Assessment of the Deterioration State of Post-Installed Bonded Anchors Using Ultrasonic

Abstract

The assessment of already installed anchorages for a possible exceeding of the service load level is a question that is gaining more and more importance, especially in building maintenance. Bonded anchors are of particular interest here, as the detection of a capacity reduction or load exceedance can cause damage to the concrete-bonded mortar behavior. This article investigates the extent to which ultrasonic methods can be used to make a prediction about the condition of anchorages in concrete and about their load history. A promising innovative assessment method has been developed. The challenges in carrying out the experimental investigations are the arrangement of the transducers, the design of the test set-up and the applicability of direct, indirect or semidirect ultrasonic transmission. The experimental investigations carried out on a test concrete mix and a bonded anchor system show that damage to the concrete structure can be detected by means of ultrasound. The results indicate the formation of cracks and therefore a weakening of the response determined by means of direct, indirect and semidirect ultrasonic transmission. However, for application under non-laboratory conditions and on anchors with unknown load history, the calibration with a reference anchor and the identification of the maximum load is required. This enables a referencing of the other loaded anchors to the unloaded conditions and allows an estimation of the load history of individual anchors.

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

“…Elastic-wave-based techniques have become an essential part of the non-destructive testing (NDT) portfolio in civil engineering. Today, methods such as the impact echo [33,34], US transmission and reflection [7,8] are well-established for material testing [35][36][37]. Measurements with US waves-waves featuring frequencies ≥ 20 kHz-are able to analyze the thickness of components and detect major faults.…”

“…Acoustic Ultrasonic (US) measurement methods are characterized by the fact that a wide volume can be investigated already with a single transmitter-receiver pair. Traditional transmission and reflection methods mainly analyze the direct wave between the transmitter and receiver by means of the time of flight [7,8]. Thus, they provide information on changes or larger defects on the direct path only.…”

Ultimate Shear Force of an Any Anchor Group Post-Installed into Concrete

“…There has been much valuable work conducted in the field of adhesive and mechanical anchors intended for use in concrete, and concrete anchors have been the subject matter of many valuable papers. However, a detailed insight into those documents reveals that most of the papers are devoted to the anchor’s extraction strength, i.e., pull-out resistance [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ], and to cast-in anchors, i.e., anchors installed in new structures, before pouring the concrete [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. As a result, only a minor part of those papers deals with the anchors’ shear strength and with post-installed anchors.…”