False

Bending stresses are not zero in a three hinge arch. When a load is applied to the arch, it causes the arch to deform. This deformation results in bending stresses within the arch structure.

Explanation:
1. Three hinge arch:
- A three hinge arch is a type of arch structure that has two hinges at the supports and one hinge at the crown. This allows for rotation at the hinges and allows the arch to move and deform under load.

2. Bending stresses in arches:
- When a load is applied to an arch, it causes the arch to deform and undergo bending. Bending is the result of tension and compression forces acting on different sections of the arch. These forces create internal stresses known as bending stresses.
- Bending stresses are highest at the crown of the arch and decrease towards the supports. The maximum bending stress occurs at the section of the arch where the curvature is highest.

3. Bending stress distribution in a three hinge arch:
- In a three hinge arch, the hinges allow for rotation and movement of the arch. This redistribution of forces results in a more uniform distribution of bending stresses along the arch compared to a fixed arch.
- However, this does not mean that bending stresses are zero. The arch still experiences bending and therefore bending stresses are present.

4. Other types of stresses in arches:
- In addition to bending stresses, arches also experience other types of stresses such as axial stresses, shear stresses, and torsional stresses. These stresses depend on the geometry of the arch and the applied loads.

Conclusion:
In conclusion, the statement that bending stresses are zero in a three hinge arch is false. Bending stresses are present in a three hinge arch, although their distribution may be more uniform compared to a fixed arch.