This article presents a review of recent developments in parametric based acoustic emission (AE) techniques applied to concrete structures. It recapitulates the significant milestones achieved by previous researchers including various methods and models developed in AE testing of concrete structures. The aim is to provide an overview of the specific features of parametric based AE techniques of concrete structures carried out over the years. Emphasis is given to traditional parameter-based AE techniques applied to concrete structures. A significant amount of research on AE techniques applied to concrete structures has already been published and considerable attention has been given to those publications. Some recent studies such as AE energy analysis and b-value analysis used to assess damage of concrete bridge beams have also been discussed. The formation of fracture process zone and the AE energy released during the fracture process in concrete beam specimens have been summarised. A large body of experi...

A review of recent developments in parametric based acoustic emission techniques applied to concrete structures

The hybrid experimental-numerical stress-analysis technique, which saw limited applications during the 1950's, has been resurrected with the vastly improved numerical techniques of the 1970's. By inputing the experimental results as initial and boundary conditions, modern computer codes are executed in its generation and application modes to yield results which are unobtainable when only one of the two techniques is used. The hybrid technique thus exemplifies the complementary role of the experimental and numerical techniques.

Hybrid experimental-numerical stress analysis

Dynamic fracture toughness versus crack velocity relations of Homalite-100, polycarbonate, hardened 4340 steel and reaction bonded silicon nitride are reviewed and discrepancies with published data and their probable causes are discussed. Data scatter in published data are attributed in part to the observed fluctuations in crack velocities. The results reaffirmed our previous conclusion that the dynamic fracture toughness versus crack velocity relation is specimen dependent and that the dynamic arrest stress intensity factor is not a unique material property.

Dynamic fracture toughness

Acoustic Emission Methods

A study of the combined use of laser-speckle and finite-element methods for stress analysis is described. The speckle technique provides displacement data which can be directly input to a finite-element computer program for the determination of stresses. The displacement data can be used as boundary conditions for the examination of a subregion of the structural component to be analyzed. A substantial reduction in computational effort can be realized over conventional finite-element analysis of the entire structure. Also, a sizeable reduction in the required amount of experimental data may occur since direct numerical differentiation of the data is not required for strain evaluation. Acceptable accuracy may be obtained even when experimental displacement data may be too scarce for traditional numerical differentiation. Random error in experimental displacement is illustrated to have localized effects on the calculated stress field.

Integration of laser-speckle and finite-element techniques of stress analysis

Acoustic emissions (AE) detected by two transducers mounted on a reinforcing bar in a reinforced-concrete block, which is subjected to cyclic tension-compression loading, are used to assess the locations of re-bar debonding. Preliminary uniaxial-tension tests of the re-bar were conducted to establish the proper level of AE sensitivity which was then verified by uniaxial-tension tests of re-bar embedded in a concrete block. The main tests consist of simulated beamcolumn connection with a 90-deg hooked No. 8 Grade 60 rebar subjected to various cyclic-loading histories. Reasonably good correlations were established between the debonding regions indicated by the AE signals and those detached by dye injected into the cracked concrete.

Y-L A. Chan

Papers

A feasibility study of detecting reinforcing-bar debonding by acoustic-emission technique