Please use this identifier to cite or link to this item:
http://hdl.handle.net/11375/27488
Title: | EXPERIMENTAL AND ANALYTICAL STUDIES ON THE EVALUATION OF ELASTOMERIC BRIDGE BEARINGS |
Authors: | Ahmadisoleimani, Seyedsaleh |
Advisor: | Balomenos, Georgios Konstantinidis, Dimitrios |
Department: | Civil Engineering |
Publication Date: | 2022 |
Abstract: | Elastomeric bridge bearings (composed of alternating rubber layers and steel laminates surrounded by a rubber cover all around) have been historically introduced between the girder and the pier or abutment to accommodate service-level movements and rotations. During a seismic event, these bearings can also experience deformation demands that are considerably larger than the service-level demands. The manufacturing process of these bearings involves compression molding during which imperfections such as vertically misaligned, rotationally misaligned, and bent steel laminates might develop. The current quality control procedures for bearings involve costly, time-consuming, destructive tests on sample bearings. Therefore, there is a need for an efficient, nondestructive methodology for quality control testing of bearings. In addition, these bearings are a key component of the bridge, and thus the effects of manufacturing imperfections on different aspects of the bearing’s performance must be understood and quantified. In the first phase of this research, an efficient vision-based assessment methodology was developed for the nondestructive identification of the internal structure of elastomeric bridge bearings and their potential imperfections. The developed methodology requires the application of three-dimensional digital image correlation (3D-DIC) and relies on the local extrema forming in displacement and strain fields on the vertical sides of compressed bearings. In the next two phases, extensive nonlinear 3D FEA studies were undertaken to evaluate the effects of imperfections on the behavior of bearings under maximum service loading and under large lateral displacements resulting from seismic actions. Based on the FEAs results, imperfections are not expected to trigger shear delamination in bearings and their increased vertical deflections due to imperfections would be also minimal. However, imperfections can appreciably increase the tensile stresses in the laminates and lead to greater extents of plasticity in them. In the third phase of this research, the examined bearings were subjected to simultaneous axial loading and five cycles of lateral displacements with increasing amplitudes, up to 200% of their total rubber thickness. It was found that imperfections do not cause a considerable difference in the overall deformed shape of bearings but can expedite the rollover of bearings in lower shear strains and increase their risks of instability. Although all the examined bearings exhibited fairly stable hysteretic response, their effective lateral stiffness and lateral force could increase up to 18% and 40%, respectively, due to imperfections. Imperfections could also increase damage measured using a plastic-energy-based damage factor by up to more than five times for bearings subjected to the five-cycle displacement protocol. However, the yielded laminates in all examined bearings under maximum service loading or cyclic lateral displacement were far from fracturing. The increase of plastic damage during a strong earthquake and due to imperfections is not expected to cause immediate failure of bearings, provided that no or limited plastic damage occurs prior to that and under the service-level condition. The proposed nondestructive methodology can be adopted by departments/ministries of transportation as an alternative to the current destructive approaches for quality control of elastomeric bearings. For bearings subjected to maximum service loading, the use of sufficiently thick laminates (e.g., 4-mm-thick) is suggested to prevent plastic damage to the laminates, and thus alleviate concerns about the service-level performance of the bearings. Considering the risks of rollover, instability, and spread of plastic damage in the laminates under cyclic loading, slender bearings with laminate thicknesses of 2 mm, or less, and slender bearings in which the majority of laminates feature relatively large rotational misalignments (in the order of 0.025 rad, or more) should be avoided. |
URI: | http://hdl.handle.net/11375/27488 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
Ahmadisoleimani_Seyedsaleh_2022April_PhD.pdf | 17.98 MB | Adobe PDF | View/Open |
Items in MacSphere are protected by copyright, with all rights reserved, unless otherwise indicated.