lower purlin tiebeam

例句：

1. 1. Thelower purlin tiebeam is essentialfor supporting the roof.
   下弦梁对于支撑屋顶至关重要。
2. 2. The engineer used a specialtool to adjust the lower purlin tiebeam.
   工程师使用特殊工具调整下弦梁。
3. 3. The lower purlin tiebeam was damaged during the storm, requiringrepairs.
   暴风雨期间下弦梁受损，需要进行修复。