Title: Effects on Impact-Echo Signals Caused by Steel Reinforcing Bars and Voids Around Bars

Author(s): Chia-Chi Cheng and Mary Sansalone

Publication: Materials Journal

Volume: 90

Issue: 5

Appears on pages(s): 421-434

Keywords: concretes; cracking (fracturing); finite element method; impact tests; nondestructive tests; reinforcing steels; stresses; voids; Materials Research

DOI: 10.14359/3870

Date: 9/1/1993

Abstract:
In previous research on the development and use of the impact-echo method, the effects caused by steel reinforcing bars on impact-echo signals obtained from reinforced concrete structures have been observed, but not explained fully. The main purposes of this paper are to explain the interaction of transient stress waves with steel bars in concrete and to show the effects that bars have on impact-echo signals. Numerical (finite element) and experimental results are shown to demonstrate the effects that different variables (bar diameter, bar depth, impact duration, and impact-echo test configuration) have on impact-echo results. Equations for the relationships between bar diameter, bar depth, and the measured impact-echo response are presented. It is shown that these relationships can be used to identify the effects caused by bars on impact-echo signals obtained from reinforced concrete structures. Finally, the changes in the impact-echo response caused by the presence of a void around the top or bottom of a bar are also explained.