The educational version of RISA-2D, a computer program developed by RISA Technologies for use with Fundamentals of Structural Analysis by Leet, Uang, and Gilbert is a first-order, interactive computer program for the analysis of two-dimensional (planar) structures, such as beams, trusses, and frames. RISA-2D was developed to make the definition, solution, and modification of two-dimensional determinate or indeterminate structural problems simple and fast. The program allows you to draw and edit a model of the structure on the computer screen. The final results–reactions, axial force, shear, and moment diagrams, as well as the deflected shape–can be displayed graphically. This educational version, limited to structures with a maximum of 50 joints and 50 members, will permit you to analyze the majority of problems in a basic course in structural analysis.

A first-order analysis assumes that joint displacements are small enough so that a valid analysis can be based on the initial geometry of the structure. Since the program does not account for the effect of additional forces and deflections produced by large joint displacements, forces and deflections of slender members carrying compression or compression and moment (such as long slender arches or columns in rigid frames) may be underestimated significantly if the structure is flexible and the applied loads are large.

The computer solution is based on the direct stiffness method covered in Chapters 16, 17, and 18 of the textbook. In this procedure the stiffness of each element of the structure is calculated. These stiffnesses are then combined to produce the global stiffness matrix of the structure. The global stiffness matrix is solved for the applied loads to calculate joint deflections, which in turn are used to calculate the individual element forces and deformations.

If for any reason a structure is unstable, the computer program will flash a warning on a red screen and will not carry out the analysis. To introduce RISA-2D, we will first use the program to analyze a truss and a frame. A Help file is also provided for a more detailed description of the program's features.