Ductility Evaluation Of Girder Bridges In Service

The serious consequence of bridge damage caused by the devastating earthquakes in recent 30 years demonstrate the importance of the correct seismic design for highway bridges. The concept of ductile seismic design of structures has been worldwide accepted and paid much attention since the San Fernando, California Earthquake of America in 1971. And the research of seismic design of bridges has also been taken into account increasingly in China since the Tang Shan earthquake in 1976. At present, a ductility theory is adopted in anti-seismic design specification of America, New Zealand, Japan and Europe countries. However, the 89 specification is still used in China.Existing highway bridges in China have substandard seismic characteristics, even a considerable number of them had been not nominally designed for seismic forces. In the circumstances, it is quite necessary that analyze and assess the seismic capability of existing highway bridges in China, in order to strengthen the poor ductility bridges in appropriate methods to enhance the seismic capability.Combination of the development and application of the anti-seismic specifications for highway bridges of China, the reinforced concrete beam bridge piers are researched in the paper in order to discuss the anti-seismic sensitive parameter, i.e. ductility of existing bridges. At the same time, the ductility ability of bridge structures in 1960s, 1970s and 1980s are analyzed systematically and the probable extent is confirmed. In addition, the factors which could influence the ductility ability of R.C. bridge piers are discussed and the main factors are defined.Moreover, the procedure to study the ductility ability of R.C. bridge piers is worked out. The experiments and calculation samples show that the procedure is creditable and practicable.The research results in the paper are practical in engineering, and can be referenced for revising the seismic design specification of bridges.