Interpretation of Impact-Echo Testing Data from a Fire-Damaged Reinforced Concrete Slab Using a Discrete Layered Concrete Damage Model

Abstract

The main objectives of this study are to investigate the spectral responses of a fire-damaged concrete slab using Impact-echo (IE) testing, and to develop a simplified model for interpreting the frequency shift due to heat-induced concrete damage after the fire. For these purposes, a reinforced concrete slab specimen (1000 mm (width) by 5000 mm (length) by 210 mm (thickness)) was fabricated in the laboratory. Heat damage in the concrete slab specimen was induced by exposing the bottom of the specimen to the temperatures corresponding to the standard fire curve described in the ASTM E 119 for 3 h. Impact-echo testing was performed on the bottom surface of the concrete slab specimen before and after inducing the fire damage. It was observed that the spectral responses of the fire-damaged concrete were dominated by several non-propagating waves, which resulted in main peak frequencies around 4500 Hz and 5100 Hz. A discrete layered concrete damage model developed in this study was used to reconstruct the variation of the P-wave velocity with the depth of the fire-damaged concrete. It was demonstrated that the predicted P-wave velocity profile using the simplified model showed a good agreement with the measured values from the five core samples, which measured 100 mm (diameter) by 200 mm (height) cylinders, using ultrasonic pulse velocity (UPV) measurements at eight different depths. In addition, the peak frequencies predicted by the simplified model were consistent with the measured peak frequencies. The experimental results in this study demonstrated that IE testing is effective for evaluating the post-fire damage of reinforced concrete slabs. Particularly, the simplified model in this study can be effective for better interpreting the spectral responses of fire-damaged concrete slabs by IE testing.

Detection and evaluation of heat damage in reinforced concrete beams using linear and nonlinear guided waves

“…Monte et al 21 used ground penetrating radar to study the development of water pore pressure in concrete subjected to heated temperature, which can result in the spalling of concrete. Ground penetrating radar has proven to be useful in detecting cracks or delamination in RC structures as studied by Miramini et al 22 , Lee et al 23 used the impact echo method to study heat-damaged slabs. The change in ultrasonic pulse velocity across the various depth of the slab can also predict the damage state.…”

Study on Impact–Echo Response of Concrete Column near the Edge

“…The interpretation of non-propagating waves is an important process in IE data analysis. The fundamental thickness stretch mode normally dominates the spectral response of a plate if there are no near-surface defects, such as cracking, debonding, and honeycombs, in the concrete [13]. In the process of test and simulation detection, the predominant frequency detected in the middle of the column is the eigenvalue of the fundamental thickness stretch mode of the column.…”

The Experimental Registration of the Evanescent Acoustic Wave in YX LiNbO3 Plate

“…Earlier it has been shown that when Lamb waves are reflected from the edge of the plate, not only propagating waves are excited, but also evanescent waves that exist only near the edge of the plate [ 1 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The existence of evanescent Lamb waves has been experimentally proven at free-edge boundaries [ 31 , 32 ], in phononic crystals [ 7 , 19 ], elastic metamaterial [ 18 ] and the possibility of their using for non-destructive control has been confirmed in [ 33 , 34 , 35 , 36 ]. These waves also could be used for development of a planar acoustic transducer for near field acoustic communication [ 37 ], passive pressure sensors for harsh-environment applications [ 38 ], new air-coupled ultrasonic for non-destructive techniques [ 39 ] and in acoustofluidic chips for microscale manipulation [ 40 ].…”