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International Concrete Abstracts Portal

Showing 1-5 of 61 Abstracts search results

Document: 

SP94-59

Date: 

July 1, 1987

Author(s):

D. Manning and K. Bassi

Publication:

Symposium Papers

Volume:

94

Abstract:

The historical development of using bearings in Ontario and the current design requirements contained in the Ontario Highway Bridge Design Code and the Ministry's bearing specifications are reviewed. Numerous instances of unsatisfactory bearing performance, especially of proprietary rotational and sliding bearings, are described. Examples are given of unsatisfactory performance resulting from poor bridge design practices, improper bearing design, poor manufacturing procedures, and incorrect installation. In all cases, the action that has been taken to prevent a recurrence of the deficient performance is presented. The basic philosophy in design is to use the minimum number of bearings consistent with the articulation of the structure. The severity of the service environment has been recognized with the result that a high degree of corrosion protection is specified and a provision made for bearing replacement. All bearings are required to have a capacity for rotation about all three axes, which means that rockers, rollers, sliding plates, and cylindrical bearings are no longer used. The paper also describes the contractual relationships involved in the supply of highway bridge bearings and concludes that while a performance specification and guarantee would be desirable, such an approach is not practical.

DOI:

10.14359/1690


Document: 

SP94-50

Date: 

July 1, 1987

Author(s):

W. Buchler

Publication:

Symposium Papers

Volume:

94

Abstract:

The state of the art in the design of pot bearings and, in particular, the relationship between the stress condition in the pot and the adjacent structure are overviewed. The difficulties encountered in performing precise calculations are discussed. Safe and simple design criteria are obtained through the analysis of the ultimate state. The most recent research programs on bearing plates, the factors relevant to the stress condition under the distribution plate, and deformations are reported. Formulas for the design of the pot and the distribution plate are given. The transmission of horizontal forces through the bearing is analyzed. The necessary formulas are presented as well as current values for friction between various materials and the strength of typical shear connectors in use. A bibliography covering many aspects of the theoretical and practical research performed on this subject concludes the paper.

DOI:

10.14359/1685


Document: 

SP94-36

Date: 

July 1, 1987

Author(s):

G. Watiez

Publication:

Symposium Papers

Volume:

94

Abstract:

The following points guide an engineer in the selection of expansion joints. First, one should take into consideration that there are two different approaches in the field of highway expansion joints--that of companies specializing in waterproof joints (generally elastomeric) and who have extrapolated their technique for applications under traffic conditions and that of construction engineers whose main concern is to protect this vulnerable section that constitutes an opening especially introduced to allow freedom of movement. Second, expansion joints should satisfy a list of criteria: stability, ride, low-noise level, waterproofness, low maintenance costs, and durability. Solutions that more or less satisfy the essential criteria can be considered either as the good qualities or the defects of an expansion joint system. The resolution of one requirement is often made to the detriment of another. The real needs must therefore be clearly defined. Third, a description of the principals selected among a solution presented and that constitute a joint system fitted by prestressing should be offered. In summary, an expansion joint must be both simple, robust, and installed absolutely correctly.

DOI:

10.14359/1712


Document: 

SP94-42

Date: 

July 1, 1987

Author(s):

M. Bujtas

Publication:

Symposium Papers

Volume:

94

Abstract:

A concept of pot bearing rotation and its relation to vertical load, rotating moment, and eccentricity are examined. At certain low load and rotating combinations, uniform piston contact with the elastomer or the upper element will not occur, resulting in an uneven load transfer and increased eccentricity. Factors that may be traced to this phenomenon are presented. The rotating moment expression used contains an empiric "alpha factor" variable with three known values. Derived from early rotation tests, this "alpha" is based on the diameter-to-height (D/h) ratio of the confined elastomer. An expression for "alpha" was formulated to provide unique factors for each case. Eccentricity and eccentric neutral stress points were computed in all cases. Critical loads are indicated where piston contact loss is possible. This occurs when the eccentricity is less than the eccentric neutral stress point and at the maximum kern of the inner pot section. Piston separation here is likely, due either to the extreme eccentricity or the confined elastomer's resistance to deform at low pressures. Its importance should not be overlooked as future studies may provide substantiation. However, in assuming static equilibrium, complete piston contact is assured so long as the eccentricity remains within the kern of the pot section.

DOI:

10.14359/3413


Document: 

SP94-57

Date: 

July 1, 1987

Author(s):

J. Breen

Publication:

Symposium Papers

Volume:

94

Abstract:

The paper is the text of the keynote address presented at the Second World Congress on Joint Sealing and Bearing Systems for Concrete Structures. The speech centers on Breen's structural engineering experience with reinforced and prestressed concrete and long-span bridges.

DOI:

10.14359/3777


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