Detection of Multiple Cracks in Four-Point Bending Tests Using the Coda Wave Interferometry Method.

Xin Wang,Joyraj Chakraborty,Ernst Niederleithinger,Antoine Bassil

doi:10.3390/s20071986

Abstract

The enlargement of the cracks outside the permitted dimension is one of the main causes for the reduction of service life of Reinforced Concrete (RC) structures. Cracks can develop due to many causes such as dynamic or static load. When tensile stress exceeds the tensile strength of RC, cracks appear. Traditional techniques have limitations in early stage damage detection and localisation, especially on large-scale structures. The ultrasonic Coda Wave Interferometry (CWI) method using diffuse waves is one of the most promising methods to detect subtle changes in heterogeneous materials, such as concrete. In this paper, the assessment of the CWI method applied for multiple cracks opening detection on two specimens based on four-point bending test is presented. Both beams were monitored using a limited number of embedded Ultrasonic (US) transducers as well as other transducers and techniques (e.g., Digital Image Correlation (DIC), LVDT sensors, strain gauges, and Fiber Optics Sensor (FOS)). Results show that strain change and crack formation are successfully and efficiently detected by CWI method even earlier than by the other techniques. The CWI technique using embedded US transducers is undoubtedly a feasible, efficient, and promising method for long-term monitoring on real infrastructure.

Highlights

Infrastructure is the foundation for economic development of the society of a country
Reinforced concrete structures are designed for a service life of more than 50 years
At the end of the test, fourteen cracks appeared at the beam at BAM and eight cracks occurred in the beam at NEOSTRAIN

Summary

Introduction

Infrastructure is the foundation for economic development of the society of a country. RC is the most widely used material in the construction industry due to its durability, rapid construction, and low maintenance cost. The combination gives the advantage of using two materials as a composite material (RC); concrete has a strong compressive strength and steel has a high tensile strength. This allows almost unlimited range of uses of RC in infrastructure [1]. Mechanical and environmental factors or even excessive use accelerate the deterioration of concrete structures. When damage in the structure reaches a certain level, the structure could collapse if necessary maintenance is not carried out in time. Most degradation and failure mechanisms are associated with the enlargement of cracks

Methods

Discussion

Conclusion