Evaluation of the Shear Modulus of Elastomeric Bridge Bearings Using Modal Data
Evaluation of the Shear Modulus of Elastomeric Bridge Bearings Using Modal Data

Author: Reza Akbari

Publisher:

Published: 2009

Total Pages: 10

ISBN-13:

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The current methods for the determination of the shear modulus for elastomeric bearings consist of the testing on a rather small part of the specimen cut from the manufactured bearing. Hence, such tests are destructive and at the same time, may not essentially represent the corresponding properties of the full size specimen with sufficient accuracy, due to the so-called "size effects." Here, a modal-based nondestructive test method has been proposed which requires a rather simple modal testing apparatus and can be applied to find some important dynamic characteristics of the elastomeric bearings as well as its shear modulus. After the derivation of the dynamic characteristics of the specimens from modal analysis, the shear modulus has been obtained from modal analysis in conjunction with finite element analysis with different material properties that requires a series of finite element analyses based on a simple trial and error procedure. Four test specimens have been used and several tests have been carried out on each. Two of the test specimens were new elestomeric bearings and the other two were used bearings which have been in service for 35 years. The results demonstrate that the proposed method is a suitable manner in which important characteristics of the elastomeric bearings can be quantitatively obtained. Comparison of the results obtained from this method and conventional tests by ASTM have been discussed and some comments have been given on the results of tests on the new and old specimens.

Evaluation of Elastomeric Bearings for Seismic Design
Evaluation of Elastomeric Bearings for Seismic Design

Author: Cale Ash

Publisher:

Published: 2002

Total Pages: 256

ISBN-13:

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Elastomeric bridge bearings have been used by various states in the mid-America region to accommodate thermal movement of bridge decks for over thirty years. Their potential role for mitigating damage in the infrequent but high consequence earthquakes that characterize the central United States is explored in this project. The potential protective role of conventional elastomeric bearings is critically influenced by material properties such as shear modulus, known to be temperature dependent. The degree of influence at low temperatures is determined through experimental studies. Slip characteristics of in-service aged and contaminated Teflon interfaces are determined. Full-scale bearings taken from existing bridges in addition to new bearings form the basis of these tests. Materials tests performed on the elastomer characterize the properties of aged bearings. The influence of these physical properties on possible bridge damage caused by earthquake ground shaking is assessed through computational simulations. A retrofit bearing with improved details for seismic isolation is designed and tested. An apparatus for testing the bearings was developed to simulate actual loading conditions. The apparatus provides a temperature-controlled chamber to allow for low temperature testing. Test protocols are developed to address the influence of testing parameters such as low temperature exposure and compressive stress. The prototype retrofit bearing design was also tested in this setup. The seismic response of a representative bridge is assessed by computational simulations conducted using the nonlinear analysis software DRAIN-2DX.

Elastomeric Bearing Research
Elastomeric Bearing Research

Author: John C. Minor

Publisher: Highway Research Board

Published: 1970-01-01

Total Pages: 53

ISBN-13: 9780309018975

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The design and development of elastomeric bridge bearings has been almost entirely empirical, and many conflicts exist regarding current specifications and practices. An effort was made to define and separate those parameters that significantly affect the behavior and performance of elastomeric bridge bearings, toward the end of improving current designs and establishing design criteria. The research included a survey of the literature and available test data, an evaluation (testing) program, and the analysis of data generated.

Instrumented Elastomeric Bridge Bearings
Instrumented Elastomeric Bridge Bearings

Author: Douglas K. Nims

Publisher:

Published: 2000

Total Pages: 346

ISBN-13:

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This report presents the results of tests and analyses performed on elastomeric bridge bearings. The focus of this research was the measurement of bearing deformations in the field and assessment of the feasibility of using instrumented elastomeric bearings to monitor bridge condition. The bearing deformations were successful measured in the field during the deck concrete pour and a static truck test. Shear, compression, rotation, and fatigue tests have been carried out in the laboratory and at the manufacturer's facility. Full scale bearings (shape factor 11) were tested at the manufacturer and installed in the field. Model bearings (shape factor 11 and one-quarter the plan area of the full scale bearings) were tested at the manufacturer and in the laboratory. Test bearings (shape factors 5,7, and 10) were tested in the laboratory. The bearing material was 50 Durometer neoprene. The analyses support the testing and considered the bridge-bearing system. The stiffnesses of the bearings are explicitly included in the analyses. A singular characteristic of this experimental research is the focus on the in-service behavior of the bearings.

Stiffness Evaluation of Neoprene Bearing Pads Under Long Term Loads
Stiffness Evaluation of Neoprene Bearing Pads Under Long Term Loads

Author: Ronald A. Cook

Publisher:

Published: 2009

Total Pages: 292

ISBN-13:

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"The objective of this project was to evaluate the interaction between the shear modulus of steel reinforced neoprene bearing pads and shear strain rate. The following interactions related to variations in the shear modulus were investigated for pads with various shape factors: product approval strain rates vs. short-term field strain rates, short-term field strain rates vs. long-term field strain rates, reduction in shear modulus due to load cycles, and effects of compressive stress"--Technical report documentation page.