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International Concrete Abstracts Portal

Showing 1-5 of 18 Abstracts search results

Document: 

SP143-01

Date: 

May 1, 1994

Author(s):

M. H. Maher, B. Chen, J. D. Prohaska, E. G. Nawy, and E. Snitzer

Publication:

Symposium Papers

Volume:

143

Abstract:

A novel fiber optic sensor was tested on reinforced concrete beams with the objective of monitoring strain due to flexural deformations. A fiber optic Bragg grating (FOBG) sensor, developed recently at the United Technologies Research Center (UTRC) for monitoring of strain in structural composites, was used. The FOBG sensor was tested in beam models to measure load-induced strain. Results showed that the FOBG sensor can be accurately and effectively used to monitor strain for both existing and new concrete structures. A number of issues, such as sensor bonding to the structural component, sensor placement, and practical instrumentation techniques, were addressed in this study.

DOI:

10.14359/4579


Document: 

SP143-06

Date: 

May 1, 1994

Author(s):

M. Sugita, H. Yanagida, and N. Muto

Publication:

Symposium Papers

Volume:

143

Abstract:

Carbon fiber glass fiber reinforced plastic (CFGFRP) is used in concrete structures as a reinforcement material. Appropriate materials design indicates that CFGFRP should be a hybrid of a conductive material with a small ultimate elongation value and an insulating material with a large ultimate elongation value. In the present study, the authors evaluated three types of carbon fiber tows used in CFGFRP composites. They observed a very clear and significant change in electrical resistance at the transition point where carbon fiber tows fractured, and found that this point could be easily controlled though the use of carbon fibers with different ultimate elongation values. The electrical resistance characteristics of CFGFRP-reinforced concrete change along with changing loads. Furthermore, a permanent residual electrical resistance could be observed after the removal of load, and its change was dependent on the maximum load applied. The information on the fracture position was obtained by the arrangement of the CFGFRP composites. Monitoring changes in electrical resistance during and after loading is thus a promising method for anticipating the fracture of CFGFRP-reinforced concrete.

DOI:

10.14359/4317


Document: 

SP143-03

Date: 

May 1, 1994

Author(s):

R.L. Nigbor

Publication:

Symposium Papers

Volume:

143

Abstract:

This review paper discusses current and near-future technologies for measurement of full-scale structural performance. Modern instrumentation and measurement methodologies can provide signals and data for use in evaluating the performance of civil structures. Applications exist in model verification, extreme event monitoring, health monitoring, and serviceability monitoring. Examples are provided, and future developments are discussed.

DOI:

10.14359/10046


Document: 

SP143-15

Date: 

May 1, 1994

Author(s):

S. Pessiki and M. R. Johnson

Publication:

Symposium Papers

Volume:

143

Abstract:

Describes tests that were performed to evaluate the feasibility of using the impact-echo method to evaluate the in-place strength of concrete in plate-like elements such as slabs and walls. In the impact-echo method, a stress pulse is introduced into an object by mechanical impact on its surface, and this pulse undergoes multiple reflections (echoes) between opposite faces of the object. The surface displacement of the object, caused by the reflected pulse, is monitored at a location adjacent to the point of impact, and the frequency of successive arrivals is determined. Knowing the thickness of the test object, the compression wave (P-wave) velocity is determined. A previously established concrete strength-P-wave velocity relationship can be used to estimate in-place strength. Results indicate that the impact-echo method can be used to determine P-wave velocity through a large volume of early-age concrete such as the slab specimens tested in this study. Use of the impact-echo method to nondestructively estimate the in-place strength of concrete is more appropriately limited to the estimation of early-age strength.

DOI:

10.14359/4587


Document: 

SP143-05

Date: 

May 1, 1994

Author(s):

R. A. Cook and F. E. Fagundo

Publication:

Symposium Papers

Volume:

143

Abstract:

A new type of short-span bridge system has been developed and implemented over the Albermarle Sound south of Edenton, North Carolina. The new system incorporates precast flat-slab sections that are post-tensioned for continuity. The new system has the potential to replace traditional trestle-type bridges constructed using simple-span prestressed beams with a cast-in-place deck. A continuous two-span, half-scale model of the bridge system was built and tested under various load conditions. The bridge was evaluated analytically and experimentally for the transfer load case (dead load plus prestress), the maximum negative moment service load case, cracking load, and ultimate load. The model bridge performed as expected for all cases. Comparisons between analytical and physical models showed good correlation for all types of tests. At service load levels, the bridge exhibited a linear elastic response with no evidence of cracking. The ultimate load and deflections of the new bridge system were readily predicted by standard behavioral models for prestressed concrete.

DOI:

10.14359/4600


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