prestress without bond

例句：

1. 3. 例句：1. The steel beams are prestressed to resist the weight of the building.
   这些钢梁被预应力以抵抗建筑的重量。
2. 2. The bridge was built with prestressed concrete, which made it stronger and more durable.
   这座桥是用预应力混凝土建造的，这使得它更坚固耐用。
3. 3. The engineer used a prestressing machine to reinforce the old concrete beams.
   工程师使用预应力机器来加固旧的混凝土梁。