Suspension Bridge with Two-Hinged Stiffening Girder

A suspension bridge is a type of bridge in which the roadway is suspended from cables that are anchored to towers or piers. The cables are supported by a stiffening girder, which distributes the load of the roadway to the cables. A two-hinged stiffening girder is a type of girder that is hinged at both ends, allowing it to rotate freely.

Statically Determinant and Indeterminate Bridges

In structural engineering, a bridge can be classified as either statically determinant or indeterminate. A statically determinant bridge is one in which the internal forces can be determined by using the equations of statics alone. An indeterminate bridge is one in which the internal forces cannot be determined by using the equations of statics alone.

Degree of Indeterminacy

The degree of indeterminacy of a bridge refers to the number of unknown internal forces that cannot be determined by using the equations of statics alone. For example, a simply supported beam has two supports and is statically determinant. The degree of indeterminacy is zero, because all internal forces can be determined by using the equations of statics alone.

Explanation of the Answer

In the case of a suspension bridge with a two-hinged stiffening girder, the girder is hinged at both ends, which makes it a statically indeterminate structure. However, it is only indeterminate of one degree, because the internal forces can be determined by using the equations of statics and the compatibility conditions of the deformations at the two hinges.

Therefore, the correct answer is option B, indeterminate of one degree.