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In accordance with the requirements of MOHURD Notice on printing and distributing the development and revision plan of engineering construction standards and specifications in 2015 (JIAN BIAO [2014] No. 189), this standard is developed by the drafting team through extensive investigation, careful summarization of practical engineering experience, reference to relevant international standards and foreign advanced standards and on the basis of widely solicited opinions.
The main technical contents of this standard: 1. General provisions; 2. Terms and symbols; 3. Basic requirements; 4. Cast-in-situ prestressed concrete frame and portal structure; 5. Prestressed concrete slab-column structure; 6. Prestressed concrete frame structure assembled by prestressed tendons.
The following main technical contents of this standard have been revised: 1. the seismic influence coefficient curve has been adjusted; 2. the value taking method of equivalent damping ratio of the structure has been supplemented; 3. the design requirements of slab-column structure and slab-column-brace structure have been added; 4. the design requirements of precast concrete frame structure assembled by prestressing tendons have been added; 5. the relevant provisions of prestress strength ratio have been adjusted; 6. the relevant provisions of unbonded prestressing fiber reinforced composite tendon have been added.
Standard for seismic design of prestressed concrete structures
1 General provisions
1.0.1 This standard is prepared with a view to implementing the national laws and regulations on building construction and earthquake prevention and disaster mitigation, executing the prevention first policy and reducing the earthquake damage and economic loss, and avoiding casualties after taking seismic fortification measures for prestressed concrete structure.
1.0.2 This standard is applicable to the seismic design of prestressed concrete structure in areas with seismic precautionary intensity of 6, 7 and 8 degrees.
1.0.3 In addition to this standard, the seismic design of prestressed concrete structure shall also comply with the current relevant standards of the nation.
2 Terms and symbols
2.1 Terms
2.1.1
prestressed concrete structure
concrete structure, configured with prestressing tendons, whose prestress is generated by tensioning or other methods
2.1.2
post-tensioned bonded prestressed concrete structure
prestressed concrete structure, such as prestressed concrete frame, portal frame and the like, that is unbonded by grouting in the pipes and whose prestress is generated by tensioning prestressing tendons and anchoring, after the concrete has the specified strength
2.1.3
post-tensioned unbonded prestressed concrete structure
prestressed concrete structure which is configured with unbonded prestressed tendons with anti-corrosion lubricating coating and external sheath and is not bonded with concrete
2.1.4
damping ratio
ratio of actual damping to critical damping
2.1.5
ratio of axial compressive force to axial compressive ultimate capacity of section
ratio of axial compressive force of vertical concrete member to its specified axial bearing capacity, which is the axial compressive force of prestress action to participate in the combination for prestressed concrete columns
2.1.6
slab-column structure
structural system composed of horizontal members as slabs and vertical members as columns, in which the floor slab can be flat, hollow or multi-ribbed slab, and the slab-column joints can be provided with column caps or supporting plates
2.1.7
slab-column-brace structure
structural system composed of slab-column frames and brace composed of beamless slabs and columns, with the brace of ordinary steel or buckling restrained brace
2.1.8
slab-column-wall structure
structural system in which slab-column frame composed of beamless slabs and columns, together with seismic wall, bears vertical and horizontal actions
2.1.9
slab-column-frame structure
structural system in which slab-column frame composed of beamless slabs and columns, together with beamed frame, bears vertical and horizontal actions
2.1.10
monolithic precast concrete frame structure assembled by prestressed tendons
monolithic precast concrete frame structure assembled by concrete beam-column member through prestressing tendons
2.1.11
precast concrete frame structure assembled by unbonded prestressed tendons with dry connections
integral frame structure assembled by precast concrete beam-column members through unbonded prestressing tendons and energy-dissipating reinforcements, in which the prestressing tendons provide the deformation recovery capability of the structure, and the energy-dissipating reinforcements absorb and dissipate earthquake energy
2.1.12
energy-dissipating reinforcement
reinforcement which absorbs and dissipates seismic energy by yielding, provides bending bearing capacity and meets the requirements of seismic performance in the precast concrete frame structure assembled by unbonded prestressed tendons with dry connections
2.2 Symbols
2.2.1 Material performance
Ep——the elastic modulus of prestressing tendon;
Es——the elastic modulus of reinforcement;
fc——the design value of axial compressive strength of concrete;
fptk——the standard ultimate strength of prestressing tendon;
fpy——the design tensile strength of prestressing tendon;
fstk——the standard ultimate strength of reinforcement;
fy——the design tensile strength of reinforcement;
——the design compressive strength of reinforcement;
fyk——the standard yield strength of reinforcement;
fyv——the design tensile strength of stirrup;
σp——the stress of prestressing tendon;
σpe——the effective stress of prestressing tendon;
σ0——the stress of energy-dissipating reinforcement;
εpu——the strain of prestressing tendon when its stress reaches 0.95 fptk.
2.2.2 Actions and effects
Fc——the pressure generated by concrete interface of joint surface;
N——the design value of axial pressure;
NG——the design axial pressure of column under the action of representative gravity load of the slab of this floor;
Npe——the total effective pre-applied force of prestressing tendon;
M——the flexural capacity at the joint surface;
Mp——the flexural capacity of unbonded prestressing tendons at the joint surface;
Mpu——the ultimate flexural capacity of unbonded prestressing tendons;
Ms——the flexural capacity of energy-dissipating reinforcements at the joint surface;
Msu——the ultamate flexural capacity of energy-dissipating reinforcements;
Mu——the ultimate flexural capacity of the section;
R——the design value of the load-carrying capacity of structure member;
S——the design value of the action combination effect;
VGk——the shear force generated by the standard value of permanent load at the joint surface;
Vj——the design combined shear in joint core area of beam-column;
VQK——the shear force generated by the standard value of variable load at the joint surface;
VuE——the shear bearing capacity of seam under seismic design situation;
——the sum of the design values of the combined bending moment of the left and right equivalent beam end sections of the joint in the clockwise or counterclockwise direction.
——the sum of the bending moment values of the anti-seismic flexural bearing capacity of the normal section of the joint actually allocated in the counterclockwise or clockwise direction.
——the sum of the design values of the combined bending moment of the upper and lower beam end sections of the joint in the clockwise or counterclockwise direction.
2.2.3 Geometric parameters
Ap——the sectional area of prestressing tendon;
As——the sectional area of ordinary reinforcement;
Asv——all sectional areas of transverse reinforcement arranged within the same stirrup spacing;
Asvj——the total sectional area of stirrups in the same sectional checking direction within the effective checked width of the core area;
——the distance from the resultant force point of the beam compressive reinforcement to the compression edge;
bd——the effective width of flat supporting plate or column cap;
bj——the effective checked width of section in the joint core area;
by——the calculated width of equivalent frame beam;
db——the diameter of energy-dissipating reinforcement;
Hc——the calculated height of column;
hb——the sectional height of beam;
hj——the sectional height of the joint core area;
hs——the distance from the resultant force point of the longitudinal tensile ordinary reinforcement to the sectional compression edge;
Lu——the unbonded length of energy-dissipating reinforcement near the joint surface;
Lups——the unbonded length of prestressing tendon;
lax, loy——the calculated span of equivalent beam;
s——the spacing between stirrups;
x——the height of the concrete compression zone of the equivalent rectangular stress diagram;
Δs——the elongation value of energy-dissipating reinforcement under limit state.
2.2.4 Calculation coefficients and others
T——the natural vibration period of the structure;
Tg——the characteristic period of ground motion;
α——the seismic influence coefficient;
αb——the strain permeability coefficient of energy-dissipating reinforcement;
αmax——the maximum seismic influence coefficient;
β1——the height adjustment coefficient of neutral axis;
βc——the influence coefficient of concrete strength;
γ0——the structural importance coefficient;
γRE——the seismic adjustment coefficient of bearing capacity;
λNp——the ratio of axial compressive force to axial compressive ultimate capacity of section of prestressed concrete columns;
ηc——the amplification coefficient for bending moment at the column end;
ηj——the constraint influence coefficient of orthogonal beam;
μ——the friction coefficient;
ψ——the reduction coefficient.
3 Basic requirements
3.1 General requirements
3.1.1 For prestressed concrete structures designed according to this standard for seismic resistance, the maximum height of the building should not exceed the limits specified in Table 3.1.1-1 and Table 3.1.1-2. For structures with irregular horizontal and vertical planes or those with large span, the applicable maximum height should be reduced appropriately; for Class B buildings, the applicable maximum height may be determined according to the local seismic precautionary intensity; the buildings with height beyond those specified in this table shall be specially researched and demonstrated, for which, effective reinforcement measures shall be taken;
Table 3.1.1-1 Applicable maximum height of cast-in-situ prestressed concrete building m
Structural system Seismic intensity
6 7 8 (0.2g) 8 (0.3g)
Frame structure 60 50 10 35
Frame-wall structure 130 120 100 80
Partial frame-supported wall structure 120 100 80 50
Frame-corewall structure 150 130 100 90
Slab-column-wall structure 80 70 55 40
Slab-column-frame structure 22 18 15
Slab-column structure 18 15 12
Slab-column-brace structure 60 50 40
Notes:
1 The building height refers to the distance from outdoor ground to main roof slab top, excluding the part partially protruding from the roof;
2 Special-shaped column frames are excluded from the frame mentioned in the table.
Table 3.1.1-2 Applicable maximum height of building of precast concrete assembled by prestressing tendons m
Structural system Seismic intensity
6 7 8 (0.2g) 8 (0.3g)
Monolithic precast concrete frame structure assembled by prestressing tendons 60 50 40 30
Precast concrete frame structure assembled by unbonded prestressing tendons with dry connections 22 18 15 —
3.1.2 For prestressed concrete structure, different seismic grades shall be adopted according to the seismic precautionary categories and intensities, structure types and building heights, and the requirements of corresponding calculation and construction measures shall be met.
1 The seismic grade of Class C buildings shall be determined in accordance with those specified in Tables 3.1.2-1 and 3.1.2-2.
2 For Classes A, B and D buildings, the seismic precautionary criterion shall be determined according to GB 50223 Standard for classification of seismic protection of building constructions, and the seismic grade shall be determined according to this table;
3 Where the building height is approximate or equal to the threshold, the seismic grade shall be determined in combination with the irregularity, site and foundation conditions of the building;
4 When the frame-corewall structure with a height less than 60m is designed according to the requirements of frame-wall structure, its seismic grade shall be determined according to the requirements of frame-wall structure in Table 3.1.2-1 of this standard;
5 The seismic grade of non-prestressed member such as seismic wall shall be implemented according to the relevant requirements of the current national standard GB 50011 Code for seismic design of buildings.
Table 3.1.2-1 Seismic grade of cast-in-situ prestressed concrete structure member
Structural system Precautionary intensity
6 7 8 9
Frame structure Height (m) ≤24 >24 ≤24 >24 ≤24 >24 ≤24
Frame IV III III II II I I
Large-span frame III II I I
Frame-wall structure Height (m) ≤60 >60 ≤24 25~60 >60 ≤24 25~60 >60 ≤24 25~50
Frame IV III IV III II III II I II I
Partial frame-supported wall structure Height (m) ≤80 >80 ≤80 I I
Frame-supported storey frame II II I I I
Frame-corewall structure Frame III II I I
Slab-column-wall structure Height (m) ≤35 >35 II I I
Column, joint and frame of slab-column III II
Slab-column-frame structure Height (m) ≤12 >12 ≤12 >12 ≤12 >12 I
Column, joint and frame of slab-column structure III II II I I I
Slab-column structure Height (m) ≤12 >12 ≤12 >12 ≤12 I I
Column, joint and frame of slab-column structure III II II I I
Slab-column-brace structure Height (m) ≤24 >24 ≤24 >24 ≤24 >24
Column, joint and frame of slab-column structure III II II II I I
Ordinary steel brace III II II II I I
Note: The large-span frame refers to the frame with a span of not less than 18m.
Table 3.1.2-2 Seismic grade of member of precast concrete structure assembled
by prestressing tendons
Structural system Precautionary intensity
6 7 8
Monolithic precast concrete frame structure assembled Height (m) ≤24 >24 ≤24 >24 ≤24 >24
Frame IV III III II II I
Large-span frame III II I
Precast concrete frame structure assembled by unbonded prestressing tendons with dry connections Height (m) ≤12 >12 ≤12 >12 ≤12 >12
Column III II II I I I
Frame beam III III III III III III
3.1.3 If the construction site is Category I, Categories A and B buildings shall be allowed to adopt details of seismic design according to the requirements of seismic precautionary intensity in this area; Category C buildings shall be allowed to adopt details of seismic design according to the requirements of seismic precautionary intensity in this area lowering by one degree, while according to the requirements of seismic precautionary intensity in this area in the case of seismic precautionary intensity of 6. For areas with the design basic acceleration of ground motion of 0.15g or 0.30g, if the construction site is Category III or IV, unless otherwise specified in this Specification, the details of seismic design should be taken according to the requirements of different categories of buildings with seismic precautionary intensity of 8 (0.20g) or 9 (0.40g) respectively.
3.1.4 Unbonded prestressing tendons shall not be used for frames with seismic grade I, tension members of load-bearing structures and transfer storey girders; such tendons should be used for plate members with dispersed prestressing tendons; such tendons may be used for the secondary beam of the floor. Bonded prestressing tendons should be used for post-tensioned prestressed cast-in-situ frame and portal frame, and the following requirements shall be met if unbonded prestressing tendons are used:
1 Reliable anti-looseness measures shall be taken for anchorage;
2 The requirements in 3.1.5 of this standard shall be met if unbonded prestressing tendons are used.
3.1.5 Under the combination of earthquake action effect and gravity load effect, unbonded prestressing tendons may be used in frame beams of seismic grade II, III and IV when one of the following three conditions is met; unbonded prestressing tendons may be used in cantilever beam when the first or second paragraph is met.
1 The design bending moment of the end section of the frame beam and the root section of the cantilever beam borne by the non-prestressing tendons shall not be less than 50% of the design value of combined bending moment ;
2 Prestressing tendons are only used to meet the deflection and crack requirements of members;
3 In the case of seismic wall or tube, under specified horizontal earthquake action, the seismic overturning moment undertaken by the bottom frame shall be less than 50% of total seismic overturning moment.
3.1.6 When prestressing tendons are configured in frame columns, bonded prestressing tendons shall be used for frame columns of seismic grade I, and should be used for frame columns of Seismic Grades II and III.
Foreword ii
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Basic requirements
3.1 General requirements
3.2 Earthquake action and seismic checking for structures
3.3 Materials and anchorages
4 Cast-in-situ prestressed concrete frame structure and portal structure
4.1 General requirements
4.2 Prestressed concrete frame beams
4.3 Prestressed concrete frame columns and joints of frame
4.4 Prestressed concrete portal structure
5 Prestressed concrete slab-column structure
5.1 General requirements
5.2 Essentials in calculation
6 Precast concrete frame structure assembled by prestressing tendons
6.1 General requirements
6.2 Monolithic precast concrete frame structure assembled by prestressed tendons
6.3 Precast concrete frame structure assembled by unbonded prestressed tendons with dry connections
Explanation of wording in this standard
List of quoted standards
