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Non-destructive testing as a tool in reinforced concrete buildings refurbishments
Abstract
Purpose
This paper aims to report a case study regarding the combined use of several non‐destructive techniques (NDTs) as a tool in the management of diagnosis and refurbishment of a damaged reinforced concrete building.
Design/methodology/approach
Four types of NDTs have been selected and carried out on the pillars of the building: visual inspection, electromagnetic rebar location, sonic test and rebound hammer test. The campaign has been planned and run in order to get the highest amount of reliable data about materials degradation and structural safety with limited costs and limited interference with the functionality of the building.
Findings
The diagnostic campaign highlighted the usefulness of the selected techniques in the diagnosis of the type and the amount of degradation, thus permitting a plan of refurbishments to be defined, and to get a realistic estimation of restoration costs.
Practical implications
NDTs' ability to specifically identify a type of damage may be viewed as a reliable tool in assessing and managing the structural life‐cycle cost.
Originality/value
The presented case study highlighted that NDTs are very likely to locate and quantify the damage of materials and buildings, so that they can be considered as one of the most important parts of health monitoring of civil structures and infrastructures.
... LIM e CAO [13] indicam a combinação múltipla entre diferentes métodos de END para a obtenção de maior nível de confiabilidade dos resultados. Segundo [14,6], a combinação de mais de um método de END tem-se tornado mais popular, pois oferece maior confiabilidade e menores erros quando comparado a resultados obtidos com a utilização de apenas um método. O método SonReb é um desses métodos, segundo os referidos autores e, é baseado na combinação dos resultados dos ensaios de esclerometria e VPU. ...
... Conforme ainda [14,6], o método SonReb é mais preciso do que aquele com a utilização isolada de apenas um END, pois leva em conta dois parâmetros (IE e VPU) que são influenciados de diferentes formas por fatores relacionados à densidade e dureza da superfície do concreto analisado. A metodologia SonReb tem como referência os procedimentos indicados na RILEM NTD 43 [15] que, indica a combinação dos ensaios END propondo-se a construção de curvas de Iso-resistência. ...
... LIM e CAO [13] indicam a combinação múltipla entre diferentes métodos de END para a obtenção de maior nível de confiabilidade dos resultados. Segundo [14,6], a combinação de mais de um método de END tem-se tornado mais popular, pois oferece maior confiabilidade e menores erros quando comparado a resultados obtidos com a utilização de apenas um método. O método SonReb é um desses métodos, segundo os referidos autores e, é baseado na combinação dos resultados dos ensaios de esclerometria e VPU. ...
... Conforme ainda [14,6], o método SonReb é mais preciso do que aquele com a utilização isolada de apenas um END, pois leva em conta dois parâmetros (IE e VPU) que são influenciados de diferentes formas por fatores relacionados à densidade e dureza da superfície do concreto analisado. A metodologia SonReb tem como referência os procedimentos indicados na RILEM NTD 43 [15] que, indica a combinação dos ensaios END propondo-se a construção de curvas de Iso-resistência. ...
RESUMO A resistência à compressão do concreto e seu módulo de elasticidade são propriedades mecânicas de fundamental importância no projeto de novas estruturas. Para o caso ainda de estruturas já existentes que, porventura tenham a necessidade de serem reforçadas, as estimativas das propriedades do concreto existente são necessárias para o cálculo da capacidade de carga do elemento estrutural. A presente pesquisa tem como objetivo apresentar parâmetros para a estimava das propriedades mecânicas do concreto (resistência à Compressão e módulo de Elasticidade) por meio de ensaio não-destrutivos (END) e estabelecimento de curvas de correlação em concretos com resistência nominal classes C20 a C50. Para a elaboração das curvas fez-se uso de três métodos não destrutivos, entre eles, o ensaio de velocidade de propagação de onda ultrassônica (VPU), índice esclerométrico (IE) e o ensaio de resposta acústica (RA). Para estimar as propriedades de resistência (fc) e módulo (Ec) foram desenvolvidas curvas de correlação simples, IE x fc e VPU x fc e múltiplas VPU x IE x fc. A partir da correlação múltipla foram elaboradas curvas de Iso-resistência conforme a metodologia denominada SonReb. Para a estimativa do módulo de Elasticidade estático (Ec), fez-se um estudo de correlação com módulo dinâmico (Ed). Os resultados demonstram que há relação entre os módulos, bem como a influência da resistência à compressão do concreto na determinação do módulo de elasticidade dinâmico. A estimativa das propriedades do concreto por meio de curvas de correlação apresentou resultados satisfatórios, onde, as equações analíticas apresentaram margem de erro menores do que 10%.
... Condition assessment for reinforced concrete (RC) has attracted a considerable amount of attention from the research community, practicing engineers and surveyors, as a result of structural degradation due to aging (e.g. Xia and Hao, 2003;Concu et al., 2011). Traditional approaches to examine dynamic response parameters have been based upon visual or localized experimental procedures such as a rebounded hammer. ...
... With such approaches the location of the damage must be known a priori and the inspection area must be accessible (Xia and Hao, 2003). Moreover, such methods are largely based on the experience of the observer who may not be able to ascertain the level of degradation or safety of the structure (Concu et al., 2011). ...
Purpose
– Condition assessment on reinforced concrete (RC) structures is one of the critical issues as a result of structure degradation due to aging in many developed countries. The purpose of this paper is to examine the sensitivity and reliability of the conventional dynamic response approaches, which are currently applied in the RC structures. The key indicators include: natural frequency and damping ratio. To deal with the non-linear characteristics of RC, the concept of random decrement is applied to analyze time domain data and a non-linear damping curve could be constructed to reflect the condition of RC structure.
Design/methodology/approach
– A full-scale RC structure was tested under ambient vibration and the impact from a rubber hammer. Time history data were collected to analyze dynamics parameters such as natural frequency and damping ratio.
Findings
– The research demonstrated that the measured natural frequency is not a good indicator for integrity assessment. Similarly, it was revealed that the traditional theory of viscous damping performed poorly for the RC with non-linear characteristics. To address this problem, a non-linear curve is constructed using random decrement and it can be used to retrieve the condition of the RC structure in a scientific manner.
Originality/value
– The time domain analysis using random decrement can be used to construct a non-linear damping curve. The results from this study revealed that the damage of structure can be reflected from the changes in the damping curves. The non-linear damping curve is a powerful tool for assessing the health condition of RC structures in terms of sensitivity and reliability.
... Condition assessment for reinforced concrete (RC) has attracted a considerable amount of attention from the research community, practicing engineers and surveyors, as a result of structural degradation due to aging (e.g., Xia and Hao, 2003;Concu et al., 2011). Traditional approaches to examine dynamic response parameters have been based upon visual or localized experimental procedures such as a rebounded ...
... With such approaches the location of the damage must be known a priori and the inspection area must be accessible (Xia and Hao, 2003). Moreover, such methods are largely based on the experience of the observer who may not be able to ascertain the level of degradation or safety of the structure (Concu et al., 2011). ...
Forecasting the supply of labor in the construction industry is pivotal to long-term economic growth. A labor supply model using a stock-flow approach was developed in this research for use in the construction industry. The model was tested using Hong Kong census statistics and data derived from interviews with 3,000 randomly selected construction workers. The findings were determined using a stockflow model, which enabled the determination of future aging distribution trends and workforce supply for specific trade types. The developed stock-flow model can be effectively used in countries in which registration schemes for construction workers are in use.
... For decades, concrete experts have been used interested in using non-destructive methods to determine concrete properties [25]. Non-destructive testing (NDT), which is the process of non-invasively inspecting, testing, and evaluating materials, components, or assemblies, including buildings, proves to be particularly useful [26][27][28][29][30]. In the early 1930s, different techniques were proposed to laboratory specimens based on vibration methods. ...
Taking advantage of studies in microstructure and recognizing the concrete pores lead to more compacting and enhancing its strength and durability. This experimental study has examined compressive strength, ultrasonic wave velocity, the microstructure of the concrete transition zone, and the relationship between them using different types of aggregates, silica, dolomite, limestone, and granite, at the desired ages; moreover, it has addressed the microstructure and pastes at the interval of 20-40 μm from the transition zone using the Ultrasonic and the Scanning Electron Microscope (SEM). The results indicate that the aggregate type has a significant impact on the compressive strength of concrete specimens and the ultrasonic wave velocity of specimen's changes due to the increase of the strength and change of aggregate type. The effect of aggregate on the microstructure and the thickness of the transition zone has been very different. Increasing the thickness of the transition zone decreases the transition velocity of ultrasonic waves in concrete. The transition zone has surrounded the aggregate, and its averaged thickness, after 28 days of being in the saturated medium, was 0.33 - 3.86 μm, which the value in concrete containing different types of aggregates margin, silica, dolomite, limestone, and granite, is 0.33 μm, 1.62 μm, 0.45 μm, 3.86 μm, respectively, and all cracks with less than this diameter at the aggregate margin, will be in the Interface Transition Zone (ITZ).
... For decades, concrete experts have been used interested in using non-destructive methods to determine concrete properties [25]. Non-destructive testing (NDT), which is the process of non-invasively inspecting, testing, and evaluating materials, components, or assemblies, including buildings, proves to be particularly useful [26][27][28][29][30]. In the early 1930s, different techniques were proposed to laboratory specimens based on vibration methods. ...
... Moreover, to monitor the aging so as to properly manage and increase the structure service life. Besides, to permit to define a plan of refurbishments (Concu, G et al., 2011). ...
Purpose
This research aims to study the materials that compose older reinforced concrete bridges which are damaged and degrading to explain the mechanisms and origins of various disorders. Therefore, this work will contribute to providing answers on the capacity of nondestructive evaluation method during the diagnosis. In addition to the characterization of affected structures, it will aim to provide effective solutions for different serious pathologies.
Design/methodology/approach
In this context, two bridges located on NH16 and NH21, respectively, were studied in Annaba city (north-east Algeria), specifically in El-Hadjar municipality located in the central industrial zone of Pont-Bouchet. This study makes it possible to make conclusions from the in-depth diagnosis based on disorders exposition causes and mechanical characteristics evolution by non-destructive testing (NDT) tools. Furthermore, solutions are proposed, including conservation maintenance of these degraded structures.
Findings
All degradations can be the result of several factors: either human (poor design) or chemical (surface water, wastewater and groundwater quality (acidic or basic)). In addition to other natural causes (geological formations, flood phenomena or climate), NDT tools play a major role in the evaluating mechanical performance of degraded structures (resistance and hardness).
Research limitations/implications
The NDT techniques can be transmitted to civil engineering experts because their training is limited regarding mechanical and structural construction.
Practical implications
NDT tools are the most suitable for in-situ assessing, and the concrete constructions health state, so far from financial problems.
Social implications
Degraded bridge diagnosis by NDT testing is necessary for a thorough safety evaluation (mechanical performance, strength and deformability), to protect human lives and design durability.
Originality/value
This is an original paper which contains new information at different scales and from special fields, based on an evaluation using NDT tools on real degraded structures. It can be used to improve the knowledge of materials employed in a bridge without performing expensive direct tests or the need for destroying it.
Keywords
Bridge; Reincforced Concrete; Non-Destructif Testing NDT; Pathology; Agressive environment; Repair.
... The VT is uncertain, semiquantitative, and additional testing using other methods is necessary. The VT method can be utilized only to evaluate the external conditions of the structure [82]. ...
Available at http://dx.doi.org/10.1016/j.measurement.2021.109655 in open access. This paper aims to introduce a new nondestructive method dedicated to rebar concrete debonding detection (which may be caused by corrosion). The Magnetic Force Induced Vibration Evaluation (M5) method is designed to reduce damping (one of the biggest problems of currently known modal analysis methods) and enables evaluating elements inaccessible to traditional methods. The method's concept is to directly induce rebars' vibrations (not a whole structure), measure them, and analyze the frequency spectrum changes. Past studies have already proved that vibrational characteristics are susceptible to a structure debonding. The novelty of the method is related to excitation and detection of vibrations in the tested elements. The M5 method is presented against the background of other nondestructive methods used currently in building diagnostics. The comparison contains the classification and review of these methods. Two versions of the excitation subsystems were proposed and tested. In both cases, the excited vibrations, which are the reaction of reinforcing bars to an alternating magnetic field, are measured using a magnetically coupled accelerometer. With such solutions, the proposed method is fully non-contact and allows for achieving high sensitivity and repeatability. The usefulness of the method was demonstrated by measuring several concrete test specimens with simulated debonding and real samples collected from the dismantled element of the bridge slab.
... The VT is uncertain, semiquantitative, and additional testing using other methods is necessary. The VT method can be utilized only to evaluate the external conditions of the structure [82]. ...
https://api-ewyszukiwarka.pue.uprp.gov.pl/api/collection/2b89833f437d0cfb7f872f62d08ba199
The measuring transducer for non-destructive testing of the condition of reinforcing bars in reinforced concrete structures, containing the source of vibration excitation and vibration recording elements, is characterized by the fact that it has a vibration generating unit and a vibration measurement system. The vibration inducing assembly consists of a rotating disk (1) with at least two cylindrical permanent magnets (2) mounted on its periphery, mounted on the axis (4) by means of a bearing (3), connected to the drive via a drive belt (8). All these elements are attached to the support plate (5) equipped with a base (6). The vibration measurement system consists of an accelerometer (9), a conditioning system, an analog-to-digital converter and a control unit. The drive (7) is a crank or an electric, pneumatic or hydraulic motor. The method of non-destructive examination of the state of rebars in reinforced concrete structures, consisting in the assessment of the frequency characteristics of vibrations induced in the structures, is characterized by the fact that the vibrations are excited using a variable magnetic field resulting from the rotation of permanent magnets.
Przetwornik pomiarowy do nieniszczącego badania stanu prętów zbrojeniowych w konstrukcjach żelbetowych, zawierający źródło wzbudzania drgań i elementy rejestrujące drgania, charakteryzuje się tym,, że ma zespół wzbudzający drgania oraz układ pomiaru drgań. Zespół wzbudzający drgania składa się z obracającej się tarczy (1) z zamocowanymi na jej obwodzie co najmniej dwoma cylindrycznymi magnesami trwałymi (2), osadzonej na osi (4) za pomocą łożyska (3), połączonej poprzez pasek napędowy (8) z napędem. Wszystkie te elementy przymocowane są do płyty wsporczej (5) wyposażonej w podstawę (6). Układ pomiaru drgań składa się z akcelerometru (9), układu kondycjonowania, przetwornika analogowo-cyfrowego i jednostki sterującej. Napęd (7) stanowi korba lub silnik elektryczny lub pneumatyczny lub hydrauliczny. Sposób nieniszczącego badania stanu prętów zbrojeniowych w konstrukcjach żelbetowych, polegający na ocenie charakterystyki częstotliwościowej wzbudzanych w konstrukcjach drgań, charakteryzuje się tym, że drgania wzbudza się wykorzystując zmienne pole magnetyczne powstałe w wyniku ruchu obrotowego magnesów trwałych.
... Ongoing research is focused on the identification of the mechanical property of concrete throughout ultrasonic method and combined method [15][16][17][18][19]. Although the traditional non-destructive methods had a significant enhancement [20] in the last period, a benchmark Finite Element (FE) model for the evaluation of the structural vulnerability is often necessary also improved with several tuning methods [21]. ...
In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destructive and quick test procedure to evaluate the efficiency of short-span bridges. The Fast-FWD is an instrument that can produce a broadband dynamic force up to an impact value of 120 KN: The impact is constant and replicable, providing accurate action measures of bridge stiffness in a truly short period (30 ms). In this paper, a single-span reinforced concrete bridge is investigated, using the Fast-FWD. The considered bridge, approximately 12.0 m long and 15.5 m wide, was in critical condition. The bridge is in a suburban principal road near to the City of Cagliari in Sardinia (Italy), with an Annual Average Daily Traffic of 13,500 vehicles/day, and was suddenly closed, creating serious problems for urban mobility. In these conditions, the investigation through other standard techniques is time-consuming and labor intensive. For this reason, it is important to introduce methods that can be rapid, accurate and cost-efficient. In this paper, bridge stiffness values obtained during the in situ experimental campaign were compared with finite element models values. The Fast-FWD has the potential to provide engineering information that can help us to better understand bridge condition, in a rapid and cost-effective procedure.
... In VI, features such as concrete cracks and spalling are considered to be signs of active corrosion [2]. However, VI methods are judgment-based and semiquantitative, and must be supported by other NDT methods [12]. ...
Steel reinforcement corrosion can result in disastrous bridge failures over time. To manage the human and financial risks associated with such unexpected functional bridge failures, the reinforcements' condition should be quantified using Non-Destructive Testing (NDT) methods. In this case history, the condition of culvert C072's reinforced concrete (RC) bridge structure (located in the north of Markham, Ontario, Canada) is inspected. The inspection, carried out under the supervision of the Corporation of the City of Markham, used a passive magnetic-based NDT technology, the Infrastructure Corrosion Assessment Magnetic Method (iCAMM™). The inspection outcomes demonstrate that the sections close to the south and north ends of the bridge display the most-severe reinforcement anomalies: roughly, a maximum of 20% and 14% of the reinforcement's cross-sectional area loss are detected close to the bridging structure's south and north ends. Additionally, an area in the middle of the bridge is found to have a noticeable anomaly in the reinforcement. The results generated from the magnetic data, collected using an iCAMM™ scanner, are in good agreement with visual-investigation results and the culvert's historical information, such as the concrete's chloride content and compressive strength values, as well as information from a half-cell potential survey. Culvert C072's condition is considered moderately deteriorated and corrective actions are recommended.
... Six readings were taken at each sample, and the average value was recorded. The rebound hammer tests belongs to the catogory of surface hardness surveys [51]. ...
... Six readings were taken at each sample, and the average value was recorded. The rebound hammer tests belongs to the catogory of surface hardness surveys [51]. ...
... Six readings were taken at each sample, and the average value was recorded. The rebound hammer tests belongs to the catogory of surface hardness surveys [51]. ...
Waste foundry sand (WFS) is the by-product of the foundry industry. Utilizing it in the construction industry will protect the environment and its natural resources, and enable sustainable construction. WFS was employed in this research as a fractional substitution of natural sand by 0%, 10%, 20%, 30%, and 40% in concrete. Several tests, including workability, compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS), ultrasonic pulse velocity (USPV), Schmidt rebound hammer number (RHN), and residual compressive strengths (RCS) tests were performed to understand the behavior of concrete before and after exposure to elevated temperatures. Test findings showed that the strength characteristics were increased by including WFS at all the phases. For a substitute rate of 30%, the maximum compressive, splitting tensile, and flexural strength were observed. Replacement with WFS enhanced the 28-day compressive, splitting tensile, and flexural strength by 7.82%, 9.87%, and 10.35%, respectively at a 30% replacement level, and showed continuous improvement until the age of 91 days. The RCS of foundry sand concrete after one month of air cooling at ambient temperature after exposing to 300 • C, 400 • C, 500 • C, 600 • C, 700 • C, and 800 • C was found to be in the range of 67.50% to 71.00%, 57.50% to 61.50%, 49.00% to 51.50%, 38% to 41%, 31% to 35% and 26% to 31.5% of unheated compressive strength values for 0% to 40% replacement of WFS, respectively. The RCS decreases with increasing temperature; however, with increasing WFS, the RCS was enhanced in comparison to the control samples. In addition, the replacement of 30% yielded excellent outcomes. Hence, this study provides a sustainable construction material that will preserve the Earth's natural resources and provide a best use of WFS.
... In this context, the so called non-destructive testing (NDT), which is the process of non-invasively inspecting, testing, and evaluating materials, components or assemblies, including buildings, proves to be particularly useful [8][9][10][11][12]. When applied to buildings diagnosis, the advantages involved by NDT are multiple: ...
The paper illustrates the results of an experimental test which intends to check the efficacy of ultrasonic testing (UT) in detecting anomalies inside concrete elements. For this purpose, UT has been carried out on a small concrete wall having different defects deliberately settled inside the wall during casting. A grid of several measurements points has been arranged on the wall surfaces and for each point the ultrasonic signal has been acquired after passing through the thickness of the wall and the propagation velocity V has been extracted and analyzed. A graphic representation of V distribution has been implemented by a map where each pixel identifies one measurement point and is representative of its neighborhood. This map highlights areas with different velocity values, and allows to visually detect areas having particularly low velocity. The matching between the low-velocity areas and the artificial defects has been analyzed, and the level of accuracy of the V map in detecting and sizing the concrete inner defects has been discussed with reference to different spacing of the grid points. Finally, some considerations regarding the choice of the most suitable measurements grid have been addressed.
... Using both methods together will reduce the errors produced by using one method alone to evaluate concrete. Currently, the most widespread method of the combined use of RH and UPV can improve the reliability and accuracy of prediction results [11,21,23,24]. Since being first de- veloped by RILEM (Technical committees 7 and 43), the combined method has spread and is used in many countries and was standardized in China in 2005(CECS02, 2005) [25]. ...
... VI evaluates the external surface of the structure without directly assessing the internal conditions [14]. Even with detailed rubrics and photo imagery, VI methods are weak and semi-quantitative at best, and they must be done in conjunction with other non-destructive methods [15]. Reinforced concrete can be inspected for different types of defects using various types of non-destructive testing (NDT) methods [16]; the most common methods are potential measurement survey [17], galvanic current measurement [18], ground penetrating radar (GPR) [19], rebound hammer [20], ultrasonic [21], and radiography [22]. ...
Reinforced concrete is the most commonly used material in urban, road, and industrial structures. Quantifying the condition of the reinforcing steel can help manage the human and financial risks that arise from unexpected reinforced concrete structure functional failure. Also, a quantitative time history of reinforcing steel condition can be used to make decisions on rehabilitation, decommissioning, or replacement. The self-magnetic behavior of ferromagnetic materials is useful for quantitative condition assessment. In this study, a ferromagnetic rebar with artificial defects was scanned by a three-dimensional (3D) laser scanner. The obtained point cloud was imported as a real geometry to a finite element software platform; its self-magnetic behavior was then simulated under the influence of Earth’s magnetic field. The various passive magnetic parameters that can be measured were reviewed for different conditions. Statistical studies showed that 0.76% of the simulation-obtained data of the rebar surface was related to the defect locations. Additionally, acceptable coincidences were confirmed between the magnetic properties from numerical simulation and from experimental outputs, most noticeably at hole locations.
... Sonic and ultrasonic tests on RC structures can be very useful due to the well-known correlation between the sonic pulse through concrete and its density. These techniques can produce a detailed set of data related to the mechanical characteristics of materials, see for example [21][22][23][24] and [40][41]. In particular, the velocity of ultrasonic transit pulses in undamaged concrete can reach and exceed 5000 m/s, see [22]. ...
In order to assess decay in the mechanical characteristics offire-exposed Reinforced Concrete (RC), it is crucial to reconstructthe temperature time history and the evolution of strainand stress fields. In this paper, the state of the art of assessmentmethods is presented and applied to a real structure damagedby fire. It is a prestressed RC industrial warehouse located inthe outskirts of the city of Cagliari (Italy). The collected data ofseveral assessment methods are presented in order to producethe flowchart of an integrated approach for post-fire investigation.Among the various techniques, the authors highlight athorough laser scanner geometric survey and destructive andnon-destructive testing. In addition, the temperature distributionand its time history has been reconstructed by means ofoptical and Scanning Electron Microscopy, X-ray diffractometry,Thermogravimetric Differential Thermo-Analysis andcalibrated Colorimetry.Actually, refurbishment is needed, but the structure withstoodthe fire very well. Central columns displayed the most importantdamage, and several beams presented important deflectionshaving lost the prestressing actions of the tendons.
... In any case, if CV is higher than 0.15, the BS must perform additional, more accurate verifications. More in detail, it is necessary to execute in situ both destructive tests (such as core drilling (Concu et al., 2011) and non-destructive tests (rebound-hammer or ultrasonic pulse velocity). A specific attention must be devoted to control about the scattering of data, since it is very frequent, in these cases, that the values of concrete strength vary in a very wide range . ...
Purpose
– The purpose of this paper is to collect the numerical elaboration of resistances measured on cubes made during the concrete casting and on cores extracted after the completion of the structure, for the concrete used in the construction of the “Esaro” Dam facilities (Cosenza, Italy). In addition to the statistical treatment of the sample, aimed at assessing the analytical congruence with the homogeneous classes provided in the design, the influence of compaction degree on in place strength value was qualitatively evaluated.
Design/methodology/approach
– The reliability of the concrete during the construction phases was evaluated by two analytical control types according to Italian and European technical rules: “production controls” based on statistical processing of resistance values; “laying controls” that serve to assess the compaction degree with a statistical approach.
Findings
– Results highlighted in the assessing of compliance checks of the mixture, the fundamental relation between statistical approach and concrete laying control. They become important when is necessary to quantify, especially in the case of great infrastructure, the gap between “potential” and “structural” concrete.
Originality/value
– The advantage obtained by controlling the compaction degree in the construction phase is unquestionable. Specifically, it might allow a reduction of the drilling cores, and so minor structural damage, especially for relatively recent structures favouring extensive non-destructive tests.
In order to become the scientific conference report this article presents in details the experiment results and numerical values received in it. These results can be useful to engineers in the field of employ fiber-reinforced concrete. The research was devoted to the features of determination the compressive strength of fiber-reinforced concrete in existing structures. The methods described in standards and technical documentation, dedicated to the design, manufacture and application of fiber-reinforced concrete structures, were analyzed in case of regarding to the quality control of erected constructions. The results of fiber-reinforced concrete strength studies, carried out within the inspection work on the ground floor slab belonging to a mall under construction, are presented. The application of destructive testing of concrete cylinder samples and two ways of non-destructive testing (NDT) is considered: the anchor pull-out test and the ultrasonic pulse velocity (UPV) test. There is a comparison and analysis of the results obtained using the destructive and non-destructive methods.
Reinforced concrete (RC) is common throughout modern industrial and civil infrastructure. Adding steel reinforcing bars (“rebar”) to concrete improves tensile strength, but if exposed to adverse environmental conditions, rebar may corrode and lead to a progressively deteriorating concrete condition. Several techniques exist for assessing rebar corrosion conditions. Inspection of RC structures based on the self-magnetic concept is a Non-Destructive Testing (NDT) method that helps to quantify the steel reinforcement condition. Corrosion quantification helps to manage the human and financial risks associated with RC structural failure, premature replacement, or inadequate repair. In this study, an intact rebar and one with general corrosion are scanned with a 3D laser scanner. The captured point clouds are imported as real geometries to finite-element software, where their self-magnetic behaviors are simulated under the effect of Earth's magnetic field. Significant differences are found between the self-magnetic behavior of the corroded and intact rebars. For instance, the Y component magnetic flux density values of the intact rebar have a sinuous trend with a period of about 10 mm, equal to the distance between the rebar corrugation peaks, but no harmonic trend can be detected in the rebar with general corrosion. Self-magnetic data of the corroded and intact rebars are recorded and assessed through experiments, and the test results correlate well with the simulation outcomes.
Ultra-High Performance Fibre Reinforced Concrete is a material which is becoming increasingly popular in structural applications, mainly due to its superior mechanical characteristics. The mechanical properties of this material are of high importance and the development of non-destructive techniques is vital for the evaluation of the mechanical characteristics of existing structures. In the current study, Ultra-High Performance Fibre Reinforced Concrete with different amounts of steel fibres has been examined. Compressive and tensile tests have been conducted alongside with Ultrasonic Pulse Velocity and Rebound Hammer measurements and the development of appropriate empirical non-destructive models has been examined.
The problem of estimating mechanical properties of buildings materials is a major issue in civil engineering, especially when dealing with existing structures. In such occasion a valuable help is given by Non Destructive Testings, which allow materials characteristics to be evaluated in a non-invasive way. This paper analyses the efficacy of the SonReb method - a non destructive technique which statistically combines the results of Ultrasonic and Rebound Hammer Testing in predicting concrete compressive strength. The SonReb method has been applied on concrete specimens later on exposed to compressive strength test. The effectiveness of several empirical formulas expressing SonReb results is illustrated and discussed.
In the present paper, a critical approach to the evaluation of Schmidt hammer testing is attempted. Through a statistical
analysis of field measurements on sandstone blocks from the archaeological site of Delphi (Greece), it was shown that there
is an inconsistency in the correction method proposed by the manufacturer, in relation to the direction of rebound.
The horizontally obtained rebound values, when corrected, yielded lower values than the vertically obtained ones. When examining
the various factors potentially responsible for possible differences between the vertical and horizontal values, we conclude
that the proposed correction method is not applicable to all cases and that there are many factors that may influence the
end results.
Dans cet article nous avons tenté une approche critique concernant l'évaluation de l'essai «Schmidt Hammer Rebound».
On a effectué des mesures de terrain sur les blocs de grès qui appartiennent au site archéologique de Delphes. A partir d'une
analyse statistique de ces mesures on a montré qu'il y a une divergence apparente entre la méthode de correction proposée
par le fabricant et la direction du rebond.
Après avoir corrigé les valeurs du rebond à l'horizontale on a remarqué qu'elles sont plus basses que celles prises à la verticale.
En évaluant les divers facteurs responsables des différences possibles entre les valeurs à la verticale et à l'horizontale
on a constaté que la méthode proposée pour la correction n'est pas applicable dans tous les cas et qu'il y a plusieurs facteurs
qui peuvent influencer les résultats obtenus.
Nondestructive testing of solid material using ultrasonic waves, for defects such as cavities, nonbonding, and strength variations, is treated in this book from the physical fundamentals of ultrasonics and materials up to the most sophisticated methods. The book is written at a level which should make it accessible to readers with some knowledge of technical mathematics. Physical laws are explained in elementary terms, and more sophisticated treatments are also indicated. After the fundamentals, instrumentation and its application is extensively reported. Tricks and observations from thirty years of experience in the field are included. The third part of the book presents test problems related to special materials or ranges of modern heavy industry, including recent applications such as those in nuclear power plants. This fourth edition features improved presentation of certain fundamental physical facts, updated reports on electronic instrumentation, and new applications in the nuclear and space industries.
The provision of sufficient cover thickness is a fundamental aspect of preventing corrosion of steel reinforcement. Arguments range over concrete quality specification, formula for calculating design life and the definition of design life itself but if cover is not achieved with reasonable consistency, structures will fail prematurely, possibly spectacularly.
Cost-competent maintenance and management of civil infrastructure requires balanced consideration of both the structure performance and the total cost accrued over the entire life-cycle. Most existing maintenance and management systems are developed on the basis of life-cycle cost minimization only. The single maintenance and management solution thus obtained, however, does not necessarily result in satisfactory long-term structure performance. Another concern is that the structure performance is usually described by the visual inspection-based structure condition states. The actual structure safety level, however, has not been explicitly or adequately considered in determining maintenance management decisions. This paper reviews the recent development of life-cycle maintenance and management planning for deteriorating civil infrastructure with emphasis on bridges using optimization techniques and considering simultaneously multiple and often competing criteria in terms of condition, safety and life-cycle cost. This multiple-objective approach leads to a large pool of alternative maintenance and management solutions that helps active decision-making by choosing a compromise solution of preferably balancing structure performance and life-cycle cost.
As early as 1971 Rosenblueth and Mendoza (Rosenblueth E, Mendoza E. Reliability optimization in isostatic structures. J Eng Mech Div, ASCE 1971;97(EM6):1625–42) published a paper on structural optimization the concepts of which have been refined later by Hasofer in 1974 (Hasofer AM. Design for infrequent overloads. Earthquake Eng and Struct Dynamics 1974;2(4):387–8) and Rosenblueth in 1976 (Rosenblueth E. Optimum design for infrequent disturbances. J Struct Div, ASCE 1976;102(ST9):1807–25) particularly in the context of earthquake resistant design. In essence, these authors proposed to distinguish between structures that can fail upon completion or never and structures which can fail under rare ‘disturbances’. Furthermore they distinguished between ‘single mission structures’ and structures which are systematically rebuilt after failure. The consequences of their findings for code making, especially for setting safety targets apparently have been overlooked since then. In fact, it is rather a yearly failure rate that has to be specified and verified and not a failure probability for an arbitrary reference time. The paper thoroughly reviews Rosenblueth's and Hasofer's developments and extends the concepts to failures including ultimate limit state failure under normal and extreme conditions, serviceability failure, fatigue and other deterioration and, finally, obsolescence. Some newly needed computational tools are addressed. Partial safety factors are derived for stationary failure processes and a new verification format for fatigue and other deterioration is proposed. Tools for optimization of structural components are presented.
Measures that improve durability of a structure usually increase its initial cost. Thus, in order to make a decision about a cost-effective solution the life-cycle cost of a structure including cost of structural failure needs to be considered. Due to uncertainties associated with structural properties, loads and environmental conditions the cost of structural failure is a random variable. The paper derives probability distributions of the cost of failure of a single structure and a group of identical structures when single or multiple failures are possible during the service life of a structure. The probability distributions are based on cumulative probabilities of failure of a single structure over its service life. It is assumed that failures occur at discrete points in time, the cost of failure set at the time of decision making remains constant for a particular design solution and the discount rate is a deterministic parameter not changing with time. The probability distributions can be employed to evaluate the expected life-cycle cost or the expected utility, which is then used in decision making. An example, which considers the selection of durability specifications for a reinforced concrete structure built on the coast, illustrates the use of the derived probability distributions.
The paper describes non-destructive evaluation (NDE) techniques that have been applied to existing concrete and masonry structures. NDE techniques for detection of induced damage and characterization of retrofit and strengthening schemes are included. The theoretical basis and experimental requirements of each technique are first described. Then case studies of application of the described techniques to specific cases on concrete and masonry structures are described. Conclusions about the suitability of each technique are drawn. Copyright © 2003 John Wiley & Sons, Ltd.
The deterioration of concrete structures is a major problem in many countries throughout the world. This has prompted the search for methods of predicting the service life of both existing and new structures. Current prediction methods are still in their infancy and, before they can be used with confidence, more reliable information on the properties of the concrete in these structures will be required. In this paper a range of test methods for determining the strength and transport properties and the extent of corrosion are critically reviewed. Whilst all provide useful information the ability to measure the transport properties has been shown by many researchers to give the most reliable indication of the likely durability. In spite of this it is recommended that an holistic overview is adopted as no single test is sufficiently reliable at present. Using such an approach, durability-based design criteria can be developed for concrete and the remaining life of existing structures estimated.
The paper develops objective functions for optimizing design and maintenance strategies of aging structural components. It introduces a repair model with or without preceding inspections. Objective functions are derived for maintenance by inspection and repairs (renewals). Earlier formulations for independent repair and failure events are extended to dependent no-repair/repair and failure events. This can make formulations more realistic because no-repair/repair and failure events depend on the same deterioration processes, at the expense of numerically more elaborate computations. In addition, finite renewal (repair) times independent of failure times are considered.
The rehabilitation and maintenance market and the degrade of concrete infrastructures
CRESME Technical Report (2007), "The rehabilitation and maintenance market and the degrade
of concrete infrastructures", CRESME Technical Report, CRESME.
Testing Concrete -Part 4: Determination of Ultrasonic Pulse Velocity
EN 12504-4 (2004), Testing Concrete -Part 4: Determination of Ultrasonic Pulse Velocity.
fib (2002) "Management, maintenance and strengthening of concrete structures", Bulletin 17, fib,
Lausanne.
Guide of evaluation of concrete structures prior to rehabilitation
ACI 36. 1R-94 (1994), "Guide of evaluation of concrete structures prior to rehabilitation", ACI
Committee 364, American Concrete Institute, Detroit, MI.
Research on factors affecting concrete cover measurement
- R Barnes
- T Zheng
Barnes, R. and Zheng, T. (2008), "Research on factors affecting concrete cover measurement",
e-Journal of NDT, Vol. 13 No. 12, available at: www.ndt.net/article/v13n12/zheng.pdf
(accessed 29 November 2010).
Non-destructive material testing with ultrasonics. Introduction to the basic principles
- M Berke
Berke, M. (2000), "Non-destructive material testing with ultrasonics. Introduction to the basic
principles", e-Journal of NDT, Vol. 5 No. 2, available at: www.ndt.net/article/v05n09/berke/
berke.pdf (accessed 29 November 2010).