Bridges are one of the most critical parts of transportation networks that may suffer damages against earthquakes. Also, seismic responses of most bridges are significantly influenced by soil-structure interaction effects. Taking out expansion joints in the bridges may cause many difficulties in design and analysis due to the complexity of soil-structure interaction and nonlinear behavior. The secondary loads on an IAB include seismic load, temperature variation, creep, shrinkage, backfill pressure on back wall and abutment, all of which cause superstructure length and stress variations in girder changes. The purpose of this study is to recognize the most effective parameters of analysis IABs. Findings show that the backfill material behind the IABs has a significant effect on the performance of IABs. Using a compressible material behind the abutments would enhance the in-service performance of IABs. Finally, behaviour of abutment may be greatly affected by thermal load and soil pressure. Thermal expansion coefficient significantly influences girder axial force, girder bending moment, and pile head/abutment displacement.
Background: Bridges are one of the most critical parts of a transportation network that may be damaged during earthquakes and it is necessary to have a prediction model for bridge responses under seismic loads that can be extended to other situations. Soil stiffness significantly affects load distribution when soil, piles, abutment, and superstructure all act as a combined system to resist lateral loading on a bridge. Methods: A two-dimensional (2D) model of integral abutment bridge (IAB) with soil springs around piles and behind the abutments for 18.3m, 35.4m, and 64.5m spans respectively, was developed with finite element (FE). The input variables were bridge span, backfill height, soil stiffness behind abutment, and soil stiffness around piles. Also, Artificial Neural Network (ANN) was examined for pile lateral force, pile displacement, pile head moment, girder axial force, and abutment moment. Results: Using FE the prediction of critical response for medium span (i.e., 123.6m) and large span (i.e., 249m) by ANN was performed. Findings show that backfill stiffness has an important effect on lateral displacement. The best performance was related to high stiffness backfill with intermediate clay around the pile. Conclusion: Stiffness of clay around the pile has an important effect on lateral displacement, pile lateral force, pile bending moment, girder axial force, and girder bending moment at the abutment.
Bridges are among the most important transportation elements that may be damaged by earthquakes. An integral abutment bridge (IAB) is a bridge linking the superstructure directly to the substructure. As soil piles, abutments, and superstructures act as a combined system to resist lateral loading on the bridge, soil stiffness has a major impact on load distribution. This research attempts to determine how the structure and soil parameters affect the IABs. The parametric study consists of four variables, namely bridge span (short, medium, and large spans were 18.3, 35.4, and 64.5 m, respectively), backfill height/pressure (3.1, 4.6, and 6.1 m, respectively), stiffness of soil mixture backfills (high, intermediate, and low), and soil density around the piles (high, intermediate, and low). Because of the small width–length ratio of the bridge, a 2D model of an IAB with soil springs around the piles and abutments was developed with finite element software. Findings show that the value of the backfill pressure affects girder axial forces and girder bending moments at the IAB. Also, the stiffness of soil mixture backfills is an important factor to change lateral displacements, while less movement is related to high stiffness of soil mixture backfills with intermediate clay around the pile. It is clear that the maximum axial girder moments at the superstructure generally decrease when the stiffness of the soil mixture behind the abutments and around piles increases, similar to pile deflection and abutment displacements. In addition to maximum abutment, the head moment decreases when abutment backfill is dense and increases when piles are located in hard clay, similar to pile moments. Lastly, dense sand backfill behind abutments is recommended since it decreases pile deflections, pile lateral forces, abutment displacements, abutment head moments, and particularly pile bending moments.
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