Arches Boring machines (machine tools) 1 Closed-loop 1 Construction equipment 1 Degrees of freedom (mechanics) 1 Efficiency 1 Graphical-type synthesis method 1 Machine design 1 Manipulators 1 Mechanism design 1 Screw theory 1 Single degree of freedoms 1 Single-DOF closed-loop mechanism 1 Single-degree-of-freedom closed-loop mechanism 1 Steel arch splicing manipulator 1 Steel arches 1 Stiffness 1 Synthesis method 1 Type synthesis 1