Gas station canopy design (part 1)

The basic function of the gas station canopy is to shelter personnel, vehicles and fuel dispensers from the wind and rain, and it is also an important part of the overall image of the gas station, and even the most important image recognition mark of the gas station. With the first establishment of Sinopec’s image standard for gas stations more than ten years ago, other business entities also began to pay attention to the creation of the image standard for gas stations, so that the appearance of the gas station canopy form, basically abandoned the pursuit of new and complex shaped shaped structure, to simple and generous, tends to international flat structure. This not only reflects the dialectical idea that simplicity is the most beautiful, but also reflects the advanced concept of gas station operators pursuing branding, standardization, scale and internationalization; and to improve the brand recognition of gas stations among consumers as a starting point to continuously enhance the market competitiveness of gas stations and achieve the greatest economic and social benefits.

1 Basic requirements for canopy design

1.1 Fire resistance level In order to reduce the risk of fire and secondary disasters, the fire resistance level of the gas station canopy should not be lower than two. As the canopy around (or three sides) open, conducive to the diffusion of oil vapor at the refueling site, and in the event of a fire accident, the evacuation of personnel and fire fighting conditions are better than room-type buildings. Therefore, when the canopy roof load-bearing members for the steel structure, its fire resistance limit optional 0.25h, but the canopy should be built using non-combustible materials.

2.2 Wind and snow load

Wind and snow loads caused the collapse of the canopy accident occurred repeatedly more than a decade ago. Since the sensitivity of gas station canopy to wind and snow loads is higher than that of housing structures, the relevant provisions of the current national standard GB50009-2012 “Code for Structural Loads of Buildings” should be strictly implemented in the design, and reasonable loads and combinations should be selected to fully consider the influence of wind and snow loads. Based on the increasingly serious impact of El Niño phenomenon on the human environment, the special climate situation has increased significantly during the adopted regular recurrence period, so it is recommended that the recurrence period of wind pressure value and snow pressure value should be 50 years.

3.3 Seismic design

The canopy should be reasonably designed for seismic resistance in accordance with the relevant provisions of the current national standard GB50011-2016 “Code for Seismic Design of Buildings”.

2 Design of mesh frame structure canopy

1) There are a variety of support types for the space frame, four-point support space frame with overhang is appropriate, pick out the span is generally 1/4 of the maximum span, which can better reduce the bending moment in the grid span and improve the force situation. The four-point support structure system meets the structural requirements of the gas station canopy, so the main selection of the gas station canopy is a good stiffness of the positive release quadrangular cone flat space frame.

2) The determination of the grid size is the first problem that should be solved when designing the space frame, because it directly affects the economy of the space frame. Space frame size should be determined by considering the span of the grid, the size of the column network, roofing materials, construction requirements and construction conditions and other factors.

3) The height of the space frame not only determines the size of the internal force of the rod, but also reflects the economic rationality of the web. Usually the angle between the web and the chord is designed to be 35°~60°, which can achieve more reasonable height and economy.

4) Since the space frame is a high super-stationary space rod system structure composed of many rods according to certain rules, its structural calculation is very complicated, so from the beginning of the space frame structure canopy, its design calculation relies on the computer for accurate analysis of internal force, calculation and auxiliary design, and its rod section selection and bolt ball node design.

3 H-shaped light steel structure canopy design

Since the moments of inertia of the two axes of H-beam are very different, the bending resistance in the two axes is also very different. For the gas station canopy, it is not possible to allow the establishment of diagonal tensile bracing in any direction of the H-beam column, but only by widening the flange of the H-beam to improve the stability of the weak axis direction, but its economy and practical results are not very satisfactory. The beam cantilever moment plays a great role in balancing the span moment, and the rigid connection between the beam and column of the gas station canopy does not improve the force condition of the beam, so the hinged connection should be used. At the same time, the column and the foundation take rigid connection to ensure the good stability of the column and the foundation.

From the above analysis, it can be seen that the H-beam structural load-bearing system will excessively increase the amount of steel used per unit area when used to build gas station canopies. At present, design engineers to obtain a greater moment of inertia to increase the stability of the column, the use of round or square thin-walled steel pipe and then filled with expanded concrete inside made of steel pipe concrete column, can improve its bearing capacity and reduce the amount of steel used. If the use of concrete cup foundation, the reliability of the entire structure of the column will be more improved, although this concrete steel column is still lack of corresponding norms and regulations, but from the actual application of some gas stations, the effect is better.