Collapse of Showa Bridge during 1964 Niigata earthquake: A quantitative reappraisal on the failure mechanisms

• Published in: Soil dynamics and earthquake engineering (1984) Vol. 65; pp. 55 - 71
• Main Authors: Bhattacharya, S., Tokimatsu, K., Goda, K., Sarkar, R., Shadlou, M., Rouholamin, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2014
• Subjects: 1964 Niigata earthquake; Bridges (structures); Collapse; Earthquake engineering; Failure mechanisms; Grounds; Liquefaction; Natural frequency; Seismic phenomena; Shaking; Showa Bridge; Spreading; Natural frequency; Collapse; Showa Bridge; Liquefaction; 1964 Niigata earthquake
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2014.05.004

Collapse of Showa Bridge during the 1964 Niigata earthquake has been, over many years, an iconic case study for demonstrating the devastating effects of liquefaction. Inertial forces during the initial shock (within the first 7s of the ground shaking) or lateral spreading of the surrounding ground (which started at 83s after the start of the shaking) cannot explain the failure of Showa Bridge as the bridge failed at about 70s following the main shock and before the lateral spreading of the ground started. In this study, quantitative analysis is carried out for various failure mechanisms that may have contributed to the failure. The study shows that at about 70s after the onset of the earthquake shaking, the increased natural period of the bridge (due to the elongation of unsupported length of the pile caused by soil liquefaction) tuned with the period of the liquefied ground causing resonance between the bridge and the ground motion. This tuning effect (resonance) caused excessive deflection at the pile head, resulting in unseating of the bridge deck from the supporting pier and thereby initiating the collapse of the bridge. •Quantitative study of collapse of Showa Bridge.•Identification of failure mechanisms of a bridge foundation.•Simplified method of seismic analysis of pile–soil interaction.•Analysing ground motion using Wavelet Energy Spectrum.