Elastomeric Bearings In High Demand Applications
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Author | : Liwei Han |
Publisher | : |
Total Pages | : 292 |
Release | : 2016 |
Genre | : |
ISBN | : |
Pot and disk bearings are typically used in high-demand bridge applications where significant demands are imposed on bearings at the supports to accommodate rotations and complex bridge movements from both environmental thermal loads and vehicular traffic. However, past bridge research, design, and installation experience demonstrates that less costly elastomeric bearings are not only easy to install, inspect, and replace, but also more forgiving of installation errors. The use of elastomeric bearings in high-demand applications results in much less structural restraint against bridge thermal deformation than other more sophisticated sliding bearings. Although past bridge design practice includes applications of elastomeric bearings in two steel trapezoidal box girder systems in Central Texas, the use of elastomeric bearings in high-demand application is nevertheless largely impeded by historical and current bearing design provisions at national and state levels that are unduly restrictive for large-sized elastomeric bearings as well as the scantiness of field, laboratory, and numerical investigations on them. This investigation reported in this dissertation is part of a research project including material study, full-scale testing, field monitoring, and finite-element studies, with a focus primarily on finite-element studies of elastomeric bearings in comparison with laboratory and field measurements. A three-dimensional finite-element model capable of simulating the behavior of elastomeric bearings in full-scale compression, shear, and rotation testing was first developed and validated by experimental results from the full-scale testing. More comprehensive parametric finite-element studies of elastomeric layers under axial load and rotational deformation were then carried out leading to the development of a reliable elastomeric bearing design with improved economy and serviceability, based on total shear strain approach. A three-dimensional finite-element study of a continuous curved steel trapezoidal box girder system (IH-35 NB & US-290 EB direct connector) was carried out to investigate the translational movements and rotations imposed on elastomeric bearings under thermal loads with 100-year return period, and validated by instrumentation measurements from field monitoring. Design suggestions were put forward with regard to determining demands on elastomeric bearing s under thermal loads in high-demand applications. A field investigation was finally carried out on elastomeric bearings on the instrumented bridge, two of which were found to be damaged to different extents. The results reveal that the two damaged bearings are subjected to excessive amount of transverse rotation. Further analyses by calculating the maximum shear strain of all bearings using the proposed design approach confirmed that the observed bearing damage is the direct result of the excessive transverse angle of inclination on the concrete bearing seat surface.
Author | : Todd Aaron Helwig |
Publisher | : |
Total Pages | : 1 |
Release | : 2015 |
Genre | : Bridges |
ISBN | : |
Author | : Konstantinos Victor Belivanis |
Publisher | : |
Total Pages | : 360 |
Release | : 2017 |
Genre | : |
ISBN | : |
Elastomeric bearings have been widely used in short-span bridge systems as they provide a reliable and cost-effective means of accommodating translations compared to the pot bearing alternatives. However, in higher demand applications pot and disk bearings are commonly used to accommodate significant forces and rotations and complex bridge movements from both thermal loads and daily truck traffic. Although elastomeric bearings have been designed for and utilized in twin steel trapezoidal box girder systems in Texas, classifying as higher demand applications, the lack of experimental and numerical research on such bearings, as well as some occasions of poor performance, dictate the need of further investigating their design requirements and performance. The research presented in this dissertation is part of a broader research project including material-level studies, field monitoring of bridge bearings, large-scale experimental testing, and finite element simulations. This dissertation focuses on the large-scale experimental testing and investigates the effect of several parameters on the compression and shear stiffness of elastomeric bearings. Specifically, bearing tests demonstrated the poor prediction ability current AASHTO axial stiffness prediction equations as well as a shear stiffness dependence on the level of axial load and, in some cases, on the shearing direction of the bearing. However, it was shown that both AASHTO Method A and B produce safe elastomeric bearing designs. The finite element studies demonstrated that shim misalignment and cover friction can cause a reduction in the axial stiffness of an elastomeric bearing. In addition, an extensive finite element parametric study was performed to show variations in elastomeric bearings shear stiffness with different axial loads and shearing directions with a wide range of aspect ratios and height to width ratios.
Author | : Konstantinos Victor Belivanis |
Publisher | : |
Total Pages | : 166 |
Release | : 2015 |
Genre | : Bridges |
ISBN | : |
Author | : National Cooperative Highway Research Program |
Publisher | : Transportation Research Board |
Total Pages | : 65 |
Release | : 2008 |
Genre | : Bridges |
ISBN | : 0309099188 |
At head of title: National Cooperative Highway Research Program.
Author | : Jose Sanchez |
Publisher | : |
Total Pages | : 197 |
Release | : 2011 |
Genre | : |
ISBN | : |
Elastomeric seismic isolation bearings have been shown to effectively mitigate structural and nonstructural damage during earthquakes. During strong shaking, elastomeric bearings need to carry high axial loads while being subjected to large lateral deformations. An appropriate evaluation of the critical load for moderate as well as for large displacement (shear strain above 100%) is essential to avoid an undesirable failure of the isolation device at high axial loads. This study presents results from an on-going experimental program to examine the performance limit states in seismically isolated buildings. The specific objective is to compare two different experimental procedures to evaluate the critical load of an elastomeric bearing and compare them to analytical prediction. The first procedure to evaluate the bearing critical load followed a previously used experimental method were the elastomeric bearing is held to a specified horizontal displacement while applying increasing axial load until the critical load is achieved. The second procedure proposed here first applies a constant axial load followed by a lateral displacement until reaching the stability limit of the bearings. The second procedure proposed in this thesis showed to be an accurate and direct approach to obtain the critical load directly from the stability test data and considerably minimizes the data analysis required as in the first procedure. The reduced area formulation commonly used to predict the critical load of the elastomeric bearings is compared to the experimental results. Here, it is recommended to use the effective shear modulus at small shear strains in order to get better agreement with experimental results. In addition, the shear strain and pressure distribution is computed analytically to examine the state of the bearing material at the instability point.
Author | : John F. Stanton |
Publisher | : Transportation Research Board |
Total Pages | : 416 |
Release | : 1999 |
Genre | : Technology & Engineering |
ISBN | : 9780309066143 |
Author | : |
Publisher | : |
Total Pages | : 400 |
Release | : 1995 |
Genre | : Aeronautics |
ISBN | : |
Author | : James M. Kelly |
Publisher | : John Wiley & Sons |
Total Pages | : 217 |
Release | : 2011-08-24 |
Genre | : Technology & Engineering |
ISBN | : 1119972809 |
Widely used in civil, mechanical and automotive engineering since the early 1980s, multilayer rubber bearings have been used as seismic isolation devices for buildings in highly seismic areas in many countries. Their appeal in these applications comes from their ability to provide a component with high stiffness in one direction with high flexibility in one or more orthogonal directions. This combination of vertical stiffness with horizontal flexibility, achieved by reinforcing the rubber by thin steel shims perpendicular to the vertical load, enables them to be used as seismic and vibration isolators for machinery, buildings and bridges. Mechanics of Rubber Bearings for Seismic and Vibration Isolation collates the most important information on the mechanics of multilayer rubber bearings. It explores a unique and comprehensive combination of relevant topics, covering all prerequisite fundamental theory and providing a number of closed-form solutions to various boundary value problems as well as a comprehensive historical overview on the use of isolation. Many of the results presented in the book are new and are essential for a proper understanding of the behavior of these bearings and for the design and analysis of vibration or seismic isolation systems. The advantages afforded by adopting these natural rubber systems is clearly explained to designers and users of this technology, bringing into focus the design and specification of bearings for buildings, bridges and industrial structures. This comprehensive book: includes state of the art, as yet unpublished research along with all required fundamental concepts; is authored by world-leading experts with over 40 years of combined experience on seismic isolation and the behavior of multilayer rubber bearings; is accompanied by a website at www.wiley.com/go/kelly The concise approach of Mechanics of Rubber Bearings for Seismic and Vibration Isolation forms an invaluable resource for graduate students and researchers/practitioners in structural and mechanical engineering departments, in particular those working in seismic and vibration isolation.
Author | : United States. Bureau of Mines |
Publisher | : |
Total Pages | : 1272 |
Release | : 1976 |
Genre | : |
ISBN | : |