PLANE RIGID FRAME STRUCTURAL ANALYSIS (PRFSA) PRFSA is a user-friendly computer program for predicting the in-plane behaviour of plane rigid frames. The input data for the program includes the geometry of the frame, the section and material properties of the frame elements, and the loading. PRFSA (Plane Rigid Frame Structural Analysis) is a user-friendly computer program for predicting the in-plane behaviour of plane rigid frames. The input data for the program includes the geometry of the frame, the section and material properties of the frame elements, and the loading. When a 1st or 2nd order elastic analysis is performed, the program calculates the deformations and stress resultants of the frame. The axial force stress resultant can be used to perform an in-plane buckling analysis of the frame, which calculates the buckling load factor and the corresponding buckled shape. The 1st order elastic-plastic analysis can calculate the progressive formation of plastic hinges in the frame and the corresponding load factor, deformations and stress resultants. The natural vibration analysis calculates the natural frequencies of the frame and the corresponding vibration modes. The steady state analysis calculates the forced vibration response of the frame when the applied loads vary harmonically at a given forcing frequency. The transient analysis calculates the deformations and stress resultants of the frame due to ground excitation and force excitation. The truss analysis can calculate the deformations and axial force stress resultant of the frame by assuming the frame acts as a pin-jointed truss.