Plastic Behavior of Structures was organized under the auspices of the Pressure Vessel Research Committee of the Welding Research Council.The group was organized because of the need for unified and standardized methods for limit analysis or plastic collapse determinations.A variety of different methods were being used to determine limit loads and there were questions as to the acceptability of all these different methods.During 1975-1976, three preliminary studies (1.1-1.3) were carried out by the Task Group in three different areas related to three geometries, (plates, shells, and piping and branch connections), where work had been done by other subcommittees of PVRC.After these three summary reports had been prepared, this author was employed in 1976-1978, to review these reports and to prepare the following comprehensive interpretative report on determining limit loads and plastic collapse loads in general.