For a truss with more than one redundant bar, more than one release will be required to obtain the primary frame .

对于有一个以上多余杆的桁架要得到基本体系，就要放松一个以上的约束。

youdao

Primary frame made of steel columns and beams.

主钢构由钢柱和钢梁组成。

youdao

And yet only nuclear power, which went from zero to about 8.5% of the U.S. primary energy over that time frame, has managed to steal significant market share from coal, oil and natural gas.

FORBES: Magazine Article

If that scenario was repeated nationally, more than 3, 000 primary schools would be in the frame.

BBC: Primary schools face Sats threat