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Ultrasonic inspection is a common tool for non-destructive testing in civil engineering (NDT-CE). Currently, transducers are coupled directly to the specimen surface, which makes the inspection time-consuming. Air-coupled ultrasound (ACU) transducers are more time-efficient but need a high pressure amplitude as the impedance mismatch between the air and the concrete is high and large penetration depth is needed for the inspection. Current approaches aim at eliminating the impedance mismatch between the transducer and the air to gain amplitude; however, they hardly fulfill the NDT-CE requirements. In this study, an alternative approach for ultrasound generation is presented: the signal is generated by a fluidic switch that rapidly injects a mass flow into the ambience. The acoustic field, the flow field, and their interaction are investigated. It is shown that the signal has dominant frequencies in the range of 35–60 kHz, and the amplitude is comparable to that of a commercial ACU transducer.

There is a continuing need for reassessments of existing bridges. The validity of reassessment results depends to a large extent on the information used for the calculations. In the meanwhile, the application of non-destructive testing (NDT) methods on concrete is suitable for gathering quantitative information about individual structures that are both relevant and accurate. Such measured information can be explicitly incorporated into probabilistic models used for the bridge reassessment. This way, the level of approximation of the considered model and therewith the validity of the reassessment results can be increased.

Post-tensioning systems provide safe and efficient construction solutions for long span bridges. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Condition assessment of post-tensioning systems is necessary to allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated tendon failures. A detailed experimental study conducted to assess the performance of nondestructive evaluation techniques in detecting grout defects within internal tendons is presented herein. Nondestructive evaluation techniques that include Ground Penetrating Radar, Impact Echo, Ultrasonic Tomography, and Ultrasonic Echo are evaluated in terms of detecting the location and severity of fabricated grout defects in a full-scale post-tensioned U-girder mock-up specimen. While Ground Penetrating Radar can identify the location and profile of the internal tendons, particularly metal ducts due to strong reflections, this method did not provide any information about the defect conditions within the tendon. Both Impact Echo and Ultrasonic Echo techniques are effective in identifying the location of grout defects, but could not differentiate between water, void, or compromised grout conditions. The study clearly demonstrates the need for NDE techniques that are applicable to anchorage regions, and that are capable of estimating the severity and nature of grout defects in internal tendons.

Measuring means knowing. The structural engineer’s Knowledge about structures is vitally important for the assessment of their structural safety. This contribution shows, how non-destructive testing methods can be used to collect valuable Information about existing structures. This value is expressed in this paper by the usability in probabilistic assessments and thus by the reliability of the information. The development of non-destructive testing methods in civil-engineering allows the realistic measurement and visualization of inner constructions of concrete components with a minimum of destructive interventions. The evaluation of the quality of measurement data is of fundamental importance for quantitative measurements in order to ensure the objectivity of testing and evaluation and to assess the reliability of the knowledge acquired. Both systematic and random deviations must be identified, quantified and taken into account to obtain statistically sound data. The Focus of this contribution is on the methodical path, how displayed measurement data can be processed into reliable knowledge. It is not about developing assessment methods but about providing necessary knowledge to increase their operational usability.

This data article presents characteristic acoustic and flow data of a fluidic ultrasonic transducer as well as acoustic data of a commercial piezoelectric ultrasonic transducer used in non-destructive testing for civil engineering. The flow data has been acquired using hot-wire anemometry and a Pitot tube. The three-dimensional acoustic data of both devices has been acquired using a calibrated microphone. The distribution of characteristic acoustic properties of both transducers are extracted and given in addition to the raw data. The data presented in the article will be a valuable source for reference and validation, both for developing fluidic and alternate ultrasound generation technologies. Furthermore, they will give additional insight into the acoustic-flow interaction phenomena of high speed switching devices. This article is accompanying the paper Experimental Analysis of the Acoustic Field of an Ultrasonic Pulse Induced by a Fluidic Switch (Buhling et al., 2021) published in The Journal of the Acoustical Society of America, where the data is interpreted in detail and the rationale for characteristic sound properties of the fluidic transducer are given.

With the mandatory introduction of the May 2011 directive for reassessment of bridges in Germany, the administrations of the federal and state governments have the duty to prove the stability of their bridge stock. Verification of bridge stability will be realized with consideration of the newly increased traffic loads. Particularly in older bridges, the verification can only be achieved if calculative surplus load capacity of the original structural design is taken into account in the recalculation. One option for considering these reserves is the exact determination of the dead weight of the bridge. Within this case study, it will be demonstrated how the problem can be practically solved. In order to determine the dead weight of a concrete bridge, its volume has to be calculated. as a first step, a 3D laser scanner is used to record the internal geometry of a hollow box bridge girder. For the determination of the thickness of the concrete member, the non-destructive technique ultrasonic echo is applied. The construction must be segmented in approximately equidistant parts in order to be able to carry out an economic and efficient investigation. The description of the segmentation of the point cloud, carried out in a 2D model, was presented in the first part of the publication. The subject of this presentation is the merging of 2D cross sections into a 3D model, from which the weight of the bridge can be calculated.

The reassessment of bridges is becoming increasingly important. The basic requirement for analyses of structural safety is reliable knowledge about individual structures. This paper introduces the new approach to evaluate the quality of measured data gained from non-destructive testing (NDT) to provide reliable, objective, and relevant information about existing bridges. The purpose is to relate this validated knowledge to probabilistic analyses. Bridging the gap between NDT and numerical reassessments indicates reduced numerical uncertainties and residual service time extensions. This paper deals with an application of this approach using measurement data collected by ultrasonic technique at a prestressed concrete bridge.

With the mandatory introduction of the directive for recalculation of bridges in May 2011 in Germany, the administrations of the federal and state governments have a duty to demonstrate the stability of their bridge inventory. The requisite verification will be realized under consideration of the new increased traffic loads on the construction, in a four-step process. Particularly in older bridges the verification succeeds only using the computational resources of the original structural design. One option these reserves to be considered is the exact determination of the dead weight of the bridge. Since the existing as-built documents of the construction often digress significantly from the real dimensions, there are two options to resolve the issue. In addition to the technically very complicated and relatively expensive method of weighing the construction, the calculation can also be done indirectly through a combined process of photogrammetric measurement and non-destructive testing. On a practical case study will be demonstrated how the solution of this problem can succeed. For this is done in the first step to scan in detailed the inner topography of a part of the construction by a 3D laser scanner. The results of these tests are compared with the existing stock plans of the building. The aim of this study is to determine the dead weight of structure. Therefore, in the first part of this work sectional plans were extracted of the technical drawing and the point cloud to calculate the area of the interior. Based on the calculated areas in the sectional planes, the volume calculation should take place in the next step.

The non-destructive testing methods available for civil engineering (NDT-CE) enable the measurements of quantitative parameters, which realistically describe the characteristics of existing buildings. In the past, methods for quality evaluation and concepts for validation expanded into NDT-CE to improve the objectivity of measured data. Thereby, a metrological foundation was developed to collect statistically sound and structurally relevant information about the inner construction of structures without destructive interventions. More recently, the demand for recalculations of structural safety was identified. This paper summarizes a basic research study on structural analyses of bridges in combination with NDT. The aim is to use measurement data of nondestructive testing methods as stochastic quantities in static calculations. Therefore, a methodical interface between the guide to the expression of uncertainty in measurement and probabilistic approximation procedures (e.g. FORM) has been proven to be suitable. The motivation is to relate the scientific approach of the structural analysis with real information coming from existing structures and not with those found in the literature. A case study about the probabilistic bending proof of a reinforced concrete bridge with statistically verified data from ultrasonic measurements shows that the measuring results fulfil the requirements concerning precision, trueness, objectivity and reliability.

Non-destructive testing was established over the last decades as an important tool for assessing damages, material characterization and quality assurance in civil engineering. For example, Ground Penetrating Radar (GPR) can be used to scan large areas of concrete structures to determine the spatial position of the reinforcement. With the ultrasonic echo method, the thickness of concrete structures can be easily determined even if a high density of reinforcement is given. Various methods and processes have been developed for the validation of NDT procedures aiming at ensuring the quality of measurements in practical use. The Probability of Detection (POD) for example, is an available method to compare different technical devices with each other quantitatively regarding their performance. With this method, the best suited testing device for a specific inspection task under defined boundary conditions can be selected. By using the Guide to the Expression of Uncertainty in Measurement (GUM), it is possible to quantify the measurement uncertainty of an inspection procedure for a specific task. Another important aspect to improve the acceptance of Non-destructive testing methods is the development of reference specimens. Reference specimens serve for the calibration and further development of NDT methods under realistic conditions in different laboratories under the same conditions. A particular challenge here is the most realistic representation of a damage that can occur at building sites. Possible damages include for example horizontal and vertical cracks or honeycombs in concrete. Such a reference structure was built for the development of a new design of power plant constructions. Comparative studies on the manufacturing of realistic honeycombs and delaminations were carried out in advance on a test specimen. The results of this study are presented here.