
P a1
M 1IP
M 1OP
M a1IP
M a1OP
M a1OP = 224.2
224 2 m kN
2
UC1 = 1.012
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
1.6
Q uax2 = 17.113
1.6
Q ulim2 = 15.947
2
Fy T c
P a2 := Q uax2 Q f
1.6 sin
( 2)
Q uip2 := ( 5 + 0.7
0 ) 2
P a2 = 1861 kN
1.2
Q uip2 = 10.239
1.2
Q uop2 = 6.868
Fy T c d 2
M a2IP := Q uip2 Q f
1.6 sin 2
Fy T c d 2
M a2OP := Q uop2 Q f
11.6
6 sin 2
( )
M a2IP = 452.1 m kN
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( )
UC2 :=
P2
P a2
M 2IP
M 2OP
M
+ M
a2IP
a2OP
77
M a2OP = 303.2 m kN
2
UC2 = 1.161
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
P := 8000 kN
M IP := 200 kN m
M OP := 600 kN m
Chord Loads
Pc := 3000 kN
M cIP := 600 kN m
M cOP := 0 kN m
Brace data
d := 762 mm
t := 32 mm
Yield Strength
Fy := 345 MPa
D := 1976 mm
T L := 50 mm
DP := 1976 mm
T P := 50 mm
16 July 2007
78
:= 90 deg
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
T c :=
Geometric Parameters
:=
TP + TL
d
T c = 70.7 mm
:=
= 0.386
= 13.972
2 T c
1.6
Quaxmax := 2.8 + 36
Qu for inplane
p
bending
g
moment
16 July 2007
Quax = 9.588
1.6
Quaxmax = 10.637
1.2
Quip = 4.711
4 711
2.6
Quop = 3.112
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
79
Equivalent Moment
C1ax := 0.3
C2ax := 0.0
C3ax := 0.8
C1b := 0.20
C2b := 0.0
C3b := 0.40
Py := D Tc Fy
M p := D Tc Fy
FSC := 1.2
16 July 2007
M c := M cIP + M cOP
80
Py = 1.514 10 kN
4
M p = 9.525 10 kN m
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
AA :=
Pc
Mc
FSC
+ FSC
Py
Mp
AA = 0.025
FSC P c
FSC M c
2
C 2ax
C 3ax AA
Py
Mp
Q fax := 1 + C 1ax
Q fax = 1
FSC P c
FSC M c
2
C 2b
C 3b AA
Py
Mp
Q fip := 1 + C 1b
Q fip = 1
Qf for out-off plane bending
moment
FSC P c
FSC M c
2
C 2bb
C 3b AA
Py
Mp
Q fop
op := 1 + C 1b
b
Q fop = 1
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
81
FS := 1.6
Fy T c
P a := Q uax Q fax
FS sin ( )
Fy T c d
M aIP := Q uip Q fip
FS sin ( )
P a = 10405.2 kN
M aIP = 3887.5 m kN
Fy T c d
M aOP = 2568.4 m kN
1.6 sin ( )
UC :=
82
P
Pa
M IP
M OP
M
+ M
aIP
aOP
UC = 0.826
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Design Practices
Design Based on Actual Loads
Design based on Planer connections
Design for minim
minimum
m 50% brace strength
Can length (minimum requirements)
Brace stub
Offset or Eccentricities
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
TC = TP 2 + TL 2
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Multi-planar
p
Joints
Many tubular space frames have bracing in multiple planes
For some loading conditions, these different planes interact
In AWS, an ovalizing parameter() may be used to estimate
the beneficial or deleterious effect of various branch member
loading combinations on main member ovalizing
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90
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
Computation
of Ovalizing Parameters
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
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Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
16 July 2007
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
95
Internal
e a d
diameter,
a e e , di
D-2t
bs
= 1219-2*50=1119
9 50
9
1.1(Dt)1/2= 272
Area, A
(Le*t)+(bs*ts)+(bf*tf )
Equivalent thickness, Te
A/Le
96
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36
D-2t
bs
1.1(Dt)1/2
3
bf t f
Let 3
t s bs
b
t
t
+ Le * t * ( y )2 +
+ bs t s ( y t s ) 2 +
+ b f * t f * (t + bs + s y ) 2
12
2
12
2
12
2
E i l t thi
Equivalent
thickness,
k
Te
12 I T
Le
97
Dr. S. Nallayarasu
Department of Ocean Engineering
Indian Institute of Technology Madras-36