3.6　Calculation of Ground and Foundations

3.6.1　For metallurgical equipment foundations designed in accordance with this Code，dynamic load calculation may not be required，unless otherwise specified.However，static load calculations shall be made using the static loads equivalent to the dynamic effects of the equipment and materials.

3.6.2　Loads exerted on the equipment foundations fall into the following three categories，depending on their variability over time.

1　Permanent loads，including:

1）Equipment foundations and dead weight of buildings（structures）supported on the foundations；

2）Dead weight of equipment and its fittings；

3）Dead weight of pipes supported on the equipment foundations；

4）Weight of materials on equipment and media in pipes，whose variations can be ignored during operation；

5）Dead weight of soils and floors on the equipment foundations；

6）Lateral pressure of soils；

7）Pressure of constant-level groundwater.

2　Variable loads，mainly including:

1）Weight of materials on equipment，whose variations cannot be ignored during operation；

2）Live loads generated due to equipment operation under normal and special operating conditions；

3）Live loads generated due to impact and vibration caused by movement of materials under normal and special operating conditions；

4）Live loads on roofs，floors，platforms and floors may be classified as live loads during operation and live loadsduring installation and maintenance，including the weight of the operation &maintenance personnel，tools，removable equipment or components，miscellaneous raw materials and finished products as well as the impact loads generated during placement；

5）Wind loads，dust loads，snow loads and crane loads transferred from the outdoor equipment or buildings（structures）supported on the equipment foundations；

6）Pressure imposed from the level-varying groundwater.The maximum and the minimum water level of ground water shall be determined taking into account the historical records，seasonal effects，project activities，changes after start-up and predictable factors.

3　Accidental loads.

3.6.3　Metallurgical equipment foundations shall be designed by distinguishing various conditions，such as special conditions，maintenance conditions and accidental conditions during periods of construction，installation，normal operation and production.The most unfavorable combinations of the corresponding load effects should be applied，with considerations given to the limits of the following specified categories:

1　Metallurgical equipment foundations under all the conditions except the accidental conditions shall be designed，taking into account the bearing capacity limits.

2　Metallurgical equipment foundations under normal operation and maintenance conditions shall be designed，taking into account the serviceability limits.

3　Metallurgical equipment foundations under special conditions shall be designed，taking or not taking into account the serviceability limits as specified in the respective chapters of this Code.

4　Metallurgical equipment foundations under construction，installation and overhaul conditions shall be designed，taking into account the serviceability limits according to the implementation scheme if inecessary.

5　Metallurgical equipment foundations under accidental conditions shall be designed or protected，taking into account the accidental combinations of the bearing capacity limits to prevent the main bearing structures of the equipment foundations from failure due to occurrence of the accidental conditions.

3.6.4　When determining the bottom area of metallurgical equipment foundations as per the bearing capacity of the subgrade or when determining the number and layout of piles as per the bearing capacity of a single pile，the load effects transferred to the bottom of the foundations or pile caps shall be treated as the typical combination of load effects under the normal serviceability limits.The corresponding resistance shall be considered asthe characteristic value of the bearing capacity of the subgradeor the single pile.

The coefficients of variable load combinations shall be defined according to the specifications in the respective chapters，or assumed as 1.0 when they are not covered in the chapters for live loads of the equipment and materials under the normal operating and special conditions.

The pressure applied by the foundation bottom to the subgrade or the forces exerted on the pile top shallmeet the following requirements:

1　For natural foundations，the pressure on the foundation bottom shall be as follows:

1）As to centric axial loads，the following formula shall apply:

Where:pk—Average pressure on the foundation bottom in case of typical combination of the load effects；

fa—Corrected characteristic value of the bearing capacity of the subgrade.

2）As to eccentric loads，the following formula shall also apply，in addition to formula（3.6.4-1）:

Where:pkmax，pkmin—The maximum and the minimum pressure on the edge of the foundation bottom in case of typical combination of the load effects.

3）As to foundations of blast furnaces，hot blast stoves，converters，electric arc furnaces，continuous casting machines and rolling mill equipment，the ratio of the minimum pressure to the maximum pressure on the edge of the foundation bottom shall meet the requirements in the respective chapters.

2　For piled foundations，the forceson a single pile top shall be as follows:

1）As to centric axial vertical force，the following formula shall apply:

Where:Qk—Vertical force on any single pile under the centric axial vertical force in case of typical combination of the load effects；

Ra—Characteristic value of the vertical bearing capacity of a single pile.

2）As to eccentric vertical force，the following formula shall apply，in addition to formular（3.6.4-4）:

Where:Qikmax，Qikmin—The maximum and the minimum vertical forces of the ith pile under the eccentric vertical force in case of typical combination of the load effects.

3）As to horizontal force，the following formula shall apply:

Where:Hik—Horizontal force applied to any single pile in case of typical combination of the load effects；

RHa—Characteristic value of the horizontal bearing capacity of a single pile.

3.6.5　When calculating the foundation deformation for metallurgical equipment，the quasi-permanent combination of load effects under the serviceability limits shall be used as the load effects transferred to the foundation bottom.The coefficients of quasi-permanent values are specified in the respective chapters.The installation loads，maintenance loads，emergency loads and seismic effects shall not be taken into account.Wind loads shall not be considered for outdoor equipment or buildings（structures）supported on equipment foundation，but shall be considered for high-rise equipment outdoor in case of heavy eccentricity in wind rose diagram in accordance with the current national standard Code for Design of High-Rising Structures（GB 50135）.The permissible foundation deformation shall meet the relevant requirements in the respective chapters.

3.6.6　When checking the anti-sliding，anti-overturning and anti-floating behaviors of metallurgical equipment foundations，the load effects shall be considered as the fundamental combination of the load effects under the bearing capacity limits，but the partial factor shall be 1.0.The safety factor of stability shall be as follows:

1　If sliding happens along the base，the safety factor of stability shall be no smaller than 1.3.If sliding happens around the inner circular surface of the subgrade，the safety factor of stability shall be no smaller than 1.2.

2　The anti-overturning safety factor shall be no smaller than 1.6.

3　The anti-floating safety factor shall be no smaller than 1.05.

3.6.7　Fundamental combinations of load effects under the bearing capacity limits shall be employed when determining the cross-section dimensions of the metallurgical equipment foundations，computing the internal forces of the foundations，determining the reinforcement and checking the material strength.The design value of resistance for structural members shall follow the current national standard Code for Design of Concrete Structures（GB 50010）.

3.6.8　For flexural or eccentrically-stressed reinforced concrete members in metallurgical equipment foundations or underground works such as basements，pipe tunnels and pipe corridors，the design shall be based on the typical combinations of load effects under the serviceability limits，taking into account the effects upon the foundation crack width in the normal section by long-term actions.The limits for the maximum crack width shall follow the current national standard Code for Design of Concrete Structures（GB 50010）.

3.6.9　For calculations of undamental combination of the bearing capacity limits or of typical combination of the service abilitylimits when designing the metallurgical equipment foundations，the partial factors of the fundamental combination values of loads，and the coefficients of the fundamental or typical combination values of variable loads shall be used as follows:

1　Partial factor of permanent loads:1.2 for combinations controlled by variable loads if the effects are unfavorable to the structures，or 1.35 for combination controlled by permanent loads，or 1.0 if the effects are favorable to the structures.

2　Partial factor of variable loads:Typically 1.4，or 1.3 for live loads on floors，platforms and floors whose standard valuesare greater than 4kN/m2，or 1.2 for live loads of equipment and materials under special conditions.

3　Coefficients of combination values of variable loads shall be determined in accordance with the respective chapters of this Code.The coefficients of combination values of live loads of equipment and materials under normal operating conditions and special conditions shall be 1.0 unless otherwise specified.

3.6.10　For massive foundations，monolithic foundations，small pit type foundations and basements，the foundation bottom reactions may be deemed as linearly distributed.

3.6.11　Linking beams，top slabs，cantilever beam plates，brackets，lugs and small columns which are required to provide adequate holes or space in massive or wall type equipment foundations，as well as the equipment foundations on raft type slabs or on box type foundation top slabs shall be checked separately to ensure adequate rigidity and bearing capacity.

3.6.12　Large raft type or pit type foundations should be calculated using raft model on elastic subgrade.Large continuous box type foundations may be calculated by stripe mthod，block method or by segments according to the layout and characteristics of the respective parts.Overall analyses shall be made for complex and large continuous box type foundations in full length if there is no proven reference.