Performance of Single Family House Foundations during Northridge Earthquake

The purpose of this paper is to describe typical damage to single-family house foundations caused by the Northridge earthquake. For those locations with similar earthquake intensity and duration, the raised wood floor foundation having isolated interior posts was most susceptible to damage. This was due to the following factors: (1) A lack of shear resistance of the isolated wood posts; (2) a lack of bolts or inadequate bolted condition of the sill plate to the foundation; and (3) the typical older age of this type of foundation. An interesting effect of the Northridge earthquake was seismic induced translation of the foundation. For the case study presented in this paper, the lack of reinforcement and connections between the garage and house foundation allowed for the garage to detach from the house during the Northridge earthquake. The foundation elements should have been tied together with steel reinforcement to reduce translation effects during the earthquake.