Complex sentence: The current Franklin Field is the 3rd stadium on the site, designed by Day's partner, Charles Zeller Klauder, in 1922, with the upper deck added in 1925.
Split into simpler sentences: The current Franklin Field was designed by his partner, Charles Zeller Klauder, in 1922 and 1925. The 3rd and current Franklin Field was designed by Charles Zeller Klauder in 1922, with the upper deck added in 1925.