coarse structure

例句：

1. 1. The engineer used a coarse structure to build the bridge.
   工程师使用粗糙的结构建造了这座桥。
2. 2. The rough structure of the new building is not easy to maintain.
   新建筑的粗糙结构维护起来并不容易。
3. 3. The crude structure of the model was not convincing enough for the judges.
   这个模型的粗糙结构对评委来说不够说服力。