One of the panels had become detached from the main structure.

一块镶板已从主体结构上脱落。

《牛津词典》

The main structure is made of pine logs, like many traditional structures in Finland.

主要结构是松树原木，像在芬兰许多传统的结构一样。

youdao

The main structure of the construction project must be completed by the contractor itself.

建设工程主体结构的施工必须由承包人自行完成。

youdao

This creates the main structure of the coral reef.

VOA: special.2010.08.10

He says creating a plan for the structure of the book listing the main ideas makes writing much easier.

VOA: special.2009.10.12

Triadic architecture, developed by the Maya, involved a main structure with two inward-facing buildings on either side.

MSN: The Maya may have sacrificed earliest domestic turkeys

In March 2010, fire almost completely destroyed the Muzibu Azaala Mpanga building, the main structure at the site which contained four royal Buganda tombs.

UNESCO: Brasilia Field Office News Archive

The main structure of Christ's cross was in front of me.

CNN: Amid the wreckage, worker finds affirmation of faith