Dissertations / Theses on the topic 'Rebound hammer'

The aim of this research is to assess the material properties of concrete like modulus of elasticity, compressive strength, and Poisson’s ratio using various nondestructive Testing (NDT) methods like Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH). Assessment of material properties of concrete is very important as they are used for structural design process. Various NDT methods are applied to ensure the quality of concrete specimens but they can also be used to find material properties. UPV is a NDT method which is used to test the internal condition of the concrete specimen. RH is a surface hardness testing method and can be used to test the homogeneity of the specimen. For this study, several batches of concrete samples with three different design strengths of 6000 psi, 8000 psi, and 12000 psi were casted. Modulus of elasticity and Poisson’s ratio were calculated from UPV P-wave and S-wave velocities. A Nomogram was developed by combining the longitudinal ultrasonic pulse velocities, rebound numbers, and compressive strengths measured from UPV, RH, and compressive strength tests respectively. This combined NDT correlation curve (Nomogram) can be used to estimate compressive strength of concrete if UPV and rebound values are known. The accuracy of these NDT methods were determined by comparing estimated strength to the actual strength. Furthermore, the effect of moisture content on UPV and rebound values was reviewed and also studied dynamic modulus of elasticity and its relation with static modulus of elasticity of the concrete was investigated for better understanding.

Non-destructive testing is of great value in cases where a structure's future is investigated to find out what the best measure is. It is not always the best solution to demolish and build new. Many structures can be repaired and function several more years. In this thesis the main goal is to investigate some different non-destructive techniques and learn more about difficulties and strengths. The test subjects will be a cast T-beam in a laboratory environment as well as a case study of a railway bridge in Abisko.   The different testing equipment being used in this thesis is a covermeter, a rebound hammer and ultrasonic pulse velocity. For both the T-beam and the bridge the results are overall very good. The covermeter is proven to be both easy to use and very reliable and the ultrasonic pulse velocity was more to learn about and more difficult but is giving very good results as well.   Conclusions after the thesis project is that it requires a lot of experience of the user and time to make non-destructive testing useful and competitive in the society. Getting all the pieces together it is a powerful tool that hopefully is a sustainable asset in the future, regarding both economic and environmental issues.

This thesis deals with the rebound hammer method as a tool for approximation of the time limit for handling the concrete. The theoretical part is focused on three fields of knowledge - rebound hammer test, production of precast concrete components and statistical data analysis. The following practical part deals with the design of two single-parameter linear functions for two types of rebound hammer testers - SilverSchmidt L and SchmidtOriginal N. Statistical data processing is completed by the analysis of influential points by using the Cook’s distance. The resulting statistical models are compared with commonly used relationships.

The diploma thesis deals with non-destructive testing of concrete as well as with the relationship between determined parameters and the compressive strength of concrete. The thesis is mainly focused on the ultrasonic pulse velocity method and the rebound hammer test. The experimental part of the thesis describes non-destructive tests performed on concrete blocks. The compressive strength was tested on the drill cores taken from the concrete blocks. The aim of this thesis is to find regression models of the relationship between the compressive strength and non-destructive parameters, and the subsequent analysis of the results.

A RS471/BR153 é uma importante rodovia de integração, pois atravessa o estado do RS diagonalmente (Noroeste – Sudeste). O trecho estudado nesta dissertação localiza-se entre os municípios de Herveiras e Vera Cruz, coincidente com descida do planalto até a região central do estado. Durante o detalhamento do projeto e na construção da obra foram encontrados diversos problemas geotécnicos, os quais são sucintamente descritos. O texto apresenta as condicionantes geotécnicas de três subtrechos: (a) planalto, composto de rochas ácidas de origem vulcânica e grau de fraturamento muito alto; (b) descida da serra, composto pelos derrames da formação Serra Geral (brechas ácidas e basálticas e derrames basálticos) e (c) planície, com a presença de rochas sedimentares e materiais coluvionares. Além disto, há uma região especial onde o traçado atravessa uma sela topográfica coincidente com uma falha regional, com cortes de cerca de 60 m de altura através de rochas ácidas, básicas e brechas vulcânicas. A dissertação apresenta estudos dos processos de quedas de blocos rochosos que têm ocorrido nos cortes da rodovia. Foi utilizado um procedimento que correlaciona as leituras obtidas com o martelo Schmidt (Esclerômetro) e o coeficiente de restituição normal (RN) das rochas em diversos locais. Utilizando estes dados experimentais, foram executadas simulações de queda de blocos em quatro seções transversais bastante distintas com o uso do programa RocFall. Para cada seção foram simulados cinco cenários: (a) a existência de alargamentos para construção de áreas de retenção de blocos, (b) inexistência destas áreas, (c) a existência de preenchimento de uma ou várias banquetas existentes nos taludes de corte, e (d) o abatimento da seção com eliminação das banquetas. Foram também simulados quatro tipos de elementos de proteção: barreiras de baixa altura em concreto, camadas de areia fofa, barreiras metálicas flexíveis e proteção superficial dos taludes. A existência de áreas de retenção de blocos mostrou ser uma ótima medida, com frequências de invasão de pista geralmente abaixo de 1%, podendo chegar a 6,5% em condições de grande acúmulo de material. O melhor desempenho foi obtido pela instalação de camadas de areia fofa, obtendo-se todas as frequências abaixo de 2%. O uso de barreiras rígidas de 81 cm de altura teve um bom desempenho para taludes de baixa altura, chegando a detenções de até 25% dos blocos em trajetória de invasão. As barreiras flexíveis e proteções superficiais geraram resultados satisfatórios, mas que podem ser melhorados com outras modulações e dimensões.
The RS471/BR153 is an important road of integration, that cross RS state diagonally (northwest - southeast). The segment studied on this dissertation is located between the towns of Vera Cruz and Herveiras, coincident with the descent way from the plateau to the central state region. During the design and during the road construction several geotechnical problems were faced, which are briefly described. The text presents the geotechnical constraints of 3 segments: (a) plateau, composed of acid rocks of volcanic origin and very high degree of fracturing, (b) hills of the mountain, made up of volcanic rocks of Serra Geral formation (acid and basaltic breccias, basaltic flows) and (c) the plain, with the presence of sedimentary rocks and colluvial materials. There is also a special region where the road crosses a topographic saddle which it coincides with a regional fault, with cuts of about 60 m high through acid and basic rocks and volcanic breccia. The dissertation presents studies of rock falls that have occurred in the road cuts. A procedure that correlates the readings obtained with the Schmidt hammer (rebound hammer) and the normal coefficient of restitution (RN) of the rocks was carried out for measures taken at several locations. With these experimental data, simulations of falling boulders in four very different cross sections were done using the program RocFall. For each section five situations were simulated: (a) enlargements for the construction of rockfall catchment areas (b) the absence of these areas, (c) the existence of accumulation in the benchs of the cuts, and (d) the reduction of the section with bench removal. Four types of elements of protection were tested: concrete low barriers, layers of sand, flexible metal barriers and slope surface protection. The existence of rockfall catchment areas was shown to be a very good measure with frequencies of track invasion usually below 1% reaching 6.5% on conditions of large material accumulation. The best performance was obtained by the installation of sand layers, with all frequencies below 2%. The use of rigid barriers of 81 cm high had a good performance for low-slope heights, reaching up to 25% block retention. The use of flexible barriers and surface protections also had a good performance.
La RS471/BR153 es una importante carretera de integración, atraviesa el estado de RS diagonalmente (Noroeste-Sureste). El tramo estudiado en esta disertación se localiza entre los municipios de Herveiras y Vera Cruz, y coincide con el descenso desde el altiplano hasta la región central del estado. Durante las etapas de detalle y construcción de la obra fueron encontrados diversos problemas geotécnicos que son brevemente descritos. El texto presenta los condicionantes geotécnicos de tres subtramos: (a) altiplano, compuesto por rocas ácidas de origen volcánico y grado de fracturamiento muy alto; (b) descenso de la sierra, compuesto por los derrames de la formación Serra Geral (brechas ácidas y basálticas e derrames basálticos) y (c) planicie, con rocas sedimentarias y materiales coluviales. Además, hay una región donde el trazado atraviesa una “silla” topográfica que coincide con una falla regional, con cortes de aproximadamente 60 m de altura a través de rocas ácidas, básicas y brechas volcánicas. La disertación presenta estudios de procesos de caídas de rocas que han ocurrido en algunos cortes. Fue utilizado un procedimiento que correlaciona las lecturas obtenidas con el martillo Schmidt (Esclerómetro) y el coeficiente de restitución normal (RN) de las rocas en diferentes lugares. Con estos datos experimentales, fueron ejecutadas simulaciones de caídas de rocas en cuatro secciones transversales bastante distintas usando el programa RocFall. En cada sección fueron simulados cinco escenarios: (a) existencia de sobreanchos para la construcción de áreas de retención de rocas, (b) inexistencia de estas áreas, (c) existencia de relleno en una o más gradas existentes en los taludes de corte, y (d) diminución de la pendiente de los taludes y eliminación de las gradas. También fueron simulados cuatro tipos de elementos de protección: barreras de baja altura en concreto, capas de arena suelta, barreras metálicas flexibles y protección superficial de los taludes. La existencia de áreas de retención de rocas mostro ser una excelente medida, con frecuencias de invasión de pista generalmente inferiores a 1%, pudiendo llegar a 6,5% en condiciones de gran acumulación de material. El mejor desempeño fue obtenido con la instalación de capas de arena suelta, con todas las frecuencias por debajo de 2%. El uso de barreras rígidas de 81 cm de altura tuvo un buen desempeño para taludes de baja altura, llegando a detenciones de hasta 25% de los bloques en trayectoria de invasión. Las barreras flexibles y protecciones superficiales generaron resultados satisfactorios, que podrían ser mejorados con otras modulaciones y dimensiones.

Pour évaluer la résistance mécanique du béton dans un ouvrage existant, la méthodologie courante combine des mesures non destructives (CND) comme le rebond ou/et la vitesse des ondes ultrasoniques avec la technique destructive (carottes) afin de produire une relation‘‘modèle de conversion” entre la résistance mécanique et les mesures CND. Le modèle de conversion est utilisé pour estimer la valeur locale de résistance mécanique à chaque emplacement de test en utilisant la valeur CND correspondante. Ensuite, on calcule les estimations de la résistance moyenne et/ou de l’écart-type de la résistance (variabilité de la résistance du béton). Cependant, la fiabilité d’estimation est toujours discutable en raison des incertitudes associées à l’évaluation de la résistance basée sur les mesures CND. Pour améliorer la fiabilité, les incertitudes doivent être réduites en spécifiant et en contrôlant leurs facteurs d’influence. Par conséquent, l’objectif de cette thèse est d’analyser la méthodologie d’évaluation courante afin de fournir des recommandations pratiques qui peuvent améliorer la fiabilité de l’évaluation de la résistance in-situ du béton dans les ouvrages existantes par des tests non destructifs et des carottes.Pour ce but, un simulateur a été construit afin d’analyser les effets des facteurs les plus influents en utilisant une vaste campagne de données provenant de sources différentes (études in situ ou en laboratoire et données synthétiques générées). La première contribution de ce travail est le développement d’une nouvelle approche d’identification du modèle ‘‘bi-objectif” qui peut efficacement capturer la variabilité de la résistance mécanique en plus de la moyenne. Après avoir étudié l’effet du mode de sélection des emplacements pour les carottes, une méthode a été proposée pour sélectionner ces emplacements en fonction des mesures CND ‘‘sélection conditionnelle” qui améliore la qualité de l’évaluation sans coût supplémentaire. Une dernière innovation est l’établissement de courbes de risque qui quantifient la relation entre le nombre de carottes et la précision de l’estimation. Enfin, des recommandations ont été formulées afin de fournir des estimations plus fiables
To assess concrete strength in an existing structure, the current methodology combines nondestructive measurements (NDT) like rebound hammer or/and pulse velocity with destructive technique (cores) in order to implement a relationship ‘‘conversion model” between the compressive strength and NDT measurements. The conversion model is used to estimate the local strength value at each test location using the corresponding NDT value.Then the estimated mean strength and/or estimated strength standard deviation (concrete strength variability) values are calculated. However, the reliability of these estimated values isalways a questionable issue because of the uncertainties associated with the strength assessment based upon NDT measurements. To improve the reliability, the uncertainties must be reduced by specifying and controlling their influencing factors. Therefore, the objective of this thesis is to analyze the current assessment methodology in order to provide practical recommendations that can improve the reliability of assessing the in-situ strength in existing concrete structures by nondestructive tests and cores.To this end, a simulator was built in order to analyze the effects of the most influencing factors using a large campaign of datasets from different sources (in-situ or laboratory studies,and generated synthetic data).The first contribution of this work is the development of a new model identification approach“bi-objective” that can efficiently capture the strength variability in addition to the mean strength. After studying the effect of the way of selection the core locations, a method was proposed to select these locations depending on the NDT measurements “conditional selection” that improves the quality of assessment without additional cost. A third innovation was the development of a procedure to identify the relation between the number of cores and the accuracy of the estimation. Finally recommendations were derived in order to providemore reliable estimated values

High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.

Appréhender les caractéristiques mécaniques du béton in situ est essentiel pour déterminer la capacité structurelle à la fois des structures existantes et des nouvelles constructions. La méthodologie récente d'évaluation de la résistance du béton dans une structure existante consiste à intégrer des techniques de Contrôle Non Destructif (CND) avec des mesures destructives (carottage) pour établir un modèle de conversion qui corrèle la résistance mécanique avec les mesures non destructives. Par la suite, le modèle de conversion est appliqué pour estimer la résistance mécanique locale à chaque emplacement de test en fonction des valeurs CND correspondantes.Le test du rebond (RH) et le test de la vitesse des ondes ultrasonores (UPV) sont largement utilisés pour estimer la résistance à la compression du béton. Cependant, l'exactitude des résultats obtenus par ces méthodes peut être influencée par divers facteurs. Pour atténuer ces effets, la combinaison stratégique de ces deux tests non destructifs offre un moyen efficace d'évaluer la résistance du béton dans les structures existantes. Par conséquent, l'objectif de cette thèse est d'analyser la méthodologie d'évaluation des structures en combinant des techniques non destructives et de fournir des recommandations pratiques qui peuvent améliorer la fiabilité de l'évaluation de la résistance in-situ du béton. À cette fin, un simulateur a été développé pour analyser la méthodologie d'évaluation non destructive en utilisant un vaste ensemble de données provenant de diverses sources, notamment des études in situ, ainsi que des données synthétiques générées.La principale contribution de cette étude est de proposer une nouvelle approche d'identification de modèle basée sur l'optimisation multi-objectifs pour prédire la résistance moyenne du béton et sa variabilité, en se basant sur la combinaison des mesures CND. Des simulations Monte Carlo ont été réalisées pour vérifier les performances en tenant compte de l'incertitude des mesures CND et de la variabilité du béton. Les résultats ont mis en évidence l'efficacité de la méthode multi-objectifs dans la détermination de la résistance moyenne et la variabilité de la résistance, par rapport à d'autres approches. De plus, cette approche innovante permet d'obtenir une précision améliorée dans l'estimation des propriétés du béton avec un nombre réduit de prélèvements par rapport aux méthodes traditionnelles.En outre, l'efficacité de diverses stratégies d'échantillonnage suggérées a été évaluée dans cette étude afin de sélectionner les emplacements optimaux pour les extractions de carottes. Une représentation précise et approfondie de la structure examinée peut être obtenue en choisissant soigneusement les emplacements de carottage. À travers des comparaisons approfondies, l'étude vise à déterminer le plan d'échantillonnage qui correspond le mieux aux objectifs spécifiques de l'évaluation de la résistance du béton. Il est suggéré d'utiliser l'échantillonnage4 par optimisation de la variance, qui semble être une alternative appropriée pour réduire les incertitudes inhérentes au processus d'évaluation non destructive [...]
Understanding the in situ mechanical properties of concrete is essential for determining the structural capacity of both existing structures and new constructions. The recent methodology for assessing concrete strength in an existing structure involves integrating nondestructive testing (NDT) techniques with destructive measurements (coring) to establish a conversion model that correlates mechanical strength with nondestructive measurements. Subsequently, the conversion model is applied to estimate the local mechanical strength at each testing location based on the corresponding NDT values.The Rebound Hammer (RH) test and the Ultrasonic Pulse Velocity (UPV) test are widely used for estimating the compressive strength of concrete. However, the accuracy of the results obtained from these methods can be influenced by various factors. To mitigate these effects, the strategic combination of these two nondestructive tests provides an effective way to evaluate concrete strength in existing structures. Therefore, the aim of this thesis is to analyze the assessment methodology of structures by combining nondestructive techniques and to offer practical recommendations that can enhance the reliability of in-situ concrete strength. For this purpose, a simulator was developed to analyze the methodology of nondestructive assessment using an extensive dataset derived from various sources, including in-situ studies, as well as generated synthetic data.The primary contribution of this study is to propose a new model identification approach based on multi-objective optimization to predict the mean strength of concrete and its variability, based on the combination of NDT measurements. Monte Carlo simulations were carried out to check the performance by considering the uncertainty of NDT measurements and the variability of concrete. The results highlighted the effectiveness of the multi-objective method in determining both the average strength and the variability of strength compared to other approaches. Furthermore, this innovative approach enables enhanced accuracy in estimating concrete properties with a reduced number of cores compared to traditional methods.In addition, a thorough and accurate representation of the structure under examination can be achieved by carefully choosing the core locations. The efficacy of various suggested sample strategies has been evaluated in this study in order to select the optimal locations for the core extractions. Through these thorough comparisons, the study aims to discover the sampling plan that best aligns with the specific objectives of evaluating concrete strength. It is suggested to use variance sampling, which appears to be a suitable alternative for reducing inherent uncertainties in the nondestructive assessment process [...]

The master‘s thesis focuses on testing the shotcrete prepared in laboratory conditions. The main observed properties are compresive strenght of shotcrete and modulus of elasticity. The aim is assessment of methods for measuring those parameters. The calibrating correlations for strenght characteristics of shotcrete are given by obtaining the results of used methods. The shotcrete composition, amount and type of accelerating additive as well as economic aspect of using shotcrete is also assessed.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
102
Using Non-destructive testing methods to examine the compressive strength of the concrete is quite economic and feasible. The Rebound Hammer Test is one of the most popular Non-destructive testing for measuring concrete strength in the industry. However, when compare with the actual concrete strength, the Rebound Hammer Testing results have over 20% mean absolute percentage error.As a result, the CNS 10732 standard suggests Rebound Hammer Test only be used to assess the uniformity and probable strength of concrete. It could not be used for alternative method for assessing the strength of the concrete. In view of this, this research intended to use support vector machine (SVMs) as the main artificial intelligence prediction method. In addiction artificial neural networks (ANNs) and adaptive neural fuzzy inference systems (ANFIS) are applied for comparison as well. The data is collected from 838 Silver Schmidt electronic hammer lab tests to develop a prediction model and predictive analysis. Then calculate the mean absolute percentage error to determine the prediction ability of compressive strength predictive model. The objective is establish the prediction model suitable for the rebound hammer test and to improve its accuracy. The results show that the mean absolute percentage errors (MAPE) for SVMs prediction model was 6.76%, however ANNs and ANFIS models have mean absolute percentage error of 7.27% and 6.82%, all of them can effectively improve the reliability of the prediction strength. It is recommended that the artificial intelligence prediction models can be applied in the Silver Schmidt Rebound Hammer Tests to improve the prediction accuracy.

碩士
逢甲大學
土木及水利工程所
90
To obtain as well as examine a field concrete strength, it is quite common to take it for grant that the best representative data is obtaining from the compression strength test of a set of drilled cores from the field site. Because this method may cause some damages to a structure, also it is a time-consuming and expensive process. People usually use this method as the last resort. Instead, nondestructive instruments are provided as daily or routine means to detect the compression strength and the status of a construction site. Among those available nondestructive method for inspecting the concrete strength of a structure, the rebound hammer test may be the best choice. However, due to the limitations and some defects existed in a hammer, accurate as well as confident testing results are still in dispute nowadays. In order to examine the usefulness and accuracy of the hammer test results, this study goes though detail tests in eight new construction sites. Not only hammer tests are applied on selected structures, sonic information is recorded down in every test, and drilled core samples are obtained in field for further compression strength tests on lab. This study did find out some important factors affect the rebound number in a test. Also, the correlated relationships between time domain sonic waves and the associated rebound number are provided and discussed.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
103
In the construction industry, using non-destructive testing (NDT) methods for examine the compressive strength of the concrete is quite economic and feasible, without damaging the structure. One of the most common NDTs for measuring the concrete compressive strength on site is The Rebound Hammer Test. Rebound hammer has some advantage like the costs are low, operate easier and convenient to carry. But, rebound hammer test estimations have an average of over 20% mean absolute percentage error when comparing to the compressive strength obtained by destructive the tests. In light of this, this research proposes using Support Vector Machine (SVM) and Bootstrap to obtain the concrete compressive strength by the rebound value from the test hammer, to develop a prediction model for concrete compressive strength estimation. This research expected upgrading the predictive ability of rebound hammer test. Research data adopt Shih-Shian Wei (2012) the 838 lab concrete Rebound Hammer tests, the data are collected to train and validate by applying the SVM and the Bootstrap model, then compare the prediction results. The results shows that the SVM model and the bootstrap model prediction results have successfully reduced the average mean absolute percentage error to 8% below. It is confirm that SVM and Bootstrap can be applied to rebound hammer test results. The research results can provide a reference, when the destructive tests unable to use. It is effectively improve the reliability of the non-destructive testing (NDT) prediction strength. Also, reduce the trouble of core-drilling methods, avoid the structure damaging and the building exterior.

碩士
國立中興大學
土木工程學系
94
Rebound hammer is widely used for evaluation of concrete quality in the construction industry due to its simplicity and ease of operation. The objective of the thesis is to study the application of the rebound hammer to pozzolanic concrete. The mixture proportions of concrete used in the studies include various water/binder ratios (W/B) ranging from 0.54 to 0.69. Fly ash and slag were used to equally substitute 30% of cement. A total of 30 mixture proportions were used to construct concrete cylinders as specimens and a series of rebound and compressive tests were performed on these specimens. The compressive strength of the specimens ranged between 210 and 420 kgf/cm2. The relationship between the rebound number and compressive strength of concrete was established. Experimental results show that the correlation between the rebound number and strength is good for each mixture proportion. To make practical application convenient, a combination of the experimental data for various mixture proportions was adopted to propose a more general relationship curve. The relationship curve was used to estimate the strength of each concrete cylinder according to its rebound number. The difference between the estimated value and the real strength was within 15%. Two plate-like specimens were made with W/B ratios of 0.64 and 0.57 respectively and two kinds of curing conditions including wet and dry curing were considered. The rebound tests were carried out on the wet and dry plate-like specimens. It is found that the rebound number for the dry specimen is higher than that for wet specimen. According to literature, a reduction factor of 20% was used to account for this difference. The Danish statistical method proposed by ACI 228 was adopted to evaluate the ten-percentile strength of the concrete plates. Experimental results show that 90% of the cores have the compressive strength higher than the estimated value by Danish method and the lowest strength among all the cores is close to the estimated value.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
95
The compressive strength is regarded as one estimated indicator of the concrete quality. Generally, we pick compressive specimens and core specimens to estimate the whole quality of structure. If estimating the true quality of concrete by some nondestructive test method that not only does not damage the structure, but can monitor overall for a long time. The first part of this research is to establish the related equation between nondestructive testing and compressive strength of concrete; the second part, put the testing value of the in-place concrete into this equation, then count out the calculated compressive strength, and compare it with real one, finally discuss the feasibility of nondestructive testing to estimating strength. The experimental project mainly includes the ultrasonic wave propagation velocity measurement, rebound hammer, electrical resistivity, compressive strength testing, rapid chloride ion penetration test, Field emission scanning electron microscope (FE-SEM). The results show that the model established by nondestructive techniques using ultrasonic pulse velocity, rebound hammer count and compressive strength, has high degree of relevancy. The compressive strength can be calculate with error of ±10％ and +20％ respectively. It’s referable to calculate the compressive strength with the two methods of nondestructive test. With increasing age, the hydrate fill paste pore and then make concrete dense, increase electrical resistivity , lower the permeability of chloride ions.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
105
Using the Rebound Hammer Method to test the compressive strength of concrete is one of the most convenient non-destructive testing (DNT) methods. It will not damage the existing structure and can obtain the results immediately. The Artificial Intelligence methods, such as SVMs, ANNs and ANFIS, are successfully applied in different fields. Previous researches on concrete compressive strength mainly used concrete cylinder samples in the lab. It is the goal of this research to develop a compressive strength prediction model that will work for both lab and on site Rebound Hammer Tests. A total of 100 on site Rebound Hammer Test data are obtained from a residential building in New Taipei City. The data are used to build and test the proposed ANNs, SVMs and ANFIS models. The prediction results are compared with core sample destructive test results and the difference is measured in MAPE. Also, the developed model will be tested using the lab sample data collected by Wei (2012). For data collected in the existing residential building, the analysis results show that the MAPE were 15.66% and 16.75% in the linear and nonlinear predictive model established by regression analysis. And the prediction models established by SVMs, ANNs and ANFIS yield the MAPE’s of 16.08% , 18.67% and 10.01%, respectively. At last, using the 2012 data from the lab to feed in the prediction model established, the results show that the average MAPE was 14.8% and 11.33% in the linear and nonlinear predictive model established by regression analysis. And the MAPE’s for SVMs, ANNs and ANFIS models are 20.12%, 18.67% and 15.88%, respectively.

碩士
國立嘉義大學
土木與水資源工程學系研究所
96
The main purpose of this article is to research how to increase the precision of concrete Rebound Hammer Test. There are many factors which influences the strength of concrete including amounts of coarse or fine aggregate, water-cement ratio, amounts of cement, curing period, maintenance, slump, and design strength etc. Although the national quality control system uses the compressive strength of 28 days curing cylindrical specimen as the qualified standard, the representation of the at-site specimens are still debatable. Nowadays the technologies of non-destructive inspection and instruments have been improved and become more popular. The Rebound Hammer Test has the characteristics of easy to take and acquiring results quickly, so it could replace the Drilled Specimen Test further. The test results of rebound hammer always show trends of poor data precision through regression analysis. This research studies that by the utilization of artificial neural network training increasing the precision of the Rebound Hammer Test. In this research we had collected 168 data of rebound hammer and compressive test and 48 verified data additionally. Applying different models of regression including linear, logarithmic, polynomial, power, and exponential, we had found that the bias of the logarithmic regression equation had lowest standard deviation. Its value was 24.07% and 27.36% respectively. For the sake of lowering standard deviation, in this research we utilized artificial neural network program QwikNet ver.2.23 to train and analysis the data. Firstly, by linear analysis we acquired the standard deviation of bias 13.18% and 18.69% respectively. Secondly, by non-linear analysis we acquired the standard deviation of bias 7.45% and 7.64% respectively. Comparing the three analysis results above, the artificial neural network non-linear analysis has the best result. So we have proved that the artificial neural network analysis could increase the precision of the Rebound Hammer Test.

碩士
國立高雄應用科技大學
土木工程與防災科技研究所
104
Abstract In the Rebound Hammer Test, the hammer rebound value can be used to estimate the concrete compressive strength. To prevent error, cautions should be taken regarding the angle of the hammer stroke, smoothness and thickness of the testing surface, etc., when conducting the test Previous researches have shown that support vector machine (SVMs) 、artificial neural networks (ANNs) and adaptive neural fuzzy inference systems (ANFIS) are effective artificial intelligence (AI) prediction methods. And they are successfully adopted in various fields. Therefore, this research would like to adopt these three AI techniques to develop concrete compressive strength prediction models for the rebound hammer test. In light of this, Rebound Hammer test results (315 samples) are obtained from a material testing la in Chia-Yi to develop and validate the AI prediction models. Also, the prediction models will be applied to the test data (838 samples) obtained from Shih-Shian Wei (2012) to determine if the prediction model is still effective when adopting data from other test labs. The results show that ANFIS prediction model yields the best result, with the mean absolute percentage errors (MAPE) of 6.76%. In the mean time, Linear Regression, SVMs and ANNs models have mean absolute percentage error between 8%~9%. When adopting the linear regression equations from previous researches, the MAPE’s were around 10~70%. If the obtained models are validated using the test sample data from Wei (2012), the MAPE for ANFIS prediction model was 18.61%. And the MAPE’s for Linear Regression, SVMs and ANNs models are between 19%~21%. For the collected sample, the research results have shown that prediction models obtained from one testing lab is not effective when validated with test samples from other labs. Keyword：Non-destructive testing, Rebound Hammer Test, Support Vector Machine, Artificial Neural Networks, Adaptive Neural Fuzzy Inference Systems

碩士
國立中興大學
土木工程學系所
95
A strength-evaluation technique for ready-mixed soil material (RMSM) was derived from the penetration resistance method for concrete (ASTM C803). A modification of the penetration method was made to be applicable to low-strength RMSM. In order to improve the durability and practical application of RMSM, recycled coarse aggregates were added into RMSM. The strength-evaluation technique for RMSM does not need to take into account the effect of coarse aggregates. Thus, there is a need to investigate the capability of the original nondestructive technique for evaluating the strength of the RMSM containing coarse aggregates. In this thesis, the penetration method and rebound hammer method were used as the in-place strength evaluation method for RMSM containing recycled coarse aggregates and investigates these two method’s applicability. Six different RMSM mixtures including recycled coarse aggregates were considered, and the compressive strength ranges between 50 and 160 kgf/cm2. The nondestructive and compressive tests were performed at six different ages. The relationship between the exposed length of the penetration pin and the compressive strength of RMSM containing recycled coarse aggregates was established. Similarly, the relationship between the rebound number and the compressive strength of RMSM containing recycled coarse aggregates was also established. Then, three different mixtures were used to make plate specimens for verifying the fore-mentioned relationships. The rebound hammer used in the studies is not suitable for RMSM with the relatively low strength mixtures. All the regression results have R-squared values more than 0.9. The verification results show that the strengths estimated by using regression results of the fore-mentioned relationships are consistent with the compressive strength of cores and the difference between the estimated strength and core strength is below 16 percent. It is concluded that the probe penetration method and rebound hammer method are applicable to evaluate the strength of RMSM containing recycled coarse aggregates.

iv Summary Schmidt hammer is the instrument which is used for the assessment of rock mechanical properties and this instrument is classified as the indirect method. This method is based on the assessment of rebound value (R) of the Schmidt hammer, which is measurred by the amount of rebound of the impact plunger from the surface of tested rock. Schmidt hammer is called as the non-destructive method of rock assessment and it is called as in situ testing method as well. The main objective of this work is provement, that Schmidt hammer testing is destructive method and define degree of damage which is caused in the rock mass. Sedimentary rocks were used for the testing, mostly sandstones and arkose sandstones with different types of cement. This made it possible to test the fraction of the rock mass and the relation between fraction and type of cement. The clasts of the rocks had different properties than it was possible to find the relation between grain size and fraction of the rock. Already in procedure of the testing by Schmidt hammer it was obvious, that this metod is definitely destructive. Rock surface after hitting by plunger of Schmidt hammer gains macroscopically observeable destruction. On the surface is the circular track of the plunger and the surface is grinded. It is possible to wipe the small...

There has been increasing interest in evaluating the performance of existing reinforced concrete (RC) bridges just after natural disasters or man-made events especially when the defects are invisible, or in quantifying the improvement after rehabilitations. In order to obtain an accurate assessment of the reliability of a RC bridge, it is critical to incorporate information about its current structural properties, which reflects the possible aging and deterioration. This dissertation proposes to develop an adaptive reliability analysis of RC bridges incorporating the damage detection information obtained from nondestructive testing (NDT). In this study, seismic fragility is used to describe the reliability of a structure withstanding future seismic demand. It is defined as the conditional probability that a seismic demand quantity attains or exceeds a specified capacity level for given values of earthquake intensity. The dissertation first develops a probabilistic capacity model for RC columns and the capacity model can be used when the flexural stiffness decays nonuniformly over a column height. Then, a general methodology to construct probabilistic seismic demand models for RC highway bridges with one single-column bent is presented. Next, a combination of global and local NDT methods is proposed to identify in-place structural properties. The global NDT uses the dynamic responses of a structure to assess its global/equivalent structural properties and detect potential damage locations. The local NDT uses local measurements to identify the local characteristics of the structure. Measurement and modeling errors are considered in the application of the NDT methods and the analysis of the NDT data. Then, the information obtained from NDT is used in the probabilistic capacity and demand models to estimate the seismic fragility of the bridge. As an illustration, the proposed probabilistic framework is applied to a reinforced concrete bridge with a one-column bent. The result of the illustration shows that the proposed framework can successfully provide the up-to-date structural properties and accurate fragility estimates.