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International Concrete Abstracts Portal

Showing 1-5 of 17 Abstracts search results

Document: 

SP168-13

Date: 

April 1, 1997

Author(s):

Shigen (Eric) Li, Gregory C. Frantz, and Jack E. Stephens

Publication:

Symposium Papers

Volume:

168

Abstract:

A test method, which uses pull-off test and partial coring techniques, was developed in this study. This test method is particularly suitable for assessing the durability of bonding new to old concrete subjected to freeze-thaw cycling and exposed to deicing salt. This test method also combines bond evaluation and ASTM C-672 test ( Standard Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals ) into one test method. Laboratory experimental research investigated important factors which influence the test results and their scatter. Test results show that this test method is very promising.

DOI:

10.14359/5944


Document: 

SP168-05

Date: 

April 1, 1997

Author(s):

Michael E. Kalinski

Publication:

Symposium Papers

Volume:

168

Abstract:

An unidentified vehicle recently struck the bottom of a railroad overpass and damaged one of the concrete beams in the overpass. The damaged beam was taken intact to the University of Texas where the Spectral-Analysis- of-Surface-Waves (SASW) method was used to nondestructively delineate the damaged zones. SASW measurements performed on the beam revealed a significant velocity contrast between damaged and undamaged zones. These measurements were consistent with visual inspection of the beam and also indicated the presence of cracking that was not visibly detectable. In addition, SASW measurements taken while repairing the beam revealed how surface wave velocity measurements can be used to monitor improvements in the integrity of a beam after each repair step.

DOI:

10.14359/5951


Document: 

SP168-09

Date: 

April 1, 1997

Author(s):

Randall Poston and Mary Sansalone

Publication:

Symposium Papers

Volume:

168

Abstract:

This paper presents both a brief explanation of the impact response of bar-like structures and an application involving the use of the impact-echo method for detecting cracks in the beams and columns of a post-tensioned parking garage structure. The information gained from the impact-echo tests was used to aid in specifying repair measures for the structure. In the process of implementing repair measures, selected impact-echo results were verified. This field study was performed in 1991. This paper was presented at the AC1 Fall Convention in 1992.

DOI:

10.14359/5956


Document: 

SP168-06

Date: 

April 1, 1997

Author(s):

Jiunn-Ming Lin and Mary Sansalone

Publication:

Symposium Papers

Volume:

168

Abstract:

Dilatational or P-wave speed in concrete is needed in impact-echo testing if the dimensions of structural elements or the location of flaws is to be determined. Previously the P-wave speed had to be determined from cores or from performing a test on a portion of the structure having known dimensions and no flaws. In cases where neither approach was possible, an estimate had to be made of the wave speed. This paper presents the details of a method for independently determining P-wave speed in concrete using a Rayleigh-wave speed measurement between two points on the surface. Such a procedure increases the power, versatility, and ease of use of the impact-echo method. In this paper the Rayleigh wave speed procedure is explained. Systematic errors involved in the measurement procedure areexamined, and the accuracies that can be expected using the procedure in conjunction with the impact-echo test procedure are discussed. Appropriate uses of the procedure are given, and the limitations of the method are stated. It is shown that the Rayleigh wave technique is an easy to use technique for estimating wave speeds. Typically, speeds within about 4% of the actual wave speed can be obtained.

DOI:

10.14359/5953


Document: 

SP168-04

Date: 

April 1, 1997

Author(s):

M. Ohtsu, M. Shigeishi, T. Okamoto, and S. Yuyama

Publication:

Symposium Papers

Volume:

168

Abstract:

Acoustic emission (AE) has the potential to be an effective tool in evaluation of concrete structures under the action of loads causing cracking. In conventional testing, several AE parameters are investigated to elucidate microfracturing behavior in concrete. To identify internal cracks, the AE location technique is available, which is based on measuring arrival time differences. By employing multi-channel AE observations, the location of a crack responsible for an AE source can be determined. To obtain quantitative information on crack kinematics, the procedure is further studied and a technique for kinematic characteristics of internal cracks is developed. The AE source is mathematically represented by a moment tensor, by which the classification of cracks into tensile and shear cracks and the determination of crack directions can be made. To implement the procedure into a conventional AE system, software named SiGMA (Amplified Green’s function for moment tensor malysis) has been developed. The analysis is readily available on an AE waveform analyzer system consisting of a digital waveform-recorder and a microcomputer (controller). The procedure is applied to a uniaxial compression test of a plate specimen with a through-thickness slit and to a tensile test of a reinforced concrete rigid frame. The crack locations, the classification of crack types, and the determination of the directions of crack motion are in good agreement with experimental findings. The results show the procedure certainly provides a new technique for kinematic identification of internal cracks.

DOI:

10.14359/5950


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