View of the Imperial County Services Building after the 1979 El Centro (California) earthquake. Support framework is visible. This six-story reinforced concrete frame and shear wall structure was built in 1969 at a construction cost of $1.87 million, and was designed to be earthquake resistant. However, during the quake, the concrete at the base of the support columns was shattered, and the vertically reinforced bars were severely bent allowing the east portion of the building to sag about 30 cm. The extra load on the columns at the east end of the building came from the discontinuous shear wall at this end of the building. Rotational forces were not dissipated by the shear wall causing a compressional load on the columns. The building had to be replaced at an estimated cost of seven million dollars.

Image Credit: G. Reagor. U.S. Geological Survey