1, the rear positions of the first four beams and the last eight beams are to the left. If it is slight, we only need to stretch in the opposite direction of deformation.

2. For the main girder with serious deformation, we need to fix the stretching position with proper fixture, then straighten the deformed main girder and stretch it in the opposite direction of the main girder deformation. For the severely deformed girder, we need to stretch it several times more.