Abstract
Pile supported river bridges still continue to collapse after most major earthquakes in the event of liquefaction. The identified failure mechanisms of piles in liquefied soil are: bending failure due to the inertial loads of the superstructure and kinematic loads due to the lateral spreading of soil; shear failure due to shear loads; buckling instability failure due to vertical loads and associated imperfections; settlement failure due to loss of effective stress in the liquefied zone and finally failure due to the effects related to the elongation of natural period of the piers (also referred to as dynamic failure). This paper revisits the collapse of Shengli Bridge (due to 1976 Tangshan Earthquake) and Panshan Bridge (due to 1975 Haicheng Earthquake) based on the aforementioned failure mechanisms. It has been concluded that pile supported bridges in liquefiable soil can collapse due to each of these five failure mechanisms or due to a suitable combination thereof. It is therefore quite imperative to design pile foundations in liquefiable soil by taking all the failure mechanisms into consideration. The simplified calculation procedure presented in this paper can also be used to carry out the design of bridge piles in the liquefiable soil.