International Concrete Abstracts Portal

SP-93 This ACI publication is a collection of over 40 papers from 10 different countries examining concrete in transportation-related applications. The combined expertise of representatives from industry, universities and government agencies is brought together, providing information and ideas on the design, use and performance of concrete in six different transportation-related areas. These six strategic areas include: concrete pavements, railroad systems, transit systems, concrete repair, bridges and marine structures. Concrete in Transportation will give the reader valuable information and substantial insight into the problems and solutions inherent in concrete and the infrastructure.

In recent years, approximately 50 large port and harbour reinforced concrete structures have been investigated in China. Analysis of temperature stress and cracking of Concrete has been made on the basis of the results of observa-tion and field testing using remote transducers embedded in the six large dry docks. Concrete temperature and stress have been calculated by several methods. Results of our study indicate that temperature cracking may be caused by high temperature stress even when careful attention is paid to concrete quality, design and construction loads, if adequate measures for reducing temperature stress have not been taken. Temperature stress appears to be mainly related to temperature change, temperature difference and restrained conditions. According to the local conditions in China, measures to prevent temperature cracking are recommended as: carefully analyzing and calculating temperature differences and concrete stress during initial stages of construction, decreasing cement contents, selecting good types of cement and aggregate, appropriate grading and proportioning of concrete, reducing concrete placing temperature, peak temperature, temperature differences and degree of restraint, appropriately selecting the dimensions of concrete blocks, subdivisions and lifts, using steel forms, limiting delay time between concrete placement, good curing and winter proofing the concrete. If measures as above are taken good results can be obtained. This research has been verified in practice in port and harbour engineering in China.

The Vesuvius to Crofton ferry plies the waters of the Strait of Georgia between the east coast of Vancouver Island and the west coast of Saltspring Island. At each end a floating pontoon supports the seaward end of the loading ramp. Prior to 1978, the pontoons were constructed of timber and Styrofoam but they had become waterlogged and badly deteriorated. It was therefore decided to replace them with concrete pontoons to utilize the durability of the material. Tenders were called for the design and construction of the pontoons and Dillingham Construction was the successful bidder. The pontoons were built as hollow boxes without a bottom slab. The walls and top were constructed of high quality reinforced concrete and the inside was filled with closed cell polystyrene to provide the necessary flotation. During the design, care was taken to ensure that the resistance to sea water attack and impact loads was maximized. They were fabricated in the graving dock at Dillingham's yard in North Vancouver and towed out to the site. They have now been providing satisfactory service for over seven years with no signs of deterioration. This rather novel project has shown that floating concrete struc-tures can be built economically and require little maintenance.

Transportation has always been an issue when considering concrete as a structural material. The bulk and weight of concrete have led engineers and planners to consider using the most locally available concrete materials to reduce the transportation effort required to build fixed structures which may support or interface with other vehicles such as ships, trains, and cars. tation function. These vehicles perform the primary transpor-Conventional wisdom defines the supporting concrete structures as massive, bulky, heavy, and stationary. Thus, as far as the concrete elements themselves are concerned, transportation issues are usually thought of as limitations and constraints. Viewing concrete from the perspective of the possibilities of floating concrete structures as a transportation medium leads one's thinking in a different direction. In the global community, many opportunities exist for the application of this little-used transportation technology to address a host of problems facing the people of the world. Engineers and planners have the opportunity to consider floating concrete structures as a transportation medium that opens up possibilities that are nonexistent with more conventional mediums. Floating concrete structures are a surprisingly economical response to a variety of needs. Limitations and advantages are considered from all angles. These issues include transportation, construction, economic, social and political, functional, environmental, scheduling, engineering and risk-related limits, and areas of particular sensitivity. In a series of pointed questions, the authors raise possibilities in the areas of global concern. Our challenge, they maintain, is to visualize bold ways to use the unique possibilities of large-scale floating concrete structures to meet needs that really make a difference to humanity.

With limited land space in urban areas, more and more s tructures are being built underground. The housing of under-ground transport facilities requires the construction of structures such as tunnels and shafts. The progress of such works has often been affected by poor soil conditions and the ingress of water. To overcome problems associataed with the use of poured-in-place concrete in such conditions, an increasing number of projects rely on the use of precast concrete. This paper discusses the role of precast concrete segments in the lining of bored tunnels, the use of prefabricated diaphragm walls for cut-and-cover tunnels and precast concrete elements for immersed tube tunnels. Constructional aspects of the London Underground Piccadilly Line Extension, Toronto Subway, Hong Kong Mass Transit Railway, Ahmed Hamdi Road Tunnel, Suez and the Lyon Metro are discussed. The topics elaborated include the manufacture of precast concrete elements, their delivery to site, erection procedures, grouting, waterproofing and protection of concrete against aggressive environment.