1. It eliminates the need for pinned joints
2. It reduces vertical deflection by shortening the span
3. It allows for free thermal expansion of the arch crown
4. It stabilizes the arch against out-of-plane buckling and lateral deformation

Explanation

Triangulated members in spatial structures form stable load paths that distribute forces efficiently. In an arch, where vertical and horizontal thrusts must be managed, adding triangulated bracing provides resistance to out-of-plane buckling and improves torsional rigidity. This makes the arch stable in three dimensions, preventing collapse under asymmetric or lateral loading.

Learning Resources:
• “Structural Principles” – Understanding triangulation in truss and arch systems
• Case Study: Burgoyne Bridge (St. Catharines, Ontario) – A steel arch with triangulated members that enhance spatial stability

• Mola Visualization: Build a planar arch using pinned members and apply a lateral load—observe instability. Then rebuild using triangulated 3D members (as shown in image). Notice how the form resists buckling and maintains shape under multi-directional forces.