Do you want to calculate the meters used in the truss? (12+9)*2=42 meters, which is the number of meters of single-story truss, which is the near side in your drawing. It depends on whether you want to build a double layer or a single layer. If it is a double layer, it is 42 * 2 = 84m, and if the middle reinforcing beam is 9m high, it is 9+0.5+0.5 =10m. Then the truss is 94 meters in total. If a single-layer truss is built, the length of two beams in the back layer will be correspondingly less, that is,12m * 2 = 24m, so the total usage is 70m. Truss materials are generally divided into stainless steel welding and iron frame welding. Truss specifications are divided into: 500pxx500px, 250pxx500px. The common function of truss is to build a background board. The size of the truss should be determined according to the actual site. If the indoor structure is 375px-500px away from the ceiling, the safety of the outdoor structure should be ensured, and the counterweight should be pressed in case of strong wind.