Influencing factors of gas station canopy structure selection

1 The basic principles of canopy structure selection

1) The principle of reasonable force. The structure must first ensure safety and reliability, under the premise of selecting the most reasonable force structure program.

2) The principle of economic reasonableness. When selecting the structure, the overall economic comparison between different structures should be carried out first, and the overall cost of the structure, roof enclosure, gable, foundation, column and construction conditions, construction methods, etc. should be evaluated, and then selected as the lowest.

2 Influencing factors of canopy structure selection

The selection of the canopy structure is influenced by many factors, its area and shape need to be determined according to the location of the site, the structure type is subject to its appearance image, supporting column point arrangement, gable image thickness, etc.

2.1 Span and overhang size

The span of the canopy refers to the maximum distance between columns on the same axis. For the larger span (generally above 24m) of the canopy, the space frame structure is generally preferred. If steel structure is chosen, the size of the main beam will be larger, and the amount of steel used per unit will be much more than that of the net frame structure, and the economy is not as good as that of the space frame structure. When the overhang size is larger (generally above 5m), the choice of steel structure, the end of the overhang beam will produce a larger bending distance to the main beam, resulting in the steel beam size is also larger, so that the unit area of the canopy steel consumption increased, that is, its overall economy is poor. Considering the smooth passage of various fueling vehicles, combined with the actual situation in China and other existing norms and standards, the current national standard GB50156-2021 “Technical Standards for Automobile Fueling and Hydrogen Refueling Stations” stipulates that the effective height of the canopy should be not less than 4.5m, while in actual application, the height of the canopy is mostly much higher than this value. The height of the canopy should be reasonably calculated according to the size of the projected area of the canopy and the protection angle of the dispenser, and a suitable height-to-span ratio should be considered to achieve a good visual effect. For the commonly used 4-pillar canopy, the column height of 5.5~6.5m is appropriate; for 6-pillar canopy, the column height of 6.5~7.5m is appropriate.

2.2 Location and type of stressed column points

Usually, the horizontal projection of the gas station canopy and the column line are designed as rectangular, in order to obtain the symmetry of the column point force. However, when there are irregularities in the arrangement of column points due to the constraints of land use, resulting in the steel structure steel beams are difficult to arrange or steel beams are obviously unreasonable, it is appropriate to give preference to the grid structure. Because the space frame structure support setting has arbitrary, is through changing the horizontal position parameters of the support ball node, it is easy to achieve the positioning of the support column. The design of the space frame is generally to determine the location of the column points first, and then the design of the grid size. The canopy column is generally designed as an axially stressed member without bearing the bending distance, in order to reduce the force requirements on the column and reduce the cost of the column and its foundation for the purpose. The most used in the actual project is reinforced concrete column, followed by steel column and steel pipe concrete column. Reinforced concrete columns are mostly used for the construction of mesh shelters. The overall stiffness and force characteristics of the space frame determine that the top of the column only bears axial tension or pressure, as well as a small horizontal thrust caused by wind load. When using steel structure, such as the steel beam itself bending distance can be transferred to the top of the column, often produce adverse effects on the column, generally to adjust the force layout of the steel beam; if the design is more difficult to choose the mesh structure.

2.3 Shape and modeling factors and gable height

1) shaped irregular or space shaped complex canopy, generally choose the mesh frame to meet the principle of reasonable force and economic rationality.

2) Based on image standards, gas stations have clear requirements for the height of the canopy through the eaves: within 800mm of the smaller eaves height, it is appropriate to use H-shaped steel structure type. Such as the use of mesh frame structure is usually higher steel consumption, less economical.

2.4 Construction conditions

The construction method of the space frame has full scaffolding aerial bulk method, aerial picking method, ground assembly overall lifting method, etc.. Construction methods are diverse and flexible：one construction method can be used alone, or a variety of construction methods can be mixed, and the environmental requirements for the construction site are not too high. Most of the steel structures are prefabricated in factories, assembled on site, and installed by the whole crane, which must have the cooperation of cranes in construction and have high requirements for the site.