International Concrete Abstracts Portal

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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-10 of 13 Abstracts search results

Document: 

SP88-12

Date: 

November 1, 1985

Author(s):

James T. Kunz and Jerry W. Eales

Publication:

Special Publication

Volume:

88

Abstract:

Thermal infrared and ground penetrating radar remote sensing technologies have been applied to the non-destructive evaluation of existing concrete bridge decks. Delaminations in a concrete bridge deck can be identified rapidly and effectively with the use of a thermal infrared scanner. This technique pro-vides an efficient and economical alternative to traditional sounding techniques utilized to identify delamination. The thermal infrared technique can be used to identify delaminations on exposed concrete bridge decks and decks overlaid with asphalt. Ground penetrating radar can be utilized to rapidly identify and evaluate various bridge deck conditions. The equipment can be used to measure deck thickness, identify thin, weakened areas and determine the position of reinforcing steel within the deck.

10.14359/6268


Document: 

SP88-11

Date: 

November 1, 1985

Author(s):

Frank F. Liou

Publication:

Special Publication

Volume:

88

Abstract:

The Nelson Street Bridge in downtown Atlanta, Georgia is a ten-span continuous concerete arch bridge. Designed for carrying electric street cars, it was built in 1906. The bridge is present-ly carrying local street traffic over active tracks of the Southern Railway System and automobile parking areas. Strength evaluation procedures contrasted the latest design speci-fications and modern analysis techniques with the original design approach in every aspect. A slab-grid model was used for analyzing lateral wheel load distribution on a multiple arch and slab system. The distribution factors were then compared with those recommended by current AASHTO specifications for concrete slabs on concrete T-Beams. Arch geometry was accurately simulated, and moving axle loads were generated in a computer program. Force envelopes were produced for arch sections spaced from one foot to six feet along the arch, using critical loading positions. Sections were then checked for combined compression and bending. This approach is particularly effective when the spacing of arches is unequal and span lengths vary. Concrete cores were taken from the bridge and tested for compres-sive strength and chemical properties. Test results were satisfac-tory when compared with recommendations in the AASHTO Manual for Bridge Rating and turn-of-the-century books on concrete design. Sound arch sections from original contract plans, and existing sec-tions with concrete and steel losses determined by field inspection were used for evaluating section capacities.

10.14359/6267


Document: 

SP88-10

Date: 

November 1, 1985

Author(s):

Gary J. Klein and Predrag L. Popovic

Publication:

Special Publication

Volume:

88

Abstract:

Because prior AASHTO design codes permitted a much greater shear stress in concrete than allowed by current codes, the shear strength of existing bridges may be questioned. This paper offers an approach to shear strength assessment of bridge beams. The condition of the existing structure, theoretical strength based on recent research, and the unique characteristics of older concrete bridges are considered. Field investigation and rating methods are discussed, and a case study is presented.

10.14359/6266


Document: 

SP88-09

Date: 

November 1, 1985

Author(s):

F. E. Fagundo and J. M. Richardson

Publication:

Special Publication

Volume:

88

Abstract:

Precast panel deck bridges have been in use for many years. Although some cracking is inherent in this structural system, recent concern has been expressed because of the greater degree of cracking exhibited on the surface of some decks compared to conventional cast-in-place bridge decks. Full scale structural testing was initiated to estimate the strength and evaluate the performance of the deck panel system. In this program two deck panel bridges, each with different panel support details, and a conventional cast-in-place deck bridge were tested. Results showed that the deck panel system did not act as a continuous slab over the girders as is usually assumed for design. The conventional cast-in-place deck bridge did develop continuity. The effect is to increase the maximum positive moments in the slab but not to a degree as to render the bridges unsafe.

10.14359/6265


Document: 

SP88-08

Date: 

November 1, 1985

Author(s):

M. Ladner

Publication:

Special Publication

Volume:

88

Abstract:

The measurement of the vertical displacement during the load testing of a structure are of great importance. Therefore different methods have been developed for that purpose. For static load tests the wire supported method is normally used in Switzerland by the Swiss Federal Laboratories for Materials Testing and Research (EMPA). When this method cannot be applied because of the inaccessibility of a reference point the water levelling method can then be employed. When only local deflections of a bridge deck under a concentrated load are to be determined, then the horizontal wire levelling method may be used. If also the level of a bridge relative to a fixed point, e .g . relative to the abutment, is to be established, the electronic levelling system may then be applied. In this paper, a short description of each of these methods is given. In addition to- this, some of the aspects how errors can be eliminated are also discussed.

10.14359/6264


Document: 

SP88-07

Date: 

November 1, 1985

Author(s):

David B. Beal

Publication:

Special Publication

Volume:

88

Abstract:

A series of static live load tests were performed on two concrete T-beam bridges to evaluate stress induced in tension reinforcement and transverse load distribution factors. The purpose of these tests was to evaluate the usefulness of service load testing in evaluating the load carrying capacity of concrete bridges. The two structures were similar in dimension and reinforcing but had concrete of markedly different quality as determined from deck cores and sonic pulse velocity measurements through the deck and beam stems. The load test results showed no difference in bridge behavior attributable to concrete condition. To obtain data on failure capacity, testing was performed on two single and one double T segment taken from the deteriorated struc-ture. Rebar stress, centerline displacement, and end rotation were measured during the loading program which culminated in com-pression failure after rebar yield. The measured failure moments exceeded the nominal flexural strength as given by ordinary ulti-mate strength design methods. The consequences of these findings on the load rating process are discussed and a strategy for rating older reinforced concrete T-beam bridges is proposed.

10.14359/6263


Document: 

SP88-06

Date: 

November 1, 1985

Author(s):

Michael P. Collins and Denis Mitchell

Publication:

Special Publication

Volume:

88

Abstract:

The Modified Compression Field Theory which is capable of predicting the response of reinforced and prestressed concrete members in shear is summarized. The predictions of this theory are compared with the test results of two half-scale prestressed concrete bridge girders both before and after repair. An example of evaluating a typical bridge structure is also presented,The Modified Compression Field Theory which is capable of predicting the response of reinforced and prestressed concrete members in shear is summarized. The predictions of this theory are compared with the test results of two half-scale prestressed concrete bridge girders both before and after repair. An example of evaluating a typical bridge structure is also presented,

10.14359/6262


Document: 

SP88-05

Date: 

November 1, 1985

Author(s):

Mohamed I. Soliman and M. S. Mirza

Publication:

Special Publication

Volume:

88

Abstract:

Resulte of an experimental-analytical investigation on a reinforced concrete box girder bridge are presenredo The experimental phase consisted of tests on a - scale, 3 P? direct model of an intermediate span of a b* inuous box girder bridge. Experimental data from the tests under symmetrical and unsymmetrical loads were analysed using some of the available analy- sis methods. These results are combined with other available information to formulate some recommendations for design of box girder structures.

10.14359/6261


Document: 

SP88-04

Date: 

November 1, 1985

Author(s):

M. Ladner

Publication:

Special Publication

Volume:

88

Abstract:

After a short survey on the development of static load tests on structures, the standard test procedure used by the Swiss Federal Laboratories for Materials Testing and Research (EMPA) is presented . From the static load tests basically the following results can be gained: the elastic behavior of a structure under the applied loads as asign for the good quality of the execution the accordance of the measured deformations withthose obtained independently on a theoretic always a sign for the good quality of the design the measured spring constant of a bridge offers the possibility to qualify the bending stiffness. This qualification is based on the results of some 330 static load testing facilities.To illustrate this, three different case histories are descreibed and discussed in this paper.

10.14359/6260


Document: 

SP88-03

Date: 

November 1, 1985

Author(s):

Takeshi Oshiro and Sumio Hamada

Publication:

Special Publication

Volume:

88

Abstract:

Recently, significant deterioration of concrete surface and corrosion of reinforcing bars have been observed, and the necessity for the structural evaluation of such bridges becomes urgent for safety considerations. The primary objective of this study is to investigate the structural performance of two deteriorated reinforced concrete bridges and isolated test beams cut out of the same bridges at the time of replacement. Field and bending tests were conducted from which the strength of existing bridges and isolated beams was observed. Correlations of the values of strength obtained from these two tests give important data to be used for evaluation of existing deteriorated bridges. From the results of general investigations, field tests and bending tests, the following conclusions are drawn; (1) From the results of field tests of Nakama Bridge, strains of reinforcing bars and deflections are rather close to Theory II uncracked gross section), whereas those of Yaka Bridge are located between Theories I (cracked section) and II. This indicates the varying effects of deterioration on main beams. (2) Beams in bending tests yield larger strains and deflections compared with those from tests; this shows that the rigidity of a beam that is part of an existing bridge is much higher than that expected from an isolated beam. (3) According to general investigations, these two bridges were highly deteriorated in appearance. However, ultimate strength of test beams is higher than that computed by ACI Code, indicating no significant losses of strength.

10.14359/6259


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