Performance of Reinforced Concrete Components and Buildings during the August 17, 1999 Kocaeli (Izmit), Turkey Earthquake

A large number of reinforced concrete buildings were heavily damaged or collapsed during the 7.4 magnitude earthquake that struck northwestern part of Turkey on August 17, 1999. Recorded peak ground accelerations were relatively low (0.3g-0.4g) compared to the magnitude of the structural damage, and the elastic acceleration response spectra from the recorded motions were comparable with the elastic design spectra specified in the current Turkish seismic code. A brief description of seismic code requirements is presented and compared with observed details. Other than the damage caused by liquefaction and poor soil conditions in some regions, major causes for large destruction were due to weaknesses and vulnerability of typical threeto six-story nonductile reinforced concrete buildings and their components to seismic loads. These weaknesses include: reinforced concrete columns with insufficient confinement and lateral reinforcement, 90-degree hooks at the end of column ties, short columns, poor detailing in beam-column joint regions, strong-beam and weak-columns, less infill walls in the first stories leading to soft stories, not having proper moment resisting frame system due to irregular column orientation, and poor quality of construction. Buildings with shear wall components performed well.