Non-destructive testing, digitization, and digital twins in historic buildings: a systematic review

Linear transport infrastructures, as bridges and viaducts, are exposed to natural hazards or endogenous events, which can affect their operation and structural integrity. Recent unpredicted bridge failures and collapses highlight the need for effective structural monitoring operations, especially for aged concrete structures. Non-Destructive Testing (NDT) methods, such as Ground Penetrating Radar (GPR) and Mobile Laser Scanner (MLS), have been used for the assessing and monitoring of such structures in recent years. Our paper reports on the outcomes of the integrated monitoring method based on the use of GPR and MLS technologies for the structural assessment of bridges and the prevention of damages induced by structural subsidence. The analyses we made aim to assess the structural integrity of the Olivieri Viaduct, located in Salerno, Italy. Designed for this, a GPR inspection was made using multifrequency GPR systems equipped with both ground-coupled and air-launched antennas. In addition, MLS surveys were carried out to analyze and quantify pavement surface irregularities. The surface and structural condition of the pavement as measured by MLS has been integrated with GPR outcomes to identify and classify potential damage sources likely responsible for layer deterioration and surface decay. This study confirms that an integrated nondestructive monitoring approach based on GPR and MLS technologies can be successfully implemented to assess the health-condition of critical assets, clearing the way for integrated approaches in continuous monitoring of transport infrastructure.

Monitoring of critical civil engineering infrastructures has become a priority for public owners and administrative authorities. Several laws and regulations have been issued on this topic, emphasizing the crucial role of Building Information Modeling (BIM)- based procedures for the design and management of civil infrastructures. This study aims at examining the potential of an interoperable and upgradeable BIM model supplemented by ground-based non-destructive survey data, such as Mobile Laser Scanner (MLS) and Ground-Penetrating Radar (GPR), for the analysis of the potential distresses identified in a transport infrastructure’s pavement. The main goal of the work is to implement an infrastructure management process that aims to reduce the limits associated with the separate observation of these assessments and to provide a more efficient way to store data regarding the status of a linear transport infrastructure, to the advantage of an integrated analysis. As on-site surveys are carried out, preliminary analyses on the condition of the inspected infrastructure are performed by relying on the information provided by Non-Destructive Testing (NDTs) inspections. Subsequently, a digital informative model capable of storing the data obtained by the surveys is generated, integrating both the MLS and GPR information to accurately represent the status of the infrastructure’s pavement in a three-dimensional environment. Data obtained from these instruments were used as the input for the digitalization process, making use of parametric digital elements capable of adapting their configuration to the information provided by the NDT surveys. As more analysis on the surveys’ results is carried out, potential distresses in the deep layers of the pavement are identified, and the information related to these elements is then integrated into the BIM model previously created. The process hereby described allows for an analysis of the three-dimensional configuration of the pavement, along with potential distresses and their location into the road’s superstructure. This digitalization process has shown promising viability for data management aimed at supporting asset managers in various management phases.

Ports are critical infrastructure assets that play a key role in the functional and spatial activities related to maritime transportation. In today's digital age, the creation of Digital Twins (DTs) of port systems has become increasingly important in order to proactively address maritime issues. While port DTs are primarily used for logistics and operation, DT technologies can also aid in managing the performance of port infrastructure over its lifespan. This study presents a conceptual framework for developing Spatial Digital Twins (SDTs) of port concrete pavements at mooring facilities using Structural Health Monitoring (SHM) data. The framework incorporates Non-Destructive Testing (NDT) techniques including Ground Penetrating Radar (GPR), Falling Weight Deflectometer (FWD), and Unmanned Aerial Vehicle (UAV) camera-based methods. Moreover, Geographic Information Systems (GIS) tools are also employed to facilitate the creation of digital replicas using geospatial information. A contextualization of a UAV-driven application is presented for the concrete pavements of a Greek port, specifically Lavrio port with a focus on digitally representing structural surface defects, particularly cracking, with computer vision-based techniques. By showcasing how Spatial Digital Twins enable real-time representations of port concrete pavements, this study is valuable for understanding maintenance needs and offers practical insights for digital twin applications in port infrastructure management.

The University of Colorado at Denver (UCD) has been involved in cooperative research efforts with the City and County of Denver (CCD) since 1997. The CCD public works department owns, inspects, and maintains 531 bridges in its inventory of which 264 are considered major structures spanning over 6.1 m (20 ft) in length. In this paper, a comprehensive nondestructive analysis of a major structure, the Lawrence Street Bridge, will be presented. The Lawrence Street Bridge is a two-span (each span 23.2 m (76 ft) in length), prestressed concrete girder bridge that spans over Cherry Creek and an adjacent bike path, in downtown Denver. The total bridge width is 19.1 m (62.5) ft. The current structure was built in 1958 and replaced an existing bridge at the site. The original abutments remain, however, and consist of masonry abutment walls founded on concrete footings with timber piles. The pier was comprised of cast-in-place concrete cap and columns. There were five 710-mm (28-in) diameter columns spaced at approximately 5.8 m (19 ft) on center. The pier cap was 27.6 m (90.5 ft) long, 1.07 m (3.5 ft) in height, and varied from 0.76 m (2.5 ft) at the bottom, to 1.07 m (3.5 ft) wide at the top The primary focus of the condition assessment was the existing pier cap and columns. Each span of the two-span superstructure was simply supported with an expansion joint over the pier. Over the years, water had leaked through this expansion joint and directly onto the supporting pier and foundation system. Water penetration and cyclical climatic changes of freezing and thawing had resulted in the deterioration of the supporting substructure system below. The cap suffered from spalling, cracking and exposed steel reinforcement that was corroding. The supporting columns exhibited cracking, from the top downward. In the spring of 2003, a team of UCD researchers began an in-depth nondestructive inspection analysis of the bridge substructure. The objective of the pier analysis was twofold: the first was to provide an assessment of the existing structural condition in order to determine rehabilitative design options. The second was to provide a case study comparing the data from different types of nondestructive and destructive testing. The testing methods performed were as follows: (1) Nondestructive Testing is (a) Visual Inspection, (b) Hammer Sounding, (c) Surface Hardness, (d) Ultrasonic Pulse Velocity, (UPV) (e) Acoustic Tomography, and (f) Ground Penetrating Radar (GPR) Scan; (2) Destructive Testing is (a) Coring and (b) Partial Concrete Removal for Rehabilitation. This particular project was unique in that it provided an opportunity to apply a succession of nondestructive testing methods that ultimately allowed the researchers to identify areas to be further examined using more intensive nondestructive testing as well as destructive testing. Because portions of the concrete cap and columns were removed during rehabilitation, the data from the nondestructive analysis was compared with actual visual inspection of what was found beneath the surface. This paper describes how the nondestructive testing methods were implemented at the bridge site, provides data analysis of the nondestructive test results, and lastly, compares the structural assessments made from nondestructive testing data with observations made during destructive testing and partial concrete removal of the substructure.

Information about the reinforcement in existing concrete structures is of great importance in order to determine the moment capacity. If the rebar drawings are available, then knowledge about the rebar could be derived from the drawings. However, the rebar drawings are often not available for existing old structures or the information on the drawings could be doubted. Further investigation about the applied amount of reinforcement can be done by the use of destructive or non-destructive testing methods. Destructive investigation is often not preferred due to the required amount of labour and due to the influence on the esthetical quality of the concrete. Therefore, non-destructive methods are more preferable. Non-destructive testing (NDT) methods makes it possible to obtain information about the concrete cover depth, the number of existing reinforcement bars and the diameter of the reinforcement bars in an existing concrete structure. The ground penetrating radar and the cover meter are often used in order to obtain information about the reinforcement. Herewith the following question arise: What is the reliability of the information that has be achieved with this NDT techniques? Concrete cover depth measurements with NDT devices have a major accuracy. However, the rebar diameter measurements with NDT devices have a large spread in the measurement results and therefore a less accuracy.

The growing application of Fiber-Reinforced Polymer (FRP) composites in rehabilitating deteriorating concrete infrastructure underscores the need for reliable, cost-effective, and automated nondestructive testing (NDT) methods. This review provides a comprehensive analysis of existing and emerging NDT techniques used to assess externally bonded FRP (EB-FRP) systems, emphasizing their accuracy, limitations, and practicality. Various NDT methods, including Ground-Penetrating Radar (GPR), Phased Array Ultrasonic Testing (PAUT), Infrared Thermography (IRT), Acoustic Emission (AE), and Impact-Echo (IE), are critically evaluated in terms of their effectiveness in detecting debonding, voids, delaminations, and other defects. Recent technological advancements, particularly the integration of artificial intelligence (AI) and machine learning (ML) in NDT applications, have significantly improved defect characterization, automated inspections, and real-time data analysis. This review highlights AI-driven NDT approaches such as automated crack detection, hybrid NDT frameworks, and drone-assisted thermographic inspections, which enhance accuracy and efficiency in large-scale infrastructure assessments. Additionally, economic considerations and cost-performance trade-offs are analyzed, addressing the feasibility of different NDT methods in real-world FRP-strengthened structures. Finally, the review identifies key research gaps, including the need for standardization in FRP-NDT applications, AI-enhanced defect quantification, and hybrid inspection techniques. By consolidating state-of-the-art research and emerging innovations, this paper serves as a valuable resource for engineers, researchers, and practitioners involved in the assessment, monitoring, and maintenance of FRP-strengthened concrete structures.

The work purpose was to conduct a comparative analysis investigating the damage caused to a high-rise building (HRB) under dynamic impacts of two types: periodic industrial explosions at the iron ore quarry of «UGOK» mining and processing plant in Kryvyi Rih and a rocket strike on HRB in Kyiv on February 26, 2022. fib bulletin 59 was used as the basis. The study demonstrates how the life cycle curve of HRB transforms under periodic dynamic impacts and a one-time combat action influence compared to the standard fib bulletin 59 curve. The applied methods included visual and instrumental inspection of buildings using non-destructive testing methods, geodetic and vibration instruments with IoT for refining initial-boundary conditions during the creation of the HRB Construction 4.0 (Digital Twins). Therefore, its experimental verification was conducted. The calculation package LIRA-CAD was used for calculations. It can be noticed while comparing vibration displacement projections at identical points of buildings 6-A and 6-B. Under current conditions, the operational lifespan of 6-A decreases by approximately ΔT ≈ 30 years. To restore the building to a safe technical state, allow residents to return, and extend its operational lifespan beyond the current estimate (≈ 70 years), comprehensive restoration work is required. A methodology for using a Construction 4.0 (Digital Twins) as an element of the straightening control system has been developed. It allows for the adjustment of tilt-eliminating works based on the current monitoring and calculation of the digital spatial model of the multi-story building and the stress-strain state of the "reshaped soil base – tilted strip foundation" system. The successful implementation of the methodology is also demonstrated. A multi-story building in Zaporizhzhia, Ukraine, was straightened without relocating the residents or shutting down essential utilities (elevators, water supply, etc.). Three stages of Digital Twin (Construction 4.0) formation for the specified objects are considered: formation of a Digital Model; formation of Digital Twins, when methods and means of non-destructive testing are involved, and the last stage – Digital Twin, when the results and recommendations of the results of the first two stages are taken into account when reconstructing or restoring the original physical object for the Digital Twin.

Bridge deck condition assessments in Indiana are primarily reliant on visual inspection. The condition of bridge decks, however, is highly dependent on deterioration under the surface, which includes the corrosion of steel reinforcement and concrete delamination. The implementation of reliable nondestructive testing (NDT) methods can provide information about such internal deterioration, but considering the multiple NDT methods currently available, guidance is needed to find the best approach for assessing bridge decks in the state’s bridge inventory. A research program was conducted to examine various NDT methods with the objective of recommending an effective NDT strategy for network-level and project-level bridge inspections in Indiana that will complement information from traditional bridge inspections and provide asset engineers with improved information for long-term programming decisions. For the study, several consultants used various NDT methods to inspect a set of bridge decks that represented a range of desired test variables. Based on the test results, it was determined that aerial infrared thermography (IRT) is a good network-level method that is capable of scanning a large number of bridges and providing an initial assessment of bridge deck conditions. If significant delamination activity is detected, then follow-up network-level scanning limited to the problematic bridge decks should be performed using vehicle-mounted IRT. For project-level scanning of individual bridge decks, impact echo was found to be reliable and repeatable. For bridges with high-traffic volume for which project-level scanning is needed, a pole-mounted IRT system was found to be effective for evaluating the deck condition.

In general, the inspection of the damage on concrete bridge deck is usually done by visual inspection and coring test together with simple survey such as chain drag and hammer sounding. These methods may not be able to verify damage condition correctly. However, at present, there are many nondestructive testing methods which is used to investigate the damage on concrete bridge deck together with simple testing methods. For this study, ground penetrating radar, half-cell potential and impact echo test were selected to evaluate damage condition of concrete bridge deck. The results from simple methods can be detect only damage on the concrete bridge deck or damage that located closed to concrete bridge surface. While nondestructive test i.e. ground penetrating radar can detect deterioration of bridge deck by measuring the amplitude of reinforcing steel in the concrete. Moreover, half-cell potential able to gives location where there is possibility of rust corrosion in reinforcing steel. In addition, impact echo test can evaluate integrity of concrete bridge whole concrete depth as well. In the end, all survey results will be random sampled to confirm data results.

High performance multifunctional structural components and other system components are evolving for applications in the aerospace industry. The efficient operation and reliability of these structures must be ensured by suitable means for inspection and maintenance. However, inspection on complex structural elements via traditional non-destructive testing (NDT) methods presents challenges for the accurate detection and characterization of flaws. The combination of NDT methods offers considerable advantages over existing NDT technologies and ensures not only accuracy in the inspection, but also another perspective on flaws which otherwise would not have been identified. Large sets of data are generated through these inspections and require robust data fusion technologies for visualisation and interpretation. Emerging technologies such as artificial intelligence, internet of things and automation direct towards the new paradigms NDT 4.0 and digital twin. The measurement data for assessing the health and faulty conditions of the structure using integrated sensors and NDT methods can be represented in a digital replication of the structure called the digital twin. Technologies such as drones, augmented reality and remote NDT can help to improve the efficiency of inspections. Therefore, this review represents current technologies and concepts for NDT 4.0 and the digital twin concepts which are suitable to save time, optimize processes and maintenance costs.

Electric characterization of construction materials through radar data inversion

<p>Street trees are widely recognised to be an essential asset for the urban environment, as they bring several environmental, social and economic benefits [1]. However, the conflicting coexistence of tree root systems with the built environment, and especially with road infrastructures, is often cause of extensive damage, such as the uplifting and cracking of sidewalks and curbs, which could seriously compromise the safety of pedestrians, cyclists and drivers.</p><p>In this context, Ground Penetrating Radar (GPR) has long been proven to be an effective non-destructive testing (NDT) method for the evaluation and monitoring of road pavements. The effectiveness of this tool lies not only in its ease of use and cost-effectiveness, but also in the proven reliability of the results provided. Besides, recent studies have explored the capability of GPR in detecting and mapping tree roots [2]. Algorithms for the reconstruction of the tree root systems have been developed, and the spatial variations of root mass density have been also investigated [3].</p><p>The aim of this study is, therefore, to investigate the GPR potential in mapping the architecture of root systems in street trees. In particular, this research aims to improve upon the existing methods for detection of roots, focusing on the identification of the road pavement layers. In this way, different advanced signal processing techniques can be applied at specific sections, in order to remove reflections from the pavement layers without affecting root detection. This allows, therefore, to reduce false alarms when investigating trees with root systems developing underneath road pavements.</p><p>In this regard, data from trees of different species have been acquired and processed, using different antenna systems and survey methodologies, in an effort to investigate the impact of these parameters on the GPR overall performance.</p><p> </p><p><strong>Acknowledgements</strong></p><p>The authors would like to express their sincere thanks and gratitude to the following trusts, charities, organisations and individuals for their generosity in supporting this project: Lord Faringdon Charitable Trust, The Schroder Foundation, Cazenove Charitable Trust, Ernest Cook Trust, Sir Henry Keswick, Ian Bond, P. F. Charitable Trust, Prospect Investment Management Limited, The Adrian Swire Charitable Trust, The John Swire 1989 Charitable Trust, The Sackler Trust, The Tanlaw Foundation, and The Wyfold Charitable Trust. This paper is dedicated to the memory of our colleague and friend Jonathan West, one of the original supporters of this research project.</p><p> </p><p><strong>References</strong></p><p>[1] J. Mullaney, T. Lucke, S. J. Trueman, 2015. “A review of benefits and challenges in growing street trees in paved urban environments,” Landscape and Urban Planning, 134, 157-166.</p><p>[2] A. M. Alani, L. Lantini, 2019. “Recent advances in tree root mapping and assessment using non-destructive testing methods: a focus on ground penetrating radar,” Surveys in Geophysics, 1-42.</p><p>[3] L. Lantini, F. Tosti, Giannakis, I., Egyir, D., A. Benedetto, A. M. Alani, 2019. “A Novel Processing Framework for Tree Root Mapping and Density Estimation using Ground Penetrating Radar,” In 10th International Workshop on Advanced Ground Penetrating Radar, EAGE.</p>

The condition assessment of civil and structural assets in gas stations is essential for ensuring operational safety, environmental protection, and long-term infrastructure sustainability. This study presents an integrated framework that combines non-destructive testing (NDT) techniques with code-conformance audits to provide a comprehensive evaluation of gas station structures, including canopies, pavements, retaining walls, and underground storage systems. Conventional visual inspection methods often fail to detect subsurface deterioration or early-stage material degradation, leading to underestimated risks and reactive maintenance. The incorporation of advanced NDT methods—such as ultrasonic pulse velocity (UPV), ground-penetrating radar (GPR), infrared thermography (IRT), and corrosion potential testing—enhances diagnostic accuracy by identifying internal defects and quantifying their severity. By aligning empirical NDT data with regulatory benchmarks defined in ACI, ASTM, and API standards, this approach bridges the gap between structural health monitoring and code compliance. The study develops a workflow that integrates field data acquisition, defect mapping, risk-based ranking, and lifecycle-based maintenance prioritization. Findings demonstrate that the combined application of NDT and code auditing enables evidence-based decision-making, reduces maintenance costs, and strengthens regulatory accountability. Furthermore, the discussion explores the economic and sustainability benefits of implementing digital asset management tools, including structural health monitoring systems and digital twins, for predictive maintenance and continuous compliance verification. The research concludes that integrating NDT with code-conformance audits represents a sustainable, cost-effective, and data-driven strategy for managing gas station infrastructure. It supports a transition from reactive to proactive asset management, ensuring structural reliability, safety, and environmental stewardship throughout the lifecycle of petroleum facilities.

Before the conservation and restoration of many types of cultural heritage, it is necessary to perform careful examination. This study aimed to determine the original building state and deterioration by applying non-destructive testing (NDT) methods in the case of a heritage building. Another goal was to determine, via NDT methods, whether the limestones observed in this study of different forms, colours, and textures were truly different. The Sivas Industry School Ironworking Atelier, which constitutes the research object, is one of the important public buildings in the city of Sivas, Turkey. Within the scope of the study, non-destructive infrared thermography (IRT), Schmidt hammer rebound (SHR) tests, and X-ray fluorescence (XRF) spectroscopy were applied. Accordingly, through IRT, deteriorations, anomalies, and material differences were investigated, and via SHR testing, uniaxial compressive strength (UCS) estimates, strength levels and hardness classes of stones were obtained. Moreover, via XRF spectroscopy, characterization analysis of stones was conducted. The data obtained could provide information to establish a basis for subsequent conservation. The innovation of this study is that although the infrared thermography technique is typically used in the investigation of materials, it was revealed that another technique such as XRF analysis is needed to better determine whether stones that seem different based on IRT are actually different. With IRT technique, anomaly and material detorioration can be determined. In addition to these two techniques, SHR tests that are non-destructive methods are needed to think about mechanical features of the material. Therefore, when determining the conditions and for characterization analysis of a cultural heritage before restoration, different techniques should be jointly used to complement each other.

The process of pavement maintenance and rehabilitation starts by collecting the data which will form the base for evaluation of pavement functional and structural condition. Collection of data can be performed by destructive and non-destructive testing. Usually preferred are the non-destructive methods, that do not damage the pavement, and the process of pavement evaluation is objective and repeatable. Non-destructive testing methods are becoming more and more popular, especially for assessing the structural condition of the pavement. Non-destructive testing by a Falling Weight Deflectometer (FWD) and the analysis of so collected data by the process of backcalculations is today the usual tool for assessing pavement bearing capacity. One of the basic input parameters for analysis of the data collected by FWD is pavement layers thickness. The practice in Croatia is to determine pavement layers thickness by coring. This destructive method affects pavement integrity, so the number of such tests should be kept to the minimum. By coring the accurate thickness of all pavement layers is obtained on specific point locations. Thus, numerous deviations in layer thickness remain unnoticed, and in the end, use of such data for the process of backcalculations does not provide ac urate values of layer moduli. Coring can be replaced with non-destructive method of testing by Ground Penetrating Radar (GPR), which provides continuous information on thickness of all pavement layers. The paper shows the method for assessing the bearing capacity of the pavement based on the data collected by FWD, GPR and coring. The calculation for layer moduli was performed by the ELMOD software, separately for the layers thickness data obtained by coring, and separately for the thickness obtained by GPR tests. Analysis and comparison of the results of calculated elasticity moduli obtained by using various methods for collecting layer thickness data were performed in the paper.