The lower concrete hall adopts the existing concrete frame structure, and the roof is made of steel grid structure. The plane size is 62.8m × 58.0m, the cantilever is 5m, and the column spacing is 6.6m. The roof is not light roof. The structural design of the project is designed for a period of 50 years and the building structure safety level is 2nd. How to choose the grid steel structure?

This project adopts a square pyramid structure. Corresponding to the column spacing of the lower structure, the grid size is 3.5m × 3.0m (to meet the building requirements, the cantilevered part is 3.5m × 3.35m), the height of the grid is 2.6m, and the height of the slab under the grid is from the ground. 18.0m. Due to the overhanging around, the grid is supported by a lower chord.

The parameters of this structural analysis are as follows:

1. Material, all steel pipes and support gusset plates are made of Q235 steel.

2, design strength and allowable slenderness ratio Q235B steel design strength f = 215N allowable slenderness ratio: pressure = 180 pull = 2003, control deflection according to the design rules, the deflection of the main grid structure is controlled at L / 250 = 42000/250mm = 168mm.