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Structural Bearings and Expansion Joints

Structural Bearings and Expansion Joints
L. P. Alford, M. E.
86 Pages

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It is my hope that this treatise will serve as a textbook for students and as information for civil engineers involved in bridge construction. My intent was to give a short guideline on bearings and expansion joints for bridge designers and not to mention all the requirements for the manufacturers of such products. These requirements are usually covered by product guidelines, which vary between different countries.

All bridges are subjected to movements due to temperature expansion and elastic strains induced by various forces, especially due to traffic loads. In former times our bridges were built of stones, bricks or timber. Obviously, elongation and shortening occurred in those bridges, but the temperature gradients were small due to the high mass of the stone bridges. Timber bridges were small or had natural joints, so that the full elongation values were subdivided into the elongation of each part. On the other hand, the elongation and shortening of timber bridges due to change of moisture is of- ten higher than that due to thermal actions. With the use of constructional steel and, later on, of reinforced and prestressed concrete, bridge bearings had to be used. The first bearings were rocker and roller bearings made of steel. Numerous rocker and roller bearings have operated effectively for more than a century. With the develop- ment of ageing-, ozone- and UV-radiation-resistant elastomers and plastics, new ma- terials for bearings became available. Various types of bearings were developed with the advantage of an area load transmission in contrast to steel bearings with linear or point load transmission, where elastic analysis leads theoretically to infinite compres- sion stresses. For the bearings the problems of motion in every direction and of load transmission were solved, but the problem of insufficient durability still exists. Whilst it is reasonable to assume the life of steel bearings to be the same as that of the bridge, the life of a bearing with elastomer or plastic parts can be shorter.


1. Bearings
1.1 Introduction
1.2 The role of bearings
1.3 General types of bearings and their movements
1.4 The layout of bearings
1.5 Calculation of bearing reactions and bearing movements
1.6 Construction of beatings
1.7 Materials for bearings
1.8 Analysis and design of bearings
1.9 Installation of bearings
1.10 Inspection and maintenance
1.11 Replacement of bearings
1.12 Codes and standards
1.13 References
2. Expansion Joints
2.1 Introduction
2.2 The role of expansion joints
2.3 Calculation of movements of expansion joints
2.4 Construction of expansion joints
2.5 Materials for expansion joints
2.6 Analysis and design of expansion joints
2.7 Installation of expansion joints
2.8 Inspection and maintenance
2.9 Replacement of expansion joints
2.10 References