International Concrete Abstracts Portal

In the roughly five hundred years since patents began to be granted, inventors have created millions of new ideas, in all branches of technology. Patents have provided the incentive to inventors to create new ideas, to develop those ideas and to take the risk of promoting those ideas. As a result of their efforts, technology exists now which would be beyond the comprehension of persons who lived in earlier times. In the period since the end of the Second World War, great advances have been made in bearings and expansion joints. Large movement joints are now sealed to prevent intrusion of foreign substances. Bearings have greatly increased in load ratings and endurance under adverse environmental conditions. Joints and bearings, as they now exist, were inconceivable less than 50 years ago. Patents have encouraged the numerous inventors who contributed to that progress. Patent systems exist to distinguish between real contributions and old ideas, and to limit the scope of patent monopolies to the new technology contributed by each inventor. Those systems are necessary to assure that patents reward progress, rather than retarding it by granting monopolies over ideas which should be freely available to all persons.

Deformation and stresses in joints between facade panels and in the ties that connect the panels to the structure depend on the movements of the panels. To enable calculation of deformation and stresses the unrestrained movements of panels must be known. These movements consist of change of length and of bending condition. There is a long-term movement due to shrinkage that goes on for years. There are annual movements due to variation of relative humidity and temperature. There are also diurnal movements caused by temperature and insolation. The report presents necessary datas for calculation of the different movements and a systematized method of putting than together to a total pattern of movements. It's illustrated by a calculated example. The purpose has been to arrive at a method for manual engineering calculation of deformation and stresses in joints and ties. The thermal movements have been studied more thoroughly than the moisture dependent movements which have not been published before. The work was carried out seven years ago and the author has not followed what has happed in the latest years

One of the research programmes in progress at the Transport and Road Research Laboratory is to investigate the thermal behaviour of concrete bridges in the United Kingdom. Part of the work involved the measurement of the longitudinal movement of bridge decks caused by changes in temperature. Some of these measurements of movement were made continuously for periods of up to five years at any one site and the types of bridge instrumented include concrete box (single and multi-cell), concrete beam and slab and solid concrete deck. A brief description of the instrumentation is given and the results discussed include measured values of daily and annual ranges of movement, the seasonal effect on the measured movement of shrinkage of the concrete and short and long term values of the coefficient of thermal expansion of the deck. It is also shown how both daily and annual maximum values of movement may be predicted from a knowledge of the temperature of the deck, which, in turn, may be derived from the variation in the shade air temperature. This knowledge enables the bearings and expansion joints to be set at their correct positions within the design range of thermal movement of the deck.

The Paper reviews recent experience in the United Kingdom and overseas relating to bridge bearing design and performance and is in three sections. 1. Trends in theory and practice of bearing design. 2. Remarks on the specification of bridge bearings in accordance with the proposed new British Standard for Bridges. (BS 5400: Part 9: Bridge Bearings). The document on bearings has been issued in draft for public comment. Following a review of comments received it is expected that the final document will be published at the end of 1981 or in early 1982. As it is the first British Standard to cover the major types of bearings used in bridges it will be of fundamental importance where British Standards are adopted or in those areas where similar principles are applied. 3. Remarks on experiences of bearing installation and performance over the last twenty years, with particular reference to those types developed during that period, such as the elastomeric bearing and those incorporating low friction sliding surfaces.

The paper deals with the difficulties involved in the calculation of particularly large bridge bearings and other criteria that might lead to the decision to specify proof-testing. Using the example of the testing-rig for 100.000 KN and the bearings for the River Orwell bridge, the testing rig itself, the specifications for the tests, the measurements and test results are described, conclusions are drawn on the basis of the tests and recommendations for future applications are given.