Research on Bearing Capacity of Tall Piers During Incremental Launching Construction Considering Horizontal Thrust Effects

In bridges with tall piers constructed using the incremental launching method， the pier top experiences displacement during construction due to the combined action of friction and superstructure weight. This horizontal displacement， coupled with the superstructure weight， further affects the bearing capacity of the pier. Furthermore， bending of the pier body caused by construction deviations further reduces the bearing capacity. To investigate the influence of horizontal thrust and construction deviations on both pier top displacement and bearing capacity during incremental launching， an approximate calculation formula for tall pier top displacement was proposed， considering both the horizontal thrust at the pier top and the presence of initial bending in the pier body. Simultaneously， a formula for calculating the ultimate bearing capacity incorporating the influence of horizontal thrust was derived based on the edge yield criterion. Taking the piers of a multi-span continuous girder bridge as the research object， a finite element model was established to verify the accuracy of the formulas， and a sensitivity analysis was conducted. The research results indicated that the errors between the formula calculation results and the finite element simulation results were within 1%. For tall piers （mostly long columns） commonly encountered in engineering， the influence of second-order bending moments could not be neglected. During incremental launching， piers subjected to horizontal thrust and initial eccentricity exhibited an increase in the eccentricity magnification factor， leading to larger bending moments at the pier base and posing a risk of failure under severe conditions. In practical engineering， horizontal thrust and initial eccentricity have a certain weakening effect on the ultimate bearing capacity of tall piers.