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D. Selected Specifications

Chinese concrete design specifications to achieve the following specifications:

  • Concrete Structure Design Code (GB 50010-2002)
  • Technical specification for concrete high-rise building (JGJ 3-2002)
  • Structural Load code for the design of building structures (GB 50009--2001 (2006 ))
  • Seismic Design Code of Buildings (GB 50011-2001)

Unless specifically stated in this document, its provisions are derived from standard reference design of concrete structures (GB 50010-2002).


Material Properties

elastic modulus of concrete;
Concrete Fatigue Deformation modulus;
modulus of elasticity of reinforced;
that the standard cube strength of concrete strength value 20N/mm2;
a side length of 150mm concrete cube compressive strength of the construction phase;
fcu, k
a side length of 150mm cube of concrete compressive strength of standard value;
fck, fc
standard value of concrete compressive strength, design values;
ftk, ft
the standard value of axial tensile strength of concrete, the design value;
f'ck, f'tk
Construction of the concrete axial compression, axial tensile strength of standard value;
fyk, fptk
in reinforced, prestressed reinforced strength standard value;
fy, f'y
ordinary steel tensile and compressive strength of the design value;
fpy, f'py
prestressed reinforcement tensile, compressive strength design value.

Capacity and Resistance

design value of axial force;
Nk, Nq
according to the standard combination of load effects, quasi-permanent combination of computing the value of the axial force;
Nux, Nuy
axial force on the X axis, Y axis of the eccentric or eccentric compression tension design value of bearing capacity;
bending moment design value;
Mk, Mq
according to the standard combination of load effects, quasi-permanent combination of calculated bending moment;
Component design flexural capacity value;
Bending cross section of the cracking moment value;
torque design value;
shear design values;
oblique section of concrete and stirrups on shear strength design values;
local load design value or the concentration of counter-force design value;
σck, σcq
the standard combination of load effects, quasi-permanent combination of checking the edge of the concrete crack under normal stress;
generated by the pre-tension concrete normal stress;
σtp, σcp
concrete principal tensile stress, principal stress;
σfc, max, σfc, min
fatigue tension zone when Checking the edge of fiber reinforced concrete compression zone or the maximum stress, minimum stress;
σs, σp
is set in the vertical plane bearing capacity of ordinary steel, prestressing stress;
according to the standard combination of load effects calculated longitudinal tensile steel stress or equivalent stress;
tensioning control stress;
prestressed concrete method to force the point of zero stress when the stress of prestressed reinforcement;
effective prestress prestressed reinforcement;
σl, σ'l
tension zone, compression zone in the corresponding stage of prestressed reinforced the value of prestress loss;
shear stress of concrete;
according to the standard combination of load effects and to consider the impact of long-term effect of the maximum crack width calculation.

Geometric Parameters

a, a'
longitudinal tensile reinforcement force point, longitudinal compressive force point to sections of reinforced near-edge distance;
as, a's
longitudinal non-prestressed tensile reinforcement force point, the longitudinal non-prestressed compression steel sections together to point to the near edge of the distance;
ap, a'p
area of longitudinal prestressing tension force point, the compression zone of longitudinal prestressing force points to the section near the edge distance;
width of rectangular section, T-shaped, I-shaped cross-section of the web width;
bf, b'f
T-shaped or I-shaped cross section in tension zone, compression zone of the flange width;
the diameter of the bar diameter or cross section;
the thickness of concrete;
e, e'
axial force point to point longitudinal tensile reinforcement force, vertical compression reinforcement force point distance;
axial force on the section center of gravity of eccentricity;
Add eccentricity;
initial eccentricity;
Height of the Cross;
effective height of cross section;
hf, h'f
T-shaped or I-shaped cross section in tension zone, compression zone of the flange height;
section radius of gyration;
radius of curvature;
longitudinal tensile reinforcement of the anchorage length;
Beam Calculation of span or length of columns;
component axis along the direction of the spacing of transverse reinforcement, the spacing of spiral reinforcement or stirrups spacing;
concrete compression zone;
y0, yn
conversion section focus, focus to the calculation of the net section of the fiber distance;
longitudinal tensile reinforcement force to the concrete compression zone the distance between the points together;
component-sectional area;
component conversion section area;
member net section area;
As, A's
tension zone, compression zone of non-prestressed longitudinal cross-sectional area;
Ap, A'p
tension zone, compression zone cross-sectional area of longitudinal prestressing;
Asv1, Ast1
in shear, by the calculation of single-leg stirrups twisted cross-section area;
Torsion calculation of longitudinal torsion access to all the cross-sectional area of non-prestressed reinforcement;
Asv, Ash
limb within the same section of vertical, horizontal steel hoop or distribution of all cross-sectional area;
Asb, Apb
the same plane bent non-tensioned, prestressed bent steel bar cross-sectional area;
Concrete local compression area;
steel mesh, spiral reinforcement or stirrups within the inner surface of the concrete core area;
Bending stiffness of the section;
cross section by pulling the edge of the elastic resistance moment;
transformed section by pulling the edge of the elastic resistance moment;
net section tensile edge of the elastic resistance moment;
section by twisting the plastic resistance moment;
moment of inertia;
transformed section moment of inertia;
net section moment of inertia.

Calculation Coefficient and Other

compression zone of concrete rectangular stress diagram of the stress value and design value of concrete compressive strength ratio;
reinforced concrete elastic modulus and elastic modulus ratio;
Concrete strength coefficient;
rectangular stress block compression zone and the neutral axis height (axis in the compression zone to the edge of the distance) ratio;
Local Compressive concrete strength coefficient;
the section of concrete to resist the plastic moment of impact factor;
eccentric compression effects of the second order moment of the axial force eccentricity magnification factor;
Calculation of cross sections of shear span ratio;
friction coefficient;
the reinforced longitudinal reinforcement ratio;
ρsv, ρsh
vertical stirrups, stirrups, or the vertical distribution of horizontal bar, horizontal distribution of steel reinforcement ratio;
indirectly, the volume of steel reinforcement ratio or the hoop;
stability factor of axial compression members;
consider the long-term effect on the deflection load increases the impact factor;
crack between the longitudinal bar strain coefficient of uniformity.

Concrete Materials

  1. Elastic modulus of concrete calculated as follows (note the provisions of 4.1.5):

    E c = 10 5 2.2 + 24.7 f c u , k
  2. Standard values of concrete compressive strength and design values were calculated the following formula (note the provisions of 4.1.3):

    f c k = 0.88 α c 1 α c 2 f c u , k

    fc = fckc = fck/1.4

    C50 and the following take α c1 = 0.76, on the C80 take α c1 = 0.82, according to the linear law of change in the middle.

    Of the C40 take α c2 = 1.0, on the C80 take α c1 = 0.87, change in the middle by a linear law.

  3. The standard value and design of axial tensile strength values were calculated as follows (note the provisions of 4.1.4):

    f t k = 0.88 ( 0.395 ) f c u , k 0.55 ( 1 1.645 δ ) 0.45 α c 2

    fc = ftkc = ftk/1.4

Reinforcement Methods

  1. Concrete grades available

    Table 1. Table 4.1.4 Design value of concrete strength 表 4.1.4 混凝土强度设计值
    Strength Category Concrete Strength (N/mm2)
    C15 C20 C25 C30 C35 C40 C45 C50 C55 C60 C65 C70 C75 C80
    fc 7.2 9.6 11.9 14.3 16.7 19.1 21.1 23.1 25.3 27.5 29.7 31.8 33.8 35.9
    ft 0.91 1.10 1.27 1.43 1.57 1.71 1.80 1.89 1.96 2.04 2.09 2.14 2.18 2.22
  2. Steel grades available for reinforcement

    Table 2. Table 4.2.3-1 Ordinary strength of reinforcing bar design value 表 4.2.3-1 普通钢筋强度设计值
    Classification Symbol fy f'y
    Hot-rolled steel HPB 235 (Q235) 210 210
      HRB 335 (20MnSi) 300 300
      HRB 400 (20MnSiV, 20MnSiNb, 20MnTi) 360 360
      400 (K20MnSi) R 360 360

Limit State Design

For the ultimate limit state, structural members shall be the basic combination of load effects or accidental combination of the following limit state design equation:

γ 0 S ≤ R (3.2.3-1)

importance factor, input by the user in the program, on the security level for the one or the design life of more than 100 years and structural components, should not be less than 1.1; on the security level for the design life span of two or 50 years of structural members, not less than 1.0; on the security level is 3 or the design life of 5 years and below the structural members, not less than 0.9; in seismic design, structural elements do not take into account the importance of factors ;
the ultimate state of the load effect combination of the design value.
design value of bearing capacity of structural members; in seismic design, seismic bearing capacity divided by the adjustment factor γ RE;

For the limit state, structural components should be separately according to the standard combination of load effects, quasi-permanent combination or standard combination, and to consider long-term effects of limit state design with the following expression:

S ≤ C (3.3.1)

limit state of load effect combination of value;
structural members meet requirements under normal use of the deformation, crack width and stress limits.