What do you think of the ball joint in the center of this metal structure?
Actually the ball joint with its oblong hole to place the bolt was made with the purpose of generating an expansion or seismic joint as can be seen in the opening of the slab. Most of the time the ball joint is not placed because it is enough to cut the beam in the center of the section to generate the two overhangs that are observed on each side of the ball joint to separate the structures into two or more bodies in order to achieve better behavior before seismic forces or before expansions due to temperature changes.
