Debido al crecimiento continuo que se tiene cada año del consumo del concreto como primer material de construcción, resulta de gran ayuda contar con distintos métodos no destructivos que nos permitan conocer, de una manera rápida y sencilla, la resistencia del concreto. Uno de los métodos no destructivos es el índice esclerométrico, que consiste en determinar nivel de compacidad de las partículas del concreto. Durante años se han hecho distintos estudios para correlacionar el índice esclerométrico y la resistencia del concreto, hallando altos niveles de relación; sin embargo, dichos estudios no toman en cuenta la edad del concreto ni el tipo de piedra que se utiliza en la mezcla, siendo parámetros que no resultan ajenos al ensayo de esclerometría. Por ello, la siguiente investigación propone el ensayo de dureza superficial (esclerometría) como un método confiable para la determinación de la resistencia del concreto analizando distintas muestras de acuerdo a su edad y tamaño máximo nominal. Estos factores serán analizados y serán almacenados en una base de datos en la que serán separados según su característica, generando distintos gráficos de regresión lineal para así aumentar el índice de confianza de correlación de Pearson. / The use of concrete as a primary construction material has seen steady increase year after year, which is why it is imperative to have at our disposal different non-destructive methods for quick and easy determination of its resistance. Once non-destructive method is the sclerometric index, which determines the level of compactness of the concrete particles. Various studies over years have found the sclerometric index to be highly correlated to concrete resistance. Nevertheless, these studies didn’t correct for factors such as the age and composition of the concrete mixture, both of which greatly influence sclerometry. They aim of this study was to determine whether superficial hardness testing (sclerometry) is an appropriate method for measuring concrete resistance, by analyzing samples of distinct age and maximum nominal size. These factors were analyzed and stored in a database which generated linear regression graphs, thereby improving the confidence interval for the Pearson correlation coefficient. / Tesis

Prestressed Concrete Cylinder Pipe (PCCP) is a large-diameter and high-pressure conduit for drinking water and wastewater transmission. Due to its large diameter, high pressure, and mode of breakdown, PCCP failures usually have catastrophic consequences. To mitigate failures, it is very important to assess the condition of the pipe and take proactive measures, such as repair, rehabilitation, or replacement. There are many challenges in assessing the condition of PCCP. PCCP has a complex structure with several layers of materials (e.g. mortar coating, prestressing wire, steel cylinder, and concrete core) working together under loading. This means that there are many factors that can cause pipe failure, and that failure mechanisms are complicated. Data collection could be difficult, and existing data are often unavailable or unreliable. Considerable research has been conducted by scholars and engineers in developing models to evaluate the condition of PCCP. There are mainly two types of models: statistical models, and numerical models using finite element method. Statistical models consider only a few factors, such as pipe age and failure rate, to predict the failure of PCCP. However, the failure of PCCP can be caused by many other factors including pipe material, and loading conditions. Models only considering a few factors are not robust enough for reliable results. The current numerical models assume that all broken wires are centrally distributed in the same location and broken wires have no prestress, thus all broken wires are completely removed from the model. These assumptions could be overly conservative when actual broken wires are distributed in different locations along the pipeline and broken wires have remaining prestress due to the bond between the wire and mortar coating. Therefore, a more comprehensive numerical model is needed to have a better understanding of the condition of PCCP. In this research, an extensive literature and practice review was conducted on PCCP failures to understand the critical factors that affect pipe condition. The available technologies commonly used to detect pipe defects were reviewed in order to better understand the accuracy and uncertainties of the collected data. Existing models were reviewed to better understand their limitations and to advance the research on condition analysis of PCCP using numerical models. Based on these comprehensive reviews, this dissertation proposed a numerical model to analyze the condition of PCCP for its long-term performance management. Detailed structural components such as concrete cores, prestressing wires, steel cylinder, and mortar coating were modelled. The interactions between different layers of pipe components were considered. An algorithm was proposed to account for the bond between the prestressing wire and mortar coating, which is a critical factor for the condition of PCCP with broken wires. A FORTRAN program was developed to assign linear stress distribution between the broken point and the full-prestress resuming point. The proposed numerical model was verified utilizing data from lab tests and forensic study. Lab test data helped to understand the functionality of the model and to verify the model parameters used in analyzing pipe components and the simulation of interactions between different layers. The forensic data helped to verify the model under actual field working conditions of the pipe. Validation of the proposed numerical model was conducted using a 66-inch Embedded Cylinder Pipe and two Lined Cylinder Pipes (42-inch and 48-inch, respectively) from a water utility. In the validation, field data were collected for model development. The simulation results were consistent with the field observation, which proved the validity and applicability of the proposed numerical model in practice. A series of sensitivity studies were conducted to investigate the impact of longitudinal and circumferential location on the structural integrity of the pipe. These investigations showed that considering the actual longitudinal and circumferential location of broken wires is very important to get accurate analysis of pipe condition, while assuming that all broken wires fail in one longitudinal location (assumptions by current numerical models for PCCP) will overestimate the actual damage to the pipe caused by broken wires. To consider the bedding condition, a critical factor for PCCP, the four most common bedding types found in practice were analyzed. Results show that poor bedding could lead to cracks in PCCP, which could cause corrosion in prestressing wires. Therefore, it is very important to account for bedding conditions in the PCCP analysis. The model presented in this dissertation is more comprehensive and robust compared with existing numerical models, and could provide a better understanding of the condition of PCCP. This is because the proposed model considers the contribution of remaining prestress in broken wires due to the bond between the wire and mortar coating. This model can consider the actual longitudinal and circumferential location of broken wires rather than centrally distribute them, and it can consider the actual bedding locations, and the interaction between different layers of materials. This model was calibrated using lab test data and forensic data, and was further validated using field data which showed consistence between simulation results and field observations. The proposed model does have limitations due to limited availability of data and assumptions. Material tests were not conducted to verify the material properties used in the model, which could cause accuracy issues in the results. A full-scale simulation of the interaction between prestressing wire and mortar coating was not considered because it could significantly increase the computation time. Lab tests were not conducted to verify the parameters used for the simulation of interaction between concrete core and steel cylinder which could lead to accuracy problems. Finally, it is acknowledged that the model was only validated in one water utility and validations in more geographically distributed utilities might further test the model's validity and robustness. Nonetheless, the comprehensiveness and robustness of this proposed model improved the analysis of the condition of PCCP. The findings and results of this research will provide guidance for better management of PCCP pipelines for water utilities, and provide reference for future research on numerical modeling of PCCP as well. / Ph. D.

Diploma thesis is focused on the description of the parameters of nonlinear material models of concrete, which are implemented in a computational system LS-DYNA, interacting with performance of nonlinear test calculations in system LS-DYNA on selected problems, which are formed mainly by simulations of tests of mechanical and physical properties of concrete in uniaxial compressive and tensile on cylinders with applying different boundary conditions and by simulation of bending slab, with subsequent comparison of some results of test calculations with results of the experiment. The thesis includes creation of appropriate geometric models of selected problems, meshing of these geometric models, description of parameters and application of nonlinear material models of concrete on selected problems, application of loads and boundary conditions on selected problems and performance of nonlinear calculations in a computational system LS-DYNA. Evaluation of results is made on the basis of stress-strain diagrams and load-displacement diagrams based on nonlinear calculations taking into account strain rate effects and on the basis of hysteresis curves based on nonlinear calculations in case of application of cyclic loading on selected problems. Verification of nonlinear material models of concrete is made on the basis of comparison of some results of test calculations with results obtained from the experiment.