3 Classification of Loads and Representative Values of Loads
3.0.1 The loads on structures in petrochemical industry are classified into three categories:
1 Permanent load:including structures self-weight，self-weight of equipment and piping，the weight of insulation on equipment and piping，soil pressure and prestress etc.
2 Variable load:including the operating loads，maintenance loads and pressure test loads on structures by equipment and piping in each case，live loads on platforms（floors）and roofs，ash loads，crane loads，wind loads，snow loads，thermal actions，ice-covered loads and surcharge loads on ground.
3 Accidental loads:including explosion pressure loads，various accidental loads，impact loads and moments of motor short circuit.
3.0.2 In the design of buildings and special structures in petrochemical industry，the different loads shall adopt different representative values according to the following requirements:
1 For permanent loads:the characteristic value shall be its representative values；
2 For variable loads:the characteristic value，combination value，frequent value or quasipermanent value shall be its representative vale according to the design requirements；
3 For accidental loads，its representative value shall be determined according to the use characteristics of the buildings and special structures in petrochemical industry.
3.0.3 The determination of the representative value of variable loads shall be based on 50-year design reference period.
3.0.4 The characteristic values of loads shall be in accordance with the requirements of each chapter of this Code.
3.0.5 For verification of limit state of bearing capacity or limit state of normal use according to the characteristic combination for variable load，the combination value or characteristic value shall be its representative value according to the specified load combination.The combination value of variable load shall be the characteristic value of variable load multiplied by the load combination value coefficient.
3.0.6 For verification of limit state of normal use according to frequent combination，variable load shall take the frequent value or quasi-permanent value as its representative value；for verification using quasipermanent combination，the quasi-permanent value of variable load shall be its representative value.The frequent value of variable load shall be the characteristic value of variable load multiplied by the frequent value coefficient.The quasi-permanent value of variable load shall be the characteristic value of variable load multiplied by the quasi-permanent value coefficient.