Structural selection and layout is qualitative to the structure, because it involves a wide range, it should be carried out under the guidance of experienced engineers. In the whole process of steel structure design, "conceptual design" should be emphasized, It is particularly important in the stage of structural selection and layout. For some problems that are difficult to make accurate and rational analysis or not specified in the code, the layout and detailed structure measures of control structure can be determined from the overall point of view based on the design ideas obtained from the mechanical relationship between the overall structural system and the subsystem, failure mechanism, earthquake damage, test phenomena and engineering experience.

       In the early stage, the conception, comparison and selection can be carried out quickly and effectively, and the obtained structural schemes are easy to calculate by hand, the mechanical behavior is clear, the qualitative is correct, and the unnecessary tedious calculation in the structural analysis stage can be avoided. At the same time, it is also the main basis to judge whether the output data of computer internal force analysis is reliable or not.

       In the industrial workshop, when there is a large hanging load or a large range of moving load, it can be considered to abandon the portal frame and use the grid structure. In areas with high basic snow pressure, the roof curve should be conducive to snow sliding (snow load is not required to be considered beyond the tangent line of 50 degrees). For example, the limestone warehouse shed of Yadong cement plant adopts three center circular reticulated shell, and the total snow load is released by nearly half compared with the sloping roof. Similar consideration should be given to areas with large rainfall.