Parametric Investigation of Integral Abutment Bridges: Behavior and Pile Buckling Analysis
Salman, Nassr Noori Ibrahim
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Integral Abutment bridges (IABs) are special types of bridges where expansion joints in the superstructure are eliminated and the thermally induced lateral demand is transferred to the supporting substructure system. As such, the substructure system moves back and forth following seasonal bridge expansion and contraction. These bridges have gained a wide popularity and have become a preferred choice among Department of Transportations and design offices around the world because they have numerous advantages over the conventional bridges, including low construction and maintenance cost, longer serviceability and higher stability, improved riding quality and better seismic performance. Although of the proven advantages of IABs, there are no uniform national guidelines for designing or constructing these structures, and each US state has its own design limitations based on experience and performance of the previously constructed bridges. Absence of the design guidelines is attributed to their complex behavior which is not fully understood. The current study is two-fold; the first part involves a calibration process for an instrumented bridge using a three-dimensional finite element (FE) model. The abutment and pile displacements were calibrated with their experimental counterparts. Several shrinkage models and temperature gradient scenarios were examined to predict the most representative parameters in simulating realistic behavior. Based on the calibration process, a parametric study was conducted to investigate the effect of bridge length, pile size and orientation, and type and stiffness of the soil around the pile on the critical bridge responses which include: abutment displacement, pile displacement, and deck and girder stresses. The second part addresses pile buckling under combined effect of axial load and lateral cyclic displacement. Eleven detailed nonlinear finite element models, experimentally validated, were established for steel HP sections with two axis orientations to estimate the displacement capacities of the piles supporting IABs. A coupon test-validated cyclic plasticity model is incorporated in the finite element analysis to capture the hysteresis of the steel behavior under cyclic loading. Displacement capacities are also compared with an available analytical method. Length limits for IABs were estimated based on displacement capacities of the HP sections and are compared with the limitations of the US Department of Transportations’ current practice. Design recommendations for IABs are also presented.
SubjectIntegral abutment bridges
Finite element simulation of IAB behavior
Pile buckling analysis
Displacement capacities of HP piles under combined axial and lateral cyclic loading