Detail of GB/T 50761-2018

Introduction of GB/T 50761-2018

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. This standard is revised from GB 50761-2012 Code for seismic design of petrochemical steel facilities by SINOPEC Engineering Incorporation jointly with organizations concerned according to the requirements of Notice on printing and distributing the development and revision plan on engineering construction standards and codes in 2015 (JIANBIAO [2014] No. 189) issued by the Ministry of Housing and Urban-Rural Development. During the revision, the drafting group has adopted the results of special studies completed in recent years, researched and summarized the experiences and lessons of major earthquakes at home and abroad, extensively solicited opinions from relevant survey, design and construction organizations throughout the country, and finalized this standard through repeated discussion, modification and trial design. This standard consists of 11 clauses and 4 annexes, covering: general provisions, terms and symbols, basic requirements, seismic action and seismic checking, horizontal equipment, vertical equipment supported by legs, vertical equipment supported by lugs, vertical equipment supported by skirt, spherical tanks, vertical cylindrical tanks and heater, etc. The main revisions are as follows: 1. The slope of the seismic design response spectrum in the linear descending segment is adjusted. 2. The classification of equipment seismic importance is improved. 3. The adjustment coefficient of seismic action is simplified. 4. The calculation method for horizontal seismic action of equipment installed on frame is supplemented and improved. 5. The damping ratios of vertical cylindrical tank and vertical equipment supported by legs are adjusted according to the completed study subjects. 6. The relevant clauses and texts are modified according to the feedback opinions and suggestions on the exposure draft of this standard. For the purposes of this standard, the Ministry of Housing and Urban-Rural Development is in charge of the administration, China Petrochemical Corporation is in charge of routine management and SINOPEC Engineering Incorporation is responsible for the explanation of specific technical contents. In case of any comment or suggestion during the implementing of this standard, please send it to the management group of Standard for seismic design of petrochemical steel equipments of SINOPEC Engineering Incorporation (Address: No. 21, Anyuan, Anhuibeili, Chaoyang District, Beijing; 100101) for future reference. Standard for seismic design of petrochemical steel equipments 1 General provisions 1.0.1 This standard is prepared with a view to implementing the national laws and regulations on earthquake prevention and disaster mitigation, executing the prevention first policy and reducing the earthquake damage and economic loss of petrochemical equipment after taking seismic fortification measures. 1.0.2 This standard is applicable to the seismic design of steel equipment such as horizontal equipment, vertical equipment supported by legs, vertical equipment supported by lugs, vertical equipment supported by skirt, spherical tanks, vertical cylindrical tanks and heaters for petrochemical purpose in the region with a design basic acceleration of ground motion not greater than 0.40g or with Seismic Fortification Intensity 9 or below. 1.0.3 For petrochemical equipment subjected to seismic design according to this standard, where suffering earthquake of corresponding seismic fortification intensity in this region, the body, supporting members anchorage structure shall not be damaged. 1.0.4 The design parameters of ground motion or seismic fortification intensity shall be determined according to relevant requirements of current national standard GB 18306 Seismic ground motion parameters zonation map of China; for project site for which seismic safety evaluation has been completed, seismic fortification shall be carried out according to the approved design parameters of ground motion or seismic fortification intensity. 1.0.5 The seismic design of petrochemical steel equipment shall not only meet the requirements of this standard, but also meet those of current national standards. 2 Terms and symbols 2.1 Terms 2.1.1 seismic design specialized design for equipment that requires seismic fortification, including seismic calculation and seismic fortification measures 2.1.2 seismic fortification intensity seismic intensity which is approved according to the authority specified by the nation as the criterion of seismic fortification of one area. 2.1.3 seismic action dynamic action of equipment caused by ground motion, including horizontal seismic action and vertical seismic action 2.1.4 seismic effect internal force or deformation generated by the equipment under seismic action 2.1.5 design parameters of ground motion seismic acceleration time-history curve, acceleration response spectrum and peak acceleration used for seismic design 2.1.6 design basic acceleration of ground motion design value of seismic acceleration with exceeding probability of 10% during the 50-year design reference period 2.1.7 characteristic period of ground motion periodic value corresponding to the start point of descending segment reflecting such factors as earthquake magnitude, epicentral distance and site category in the seismic influence coefficient curve used for seismic design 2.1.8 seismic influence coefficient statistical average ratio of the maximum acceleration response to the gravity acceleration of single-mass-point elastic system under seismic action 2.1.9 seismic fortification measures seismic design content excluding seismic action calculation and resistance calculation and including basic requirements of seismic design and details of seismic design 2.1.10 details of seismic design various detail requirements which must be taken for structural and non-structural parts generally without calculation according to seismic concept design principle 2.1.11 body equipment shell or heater frame structure 2.1.12 allowable stress design design method following the principle that the calculated section stress of an element under the design load does not exceed the allowable stress of the material 2.1.13 limits state design engineering structural design method following the principle that a structure or member meets the certain predetermined functional requirement 2.2 Symbols 2.2.1 Actions and effects Fh——the design value of total horizontal seismic action of equipment; Fv——the design value of total vertical seismic action at the equipment bottom; Fhi——the design value of horizontal seismic action acting on the mass point i; Fhji——the design value of horizontal seismic action at the mass point i in the j-th vibration mode; Fvi——the design value of vertical seismic action at the mass point i; Fhk——the design value of horizontal seismic action on the on-frame equipment; meq——the equivalent total mass of the equipment; mi, mj——the mass respectively focusing on the mass points i and j; meqv——the vertical equivalent mass of equipment; mi——the mass focusing on mass point i; mj——the mass focusing on mass point j; Sj——the effect generated by horizontal seismic action in the j-th vibration mode; Sh——the horizontal seismic effect; Xji——the relative horizontal displacement of the mass point i in the j-th vibration mode. 2.2.2 Material performance and resistance: Et——the elasticity modulus of material at design temperature; Rel——the yield strength of material; σ——the stress value under the action of load combination; [σ]——the allowable seismic stress of material; [σ]t——the allowable stress of material at design temperature; [σ]b——the allowable seismic tensile stress of material; [σ]bc——the allowable seismic compressive stress of material; τ——the shear stress value under the action of load combination; [τ]——the allowable seismic shear stress of material; [τ]b——the allowable seismic shear stress of material. 2.2.3 Calculation coefficients: α1——the horizontal seismic influence coefficient corresponding to the basic natural vibration period of equipment or structure; αj——the horizontal seismic influence coefficient corresponding to the basic natural vibration period of equipment in the j-th vibration mode; αmax——the maximum horizontal seismic influence coefficient; αvmax——the maximum vertical seismic influence coefficient; φ——the welded joint coefficient; KL——the adjustment coefficient of allowable seismic stress; Km——the amplification coefficient of seismic action of on-frame equipment; ζ——the damping ratio of equipment; η——the seismic importance coefficient of equipment; RE——the adjustment coefficient of seismic action of equipment; η1——the adjustment coefficient of descending slope of linear descending segment; η2——the damping adjustment coefficient; γ——the attenuation index of curve descending segment; γj——the participation coefficient of the j-th vibration mode; δ——the bending deformation influence index; λm——the equivalent mass coefficient; k——the calculation coefficient. 2.2.4 Others: hi, hj——the calculated height of mass points i and j respectively; T, T1——the basic natural vibration period of equipment or structure; Tg——the characteristic period of ground motion; n——the number of mass points; λ——the slenderness ratio; λc——the critical slenderness ratio; lk——the calculated length; ——the inertia radius; δe——the effective thickness of section. 3 Basic requirements 3.1 Classification of seismic importance of equipment 3.1.1 During seismic design, the seismic importance of equipment shall be classified into the following four categories according to the equipment purpose and the earthquake damage degree: 1 Category I: equipment other than those of Categories II, III and IV. 2 Category II: Category II pressure vessels specified in the technical specification for safety of special equipment, i.e., TSG 21 Supervision regulation on safety technology for stationary pressure vessel, Category II tanks classified according to current professional standard AQ 3053 Safety technical code for vertical cylindrical steel welded tank, as well as heater and vertical equipment with a height of 20~80m. 3 Category III: Category III pressure vessels specified in the technical specification for safety of special equipment, i.e., TSG 21 Supervision regulation on safety technology for stationary pressure vessel, Category III tanks classified according to current professional standard AQ 3053 Safety technical code for vertical cylindrical steel welded tank, and vertical equipment supported by skirt with a height above 80m. 4 Category IV: equipment used for fire protection. 3.1.2 During seismic design, the seismic importance of equipment shall be selected based on the seismic importance of equipment according to Table 3.1.2. Table 3.1.2 Importance coefficient Seismic importance category of equipment Category I Category II Category III Category IV Importance coefficient η 0.90 1.00 1.10 1.20 3.2 Seismic influences 3.2.1 The design basic acceleration of ground motion and characteristic period of ground motion corresponding to the seismic fortification intensity shall be adopted for the characterization of seismic influences suffered by the equipment location, except the heater. 3.2.2 See Table 3.2.2 for the correspondence between design basic acceleration of ground motion and seismic fortification intensity. Table 3 Correspondence between design basic acceleration of ground motion and seismic fortification intensity Design basic acceleration of ground motion 0.05g 0.10g 0.15g 0.20g 0.30g 0.40g Seismic fortification intensity 6 7 8 9 Note: g is the gravity acceleration. 3.2.3 The characteristic period of ground motion of seismic influence shall be determined according to the design earthquake group and site category of the equipment location. The design earthquakes are classified into three groups, with characteristic periods of ground motion adopted according to the Table 3.2.3. Table 3.2 Characteristic periods of ground motion Design earthquake group Site category I0 I1 II Ⅲ IV Group I 0.20 0.25 0.35 0.45 0.65 Group II 0.25 0.30 0.40 0.55 0.75 Group III 0.30 0.35 0.45 0.65 0.90 3.2.4 The seismic fortification intensity, design basic acceleration of ground motion and design earthquake group for central areas of main cities and towns in China may be selected according to the relevant requirements of current national standard GB 50011 Code for seismic design of buildings. 3.3 Equipment system design 3.3.1 The equipment system shall meet the following requirements: 1 Under the premise of meeting process requirements, the equipment should be arranged outdoors; 2 The equipment shall be provided with reasonable seismic action transmission path; 3 Failure of whole equipment and loss of seismic capacity due to failure of parts and components or accessory members of equipment shall be avoided; 4 For the weak parts of the accessory equipment attached to the body, measures improving the seismic resistance shall be taken; 5 The change in stiffness and mass of equipment should be gentle, and mass centers of internals and the whole equipment should be arranged at a low level; 6 Vertical equipment supported by skirt with a height-diameter ratio greater than 10 or a height greater than 10m should have a bolted structure; 7 External pipeline connected to the equipment shall be able to adapt to the displacement of the connection point between pipeline and equipment during an earthquake. 3.3.2 The materials of accessory members shall meet the following requirements: 1 The ratio of yield strength to tensile strength of the materials shall not be greater than 0.85; 2 The elongation of supporting member materials shall not be less than 15%; 3 Materials to be welded shall have a good weldability and an impact toughness meeting the design requirements; 4 Under low temperature conditions, the influence of degradation in impact toughness of materials caused by low temperature shall be considered. 4 Seismic action and seismic checking 4.1 General requirements 4.1.1 The seismic action and seismic checking of equipment shall meet the following requirements: 1 The horizontal seismic action shall be calculated and seismic checking be carried out; 2 Where the design basic acceleration of ground motion is 0.20~0.40g or the seismic fortification intensity is Intensity 8 or 9, the vertical seismic action shall be calculated and seismic checking be carried out for the horizontal equipment with diameter greater than 4m and the spacing between two supports greater than 20m as well as the vertical equipment and floor chimney of heater with height greater than 20m; 3 The seismic amplification action of the frame where the equipment is located in shall be considered for the equipment installed on frame. 4.1.2 Where the design basic acceleration of ground motion is 0.05g or the seismic fortification intensity is Intensity 6, Categories I and II equipment may not be subjected to seismic action calculation, but shall meet the requirements of seismic fortification measures. 4.1.3 The following methods should be adopted for seismic action calculation of equipment: 1 Bottom shear method may be adopted for the following equipment: 1) vertical equipment with height not greater than 10m; 2) vertical equipment with height-diameter ratio less than 5 and uniform distribution of mass and stiffness along the height; 3) equipment that may be simplified as a single-mass-point system. 2 Mode-superposition response spectrum method should be adopted for the equipment except those listed in Item 1. 3 Where the design basic acceleration of ground motion is greater than or equal to 0.30g, time-history analysis method should be adopted for supplementary calculations of the vertical equipment with height greater than 120m and height-diameter ratio greater than 25 as well as vertical cylindrical tank with volume greater than 15×104m3. 4.1.4 Where time-history analysis method is adopted, at least two groups of actual strong-motion acceleration records and a group of artificially simulated seismic acceleration time history curves shall be selected according to the equipment site category and design earthquake group, the average seismic influence coefficient curve shall be statistically consistent with the seismic influence coefficient curve used in the mode-superposition response spectrum method, and the maximum acceleration time history may be adopted according to Table 4.1.4. Table 4.1.4 Maximum seismic acceleration time history for time history analysis (cm/s2) Seismic influence Design basic acceleration of ground motion 0.05g 0.10g 0.15g 0.20g 0.30g 0.40g Frequent earthquake 18 35 55 70 110 140 Moderate earthquake 50 100 150 200 300 400 Rare earthquake 125 220 310 400 510 620 Where time-history analysis method is adopted, the bottom shear of equipment calculated by each time-history curve shall not be less than 65% of the calculation result obtained by mode-superposition response spectrum method, and the average of bottom shear calculated by multiple time-history curves shall not be less than 80% of the calculation result obtained by mode-superposition response spectrum method. 4.2 Seismic design response spectrum of ground equipment 4.2.1 The seismic influence coefficient of equipment shall be determined according to the design basic acceleration of ground motion, site category, design earthquake group, natural vibration period and damping ratio of equipment. The maximum horizontal seismic influence coefficient shall be selected according to Table 4.2.1; the characteristic period of ground motion shall be selected based on the site category and design earthquake group according to Table 3.2.3. Table 4.2.1 Maximum horizontal seismic influence coefficient Seismic influence Design basic acceleration of ground motion 0.05g 0.10g 0.15g 0.20g 0.30g 0.40g Frequent earthquake 0.04 0.08 0.12 0.16 0.24 0.32 Moderate earthquake 0.12 0.23 0.34 0.45 0.68 0.90 Rare earthquake 0.28 0.50 0.72 0.90 1.20 1.40 4.2.2 The damping adjustment coefficient and shape parameters of the seismic influence coefficient curve (Figure 4.2.2) of equipment shall meet the following requirements: 1 The shape of seismic influence coefficient curve is divided into the following parts: 1) linear ascending segment, in which the natural vibration period is less than 0.1s; 2) horizontal segment, in which the natural vibration period is from 0.1s to characteristic period of ground motion; 3) curve descending segment, in which the natural vibration period is from the characteristic period of ground motion to 5 times of the characteristic period of ground motion; 4) linear descending segment, in which the natural vibration period is from 5 times of the characteristic period of ground motion to 15s. Figure 4.2.2 Seismic influence coefficient curve α—horizontal seismic influence coefficient; αmax—maximum horizontal seismic influence coefficient; η1—adjustment coefficient of descending slope of linear descending segment; γ—attenuation index of curve descending segment; Tg—characteristic period of ground motion; η2—damping adjustment coefficient; T—natural vibration period of equipment 2 The attenuation index of curve descending segment shall be determined using the following equation: (4.2.2-1) Where, γ——the attenuation index of curve descending segment; ζ——the damping ratio of equipment. 3 The adjustment coefficient of descending slope of linear descending segment shall be determined using the following equation: (4.2.2-2) Where, η1——the adjustment coefficient of descending slope of linear descending segment, taken as 0 where it is less than 0. 4 The damping adjustment coefficient shall be determined using the following equation: (4.2.2-3) Where, η2——the damping adjustment coefficient, taken as 0.55 where it is less than 0.55. 5 Where the calculated horizontal seismic influence coefficient is less than 0.05η2αmax, 0.05η2αmax is taken. 4.3 Horizontal seismic action of ground equipment 4.3.1 Where bottom shear method is adopted, the total design value of horizontal seismic action of equipment (Figure 4.3.1) shall be calculated using the following equations: Figure 4.3.1 Calculation for total horizontal seismic action of equipment Fh=ηREα1meqg (4.3.1-1) (4.3.1-2) (4.3.1-3) Where, Fh——the design value of total horizontal seismic action of equipment, N; η——the seismic importance coefficient of equipment, as selected according to Table 3.1.2; RE——the seismic action adjustment coefficient of equipment, as selected according to Table 4.3.1-1; α1——the horizontal seismic influence coefficient corresponding to the basic natural vibration period of equipment, as determined according to 4.2; meq——the equivalent total mass of equipment, kg; λm——the equivalent mass coefficient, taken as 1 for single-mass-point system while 0.85 for multi-mass-point system; mi, mj——the mass respectively focusing on mass points i, j, kg; Fhi——the design value of horizontal seismic action acting on the mass point i, N; hi, hj——the calculated height of the mass points i, j respectively, mm; δ——the bending deformation influence index, as selected according to Table 4.3.1-2; n——the number of mass points. Table 4.3.1-1 Horizontal seismic action adjustment coefficient Equipment category RE Horizontal equipment 0.45 Vertical equipment supported by legs 0.45 Vertical equipment supported by lugs 0.45 Vertical equipment supported by skirt 0.45 Spherical tank 0.45 Vertical cylindrical tank 0.40 Table 4.3.1-2 Bending deformation influence index Basic natural vibration period of equipment T1 (s) <0.5 0.5~2.5 >2.5 δ 1.0 0.75+0.5T1 2 4.3.2 Where mode-superposition response spectrum method is adopted, the calculations for design value of seismic action and seismic effect of equipment shall meet the following requirements: 1 The design value of horizontal seismic action of equipment at the mass point i in the j-th vibration mode shall be determined using the following equations:

Contents of GB/T 50761-2018

Foreword i 1 General provisions 2 Terms and symbols 2.1 Terms 2.2 Symbols 3 Basic requirements 3.1 Classification of seismic importance of equipment 3.2 Seismic influences 3.3 Equipment system design 4 Seismic action and seismic checking 4.1 General requirements 4.2 Seismic design response spectrum of ground equipment 4.3 Horizontal seismic action of ground equipment 4.4 Horizontal seismic action of on-frame equipment 4.5 Vertical seismic action 4.6 Load combination 4.7 Seismic checking 5 Horizontal equipment 5.1 General requirements 5.2 Seismic action and seismic checking 5.3 Details of seismic design 6 Vertical equipment supported by legs 6.1 General requirements 6.2 Natural vibration period 6.3 Seismic action and seismic checking 6.4 Details of seismic design 7 Vertical equipment supported by lugs 7.1 General requirements 7.2 Natural vibration period 7.3 Seismic action and seismic checking 7.4 Details of seismic design 8 Vertical equipment supported by skirt 8.1 General requirements 8.2 Natural vibration period 8.3 Seismic action and seismic checking 8.4 Details of seismic design 9 Spherical tanks 9.1 General requirements 9.2 Natural vibration period 9.3 Seismic action and seismic checking 9.4 Details of seismic design 10 Vertical cylindrical tanks 10.1 General requirements 10.2 Natural vibration period 10.3 Horizontal seismic action and seismic effect 10.4 Vertical stable allowable critical stress of tank shell 10.5 Seismic checking of tank shell 10.6 Liquid level sloshing wave height 10.7 Details of seismic design 11 Heater 11.1 General requirements 11.2 Natural vibration period 11.3 Seismic action and seismic checking 11.4 Details of seismic design Annex A Seismic action of on-frame equipment Annex B Seismic checking of vertical equipment supported by legs Annex C Seismic checking of vertical equipment supported by lugs Annex D Flexible matrix element Explanation of wording in this standard List of quoted standards