GB 50191-2012Code for seismic design of special structures (English PDF)

2.1 Terms

2.1.1 Basic seismic intensity

The seismic intensity that may be met at general site conditions with a probability over 10% within a term of 50 years, which is equivalent to the seismic intensity once in 475 years.

2.1.2 Seismic precautionary intensity

The seismic intensity approved by national authority as the seismic precautionary basis of an area, generally using basic seismic intensity.

2.2 Symbols

2.2.1 Action and action effect

FEk and FEvk -- Characteristic value for total horizontal and vertical earthquake action of the structure;

2.2.2 Material properties and resistance

K -- Stiffness of structure (component);

R -- Bearing capacity of structural component;

f, fk, fE -- Design value, characteristic value and seismic design value of various material strength (including the bearing capacity of soil) respectively;

E -- Elasticity modulus of the material;

[theta] -- Displacement angle limit of structural layers.

2.2.3 Geometric parameters

A -- Sectional area of component;

As -- Sectional area of rebar;

B -- Total width of structure;

H -- Total height of structure, or the column height;

L -- Total length of structure (unit);

a -- Distance;

3.1 Category and Criterion for Seismic Precaution of Special Structures

3.2 Earthquake Strong Motion

3.3 Site and Base

3.3.1 In the selection of special structures site, the favourable section, ordinary section, unfavorable section and hazardous section shall be evaluated comprehensively according to the project planning, seismic activity and the relevant material for engineering geology and seismic geology. The unfavorable section shall be avoided; active seismic measures shall be taken if it is impossible to be avoided.

3.3.2 It is forbidden to construct Class A and Class B special structures on the hazardous section determined by the comprehensive evaluation. The Class C special structures shall not be constructed thereon.

3.4 Structural System and Seismic Design Requirements

3.4.1 The design of special structures shall make the plan, elevation and vertical profile regular. The irregular special structures shall be provided with the strengthening measures as required; the extremely irregular special structures shall be subjected to special research and demonstration and then be provided with particular strengthening measures; the severely irregular structural design scheme shall not be adopted.

3.5 Structural Analysis

3.6 Nonstructural Components

3.7 Materials and Construction

4.1 Site

4.1.1 In the selection of special structures site, the division of favorable, ordinary, unfavorable and hazardous sections for protection of the special structures against the earthquake shall be in accordance with those specified in Table 4.1.1.

4.1.4 The cover layer thickness at the special structures site shall be determined according to the following requirements.

4.1.5 The equivalent shear-wave velocity of soil layer shall be calculated according to the following formulae.

4.2 Foundations on Soil

4.2.1 For the following special structures, the seismic capacity checking of foundations on soil may not be carried out.

4.3 Liquefaction Soil

4.4 Seismic Subsidence of Soft Soil

4.4.1 The special structures on the soft soil in Intensities 6 and 7, when the soil and foundation meet the relevant requirements of the current national standard "Code for Building Foundation" GB 50007, may not consider the influence of seismic subsidence of the soil.

4.4.2 The seismic subsidence of soft soil layer in the soil may be evaluated with the following methods.

4.4.3 The special structures at Intensity 8 and Intensity 9, other than Class D special structures or those under the foundation base in which the non-soft soil layer thickness complies with those specified in Table 4.4.3,

4.6 Seismic Stability of Slope

4.6.1 For the special structures at Intensity 7, Intensity 8 and Intensity 9 and located nearby the slope, slope top or slope toe, the seismic stability of slope and its influence on special structures shall be determined through calculation analysis.

5.1 General Requirement

5.1.1 Earthquake action calculation of special structures shall meet the following requirements.

5.1.2 The seismic calculation of various special structures shall adopt the following methods respectively.

5.2 Horizontal Earthquake Action

5.2.1 In case of equivalent base shear method, the horizontal earthquake action calculation diagram of the structure may be according to Figure 5.2.1; the horizontal earthquake action and action effect shall meet the following requirements.

5.3 Vertical Earthquake Action

5.3.1 For the headframe and shaft tower, Television tower and the tube or tower structure with similar mass and stiffness distribution, the characteristic value of the vertical earthquake action (Figure 5.3.1) may be determined according to the following formulae. The vertical seismic action effect of structural layers may be distributed according to the proportion of representative value of gravity load borne by each component;

6.1 General Requirement

6.1.1 This Chapter is applicable to seismic design of frame and bent frame structures

which are composed of the reinforced concrete frame, frame-walls and bent frame. The applicable maximum height hereof shall meet the requirements specified in Table 6.1.1.

6.2 Essentials in Calculation

6.3 Details for Frame

6.3.1 The section size of the beam should meet the following requirements.

6.3.2 Arrangement of the beam rebar shall meet the following requirements.

6.3.3 Longitudinal rebar arrangement of the beam and spacing of stirrup legs at the beam end's densified area shall meet the following requirements.

6.4 Details for Frame-walls

6.4.1 The thickness of seismic walls shall not be less than 160mm and should not be less than 1/20 of the storey height or non-support part length, the thickness of seismic walls for reinforced bottom part shall not be less than 200mm and should not be less than 1/16 of the storey height or non-support part length.

7.1 General Requirement

7.1.1 This Chapter is applicable to the seismic design of the frame-bent structures

which are composed of composite steel frame, composite steel frame-bracing and single-layer steel bent-frame.

7.2 Essentials in Calculation

7.2.1 The seismic influence coefficient of frame-bent structures shall be determined in accordance with that under frequent earthquakes as specified in Chapter 5 of this code;

The calculation of horizontal earthquake action and action effect shall be carried out.

The horizontal seismic influence coefficient hereof shall be multiplied by the damping adjustment coefficient.

7.2.2 In the calculating of earthquake action of frame-bent structures, the calculation of the bent-frame column, beam (or truss frame) and bracing stiffness in the model shall meet the following requirements.

7.4 Seismic Checking for Beam, Column and Joint

7.4.1 Except for special explanations or specifications in this Chapter, the seismic

bearing capacity of all the frame-bent structures components and their joints shall be checked in accordance with the relevant requirements of the current national standard GB 50017 "Code for Design of Steel Structures"; the internal force of the structural components shall adopt the combined design value counted in the seismic action effect.

7.4.2 Checking of the overall stability for the frame beam may not be carried out for the floor (roofing) slab on the top of the frame beam, in case of one of the following conditions.

7.5.7 If the embedded column foot is adopted, the compressive strength of welding

nails and concrete in embedded part shall meet the following requirements.

8.1 General Requirement

8.1.1 This Chapter is applicable to the seismic design of supporting-type and hanging

boiler steel structures.

8.1.2 Boiler steel structures for thermal power plants, with the single machine capacity

of 300MW or above or the planned capacity of 800MW or above shall belong to Class B special structures, and those with the single machine capacity of 300MW or below or the planned capacity of 800MW or below shall belong to Class C special structures.

8.1.3 The boiler steel structure should be an independent structure. The plant built closely to the boiler steel structure shall be arranged with seismic joints, and the width of the seismic joint shall be 1.5 times the width of the seismic joint of reinforced concrete structure.

8.2 Essentials in Calculation

8.3 Details for Steel Structure Boilers

9.1 General Requirement

9.1.1 This Chapter is applicable to the seismic design of the reinforced concrete, steel

and masonry silos for storing bulk materials.

9.1.3 The silo structure shall be such selected to meet the requirements below.

9.1.6 Foundations of column-bearing silos in Class III and IV sites should be ring

foundations or complete foundations, and measures to increase the integrity and stiffness of the foundation shall be taken.

9.2 Essentials in Calculation

9.2.1 As for the silo, its seismic influence coefficient shall be determined according to that under frequent earthquakes as specified in Chapter 5 of this code, and the earthquake action and the action effect shall also be calculated.

9.2.3 The horizontal earthquake action of the silo shall be such calculated to meet the requirements below.

9.2.4 When the horizontal earthquake action of the cylinder-bearing silo is calculated

with the equivalent base shear method, the seismic action effect of the column-bearing buildings on the silo shall be multiplied by the amplified coefficient, and the value, thus obtained, of the reinforced concrete cylinder-bearing silo and the masonry silo may both be 4.0, and the value for the silo wall-grounding steel silo may be 3.0, but the amplified part shall not be passed downward.

9.2.5 If the horizontal earthquake action of the column-bearing silo is calculated with the equivalent base shear method, the requirements below shall be met.

9.2.6 In Class IV site at Intensity 8, and at Intensity 9, the additional horizontal earthquake action caused by gravity second-order effect shall be counted for the column-bearing silo, and the corresponding characteristic value may be calculated according to the following formulae.

9.3 Details for Silos