Delamination Detection of Reinforced Concrete Decks Using Modal Identification

Shutao Xing,Marvin W Halling,Paul J Barr

doi:10.1155/2012/156583

Abstract

This study addressed delamination detection of concrete slabs by analyzing global dynamic responses of structures. Both numerical and experimental studies are presented. In the numerical examples, delaminations with different sizes and locations were introduced into a concrete slab; the effects of presence, sizes, and locations of delaminations on the modal frequencies and mode shapes of the concrete slab under various support conditions were studied. In the experimental study, four concrete deck specimens with different delamination sizes were constructed, and experimental tests were conducted. Traditional peak-picking, frequency domain decomposition, and stochastic subspace identification methods were applied to the modal identification from dynamic response measurements. The modal parameters identified by these three methods correlated well. The changes in modal frequencies, damping ratios, and mode shapes that were extracted from the dynamic measurements were investigated and correlated to the actual delaminations and can indicate presence and severity of delamination. Finite element (FE) models of reinforced concrete decks with different delamination sizes and locations were established. The modal parameters computed from the FE models were compared to those obtained from the laboratory specimens, and the FE models were validated. The delamination detection approach was proved to be effective for concrete decks on beams.

Highlights

Delamination occurs when the corrosion in the steel rebar induces cracks and the cracks joined together to cause the concrete cover to separate from the substrate concrete
The primary purpose of this paper is to investigate the applicability of delamination detection of concrete plates by modal identification using dynamic responses measured by vibration sensors
While this paper mainly demonstrates analyses on the responses due to random and impact excitations, the modal characteristics obtained from responses due to all three different excitations match very well, for example, the differences between the 1st frequencies obtained from responses due to random and impact excitations are within 2.5%

Summary

Introduction

Delamination occurs when the corrosion in the steel rebar induces cracks and the cracks joined together to cause the concrete cover to separate from the substrate concrete. It results in the loss of structural strength and facilitates a rapid deterioration of the deck [1]. The delamination impairs both the appearance and the serviceability of the structure, and repairs can be very costly. Many methods have been developed to detect concrete delamination. Vibration sensors can be flexibly deployed and located insitu for long-term monitoring applications that include delamination detection

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