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Sadri, Afshin. "An investigation of the impact-echo technique /." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56780.
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Nondestructive testing of concrete for maintenance purposes is the focus of this thesis. The application of a new nondestructive testing technique known as impact-echo was examined. The technique is based on transient stress wave propagation for the detection of defects in concrete, as well as measuring the setting time, early age strength, and elastic properties. Impact-echo functions by a mechanical impact, where stress pulses are generated in the test subject. The stress pulses undergo multiple reflections between the top and bottom of concrete layers. The surface displacements are recorded and the frequency of the successive arrivals of the reflected pulses is determined. Thus, knowing the thickness of a given layer, together with the measured frequencies, P- and S-wave velocities can be calculated. If on the other hand, the thickness is unknown, the time-distance graph of the primary surface wave arrivals could be used to calculate the thickness. The position of the impact source relative to the receiver must be selected in such a way as to detect P- and S-waves at their maximum reflection amplitude. In this study, defects were detected using the reflected P-waves from their top surfaces. In addition, the change in elastic moduli of various types of concrete mixes was monitored for a 30-day period by measuring P- and S-wave velocities. The impact-echo elastic moduli were then compared with static and dynamic values obtained by standard methods in order to assess their accuracy.
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Algernon, Daniel. "Impact-Echo: Analyse akustischer Wellen in Beton." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980249031.
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Begum, Rushna. "Neural network processing of impact echo NDT data." Thesis, City University London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340456.
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Rezgui, Chaabouni Hajer. "Diagnostic d'ouvrages en maçonnés : Méthodes Soniques Impact-Echo." Thesis, Limoges, 2020. http://www.theses.fr/2020LIMO0060.
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Le patrimoine d’ouvrage d’art Européen et en particulier français est vieillissant. Pour pouvoir le conserver, il est nécessaire d’établir un ‘état de santé’ de ces ouvrages en les auscultant. Afin de ne pas les dégrader lors de l’auscultation des méthodes de contrôle non destructifs (CND) doivent être utilisées. Nous nous sommes intéressés en particulier, à une méthode connue sous le nom d’Impact-Echo. La pathologie qui a retenu notre attention concerne les vides ou les défauts pouvant être situés dans le remplissage des ponts en maçonnerie, au-delà des voûtes ou des murs de têtes. Afin de tirer le meilleur profit de la méthode d’auscultation, une étude numérique permettant de simuler un Essai Impact-Echo sur une structure sous forme de plaque bicouche contenant un défaut est développée. Devant la difficulté d’interprétation des résultats issus de cette simulation, un plan d’expériences factoriel numériques est introduit. Pour ce plan d’expériences quatre facteurs sont retenus. Deux facteurs liés la géométrie de la structure e1 et d, un facteur lié aux matériaux composant la structures R et un facteur purement numérique . D’autres variables de sortie, autre que la lecture de la position du pic, sont introduites. A l’issue de ce plan d’expériences, nous avons pu dégager des relations, qui ont permis de lier les facteurs d’entrée aux différentes variables de sortie. Ces relations ont été testées, dans un premier temps, sur les données ayant servi à les établir. Une compagne expérimentale a été introduite afin de valider la simulation numérique. Pour cette validation, nous avons tenté d’exploiter les essais de la compagne expérimentale à l’aide des différentes relations obtenues du plan d’expériences numériquesThe heritage of European and particularly French infrastructure is aging. To be able to preserve it, it is necessary to establish a "state of health" of these works by auscultation. In order not to degrade them during the auscultation, non-destructive testing (NDT) methods must be used. We were particularly interested in a method known as the Impact-Echo method. The pathology that caught our attention concerns voids or defects that may be located in the filling of masonry bridges, beyond the vaults or the head walls. In order to make the most of the auscultation method, a numerical study to simulate an Impact-Echo test on a bilayer structure containing a defect is developed. Faced with the difficulty of interpreting the results from this simulation, a numerical factorial design of experiments is introduced. For this experimental design four factors are retained. Two factors linked to the geometry of the structure e1 and d, a factor linked to the materials composing the structures R and a purely numerical factor . Other output variables, other than reading the peak position, are introduced. At the end of this experimental design, we were able to identify relations, which made it possible to link the input factors to the different output variables. These relations were first tested on the data used to establish them. An experimental campaign was introduced in order to validate the numerical simulation. For this validation, we tried to exploit the trials of the experimental companion using the different relations obtained from the numerical factorial design of the experiment
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Aktas, Can Baran. "Determining The Thickness Of Concrete Pavements Using The Impact-echo Test Method." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608423/index.pdf.
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Traditionally, destructive methods such as coring are used for the condition assessment of an existing concrete structure. Although these methods may yield valid data about the corresponding concrete section, they are quite expensive and time consuming. More important than these, destructive methods damage the structure being investigated and these points usually become focal points for further deterioration. For all these reasons, only a few samples can be collected from a structure and this results in a poor representation of the complete structure.
The impact-echo technique is one of the most suitable non-destructive test methods that may be used on concrete for thickness determination or for investigation of possible delaminations in the internal parts of a concrete structure without damaging the surface. It has been observed that reliable results can be obtained quickly. Unlike pulse-echo tests which are commonly used on steel, testing a heterogeneous material like concrete requires the use of low frequency sound waves as in impact-echo, in order to mitigate the effects of paste-aggregate interfaces or small air voids.
This method may be used to locate internal cracks or large air voids existing in concrete. It is known that impact-echo has been used successfully on structures with varying geometries and various purposes such as evaluation of concrete pavements, retaining walls and other reinforced concrete sections. Besides the investigation of the internal state, it may also be used when the other side of the section cannot be reached, as in the case of concrete pavements, in order to find the thickness of the section. This is especially important for quality control and for cost calculations.
Research conducted in this thesis study was concentrated on the thickness determination of existing concrete pavement sections, produced in the laboratory with dimensions of 1500 x 2000 mm four and varying thicknesses, and the accuracy associated with these results. In order to correctly determine the sensitivity, several other parameters were investigated and optimum ranges were determined for these to be used while on a field test. Among these factors were the steel impactor size, accuracy related to the data acquisition, distance between the impact point and the transducer and the location of the test point.
Finally, the accuracy of the impact-echo method for concrete pavement applications was studied. By observing the large number of data points collected, it was found out that an average error of 1.5% exists for a single impact-echo reading regardless of section thickness, but this value reduces to 0.6% when the average of all test results is used while determining pavement thickness. Results of this study show that the impact-echo technique is reliable and may be used with success for the thickness determination of concrete pavements and for locating internal voids.
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Lacroix, Francis. "Non-Destructive Condition Assessment of Concrete Slabs with Artificial Defects Using Wireless Impact Echo." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41575.
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This thesis presents the development and validation of a new wireless Impact Echo (IE) system for condition assessment of reinforced concrete slabs. The new IE prototype was compared with other commercially available non-destructive testing (NDT) devices used for similar purposes, namely Ground-Penetrating Radar (GPR) and Ultrasonic Pulse Echo (UPE). Monitoring and structural inspections are critical to effective management of civil infrastructure and NDTs can enhance the quality of condition assessments by providing objective visualizations of the interior of a structural element.
The IE method, first developed in the 1980s, has seen few advancements in the last 20 years. The method has been standardized and used on site, but the underlying technology has become outdated. The data obtained from the transducer is difficult to interpret and requires a computer to post-process it before being usable, thus limiting the direct feedback of the method when conducting tests on-site. Because of those limitations and the test being relatively more time consuming than other alternatives, the method is lacking in usability. A new prototype IE device was designed and built by the project industry partner, FPrimeC Solutions. The methodology followed the traditional approach, but it was designed to work with today’s technology. The device is operated wirelessly via a Bluetooth connection, uses smaller-sized electronic components, and connects with a user-friendly interface on a small tablet to set-up the tests and compute the results immediately. The first part of the project focused on product development by testing iterations of the prototype and providing user feedback to improve the device and accompanying software.
The second part of the project aimed to validate the new technology using a set of three large reinforced concrete slabs containing artificial defects. The studied points of interest were sound concrete, effect of boundaries and steel reinforcements, vertical cracks, presence of a hollow conduit, artificial voids and delamination. The IE results were also compared with those from commercial GPR and UPE devices. GPR was found to be the quickest method by far, although the results gathered seemed to be limited by the presence of steel reinforcement and also failed to locate certain defects. UPE was a bit slower than GPR, but was generally able to locate more accurately the artificial flaws created in the test specimens. The results showed poor definition of the flaws making it difficult sometimes to properly locate them. The UPE results also seemed to be negatively affected by the presence of reinforcement which were causing frequent abnormal values. Lastly, the IE method was used. This method was greatly improved during the first phase, but it is still a time-consuming method. The value of the data, however, has great potential when compared to the other options. It accurately located most of the flaws generated and was practically unaffected by the presence of steel reinforcing bars. Also, with further analysis of the data, it was possible to determine the depth of some of the flaws accurately.
Due to the time-consuming testing phase and the longer analysis of the data required to obtain the higher quality of results, this study suggests that IE is not likely to be the best choice for a general inspection of a large area (depending on the nature of the information needed). Rather, it is suggested to first conduct a general review of the structure using a quicker method like GPR to locate the problematic areas. After that, refining the grid at key locations to test with IE should provide the best quality of data in a reasonable amount of time.
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Guevremont, Philippe. "Application of the MSR Impact-Echo system for crack detection in concrete dams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37263.pdf.
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Tabatabaee, Ghomi Mohammad. "MODELLING AND SIMULATION OF ELASTIC & PLASTIC BEHAVIOUR OF PROPAGATING IMPACT WAVE : Impact- echo and Explosive welding process development." Doctoral thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-13332.
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A force that is applied dynamically in a short period of time is called an impact force (shock wave). Due to the concentrated application of force on a small area in a fraction of a second, unique applications have emerged that other types of loadings are not capable of performing. Explosions, an impact of a hammer, impact of waves on a shore wall, or the collision of two automobiles are examples where impact waves occur. In this research the effects of impact on solid materials and the motion of stress waves due to the impact are studied and some of their industrial applications are described. The primary objective of this work is further development of some elastic and plastic impact wave methods, aiming to reduce the energy consumption of explosive welding (EXW) as well as the cost of NDT technologies. Many numerical simulations and a vast amount of experimental work were employed to reach this goal. The impact wave creates elastic deformations that move the particles of the body. In this research we focused on dimensional measurement by calculating the time of wave travel between the source of energy and a discontinuity in the part studied. The impact echo (IE) method can be used for determining the location and extent of all kinds of flaws, such as cracks, de-lamination, holes and de-bonding in concrete structures, columns and hollow cylinders with different cross-sections and materials. In the present study, simulation of the impact-echo method was carried out numerically using direct and indirect methods. In the direct method a steel ball directly impacts on the upper surface of a concrete plate-like structure, whereas in the indirect method the impact impulse transmits to the concrete plate via a steel bar, in order to adapt the method for situations where there is no access to the plate being measured. In each method a two-dimensional finite element analysis (in axisymmetric geometry) was performed for the thickness measurement of concrete plates using the LS-DYNA program. Numerical results are presented for different values of plate thickness and different projectile speeds for both the direct and the indirect method and the indirect results are validated by comparison with the results obtained by the direct method. The method was validated against experimental measurements. A high energy impact wave produces plastic deformations in metals. In this research explosive welding was studied as an application of high energy impact waves. A new method for joining different, non-compatible metals (Al and Cu-based materials) was introduced. This method may be extended for use in offshore applications. Many 3-D numerical simulations were performed using the ABAQUS explicit commercial software. The model was validated against experimental measurements. The outcome of this research work could be summarized as follows: a) Introducing an indirect IE method in NDT technology for thickness measurement in particularly inaccessible structures. b) Introducing a new, grooved method in EXW technology to join surfaces made of different materials, in particular Al-Cu joints. The results could be employed to reduce the energy consumption and cost associated with EXW and IE technologies. The methodology can be used in many other applications in all kinds of process industries.
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Martin, Julia. "Non-destructive testing of metal ducted post-tensioned bridge beams using sonic impact-echo techniques." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/11100.
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On 25 September 1992 the Department of Transport (DoT) issued a press notice stating that it would not be commissioning any new grouted duct post-tensioned bridges in England. The decision was taken due to fears that existing grouted duct post-tensioned concrete bridges were badly corroded and could be in a state of imminent collapse. The press notice also announced that existing grouted duct post-tensioned bridges were to undergo detailed inspection. Non-destructive techniques needed to be developed to allow detailed investigation of these structures. The results of these investigations had to be accurate to a high level of confidence as decisions on repair, renovation or destruction would be made on the findings of the investigation. This thesis will give the reasons for the DoT's decision followed by an overview of possible non-destructive techniques available at the time of issue. The main body of work carried out investigates the use of the Sonic Impact-Echo method of non-destructive testing. This involves the development of suitable testing equipment and preliminary laboratory and field investigation. Detailed numerical simulations were carried out using the Finite Element Method in order to quantify the probable limits of the Sonic Impact-Echo method. Final laboratory investigations were carried out on a model with known defects. Detailed field testing was carried out on test beams manufactured by the Transport Research Laboratory in Crowthorne and by TBV Stanger at Elstree.
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Welter, John T. "Oblique angle pulse-echo ultrasound characterization of barely visible impact damage in polymer matrix composites." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1575295152635788.
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Gabrielli, Elena. "Diagnostica strutturale con il metodo Impact-echo di solette in calcestruzzo contenenti guaine per post- tensione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/371/.
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Hendricks, Lorin James. "High-Speed Apparatus and Signal Processing for Accoustic Delamination Detection on Concrete Bridge Decks." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8971.
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Maintenance and repair of deteriorating civil infrastructure are global problems requiring significant attention and resources. Accurate measurements of civil infrastructure enable lower repair and rehabilitation costs if mitigation techniques are deployed at earlier stages of deterioration. This research describes an infrastructure inspection solution to scan concrete bridge decks for internal cracking at high speeds. Internal cracking within bridge decks, known as delamination, is a particularly difficult defect to identify because it is often not detectable through visual inspection. State-of-the practice testing approaches involve the use of slow and subjective manual sounding techniques and costly lane closures. The need for an improved testing approach has led to decades of research investigating the use of acoustic impact-echo testing to detect bridge deck delaminations. The research presented here consists of a study of the acoustic radiation patterns of delamination defects when they are impacted. Acoustic data were collected on an in-service bridge deck and compared to acoustic data collected on defects in decommissioned bridge deck slabs and on simulated delaminations. This study examined cases of ideal and non-ideal delaminations on the in-service bridge deck and identified characteristics of non-ideal delaminations. An apparatus consisting of a high-speed impact-echo platform and recording suite was designed and constructed. Using this towed apparatus, an order-of-magnitude increase in scanning speed was obtained over other reported methods. Significant design effort was employed to achieve synchronization between different sensing devices using networked computer systems. Analysis was also developed to process and automatically classify acoustic responses to determine the presence and location of delaminations. Demonstrated performance against ground truth data obtained on an in-service bridge deck includes an achievement of approximately 90% probability of detection with only a 2% false alarm rate within 0.30 m. Because of the need to classify acoustic data when ground truth may not be obtainable, a new outlier rejection algorithm, which robustly removes outliers for classification on both simulated and field test data, was also developed. These contributions advance state-of-the-art bridge inspection and also lay the groundwork for additional studies of bridge deck deterioration processes. The framework also demonstrates how a tedious, subjective, and manual inspection process can be automated using advanced excitation tools, signal processing, and machine learning.
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Larsen, Jacob Lynn. "Automated Impact Response Sounding for Accelerated Concrete Bridge Deck Inspection." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6989.
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Infrastructure deterioration is an international problem requiring significant attention. One particular manifestation of this deterioration is the occurrence of sub-surface cracking (delaminations) in reinforced concrete bridge decks. Of many techniques available for inspection, air-coupled impact-echo testing, or sounding, is a non-destructive evaluation technique to determine the presence and location of delaminations based upon the acoustic response of a bridge deck when struck by an impactor. In this work, two automated air-coupled impact echo sounding devices were designed and constructed. Each device included fast and repeatable impactors, moving platforms for traveling across a bridge deck, microphones for air-coupled sensing, distance measurement instruments for keeping track of impact locations, and signal processing modules. First, a single-channel automated sounding device was constructed, followed by a multi channel system that was designed and built from the findings of the single-channel apparatus. The multi channel device performed a delamination inspection in the same manner as the single-channel device but could complete an inspection of an entire traffic lane in one pass. Each device was tested on at least one concrete bridge deck and the delamination maps produced by the devices were compared with maps generated from a traditional chain-drag sounding inspection. The comparison between the two inspection approaches yielded high correlations for bridge deck delamination percentages. Testing with the two devices was more than seven and thirty times faster, respectively, than typical manual sounding procedures. This work demonstrates a technological advance in which sounding can be performed in a manner that makes complete bridge deck scanning for delaminations rapid, safe, and practical.
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McMorris, Nicolas. "Linear and non-linear frequency domain techniques for processing impact echo signals to evaluate distributed damage in concrete." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9816.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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McHugh, John Paul. "Aspects of the impact-echo method for the detection of voids within metal ducted post-tensioned bridge beams." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/47535/.
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This thesis is concerned with the development of a non-destructive testing technique, namely the impact-echo method, for the evaluation of tendon ducts in post-tensioned prestressed concrete bridges. The impact-echo method has been shown to be useful for damage detection in concrete structures, particularly plate-like structures. However, when it is applied to beam-like rather than plate-like structures the resulting spectra are complex and difficult to interpret. One source of complications is the excitation of cross-sectional modes in the beam. This thesis discusses an investigation into the nature of these modes, and their potential applications for non-destructive testing. Finite element models have been developed to investigate cross-sectional modes where grouted and ungrouted ducts are present and the results from these are described together with an experimental validation. It is concluded that a shift in the frequency of the dominant cross-sectional mode can be used to identify large ungrouted ducts. In addition, the frequencies of the dominant cross-sectional modes can be predicted for both grouted and ungrouted cases using finite element modelling. Further finite element analysis showed that varying the compression wave speed in grout over a realistic range had minimal effect on the amplitude and frequency of the dominant cross-sectional mode.
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Di, Giovenale Andrea. "Metodo impact-echo per la diagnostica strutturale: esperienza di laboratorio su solette in calcestruzzo contenenti guaine per post-tensione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amslaurea.unibo.it/198/.
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Ellis, Wendy Annette. "The impact of C-PEP (choral reading, partner reading, echo reading, and performance of text) on third grace fluency and comprehension development /." Full text available from ProQuest Dissertations & Theses, 2009. http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3370265.
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Patil, Anjali Narendra. "Delamination Detection in Concrete Using Disposable Impactors for Excitation." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3885.
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Delaminations in concrete bridge decks result primarily from corrosion of the reinforcing bars (or rebar). This corrosion leads to volumetric expansion of the rebar. When the rebar expands, concrete cracks, and there is a localized separation of the concrete cover from the underlying concrete. Impact-echo testing is an effective technique to map delaminations on concrete bridge decks. However, mapping speed is limited by necessary retrieval of the impactor for traditional tests. To achieve higher scanning speeds, it is advantageous to use both a non-contact measurement (air-coupled impact-echo) and disposable-impactor excitation. Disposable impactors have the potential advantage of achieving greater deck scanning speeds because they do not need to be retrieved, and they can also be used with air-coupled measurement systems. This thesis reports impact excitation of concrete using disposable impactors such as water droplets and ice balls. The impact characteristics of these impactors are compared with those of steel balls and chain links. Comparing the acoustic recordings on intact and delaminated concrete surface shows that water droplets and ice balls are able to excite flexural resonant modes associated with delamination defects. The use of water droplets and ice balls for shallow delamination detection in concrete is thus demonstrated.
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Musio, Antonio. "Modelling and experimental implementation of infrared thermography on concrete masonry structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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Industrialized countries have and are based on a network infrastructure is becoming increasingly complex and difficult to manage these systems, mainly due to a lack of financial resources. Asset management is a paradigm that is adopted to properly manage the infrastructure, ensuring that the available resources are properly utilized to ensure the necessary level of service to users of the infrastructure. It includes managing the entire life cycle, including design, construction, commissioning, operation, maintenance, modification, replacement or cancellation of physical infrastructure assets.
In this context, there is a big contribution by use of technology, and then using the methods that this thesis will aim to provide a quantitative assessment of structural systems and provide sufficient assistance to any strategy of asset management.
Non-destructive tests are types of test required by biggest companies around the world. These types of investigations are also mentioned in technical specifications of products, by norms and administrative orders.
Adaptability of non-destructive techniques related to the ability to detect defects, without harming sample, puts these techniques high in context of component reliability check.
About the subject of structural diagnostics, plays an important role the use of technology, which if properly exploited can provide a quantitative assessment of infrastructure systems. For example the feedback non-destructive as infrared (IR) and ultrasound (UT ) and others, are becoming more and more accessible and have the ability to assess damage to structures and materials at an early stage
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Alhawat, Musab M. "Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica." Thesis, University of Bradford, 2020. http://hdl.handle.net/10454/18430.
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The current research project mainly aims to investigate the corrosion resistance and bond
performance of steel reinforced recycled aggregate concrete incorporating nano-silica under
both normal and corrosive environmental conditions. The experimental part includes testing
of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied
were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica
(1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm).
Different levels of corrosion were electrochemically induced by applying impressed voltage
technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the
corrosion level in addition to the ultimate bond, failure modes and slips occurred.
Experimental results showed that the bond performance between un-corroded steel and
recycled aggregate concrete slightly reduced, while a significant degradation was observed
after being exposed to corrosive conditions, in comparison to normal concrete. On the other
hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal
and RCA concretes under normal conditions. However, much better influence in terms of bond
and corrosion resistance was observed under advancing levels of corrosion exposure,
reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in
recovering the poor performance in bond for RCA concretes. More efficiency was reported
with RCA concretes compared to the conventional concrete. The bond resistance slightly with
a small amount of corrosion (almost 2% weight loss), then a significant bond degradation
occurs with further corrosion.
The influence of specific surface area and amount of nano silica on the performance of concrete
with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced
with three different types of colloidal NS having various surface areas and particle sizes. The
results showed that the performance of concrete is heavily influenced by changing the surface area
of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2
/g achieved the highest enhancement rate in terms of compressive strength, water absorption and
microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4
m2
/g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is
affected by its particle size as well as water to binder ratio.
The feasibility of the impact-echo method for identifying the corrosion was evaluated and
compared to the corrosion obtained by mass loss method. The results showed that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion in
reinforced concrete structures. A significant difference in the dominant frequencies response
was observed after exposure to the high and moderate levels of corrosion, whilst no clear
trend was observed at the initial stage of corrosion.
Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models
were able to predict the bond strength with a high level of accuracy, which was confirmed by
conducting a parametric study.Higher Education Institute in the Libyan Government MONE BROS Company in Leeds (UK) for providing recycled aggregates BASF and Akzonobel Companies for providing nano silica NS, Hanson Ltd, UK, for suppling cement
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Bonfitto, Angelo. "Diagnostica non distruttiva in strutture murarie e c.a. per la caratterizzazione, valutazione e prevenzione del rischio sismico del patrimonio edilizio esistente." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Il presente elaborato tratta la diagnostica non distruttiva su strutture in muratura e in c.a. con particolare focus sulle prove che hanno portato alla valutazione delle caratteristiche del patrimonio esistente. Elencherò prove convenzionali e prove non convenzionali descrivendo con casi studio e campagne sperimentali i risultati raggiunti. Tratterò la nuova normativa NTC 2018 con attenzione alle novità che hanno cambiato la situazione per i tecnici rispetto alla NTC 2008. Spiegherò i concetti chiave di moderne prove non distruttive e i loro sviluppi nell'indagine sul costruito.
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Manuel, Regildo Batista do Sacramento. "Estimativa de espessura do concreto utilizando o método do eco - impacto." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=6752.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorNesta pesquisa utilizou-se um equipamento experimental que utiliza o método do eco-impacto produzido no Laboratório de Ensaios Físicos do Instituto Politécnico do Rio de Janeiro (UERJ/IPRJ), para estimar a espessuras de placas de concreto através da propagação de ondas de tensão geradas por um impacto. Para determinação dessa espessura, foram investigados vários mecanismos de estruturação do protótipo do equipamento com objetivo de se obter a melhor leitura possível, por meio das literaturas existentes. Entre parâmetros avaliados no estudo, estava o modelo de sensor a ser utilizado, o tipo de impactor, a precisão relacionada à aquisição de dados e o tratamento do mesmo, a distância entre o ponto de impacto e o transdutor (sensor), e o local de teste. Os resultados experimentais concordam com as previsões teóricas e revelam que este método é eficiente para análise de estrutura de concreto. A análise da espessura e resposta em frequência de um novo protótipo desenvolvido e os testes realizados possibilitou um erro médio de espessura real para amostras sem agregados de 0,39% e para as amostras com agregados com de 0,64%. Esses resultados apontam que o equipamento produzido tem potencial e que o mesmo pode ser utilizado para avaliação de estrutura de concreto.
In this research we used an experimental device that uses the method of impact-echo on Physical Testing Laboratory of the Polytechnic Institute of Rio de Janeiro (UERJ/IPRJ), to estimate the thickness of concrete slabs through the propagation of stress waves generated by an impact. To determine this thickness, several mechanisms for structuring the prototype equipment in order to obtain the best possible reading by means of existing literatures were investigated. Among the parameters evaluated in the study was the model of sensor being used, the type of impact, the precision related to the data acquisition and processing thereof, the distance between the impact point and the transducer (sensor), and test site. The experimental results agree with the theoretical predictions and show that this method is effective for analyzing concrete structure. The thickness analysis and frequency response of a new prototype and testing allowed an average error of actual thickness for samples without aggregates and 0.39 % for samples with aggregates with 0.64 %. These results indicate that the product produced has potential and that it can be used for evaluation of concrete structure.
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Timčaková, Kristýna. "Monitorování a analýza koroze výztužné oceli v železobetonových prvcích a konstrukcích akustickými metodami." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-401591.
Full textAbstract:
The dissertation thesis deals with the study of non-destructive acoustic methods as instruments for monitoring and analysing corrosion of reinforcing steel in reinforced concrete elements. Four acoustic methods were selected for this task - the impact-echo method, the nonlinear acoustic spectroscopy method, the acoustic emission method, and the ultrasonic pulse velocity method. To verify the functionality of these methods, testing was carried out on three sets of reinforced concrete samples that had been exposed to the effects of sodium chloride, which corroded the embedded steel reinforcement in these samples. Suitable parameters were proposed for individual acoustic methods to monitor corrosion of the reinforcements. In addition, experiments were designed to demonstrate the ability of the selected acoustic methods to reveal the corrosion of steel reinforcement and its influence on the concrete matrix and to assess the condition of the degraded elements and structures. The analysis of the measurement results based on their comparison shows the advantages and disadvantages of the individual methods and of their practical applications. To verify the results, correlation with common methods that are currently used for the study of corrosion was carried out and included for example the electrical resistivity measurement of the reinforcement and simultaneous monitoring of the sample surface using a confocal microscope to record the development of microcracks during the degradation.
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Baron, Thomas. "Untersuchungen an ungeschädigten und durch Pilzbefall geschädigten Nadelholzbauteilen mit ausgewählten Prüfverfahren." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25069.
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In der Arbeit wurde gezeigt, dass mit Hilfe der gewählten zerstörungsfreien und -armen Prüfverfahren der Bezug zu festigkeitsrelevanten Parametern hergestellt werden kann. Insgesamt 58 ungeschädigte und durch Braunfäulepilze geschädigte Nadelholzbalken und daraus hergestellte Prismen wurden mit Ultraschallecho und Bohrwiderstand geprüft und grundlegende Erkenntnisse für die Prüfungen an Holzbauteilen gewonnen. Die Ergebnisse wurden mit zerstörenden Festigkeitsprüfungen kombiniert.
Bei den Ultraschallechountersuchungen wurde festgestellt, dass sich für die geprüfte Rohdichtespanne die Schallgeschwindigkeit der Transversalwellen mit steigender Rohdichte erhöht. Ein enger Zusammenhang konnte auch bezüglich des Feuchtigkeitsgehaltes nachgewiesen werden. Nach Durchführung multipler Regressionsanalysen mit der Rohdichte, dem Feuchtegehalt und der Messfrequenz als unabhängige Variablen wurden sehr gute Korrelationen innerhalb der Holzarten ermittelt, so dass die Schallgeschwindigkeit gut abgeschätzt werden konnte. Die Lokalisierung von Ästen und Rissen ist gut möglich. Schädigungen wurden prinzipiell durch Ausbleiben des Echos der Bauteilrückseite detektiert. War der Übergang in Schallausbreitungsrichtung abrupt, wurden die Wellen reflektiert und erzeugten ein Echosignal.
Die durchgeführten Bohrwiderstandsuntersuchungen belegen einen Zusammenhang zwischen Bohrwiderstand und Rohdichte sowohl für die Prismen als auch für die geprüften Balken. Die Streuung der Werte der Regressionsanalysen wurde bei Differenzierung der Bohrrichtung und des durchbohrten Bereiches des Balkenquerschnitts reduziert. Zwischen Bohrwiderstand und Rohdichte bestand auch in den Zonen des Schadensübergangsbereiches ein linearer Zusammenhang.
An Balken und Prismen wurden Festigkeitsuntersuchungen durchgeführt und die Schadensübergangsbereiche gesondert betrachtet. Eine Differenzierung von Schädigungsgraden war in der Regel möglich. Bei den geschädigten Balken wurde der reale Querschnitt ermittelt und für die weiteren Berechnungen angesetzt. Danach wurde ein mittlerer Zusammenhang von Biegefestigkeit und E-Modul für die pilzgeschädigten Balken festgestellt.
Die Kombination der ermittelten Festigkeiten mit dem Bohrwiderstand führte zu mittelgroßen bis starken Zusammenhängen. Die Differenzierung der Bereiche des Schadensüberganges war möglich.
Im Hinblick auf die Einschätzung der Biegefestigkeit bestehender Träger wurden multiple Regressionsanalysen mit modifizierten Sortierkriterien, der Rohdichte, dem Feuchtigkeitsgehalt, der Querschnittszone, dem Bohrwiderstand und dem E-Modul durchgeführt und ergaben einen sehr starken Zusammenhang, der das erhebliche Potenzial der entwickelten Methodik bei der Bewertung geschädigter Tragkonstruktionen aufzeigt.
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Scarfe, Bradley Edward. "Oceanographic Considerations for the Management and Protection of Surfing Breaks." The University of Waikato, 2008. http://hdl.handle.net/10289/2668.
Full textAbstract:
Although the physical characteristics of surfing breaks are well described in the literature, there is little specific research on surfing and coastal management. Such research is required because coastal engineering has had significant impacts to surfing breaks, both positive and negative. Strategic planning and environmental impact assessment methods, a central tenet of integrated coastal zone management (ICZM), are recommended by this thesis to maximise surfing amenities. The research reported here identifies key oceanographic considerations required for ICZM around surfing breaks including: surfing wave parameters; surfing break components; relationship between surfer skill, surfing manoeuvre type and wave parameters; wind effects on waves; currents; geomorphic surfing break categorisation; beach-state and morphology; and offshore wave transformations. Key coastal activities that can have impacts to surfing breaks are identified. Environmental data types to consider during coastal studies around surfing breaks are presented and geographic information systems (GIS) are used to manage and interpret such information. To monitor surfing breaks, a shallow water multibeam echo sounding system was utilised and a RTK GPS water level correction and hydrographic GIS methodology developed. Including surfing in coastal management requires coastal engineering solutions that incorporate surfing. As an example, the efficacy of the artificial surfing reef (ASR) at Mount Maunganui, New Zealand, was evaluated. GIS, multibeam echo soundings, oceanographic measurements, photography, and wave modelling were all applied to monitor sea floor morphology around the reef. Results showed that the beach-state has more cellular circulation since the reef was installed, and a groin effect on the offshore bar was caused by the structure within the monitoring period, trapping sediment updrift and eroding sediment downdrift. No identifiable shoreline salient was observed. Landward of the reef, a scour hole ~3 times the surface area of the reef has formed. The current literature on ASRs has primarily focused on reef shape and its role in creating surfing waves. However, this study suggests that impacts to the offshore bar, beach-state, scour hole and surf zone hydrodynamics should all be included in future surfing reef designs. More real world reef studies, including ongoing monitoring of existing surfing reefs are required to validate theoretical concepts in the published literature.
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Hsu, Ying-Yan, and 徐穎彥. "Parametric Study on Impact-Echo Phase." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/92633324775541322874.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
104
The impact-echo test can be adopted to detect the defects or inclusions in concrete structures. The conventional impact-echo analysis applies the Fourier transform to the surface response of the target structure due to an impact of a steel ball. Then, the magnitude spectrum is used to determine the frequency of the echo signals. Although the magnitude spectrum may disclose the existence of an interface in the structure, it cannot tell whether the interface comes from a crack or a rebar. Such information is crucial in the safety assessment of the structure. It is also necessary in the determination of interface depth because the impact-echo equations for crack and rebar differ. This research examines the feasibility of the impact-echo phase analysis in the recognition of rebars and cracks. The idea is based on the phase change of the reflected wave. As a wave encounters a hard interface, it reflects with a phase change of π, but as it encounters a soft interface, there is no phase change. Hence, the phases of the echo signals from a crack and a rebar should disagree. Firstly, Fourier transform was applied to the idealized signals. It is found that the phases of crack echoes are indeed close to 0, while the phases of rebar echoes are close toπ/2 . Then, numerical and model tests were conducted to verify the results. The influence of the impact source, depth of interface, and the size of inclusion on the impact-echo phase are also studied. It is found that the phase offsets of crack and rebar echoes mostly fall within two separated ranges, ( -π,π/4) and ( π/4 ,π), respectively. By the parametric study, it is found that the impact-echo phase method works under the following conditions. Firstly, when the echo frequency equals to central frequency of the impact source, one would get satisfactory results. However, if the echo frequency exceeds twice central frequency of the impact source, the phase offsets would get worse results. Secondly, as the length-depth ratio of the crack exceeds 0.2 or the radius-depth ratio exceeds 0.4, one would get worse phase offsets. Hence, it is suggested that the impact-echo test be conducted using proper impact ball. Construct both the magnitude and phase spectra in the Fourier analysis. Use the magnitude spectrum to determine the echo frequency and use the phase spectrum to determine the echo phase. Then, useπ/4 as the decision line to judge the type of inclusion. As such, one can get both the type and depth of the inclusion correctly.
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Huang, Piin-Jia, and 黃品嘉. "Fuzzy Pattern Recognition of Impact-Echo Detecting Signal." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/98973361791121164803.
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Shen, Chien-ping, and 沈健平. "Study of Signal Analysis in Impact-Echo Testing." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/94866526656925186655.
Full textAbstract:
碩士國立中興大學
土木工程研究所
81
A nondestructive test method called impact-echo is under de- velopment for locating flaws in concrete using transient stress waves. To date, the method has been used succesfully to find flaws in plate-like structures. Applications of the method to circular, square and rectangular columns have been accomplished numerically and experimentally. In this thesis, laboratory re- sults detecting single cracks in a concrete slab is presented first. In addition, two overlapped cracks with different sizes were also embedded in the slab to study whether the impact-echo method can be used to detect multiple cracks. It is shown that when the crack closer to the impact surface is smaller than the other crack, both of them can be detected simultaneously. It is suggested that tests can be performed on all accessible surfaces to locate multiple flaws in concrete structures. The signal ana- lysis of the impact-echo is exclusively based on measuring the surface displacement response of a test object subjected to point impact. In this study, a comparison of spectra transformed from displacement, velocity, and acceleration waveforms was made numerically as well as experimentally to locate accurately sha- llow flaws. These studies were aimed at determining the feasibi- lity of using different types of transducers in the impact-echo testing system.
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Hung, Shao-Yu, and 洪邵宇. "Analysis of Weak and Complex Impact-Echo Signal." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64431834018371292347.
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Hsu, Yeou-Chih, and 許有智. "Detection of Ungrouted Ducts Using the Impact-Echo Method." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/06521423300481512242.
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碩士國立中興大學
土木工程學系
84
Prestressed box girders and I-shaped beams are commonly used in bridge construction. The objective of this research is to determine whether the impact-echo method is capable of detecting voids in grouted post-tensioning tendon ducts. Numerical studies were performed first to understand how the stress waves produced by point impact interact with completely or partially grouted ducts. The feasibility of using the impact-echo method for detection of voids in ducts can be evaluated. Laboratory studies were carried out to verify the numerical results. Results obtained from these studies show that there exists a big difference between the spectra obtained from impact-echo tests on completely grouted ducts and those for partially grouted ducts. The location of the ducts containing voids can be determined by identifying the corresponding high amplitude peak in the spectrum.
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Xu, You-Zhi, and 許有智. "Detection of Ungrouted Ducts Using the Impact-Echo Method." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/39493792544003883784.
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Huang, Guang-Jun, and 黃洸駿. "The Measurement of Varied Thickness Plate by Impact Echo." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/79767443578246324396.
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碩士國立交通大學
土木工程系
91
The objective of this thesis is to use the technique of impact echo in time domain to get insight into P-wave and use the measured speed of P-wave to determine the thickness of varied thickness plate. The measured speeds of P-wave in my study include surface P-wave, internal P-wave and P-wave measured from cylinder which taking core from the plate in frequency domain. The results of study show that the estimated thickness by impact echo in time domain is feasible especially using the speed of internal P-wave but it is not feasible in true situation. However, the measurement of speeds from surface P-wave solves the problem and the error can be controlled in 5%.
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Yi, Wei-Lin, and 伊威霖. "Improvement of an Automatic Two-Dimensional Impact-Echo Scanning System." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/43196716409437244138.
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Yen, Chen-Yeh, and 顏辰燁. "A study of apparent velocity of the impact-echo test." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/g2dzg3.
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碩士國立臺灣大學
應用力學研究所
106
Impact-echo method is the most widely used nondestructive testing technique in the testing of concrete structure. Hitting the surface of the target and creating a stress wave, we can measure the vertical displacement signal near the impact point in time domain. We can determine the characteristics inside the target by studying the peaks’ frequency on the spectrum, transformed from time domain by Fourier transform. However, it exists a distinctive error between the results of the target’s thickness measured with impact-echo method and the theoretical value, which is called apparent velocity, suggesting an uncertain factor in the measuring process. The main purpose of this research is to investigate the difference between the peak of the theoretical frequency of impact-echo method and the frequency obtained by measurement, which is called apparent velocity factor beta, by analyzing circular, rectangular and infinitely large plates. Using Rayleigh-Lamb wave theory to analyze the vibration modal of infinitely large plates, Aggarwal’s theory of vibrating disks to analyze the vibration modal of circular plates and a finite element software to analyze the vibration modal of circular and rectangular plates. This research took into consideration the influence of three parameters toward impact-echo peak frequency: sampling time, material properties and aspect ratio. First analyzing the influence of the material properties, by simplifying Rayleigh-Lamb wave equation, expressing the beta of the infinitely large plate with Poisson’s ratio, making this beta only be related to Poisson’s ratio, and verifying this theoretical value with a finite element software. Then, by analyzing the influence of sampling time, we can see from the result of numerical simulations that when the sampling time is shorter than a threshold, since the number of stress wave’s lateral transfer is low, it reacted like if it was transferring on an infinitely large plate, whether the specimen is circular or rectangular, thus the result is similar to the beta value obtained by Rayleigh-Lamb wave theory. When the sampling time is above the threshold, the number of lateral transferring of stress wave in the specimen is increasing, leading to the exciting of all kinds of modals of the specimens and reflecting them on the frequency spectrum, and in this circumstance, the frequency peak corresponds to the specimen’s vibration modal . The above mentioned threshold is mainly decided by the shape and the aspect ratio of the specimen. This research tries to vary the aspect ratio of circular and rectangular specimens between 2~10, according to the results of numerical simulation, circular specimens with an aspect ratio above 4 have the threshold time of exciting the specimens modal vibration when the termination time is approximately 40 times the length of cycle of the specimens’ bottom reflected wave. Specimens with an aspect ratio below this threshold with the same sampling time tend to excite its vibration modal, influencing the measured frequency, leading to error in the estimation of the thickness. On the other hand, rectangular specimens do not show obvious difference faced with different sampling time. Measuring specimens with the same aspect ratio from short to long sampling time, we obtain frequency peaks corresponding very well to beta. Aspect ratio also greatly influences the vibration modal of specimens. When measuring over a long period, using circular plate vibration theory, we can calculate the theoretical value of modal frequency corresponding to various aspect ratio of circular plates and plot its vibration mode. We can observe that the zero-crossing point’s radius of the displacement’s first loop of the circular specimens’ top all lies within 0.60~0.66 times the thickness of the specimens. To sum up, it is suggested to use the computer to analyze the measured signals’ reactions from a short period of time to a long period of time when applying impact echo tests and observe the difference of frequency peaks and pick the results with short analyzing time to correct the thickness of the specimens with Rayleigh-Lamb theory.
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Lee, Bonjofei, and 李鵬飛. "A Study of RC Bridge Decks Using Impact Echo Method." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/07836010226978692768.
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Yang, Chun-Kuei, and 楊竣貴. "Calibration of an Impact Device and Development of Normalized Spectral Analysis of Impact-Echo Tests." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41457235697913484162.
Full textAbstract:
博士國立中興大學
土木工程學系所
94
ABSTRACT The objective of this dissertation is to introduce a new impacting device used in the impact-echo tests and to develop a calibration method for measuring the impact force. Furthermore, the dissertation is aimed at developing a new method for identifying the degree of the difference in acoustic impedance and the ratio of void at the interface of repaired structures. The impacting device was made by embedding a piezoelectric sensor into a steel sphere. The piezoelectric sensor is used to record not only the start time but also the force-time function of impact. The start time of impact is necessary information for impact-generated stress waves and time-of-flight techniques that are widely used in evaluation of the depth of surface-opening cracks in concrete. The force-time function of impact can be used to normalize the spectra obtained from impact-echo tests. A new technique based on the normalized spectra is developed to quantitatively evaluate the difference in acoustic impedance at the interface between two layered structures. In this paper, experimental studies were performed to calibrate the piezoelectric sensor embedded in the impacting device by the simple pendulum principle. The calibration result of the piezoelectric sensor was confirmed by comparing the output of the sensor with that of a ready-calibrated force sensor made by the PCB piezotronics, Inc. Both numerical and experimental results show that the normalized spectral analysis of the impact-echo tests is capable of identifying the degree of the difference in acoustic impedance and the ratio of void at the interface of repaired structures. The new technique under development has a high potential for evaluation of the bond quality at the interface of repaired structures.
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Algernon, Daniel [Verfasser]. "Impact-Echo: Analyse akustischer Wellen in Beton / vorgelegt von Daniel Algernon." 2006. http://d-nb.info/980249031/34.
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Lin, Chia-Ching, and 林佳慶. "Application of the Empirical Mode Decomposition in the Impact-Echo Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/44092159879333342301.
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Liou, Chung Hsing, and 劉中興. "NDT for Structural Integrity of Rigid Pavements by Impact-Echo Method." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/73940187551064652378.
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Chen, Chia-Shen, and 陳家紳. "The Development of an Automatic Two-Dimensional Impact-Echo Scanning System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/47049958411717157822.
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Hsu, Chia-Wen, and 許嘉文. "The revision of inclined crack based on impact-echo spectral tomography." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/38514033539819832601.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
100
Impact echo method can effectively detect internal defects of concrete, this method is to impact the structure surface to stimulate the stress wave, and then to measure the surface displacement of the Fourier transform, and then interpreted by the peak value of the spectrum of frequencies of defect sites. When using Impact echo method to detect tilt interface, the specimen surface and the reflection interface is not parallel, so force wave between the two interfaces coming back reflection is not like the rule between two parallel surfaces. Therefore, spectrum echo peak is not necessarily correspond to the measuring point just below the interface, and the echo frequency peak is not too obvious.If you use the image method to draw a spectral tomography, you will find out the inclination and position of the interface have a slight deviation. The purpose of this study is to develop an effective Spectral Tomography Tilt Interface Amendment Method to amend mutual interference cause by the stress wave returns from tilt interface . This paper presents a Spectral Migration Image Method, similar to the Earth’s Interior Migration Method, but the signal processing is not a time domain signal, but the frequency domain signal. Migration uses the oval superposition principle, the energy of each frequency in the spectrum of all measured points spread to the entire semi-elliptical, each pixel from all points of the energy overlay. As the Spectral Migration Image Method, frequency amplitude spectrum of each pixel of the image have the same proportion of the contribution will result in non-tilt interface location of the Interference signal. This article re-use of the method of weight distribution to enhance the tilt interface reflection energy and remove the image correction resulting from the Interference signal. In addition, the gradation conversion of spectrum images to enhance image contrast. By this paper, the method can make the vertical cross-section image clearly shows the shape and position of the inclined cracks. This study use the Finite Element Method to simulate six different slope of the inclined cracks, then use numerical results verify the feasibility of the proposed method. From numerical simulation results, we can see that through the Spectrum Migration Amendment Method can fix tilt crack location, enhance the signal strength of the crack area and focus on the correct thickness of the defect, and eliminate Interference signal, solve the problem of error in judgment. This study sets three model tests at the same, the experimental results can also be found that the amendment method proposed in this article can be effectively applied to the experimental signal, accurately identified the location and size of the inclined cracks.
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Lin, Jan Jer, and 林彰哲. "The Elementary Research of Impact Echo Method for Detecting Diaphragm Walls." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/78552321051379838514.
Full textAbstract:
碩士國立海洋大學
河海工程學系
83
The impact echo method is a nondestructive technique using the principle of stress wave propagation in a solid. The crack， void and flaw in a solid can be fast detected through frequency spectrum analysis. The main purpose of this thesis is elementally to determine the correspondent position of diaphragms with crack，void and honeycomb in dry or saturated sand. From this study ，one can gets some important conclusions described as follows︰ 1.The flaw positions of concrete diaphragms can be accurately detected by impact echo method. 2.The steel near upper layer in concrete diaphragms can be determined，however，it is difficult to detect the steel in the deeper layer. 3.The impact echo method is not useful for predicting the vertical crack in concrete diaphragms.
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Yang, Kai-Hsiang, and 楊凱翔. "A Study on the Applicability of the Impact-Echo Phase Method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/sa8ns2.
Full textAbstract:
碩士國立臺灣大學
應用力學研究所
107
The impact-echo test can be used to detect the inclusions or defects in concrete structures. The conventional impact-echo analysis applies the Fourier transform to the surface response of the target structure due to an impact of a steel ball. Then, the magnitude spectrum is used to determine the frequency of the echo signals. Although the traditional method can detect the possible location of the reflected surface, it is unable to distinguish the type. Take rebars and cracks as an example, concrete can be enhanced by rebars, but it can be damaged by cracks. Therefore, it is essential to determine the type of reflective surface. The impact-echo phase method is based on the change phase when stress wave is encountering the reflective surface with different acoustic impedance, so we can use the characteristic to derive the phase of rebar and crack by Fourier transform. It is found that if the ratio of echo frequency ( ) and the center frequency of the steel ball ( ) is less than 1.6, then phases of rebar echoes and the phases of crack echoes can be divided by . When phase is greater than , the reflective surface can be speculated as rebar, and when the phase is less than , the reflective surface can be speculated as crack. The objective of this study is to explore the applicability of the impact-echo phase method. Firstly, we investigated the influences of acoustic impedance, impact source and the depth of the reflective surface on the phase. To obtain quick estimate on the influence of each parameter, the three-dimensional wave propagation was simplified into a normal incident plane wave. The surface displacement due to an impact was obtained by the Green function solution and the D’Alembert solution. Then, the Fourier transform was applied to the displacement response to determine the phase at the echo frequency. The results showed that the phase obtained by one-dimensional approximation was close to the three-dimensional simulations. That confirmed the feasibility of using the one-dimensional approximation. While studying of the influence of acoustic impedance, it was found that the acoustic impedance could affect the peak of echo frequency. In a layered medium, only when there is a 3 times difference between the acoustic impedance of the upper layer ( ) and the bottom layer ( ) can the echo frequency be identified in the Fourier spectrum effectively. Moreover, the phase at the echo frequency in both and cases were close and could not divide by . This is different from the rebar/crack case, in which can serve as a divider. The major difference between a medium with a rebar or crack inclusion and a layered medium lies in the size of the reflector. Therefore, the influence of the size of the reflecting surface was further studied using three-dimensional numerical simulations. Based on the numerous numerical examples, we drew the following conclusions: 1. When and , regardless of the width (W) and depth (D) ratio, , the phase is greater than . 2. When and , regardless of the ratio, the phase is less than . 3. When and , regardless of the ratio, the phase is greater than . 4. When and , regardless of the ratio, the phase is less than . In the distinction of rebar and crack inclusions, if for the rebar, the investigator could adjust the impact source such that , then uses as a decision line to judge the type of inclusion.
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Chang, Chih-Chieh, and 張智傑. "Using Impact-Echo method to Investigate the Concrete after High-Temperature Exposure." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86049146635067502356.
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碩士朝陽科技大學
營建工程系碩士班
95
The interior chemical reactions produced by fire leads to surface deterioration of structural concrete. The aim of the present research is to evaluate the degree of deterioration non-destructively by means of stress waves. In the study, a steel ball is used as the impactor and the frequency of the principal response obtained by a receiver 20 cm away is used for concrete evaluation. Two types of specimens were investigated. One is the small specimens with dimensions 40*40*15 cm. These specimens were heated by oven with the temperatures 300, 400, 500, 600, and 800℃. The other is large concrete plate with the size 240*130*15 cm. The specimen is heat by fire with environmental temperature 600℃. The frequencies of the principle responses of the small specimens were compared to the depth of concrete deterioration obtained from drilled core. The cores were sliced into disks and the depth of the deterioration was evaluated by the variation of the dynamic elastic modulus of the disks. The relationship between the lowest primary frequency and the depth of deterioration obtained from the small specimens were used for evaluate the depth of deterioration of the big plate after fire. The test results show the depths of deterioration are about 2 cm, 6-8 cm, 10cm, and 12-13 cm while the lowest primary frequencies are 13-14 kHz, 11-12 kHz, 9-10 kHz, and 7-8 kHz, respectively.
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Liao, Chun-Yu, and 廖俊育. "Application of Impact-Echo Method on the Properties of Prestressed Concrete Beams." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/34315111887057724283.
Full textAbstract:
碩士國立臺灣海洋大學
河海工程學系
98
Bridges are the important structures to maintain the transportation between valleys. The pre-stressed beams are widely used, because of the development of pre-stressed concrete. Many pre-stress beams of old bridges are damaged, since pre-stress beams are early widely used. Many references show that the pre-stressed loss is an important element of the pre-stressed bridges safety. Therefore, the main purpose of this thesis is hoping that we can get the natural frequency of pre-stressed beams by using Impact-echo method, and also finding its relationship by using different pre-stressed value. In this thesis, we will make five piece of pre-stressed beams, which is 3.7m in length, 16cm wide and 30cm high. Three of them are curved tendon type, and the pre-stressed values are 3.2t, 4t, and 4.8t. Two of them are straight type, and the pre-stressed values are 3.2t, 4.8t. Those five pre-stressed beams use Impact-echo method in four phases which are before pre-stressed, after pre-stressed and casing un-grout, after casing grouting, and half year after casing grouting. The results show that it’s hard to focus the discussion on the relation between pre-stressed loss and natural frequency, since pre-stressed beam is compound material structure, and there are many elements which may influence the natural frequency. And the total stiffness of pre-stress beam have direct ratio for natural frequency. After casing grouting, the natural frequency has significant improvement. In conclusion, this survey verifies that Impact-echo method can be implements on the stiffness of pre-stressed beams and casing grouting quality for non-destructive testing.
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Cahyani, Erma Dwi, and 杜愛柔. "Numerical Study on Response of Layered Concrete Plate Using Impact-Echo Method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/yt92j5.
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碩士國立臺灣科技大學
營建工程系
99
The material properties of damaged concrete due to its heterogeneous nature will be changed significantly from the damaged surface to the inner intact mass. The technique of traditional Impact-echo method to determine the P-wave speed of concrete from its surface needs to be properly modified considering the characteristics of gradual changes of material properties. This study uses the numerical results from finite element analysis to propose a practical methodology which combines the Impact-echo method and time-of-flight method to properly estimate the internal concrete P-wave speed and the thickness of a multilayered concrete plate. The results of numerical simulation from the impact-echo method are based on the commercial finite element analysis software LS-DYNA in which a 2-D axisymmetric finite element model is used to simulate a concrete plate of 200 mm of thickness and 4 m of length with deteriorated multilayered gradually and linearly changed of low P-wave speed from the outer surface toward the inner mass with high P-wave speed. The variables of concrete properties in the numerical analysis include three different damaged depths, 50%, 70%, and 90%, of the concrete plate. Numerical results show that the ASTM C-1383 method procedures is capable of measuring a correct P-wave speed for a monolithic concrete plate but fails to a multilayered concrete plate with different material properties at each layer. Therefore, a modified time-of-flight method is proposed to approach the accurate results. It does not need to know prior information of these two parameters and can be combined with the impact-echo method to measure the thickness of concrete plate which is depending on time-of-flight ordinate (TOF ordinate). The increase depth of damaged, the increase of ratio of time-of-flight ordinate and thickness. It increases from 2.91 for the undamaged concrete plate to 2.94, 2.96, and 2.99 when the depth of damaged increase respectively for 50%, 70%, and 90% of total thickness concrete plate.
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Chen, Yen-Cheng, and 陳彥成. "Numerical Analysis and Experiments of Hollow Cylindrical Structure with Impact-Echo Method." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/25869p.
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碩士國立臺灣科技大學
營建工程系
100
The thesis uses the impact-echo experiment, guided-wave theory and numerical simulation to study the behavior of wave propagation of hollow cylinder. The experimental results are used to verify the correctness of the guided-wave theory and numerical simulation, which demonstrates that the instruments of impact echo method and numerical simulation can be used to detect the material properties and cross-section resonance frequencies of hollow cylinders with various materials, such as concrete, metal and plastic. In the meantime, the influences of the diameter, tube thickness and embedded depth of the hollow cylinders with different materials on the stress wave propagation were also investigated. First, the guided-wave theory was used to analyze the hollow cylinders with different kinds of material property, and the six cross-sectional resonance frequencies were compared with those from the numerical analysis of impact-echo method. The results show these two sets of resonance frequencies are quite close to each other. It indicates that the guided-wave theory can be applied to the hollow cylinders with any kind of single material. The given formula can deduce the ? values and the first to sixth cross-sectional resonance frequencies of the hollow cylinder with any single material. A simple table is thus established to quickly estimate the first to sixth cross-sectional resonance frequencies of various hollow cylinders with single material. For the composite hollow cylinders composed of different materials, only the numerical method is available to obtain the first six cross-sectional resonant frequencies. In order to investigate the effects of various parameters on the response from the numerical simulation, this study uses the variations of six parameters to analyze and discuss nine sets of combinations. The results show that a significant difference of the cross-sectional resonant frequencies occurs when the material property or the diameter is changed, but there is only a minor change if the tube thickness or embedded depth is changed.
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Lin, Li-Chuan, and 林力權. "Application of Impact-Echo Phase to Detect Reinforcing Steel Bar and Crack." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/01824982745462134217.
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碩士國立臺灣大學
應用力學研究所
102
The impact-echo test is a nondestructive testing technique for civil structures. In the test, the surface response of the target structure due to an impact is measured. Then, the Fourier transform is adopted to transform the signal from the time domain to the frequency domain. The frequencies of the peaks can be used to determine the size of the structure or the location of the defect. In practice, the inclusion of target structure is unknown. Therefore, it cannot infer the interfaces is crack or reinforcing steel bar only by observing the frequencies of peaks. The purpose of this study is to analyze the phase characteristic of stress wave that comes from crack and reinforcing steel bar. Frist, progress the impact-echo test to obtain the impact-echo signal and remove surface wave of impact-echo signal by delaying the time origin. Then, use the Fourier transform to transform the impact-echo signal to frequency domain and find the phase of echo peak. Finally, identify the echo caused by crack or reinforcing steel bar by the phase and phase slope. The explicit finite element methods was firstly adopt to simulate the stress wave propagation when stress wave encounter crack and reinforcing steel bar. Then, the model tests were used to verify the numerical results. From the numerical and experimental results, one can conclude that the phase of crack echo approximate to zero and the phase slope is high. The phase of reinforcing steel bar echo approximate to and the phase slope is small. Compared to the conventional impact-echo data analysis, the proposed methods can not only determine the defect depth but also identify the defect that is crack or reinforcing steel bar.
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Y, C. Lee, and 李義村. "Signal Recognition of Impact-Echo Test on Horizontal Cracks in Rigid Pavement Slab." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/45054736366889150697.
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Huang, Kuan-Ying, and 黃冠穎. "Using impact-echo and impulse response methods to investigate the void in substrate." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/86694899880109213458.
Full textAbstract:
碩士朝陽科技大學
營建工程系碩士班
96
The present study uses impulse response and impact-echo methods to investigate the void in substrate. The experimental variables include different materials and support condition. There are two plate-like specimens. One is concrete plate with size 630cm*180cm*20cm. The other is asphalt plate with the same size. The investigation shows the stiffness calculated from the initial slop of the mobility curve obtained by impulse response and the thickness amplitude in the simulated transfer function obtained from the impact-echo test are related to the change in depth, quality and status of support. The average mobility value of 200-700Hz showed the presence of crack and honeycombing within plate. The cavities beneath the concrete pavement can be effectively identified by the peak/average amplitude ratio. For AC specimen, because cold joints may be formed between separate pouring layer, the void in substrate at the section with internal cold joint can not be identified by the impact-echo method but can be identified by the impulse response metod.