A study of the seismic effects on a portal frame having a hole at the beam-column connection

This paper presents the results of the study on thin walled steel portal frames, which are used in Japan as basic structural frames for motorway viaducts. A serious problem found in many such frames is the development of fatigue cracks at the beam to column connection. To act as a measure against the fatigue failure, in some cases a hole is provided at the beam-column connection of the frames. In this study, dynamic analysis using real earthquake data from 3 different earthquakes were carried out to examine the influence of such a hole on the global behavior of the frame and also on the local out of plane displacement around the location of the hole. Non-linear, large displacement analysis was performed using the FEM program MSC. Marc. The hole radius was varied and used as a parameter of study. The hole had significant effect on local out of plane displacement and global behavior, specifically when the radius of the hole was larger than 100 mm.

► Dynamic analysis of portal frames using real earthquake data is carried out.
► Effects of a hole at the beam-column connection of a portal frame are studied.
► Local displacement and global displacement of the structure are correlated.
► In this study, 150 mm radius hole increased the top displacement about 20–50%.
► A hole can increase the fatigue strength, but the radius must be under a limit.