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International Concrete Abstracts Portal

Showing 1-5 of 41 Abstracts search results

Document: 

SP93-38

Date: 

September 1, 1986

Author(s):

M. LaNier, W. Cichanski, R. L. Wallace, and D. Magura

Publication:

Symposium Papers

Volume:

93

Abstract:

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.

DOI:

10.14359/6331


Document: 

SP93-37

Date: 

September 1, 1986

Author(s):

E. C. Lim

Publication:

Symposium Papers

Volume:

93

Abstract:

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.

DOI:

10.14359/6330


Document: 

SP93-28

Date: 

September 1, 1986

Author(s):

N. P. Bada

Publication:

Symposium Papers

Volume:

93

Abstract:

Several of the bridge non air-entrained concrete bearing seats on the International Control Dam have concrete deterioration from the application of de-icing salts. A 410 tonne beam and deck slab assembly was raised by twelve hydraulic lift climbing jacks assembled to a single span Bailey Bridge Structure. The concrete repair consisted of removing the deteriorated concrete, application of an epoxy bonder, wood forming, and placing of good quality concrete. The 410 tonne beam and deck slab was lowered onto new elastomeric bearing pads to its original location. The paper details the construction procedures and methods of repair to concrete in Spans 2 and 4.

DOI:

10.14359/6321


Document: 

SP93-36

Date: 

September 1, 1986

Author(s):

A. Ghali

Publication:

Symposium Papers

Volume:

93

Abstract:

Prestressing by post-tensioned tendons with parabolic profiles can be arranged in a curved bridge such that the bend-ing moments are negligibly small due to the combined effect of dead load and prestressing. However, this can result in high torsional moments for which the bridge has to be designed. The reasons and the analysis for the high torsional moments are discussed. A curved continuous bridge with two spans and three possible support conditions is analyzed numerically to get an indication about the magnitude of the torsional moments. Reference is made to an available computer program which can be conveniently used in the analysis of any framed structure. The computer program can handle curved members with varying cross section and externally applied loads as well as prestressing loads.

DOI:

10.14359/6329


Document: 

SP93-26

Date: 

September 1, 1986

Author(s):

P. Balaguru and V. Ramakrishnan

Publication:

Symposium Papers

Volume:

93

Abstract:

This paper presents the results of an experimental investigation of the properties of superplasticized fiber reinforced concrete. Essentially, two groups of specimens were tested; the first to study the relationship between compressive strength and modulus of rupture and the second to study time dependent behavior. Altogether, more than 70 mixture proportions were investigated. The first group of specimens was tested to obtain 28 day compressive strength and 28 day modulus of rupture. The second group of specimens was tested in compression, flexure and for impact resistance at 1, 3, 7, 28 and 90 days. Based on the experimental results, an empirical equation (similar to the one specified in the American Concrete Institute Code 318-83) is proposed, that relates 28 day compressive strength to the 28 day modulus of rupture. The results indicate that: (i) the flexural strength varies linearly with the logarithm of time, (ii) flexural strength gain with time is slower than compressive strength gain, (iii) higher cement content in combination with lower water-cement ratio results in higher early strengths, (iv) the toughness index slightly decreases with an increase in maturity, and (v) both first crack and ultimate impact resistance increase up to 28 days of maturity.

DOI:

10.14359/6319


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