1. The role of the steel pipeline structure can be divided into permanent and variable roles:
(1) The permanent effects shall include the self-weight of the pipe structure, the vertical earth pressure, the water weight in the pipeline and the uneven settlement of the foundation.
(2) The variable action shall include the design internal water pressure, the vacuum pressure of the pipeline, the ground pile load, the ground vehicle load, the groundwater buoyancy and temperature change.
2. In the design of steel pipe pipelines, different representative values should be used for different properties. The standard value of the action is the basic representative value of the action.
For permanent effects, the standard value should be used as the representative value. For variable effects, standard, combined, or quasi-permanent values should be used as representative values based on design requirements. The combined or quasi-permanent value of the effect should be the standard value of the effect multiplied by the combined coefficient or quasi-permanent value of the effect.
3. When the pipeline structure of a steel pipe is subjected to two or more variable functions and the basic combinations of the effect effects of the limit state of the bearing capacity are to be designed, the variable value shall use the combined value as the representative value.