For a determinate beam, what specific quantity does the ordinate of an influence line for a reaction represent when a unit load is placed at that specific point?

For a determinate beam, an influence line is a graphical representation showing the variation of a specific response, such as a reaction force, at a *fixed pointon the structure as a *unit loadmoves across the beam's span. The term 'determinate beam' signifies that all reactions and internal forces can be calculated using only the equations of static equilibrium. The 'ordinate' refers to the vertical value on this graph at any given point along the beam's length. This ordinate indicates the magnitude of the specific response (in this case, a reaction) at the fixed point for which the influence line is drawn, when the 'unit load' (a concentrated force of magnitude 1, like 1 kN or 1 lb) is positioned at the corresponding horizontal location on the beam. Therefore, when a unit load is placed at the specific point where the reaction itself occurs (the location of the support for which the influence line is being generated), the ordinate of the influence line for that reaction at that exact support location represents the full magnitude of the unit load itself, which is 1. This occurs because the entire unit load is directly transferred to and resisted by that particular support. For instance, if an influence line is drawn for the vertical reaction at support A, and a unit load is placed directly at support A, the ordinate of the influence line at point A will be 1, indicating that the reaction at A is equal to the unit load.