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Showing 1-5 of 65 Abstracts search results

Document: 

SP164-46

Date: 

November 1, 1996

Author(s):

Y. Arditzoglou, J. A. Yura and A. H. Haines

Publication:

Symposium Papers

Volume:

164

Abstract:

The 1992 AASHTO Design Specification for Bridges recommends the use of shear modulus rather than durometer in specifying the elastomer in bearings for bridges. The value of the specified shear modulus can then be used directly in the design formulas to predict bearing displacements and stresses in the full size bearing. A study was undertaken to evaluate the difference, if any, between the shear modulus from the ASTM D-4014 quadruple shear test on a small sample of the elastomer and the shear modulus from the full size bearing. Reinforced bearings were ordered from three different manufacturers with a specified shear stiffness of 100 psi (0.69 MPa) and 200 psi (1.38 MPa). The effect of the ASTM specimen size and the method of computing the shear modulus were evaluated. It was found that the ASTM test gave much higher values of shear modulus than measured in the full size tests (sometimes over 30%). Some of the reasons for the difference are given along with some recommendations for changes in the ASTM method and the AASHTO Specification for elastomeric bearings.

DOI:

10.14359/14332


Document: 

SP164-45

Date: 

November 1, 1996

Author(s):

Alessandro Martelli, Massimo Forni, Franco Bettinali, Giuseppe Bonacina and Agostino Marioni

Publication:

Symposium Papers

Volume:

164

Abstract:

Innovative antiseismic techniques have already been applied in Italy to more than 150 bridges and viaducts and over 30 buildings and other structures. For the latter, seismic isolation systems, mostly formed by high damping rubber bearings, have already been used in 20 cases. For such systems detailed numerical analyses and wide-ranging experimental campaigns have also been performed in the framework of both national and international collaborations to support applications. Proposals for design guidelines and standards have been developed for the isolation devices and both civil and industrial structures, including the nuclear plants. This paper focusses on the main features of the activities performed in support of the development of the aforesaid seismic isolation systems.

DOI:

10.14359/14331


Document: 

SP164-37

Date: 

November 1, 1996

Author(s):

A. H. Muhr

Publication:

Symposium Papers

Volume:

164

Abstract:

The linearised beam-column theory for the mechanics of laminated bearings is summarised and theory is presented for the "lift-off" behaviour seen at large shear deflections when bearings are located in recesses, rather than bolted. Experiments show that an axial load increases the dynamic shear stiffness and damping of a single high damping natural rubber layer, but in accord with the theory the shear stiffness of laminated bearings is reduced by an axial load while the damping is increased. Results of tests to failure for 17 permutations of axial load and bearing specification show that the shear capacity exceeds 70% of the plan dimension in all cases except for a squat design with thin endplates located in a recess. The shear capacity of such bearings is limited by yield of the endplates rather than rupture or instability.

DOI:

10.14359/14323


Document: 

SP164-27

Date: 

November 1, 1996

Author(s):

Hiroyuki Nagumo, Osamu Hasegawa and Yoji Suizu

Publication:

Symposium Papers

Volume:

164

Abstract:

Base isolation is one of the effective systems for providing earthquake resistance to structures, since it can reduce to a great extent a structural response to earthquakes. However, base isolation systems applied to existing road bridges cannot exhibit their full capabilities during an earthquake because the narrow space between girders of the bridge limits the movement of girders along longitudinal direction. Replacing bridge bearings is thought to be difficult since it requires extensive chipping of piers and girders, and causes lengthy traffic jams on the bridge. A recently developed base isolation system solves all these problems. The system is verified through performing three-dimensional shaking table test. The experimental results demonstrate that the acceleration of girder could be reduced to one third compared with the case without base-isolation. It is also confirmed that the relative displacement between pier and girder in a miner earthquake was 5mm. Analysis can simulate the experimental results by modeling the system into a bilinear spring. Furthermore it is showed with non-linear dynamic analysis that the model bridge, which was damaged due to Hyogo-Ken Nanbu Earthquake, can secure the aseismic safety for the earthquake by applying the system. Installation method for this system is described at the last part.

DOI:

10.14359/14313


Document: 

SP164-63

Date: 

November 1, 1996

Author(s):

Rodney H. Holland

Publication:

Symposium Papers

Volume:

164

Abstract:

Using a new bearing production technology, scalable, six inch seismic isolation bearings were built to accurately represent many characteristics of full-scale 24 to 36 inch bearings, including elastomer properties, bearing shape factor, metal layer stiffness and total elastomer height-to-width ratios. Test methods for quarter-scale bearings and components are reported that provide reliability and ultimate strength data. Because reduced-scale tests cost less, larger numbers of relevant tests can be conducted in the development stages of bearing design, thereby reducing overall development costs and increasing reliability.

DOI:

10.14359/14351


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