A three-hinged arch has hinged supports at each abutment. The external restraint provided by both the abutments is ____ .

Correct option is C

Correct Option: A

Given

A three-hinged arch has:

• One hinge at each abutment.
• One hinge at the crown.

Each hinged support (pin support) provides two reaction components:

• One horizontal reaction.
• One vertical reaction.

Since there are two hinged supports, the total number of external reaction components (external restraints) is:

2+2=4
Therefore, the external restraint provided by both the abutments is:
4
Hence, Option A is correct.

Additional Information

The external restraints provided by different types of supports are:

Although a three-hinged arch has four external reaction components, it is statically determinate because the additional hinge at the crown provides one extra independent equilibrium condition, making the structure solvable using the equations of static equilibrium alone.