Pettit truss

例句：

1. 1. The engineer designed the building with a Pettit trusses system.
   工程师用桁架系统设计了这座建筑。
2. 2. The structure was built using Pettit trusses, which made it strong and stable.
   这个结构是用桁架建造的，这使得它既坚固又稳定。
3. 3. The Pettit trusses were used to support the heavy load on the roof.
   桁架被用来支撑屋顶上的重载。