Investigation of Abutment Displacement of a Full Height Integral Bridges in Dense Granule Backfill

Abstract

Problem statement: In this study, the behavior of abutment wall in full height frame integral abutment bridges was investigated. It was seen that the effect of backfill soil resistance on behavior of abutment wall movement is mostly neglected in previous studies. In this research, the final bridge superstructure displacement under temperature-induced forces was formulated. In addition, according to the final bridge displacement, the earth pressure that acts as a resistant force on the bridge abutment using the new equation from British design manual for roads and bridges, BA 42/96 was used. Besides, in the construction of integral bridges, the deck and girders are mostly encased into abutment wall, which makes these bridge components as fixed elements. This fix connectivity makes the top abutment wall move along with the bridge deck. Moreover, the abutment wall in integral bridges is made of reinforced concrete and thus, it could be assumed as a rigid mass that has a linear deformation behavior. Approach: To implement a new method to calculate the amount of abutment wall movement at different elevations in full height frame abutment integral bridges, considering the parameters such as temperature changes, bridge deck elongation and the backfill soil resistance. First, internal forces of the bridge abutment were formulated. They were all presented as functions of bridge deck final displacement. Second, different methods to calculate the soil lateral pressure were used. Third, the numerical modeling was applied and the corresponding results due to the bridge deck elongation were extracted. Fourth, the results obtained from phases two and three were compared to obtain some conclusion. Results: The results derived in this study, consisted of four data sets. First, the existing forces such as the bridge deck elongation force, the backfill soil resistance etc. were formulated according to the bridge final displacement. Then after, the static principals revealed the amount of deck final elongation. For the second set, different correlations such as British Standard, Massachusetts manual and etc. which had considered the effect of deck final displacement in their formulas were presented and with regard to the first part, the backfill reactions were obtained. For the third set, by combining the results from set one and two, different values for the deck final displacement were derived. For the next step, according to the fix connectivity of the abutment and the bridge deck, the abutment top elevation displacement was set equal to the deck final displacement. For the bottom elevation, because of the rigidity of the wall and the rotational behavior about its foundation, the displacement was set zero. Therefore, by assuming linear deformation behavior of rigid masses, the abutment deformation profile for different elevations was concluded. For the last set, the bridge computer model was built using SAP2000 and the corresponding results were collected. Conclusion: It was seen that, generally, except for some certain cases, all the used correlations in this study were in a close agreement either with each other or with the Finite Element data. British Standard method had the closest results to the finite element data and thus preferably it is recommended while the others not denied.