Effect of seismic loading onV-H-M capacity of well foundation

抄録

Well foundations are one of the most commonly used deep foundations in bridges. Due to their ease of construction and high rigidity, these foundations are preferred in earthquake prone areas and in difficult soil conditions. As it is difficult to introduce plasticity in these massive structures, well foundations are designed to remain elastic during earthquake. These foundations have played a major role in the survival of bridges during the past earthquakes. But, there have been some failures in these foundations also, in terms of excessive displacements and rotations, due to shear fluidization of surrounding soils. This has motivated the researchers to study their response under combined vertical and lateral loads under seismic conditions. Under gravity and seismic loads, foundations are subjected to vertical load, V, shear force, H, and moment M. In the past, most researchers have studied the effect of vertical load, V, on shear, H, and moment, M, capacities of well foundations, individually. But in reality H and M are always combined, and the foundation capacity is significantly influenced by the combination of V-H-M loading. The aim of the present work is to study the characteristics features of the failure pattern due to different combinations of V, H and M loading on well foundation. ‘Probe’ analyses using finite element limit analysis (FELA) are used to develop the V-H-M capacity envelopes. The effect of seismic inertial forces, on the V-H-M capacity, is also investigated, using pseudo-static analyses, by applying constant seismic acceleration coefficient, a_h. The results of these analyses are compared with their static counterparts.