GB/T 50761-2018 PDF in English
GB/T 50761-2018 (GB/T50761-2018, GBT 50761-2018, GBT50761-2018)
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Standard for seismic design of petrochemical steel equipment
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GB/T 50761-2018: PDF in English (GBT 50761-2018) GB/T 50761-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC
P GB/T 50761-2018
Standard for seismic design of
petrochemical steel equipment
ISSUED ON. JANUARY 16, 2018
IMPLEMENTED ON. SEPTEMBER 01, 2018
Issued by. Ministry of Housing and Urban-Rural Development of PRC;
General Administration of Quality Supervision, Inspection and
Quarantine of PRC.
Table of Contents
Foreword ... 6
1 General provisions ... 8
2 Terms and symbols ... 9
2.1 Terms ... 9
2.2 Symbols ... 10
3 Basic requirements ... 13
3.1 Classification of importance factors ... 13
3.2 Seismic influences ... 13
3.3 Equipment system design ... 14
4 Seismic action and seismic checking ... 16
4.1 General requirements ... 16
4.2 Seismic design response spectral of above-ground equipment ... 17
4.3 Horizontal seismic action of above-ground equipment ... 19
4.4 Horizontal seismic action of on-framework equipment ... 22
4.5 Vertical seismic action ... 23
4.6 Combination of loads ... 24
4.7 Seismic checking ... 25
5 Horizontal vessels ... 29
5.1 General requirements ... 29
5.2 Seismic action and seismic checking ... 29
5.3 Details of seismic design ... 30
6 Vertical vessels supported by legs ... 31
6.1 General requirements ... 31
6.2 Natural vibration period ... 31
6.3 Seismic action and seismic checking ... 33
6.4 Details of seismic design ... 33
7 Vertical vessels supported by lugs ... 34
7.1 General requirements ... 34
7.2 Natural vibration period ... 34
7.3 Seismic action and seismic checking ... 35
7.4 Details of seismic design ... 35
8 Vertical vessels supported by skirt ... 36
8.1 General requirements ... 36
8.2 Natural vibration period ... 36
8.3 Seismic action and seismic checking ... 38
8.4 Details of seismic design ... 39
9 Spherical tanks supported by legs ... 41
9.1 General requirements ... 41
9.2 Natural vibration period ... 41
9.3 Seismic action and seismic checking ... 44
9.4 Details of seismic design ... 45
10 Vertical cylindrical storage tanks ... 46
10.1 General requirements ... 46
10.2 Natural vibration period ... 46
10.3 Horizontal seismic action and seismic effect ... 47
10.4 Allowable compression longitudinal stresses of tank shell ... 49
10.5 Seismic checking of tank shell ... 49
10.6 Liquid sloshing height ... 52
10.7 Details of seismic design ... 53
11 Tubular heater ... 54
11.1 General requirements ... 54
11.2 Natural vibration period ... 54
11.3 Seismic action and seismic checking ... 60
11.4 Details of seismic design ... 62
Appendix A Horizontal seismic action of on-framework equipment ... 66
Appendix B Seismic checking of vertical vessels supported by legs ... 69
Appendix C Seismic checking of vertical vessels supported by lugs ... 75
Appendix D Calculation of flexible matrix element ... 79
Explanation of wording in this standard ... 83
List of quoted standards ... 84
Standard for seismic design of petrochemical steel
equipment
1 General provisions
1.0.1 In order to implement the national laws and regulations on earthquake
prevention and disaster reduction, implement a prevention-oriented policy,
mitigate the seismic damage by seismic-fortifying the petrochemical equipment,
reduce economic loss, this standard is hereby formulated.
1.0.2 This standard is applicable to the seismic design of the petrochemical
horizontal vessel, vertical vessels supported by legs, vertical vessels supported
by lugs, vertical vessels supported by skirt, spherical tanks supported by legs,
vertical cylindrical storage tanks, tubular heater, other steel equipment which
are used in the area where the basic seismic acceleration not exceeding 0.40
g or seismic fortification intensity of 9 degrees or less.
1.0.3 For the petrochemical equipment which is subjected to the seismic design
according to this standard, when it is impacted by the fortification earthquakes
equivalent to the seismic fortification intensity of the area, the body, bracing
member, anchoring structure shall not be damaged.
1.0.4 The design parameters of ground motion or the seismic fortification
intensity shall be determined in accordance with the relevant provisions of the
current national standard “Seismic ground motion parameter zonation map of
China” GB 18306. For the construction site where the seismic safety evaluation
is completed, it shall carry out the seismic fortification according to the approved
design parameters of ground motion or the seismic fortification intensity.
1.0.5 The seismic design of petrochemical steel equipment shall, in addition to
complying with this standard, also comply with the relevant current national
standards.
2 Terms and symbols
2.1 Terms
2.1.1 Seismic design
A specialized design for equipment that requires seismic fortification, including
seismic calculations and seismic measures.
2.1.2 Seismic fortification intensity
The seismic intensity which is approved according to the authority as specified
by the state as a basis for seismic fortification of a region.
2.1.3 Seismic action
The dynamic effects of equipment caused by ground motion, including
horizontal seismic action and vertical seismic action.
2.1.4 Seismic effect
Internal forces or deformations generated by the equipment under seismic
action.
2.1.5 Design parameters of ground motion
The time-history curve of acceleration of ground motion, the response spectrum
of acceleration, the peak acceleration which are used for seismic design.
2.1.6 Design basic acceleration of ground motion
The design value of the acceleration of ground motion which exceeds the
probability of 10% in the 50-year design base period.
2.1.7 Characteristic period of ground motion
In the seismic influence factor curve for seismic design, the period value
corresponding to the starting point of the falling segment which reflects the
factors such as seismic magnitude, epicentral distance, site category, and other
factors.
2.1.8 Seismic influence factor
The statistical mean of the ratio of the maximum acceleration response to the
gravitational acceleration of a single-mass point elastic system under seismic
action.
meq - The equivalent total mass of equipment;
mi, mj - Respectively, the masses concentrated on the particles i, j;
meqv - The vertical equivalent mass of equipment;
mi - The mass concentrated at the particle i;
mj - The mass concentrated at the particle j;
Sj - The effect produced by the horizontal seismic action of the vibration-
mode j;
Sh - Horizontal seismic effect;
Xji - The horizontal relative displacement of the particle i of the jth vibration-
mode.
2.2.2 Performance and resistance of materials.
Et - The modulus of elasticity of the material at the design temperature;
Rel - The yield strength of material;
σ - The stress value under the action of load combination;
[σ] - The allowable seismic stress of the material;
[σ]t - The allowable stress of the material at the design temperature;
[σ]b - The allowable seismic tensile stress of the material;
[σ]bc - The allowable seismic compressive stress of the material;
τ - The value of the shear stress under the action of load combination;
[τ] - The allowable seismic shear stress of the material;
[τ]b - The allowable seismic shear stress of the material.
2.2.3 Calculation coefficient.
α1 - The horizontal seismic action factor corresponding to the basic natural
vibration period of the equipment or structure;
αj - The horizontal seismic action factor corresponding to the natural vibration
period of the jth vibration-mode of the equipment;
αmax - The maximum value of the horizontal seismic action factor;
4 Seismic action and seismic checking
4.1 General requirements
4.1.1 The seismic action and seismic checking of the equipment shall comply
with the following provisions.
1. It shall calculate the seismic action in the horizontal direction and make
seismic checking;
2. When the design basic acceleration of ground motion is 0.20 g ~ 0.40 g,
or seismic fortification intensity is 8 degrees or 9 degrees, for the
horizontal vessel which has a diameter of more than 4 m and the spacing
between two seats of more than 20 m, as well as the vertical vessels and
the floor chimney of the tubular heater which have a height of more than
20 m, it shall calculate the vertical seismic action and make seismic
checking;
3. For the on-framework equipment, it shall take into account the seismic
amplification of the structure in which the equipment is located.
4.1.2 When the design basic acceleration of ground motion is equal to 0.05 g
or the seismic fortification intensity is 6 degrees, the category-1 and category-
2 equipment may not be subjected to the calculation of seismic action, but it
shall meet the requirements for seismic measures.
4.1.3 For the seismic calculation of equipment, it should use the following
methods.
1. The following equipment may use the bottom shear method.
1) The vertical vessel which has a height less than or equal to 10 m;
2) The vertical vessel which has an aspect ratio of less than 5 and a
relatively uniform distribution of mass and stiffness along the height
direction;
3) Equipment that can be simplified to a single-particle system.
2. Except for the equipment in item 1 of this clause, it should use the mode
decomposition response spectrum method.
3. When the design basic acceleration of ground motion is more than or
equal to 0.30 g, the vertical vessel which has an aspect ratio of more than
120 m and the vertical cylindrical storage tanks which are more than 15 x
104 m3 should be supplemented by time-history analysis.
Fhji - The design value of the horizontal seismic action at the particle i of the
jth vibration-mode (N);
αj - The horizontal seismic influence factor corresponding to the natural
vibration period of the jth vibration-mode of the equipment, which is
determined according to the provisions of clause 4.2 of this standard;
γj - The participation factor of the jth vibration-mode;
Xji - The horizontal relative displacement at the particle i of the jth vibration-
mode.
2. The horizontal seismic effect shall be determined as follows.
Where.
Sh - The horizontal seismic effect;
Sj - The effect produced by the horizontal seismic action of the jth vibration-
mode, taking the first 2nd ~ 3rd vibration-mode. When the basic natural
vibration period is greater than 1.5 s, the number of vibration-modes is not
less than 3.
4.4 Horizontal seismic action of on-framework equipment
4.4.1 When the mass ratio of the framework to the equipment is more than or
equal to 2, the horizontal seismic action of the equipment should be calculated
in accordance with the provisions of this clause.
4.4.2 The design value of the horizontal seismic action of on-framework
equipment may be calculated as follows.
Where.
Fhk - The design value of horizontal seismic action of on-framework
equipment (N);
Km - The amplification factor of seismic action of on-framework equipment,
which is selected according to Table 4.4.2.
5. Design value of horizontal and vertical seismic action;
6. Snow load, considering the combination factor of 0.5, which takes 0 for
high-temperature parts and for the small load-bearing surface of
equipment;
7. Other loads, including the reaction force of the seat, the base ring, the lugs
and other types of supports, the force of the connecting pipeline and other
components, the force caused by the difference in temperature gradient
or thermal expansion, etc.;
8. Live loads, including major moving loads such as people, tools, repairs,
shocks, vibrations, etc.
4.7 Seismic checking
4.7.1 When using the limit state design, it shall carry out seismic checking
according to the relevant provisions of the current national standard “Code for
seismic design of buildings” GB 50011.
4.7.2 When using the allowable stress design, it shall carry out seismic checking
according to the following provisions.
1. When the equipment is subjected to seismic checking, the stress value of
the checked part under the action of load combination shall meet the
requirements of the following formula.
Where.
σ - The stress value under the combination of loads (MPa);
Φ - Welded joint factor, which takes 1.0 when compressed;
[σ] - Seismic allowable stress of the material (MPa);
τ - Shear stress value under combination of loads (MPa);
[τ] - Seismic allowable shear stress of the material (MPa).
2. The allowable stress for seismic checking of equipment shall be
determined in accordance with the following provisions.
1) The body and bearing member may be calculated as follows.
5 Horizontal vessels
5.1 General requirements
5.1.1 The seismic design of horizontal vessel shall comply with the provisions
of this clause.
5.1.2 The basic natural vibration period of horizontal vessel may be taken as
0.10 s; when multiple vessels overlap, the basic natural vibration period may
be 0.15 s.
5.2 Seismic action and seismic checking
5.2.1 For the calculation of horizontal seismic action of horizontal vessel, the
seismic influence factor may be taken as the maximum value according to the
provisions of clause 4.2.1 of this standard.
5.2.2 For the horizontal vessels installed above-ground, it shall follow the
requirements of clause 4.3 of this standard to respectively calculate its axial
and lateral seismic actions. For the on-framework horizontal vessels, it may
follow the requirements of clause 4.4 of this standard to respectively calculate
its axial and lateral seismic action.
5.2.3 The damping ratio of horizontal vessel may be 0.05.
5.2.4 For overlapping horizontal vessels, both axial and lateral directions can
be regarded as a multi-degree-of-freedom system (Figure 5.2.4). The seismic
action of overlapping horizontal vessels installed above-ground may be
calculated according to the clause 4.3 of this standard. The seismic influence
factor may be taken as the maximum value of the horizontal seismic influence
factor; the total seismic action of the overlapping on-framework horizontal
vessels and the horizontal seismic action of each particle may be calculated
according to clause 4.4 of this standard.
h - The height from the foundation’s top surface to the centroid of the
equipment (mm).
6.3 Seismic action and seismic checking
6.3.1 For the calculation of horizontal seismic action of vertical vessels
supported by legs, the seismic influence factor shall comply with the provisions
of clause 4.2 of this standard for the fortified earthquakes.
6.3.2 The seismic action of the vertical vessels supported by legs installed
above-ground shall be calculated in accordance with clause 4.3.1 of this
standard; the seismic action of the vertical vessels supported by legs installed
on-framework shall be calculated in accordance with clause 4.4 of this standard.
6.3.3 The damping ratio of the vertical vessels supported by legs may be 0.05.
6.3.4 The seismic checking of the casings, legs, connecting weld between legs
and cylinder, anchor bolts, etc. of vertical vessels supported by legs shall
comply with the provisions of clause 4.7 of this standard.
6.3.5 The seismic checking method for vertical vessels supported by legs can
be carried out in accordance with the provisions of Appendix B of this standard.
6.4 Details of seismic design
6.4.1 The number of legs shall not be less than 3, the fortification intensity shall
be 8 degrees or 9 degrees. When the diameter of the equipment is more than
800 mm, the number of legs should not be less than 4.
6.4.2 Each leg shall be provided with anchor bolts. The diameter of the bolts
should not be less than M16. The nuts shall be provided with anti-loose
measures.
8 Vertical vessels supported by skirt
8.1 General requirements
8.1.1 The seismic design of the vertical vessels supported by skirt shall comply
with the provisions of this clause.
8.1.2 When the height is greater than 20 m and the design basic acceleration
of ground motion is greater than or equal to 0.20 g or the seismic fortification
intensity is 8 degrees and 9 degrees, it shall take into account of the influence
of the vertical seismic action.
8.2 Natural vibration period
8.2.1 The vertical vessels supported by skirt can be simplified to a multi-particle
system to calculate the natural vibration period.
8.2.2 For the equal-diameter & equal-thickness vertical vessels supported by
skirt installed on the ground foundation, the basic natural vibration period may
be calculated as follows.
Where.
T1 - The basic natural vibration period of the equipment (s);
H - The height from the foundation’s top surface to the equipment’s top (mm);
m0 - The total mass of the equipment (kg);
Et - The modulus of elasticity of the material (MPa);
Di - The inner diameter of the cylinder of the equipment (mm);
δe - The effective thickness of the cylinder of the equipment (mm).
8.2.3 For the unequal-diameter or unequal-thickness floor-standing vertical
vessel, it may consider the equipment whose diameter, thickness, material
changes along height into a multi-particle system (Figure 8.2.3). The basic
natural vibration period may be calculated according to the following formula.
influence factor may take the maximum value of the horizontal seismic influence
factor of the fortified earthquake.
8.3.4 For the vertical vessel supported by skirt which has a height of more than
10 m and an aspect ratio of more than 5, it may use the vibration-mode
decomposition method for calculation.
8.3.5 The damping ratio of the vertical vessel supported by skirt may be
determined as follows.
1. When the basic natural vibration period of the equipment is less than or
equal to 1.5 s, it may take 0.035.
2. When the basic natural vibration period of the equipment is more than 1.5
s and less than or equal to 2.0 s, it may be calculated as follows.
3. When the basic natural vibration period of the equipment is more than 2.0
s, it may take 0.01.
8.3.6 The vertical seismic action of the vertical vessel supported by skirt shall
be calculated in accordance with the provisions of clause 4.5 of this standard.
8.3.7 The casing, the skirt cylinder, the foundation ring, the anchor bolt seat,
the connecting weld of skirt and casing, the connecting weld of bolt seat and
skirt cylinder, the anchor bolts of the vertical vessel supported by skirt shall be
subjected to seismic checking, meanwhile it shall comply with the provisions of
clause 4.7 of this standard.
8.4 Details of seismic design
8.4.1 The platform of the equipment should not be directly connected to other
equipment or structures.
8.4.2 The heavier auxiliary equipment outside the equipment should be
provided with a separate bracing structure, which should not be directly braced
by the equipment.
8.4.3 The internal load-bearing members of the equipment shall be securely
connected to the casing.
8.4.4 When the aspect ratio of the equipment is more than 5 and the seismic
fortification intensity is greater than 7 degrees, the equipment’s cylinder should
not be overlapped with the skirt seat.
9 Spherical tanks supported by legs
9.1 General requirements
9.1.1 The seismic design of spherical tanks supported by legs of the adjustable
and fixed tie-bar structure (hereinafter referred to as spherical tanks) which are
braced by tangential or inter-cross column around equator shall comply with the
provisions of this clause.
9.1.2 The seismic action of the spherical tanks supported by legs shall be
calculated taking into account of the impact of the stored liquid.
9.2 Natural vibration period
9.2.1 The equivalent mass of the spherical tank supported by legs under
operating conditions shall be calculated according to the following formula.
Where.
meq - The equivalent mass of the spherical tank under operating conditions
(kg);
m1 - The mass of spherical shell (kg);
m2 - The effective mass of the stored solution (kg);
m5 - The mass of the spherical tank’s thermal-insulation layer (kg);
m6 - The mass of the brace and tie-bar (kg);
m7 - The mass of accessories (kg), including manholes, adaptors, level
gauges, internal components, sprinklers, safety valves, ladder platforms,
etc.;
mL - The mass of the stored solution in spherical tank supported by legs (kg);
φ - The effective mass factor of the stored solution, which is selected based
on the fullness of the solution in spherical tank according to Figure 9.2.1.
9.3.2 The horizontal seismic action of spherical tanks supported by legs may
be calculated in accordance with clause 4.3.1 of this standard.
9.3.3 The damping ratio of the spherical tank supported by legs may be 0.035.
9.3.4 The total bending moment generated by the horizontal seismic action on
the upper segment of bracing shall be calculated as follows.
Where.
M - The total bending moment produced by the horizontal seismic action on
the upper segment of bracing (N • mm);
FEK - The design value of the horizontal seismic action on the spherical tank
supported by legs (N);
L - The distance from the equatorial plane of the spherical shell to the center
of the upper lug pin (mm).
9.3.5 The seismic verification of the braces, the connecting welds between
bracing and spherical shell, the tie-bar, the accessories of tie-bar, the baseplate
of brace, the anchor bolts, etc. shall comply with the requirements of clause 4.7
of this standard.
9.4 Details of seismic design
9.4.1 The diameter of the anchor bolt of the spherical tank’s braces shall not be
less than M24, the nut shall be provided with anti-loose measures.
9.4.2 The connecting welds between the spherical tank’s shell and the braces,
the braces and the lug plates, the tie-bar and the wing plates, the braces and
baseplates shall be the equal-strength welds of the thinner parts. The weld shall
be full and free from surface defects.
9.4.3 The tension of the tie-bar be moderate, the tension of each tie-bar shall
be substantially the same, the intersection of the tie-bars shall not be welded.
10 Vertical cylindrical storage tanks
10.1 General requirements
10.1.1 The seismic design of vertical cylindrical steel-welded flat-bottom
storage tanks (hereinafter referred to as storage tanks) which has an aspect
ratio of tank wall of not more than 1.6 and a nominal volume of more than or
equal to 100 m3 shall comply with the provisions of this clause.
10.1.2 The space between the upper surface of the stored solution of the fixed-
top storage tank and the top cover shall be less than 4% of the nominal volume
of the storage tank.
10.1.3 The calculation of the seismic action of the storage tank shall take into
account of the impact of the stored solution.
10.2 Natural vibration period
10.2.1 The basic natural vibration period of the couple vibration of the stored
solution of the storage tank may be calculated as follows.
Where.
T1 - The basic natural vibration period of the couple vibration of the stored
solution of the storage tank (s);
Kc - The factor of couple vibration period of the stored solution, which can be
found from Table 10.2.1, where the intermediate value may be calculated by
the interpolation method;
Hw - The designed maximum liquid level of the storage tank (mm);
R - The inner radius of the storage tank (mm);
δ1/3 - The nominal thickness of the tank wall at a position of 1/3 height to the
baseplate, after deducted by the negative deviation of the thickness of the
steel plate or the actual thickness (mm).
Where.
Ft - The lifting force per unit length in the circumferential direction of the
bottom of the tank wall (N/mm).
10.5.2 The anti-lifting force per unit length in the circumferential direction of the
bottom of the tank wall shall be calculated according to the following formula.
Where.
FL - The anti-lifting force per unit length in the circumferential direction of the
bottom of the tank wall (N/mm);
FL0 - The maximum anti-lifting force of the stored solution and tank’s bottom
(N/mm), which takes 0.02 HwD1ρsg x 10-9 where it is more than 0.02 HwD1ρsg
x 10-9, meanwhile the width of the inner edge plate of the tank takes 0.035D;
N1 - The gravity as undertaken at the bottom of the first ring of tank wall (N);
δeb - The effective thickness of the bottom edge plate of the tank (mm);
ReL - The yield strength of the material of the bottom edge of the tank (MPa);
ρs - The density of the stored solution (kg/m3).
10.5.3 When the lifting force (Ft) per unit length in the circumferential direction
of the bottom of the tank wall is more than 2 times the anti-lifting force (2FL),
the storage tank shall be anchored to the foundation.
10.5.4 The anchorage of storage tanks shall comply with the following
requirements.
1. The vertical compressive stress at the bottom of the storage tank wall shall
be calculated according to the following formula.
bottom of the tank wall (Ft) is more than the anti-lifting force (FL) and less
than or equal to 2 times the anti-lifting force (2FL), it shall be calculated
according to the following formula.
Where.
CL - The bottom lifting influence factor.
3. The vertical compressive stress at the bottom of the tank wall shall meet
the requirements of the following formula.
4. When the vertical compressive stress (σc) at the bottom of the tank wall is
more than the allowable critical stress of stability ([σcr]), it may use one or
more of the following measures, meanwhile it shall repeat the calculations
of item 1 and item 2 of this clause, until it meets the requirements.
1) Reduce the aspect ratio of the storage tank;
2) Increase the thickness of the first ring of tank wall;
3) Increase the thickness of the bottom edge of the tank;
4) Anchor the storage tank to the foundation.
10.5.6 When the thickness of the first ring of tank wall as obtained by seismic
checking according to this clause is more than the thickness as calculated
based on the hydrostatic pressure (excluding the corrosion allowance), the
thickness of the other rings of tank wall shall also be calculated based on the
thickness as calculated according to the hydrostatic pressure, through seismic
checking ring by ring.
10.6 Liquid sloshing height
10.6.1 The liquid sloshing wave height of the liquid level in the storage tank
under horizontal seismic action shall be calculated according to the following
formula.
11 Tubular heater
11.1 General requirements
11.1.1 Except for the ethylene cracking furnace, the seismic design of the
collection flue duct and chimney of the tubular heater, the auxiliary combustion
chamber, the sulfur tubular heater, the waste heat recovery system shall comply
with the provisions of this clause.
11.1.2 The calculation of the seismic action of the tubular heater structure shall
comply with the following provisions.
1. For the frame structur......
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