In a back-to-the-future scenario, the structural engineer for the seismic retrofit of a 1962 steel moment-resisting frame in earthquake-prone San Francisco fashioned the office building's high-tech lateral system after an ancient Japanese pagoda. The building's 14-story pivoting spine—equivalent to a pagoda's wooden "shinbashira"—turned into a $4-million-plus silver lining to a recession-related hiatus for the $110-million gut renovation and expansion of 680 Folsom Street.
Instead of a tree trunk pivoting in a well in the ground, the ultra-modern shinbashira is an 8-million-lb structural concrete core. The 232-ft-tall heavyweight sits on a single sliding friction-pendulum bearing, 3.5 ft in dia. The bearing can slide like a marble in a bowl.