The variation of influence line for stress function in a statically determinate structure is uniformly rectangular.

Explanation:

Influence lines are graphical representations that show the variation of a response function (such as stress, displacement, or reaction) at a specific point in a structure due to a unit load moving along the structure. The shape of an influence line depends on the type of response function being considered.

In the case of stress function, the influence line represents the variation of stress at a specific point in a structure due to a unit load moving along the structure. The stress function is related to the internal forces within the structure, such as axial force, shear force, and moment.

The variation of influence line for stress function in a statically determinate structure is uniformly rectangular. This means that the influence line has a constant value over the entire length of the structure.

This can be understood by considering the equilibrium conditions of a statically determinate structure. In a statically determinate structure, the internal forces can be determined using the equations of equilibrium. Since the equilibrium conditions are satisfied at all points in the structure, the variation of stress due to a unit load moving along the structure remains constant.

The uniformly rectangular influence line for stress function is characterized by a constant value of stress throughout the structure, except at the point of interest where the stress is maximum. This means that the stress is zero at all points except at the point of interest, where it reaches its maximum value.

In conclusion, the variation of influence line for stress function in a statically determinate structure is uniformly rectangular, with a constant value of stress throughout the structure except at the point of interest.