Integridad estructural

¿Cómo garantizar que nuestras estructuras son seguras y fiables? El conocimiento preciso del comportamiento de un elemento estructural cuando contiene defectos resulta imprescindible para la correcta predicción de su funcionamiento y su vida útil.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Comportamiento dinámico de sólidos transversalmente isótropos

XII Congreso Nacional de Ingeniería Mecánica, celebrado en Bilbao en 1997La formulación del problema dinámico en medios homogéneos y elásticolineales se reduce a un conjunto de Ecuaciones Integrales de Contorno. & t a s ecuaciones se resuelven numéricamente, en el dominio de la frecuencia, mediante el Método de los Elementos de Contorno. Para ello resulta necesario el conocimiento de una solución fundamental (i.e., respuesta de un medio infinito a la aplicación de una carga concentrada armónica) que pueda ser eficientemente implementada en un programa de Elementos de Contorno. En este trabajo se presentan resultados, correspondientes a la difracción de ondas por una cavidad irunersa en un sólido transversalmente isótropo, obtenidos empleando la solución fundamental de Wang y Achenb.lch (1995) y las expresiones asintóticas de Buchwald (1959) para campo lejano

Motion-Based Design of Passive Damping Devices to Mitigate Wind-Induced Vibrations in Stay Cables

Wind action can induce large amplitude vibrations in the stay cables of bridges. To reduce the vibration level of these structural elements, different types of passive damping devices are usually installed. In this paper, a motion-based design method is proposed and implemented in order to achieve the optimum design of different passive damping devices for stay cables under wind action. According to this method, the design problem is transformed into an optimization problem. Thus, its main aim is to minimize the different terms of a multi-objective function, considering as design variables the characteristic parameters of each considered passive damping device. The multi-objective function is defined in terms of the scaled characteristic parameters, one single-function for each parameter, and an additional function that checks the compliance of the considered design criterion. Genetic algorithms are considered as a global optimization method. Three passive damping devices have been studied herein: viscous, elastomeric and friction dampers. As a benchmark structure, the Alamillo bridge (Seville, Spain), is considered in order to validate the performance of the proposed method. Finally, the parameters of the damping devices designed according to this proposal are successfully compared with the results provided by a conventional design method

A crowd-structure interaction model to analyze the lateral lock-in phenomenon on footbridges

In this paper a simplified biomechanical crowd-structure interaction model is proposed and validated in order to analyse the lateral lock-in phenomenon on real footbridges. The proposed crowd-structure interaction model is organized in three levels: (i) pedestrian-structure interaction; (ii) interaction among pedestrians in the crowd; and (iii) interaction between the crowd and the structure. To this end, first, the human-structure interaction of each pedestrian is modelled via a simplified two degrees of freedom system. Second, the interaction among pedestrians inside the crowd is simulated using a multi-agent model. The considered model simulates the movement of each pedestrian from the dynamic equilibrium of the different social forces that act on him/her. Finally, the crowd-structure interaction is achieved modifying the behaviour of the pedestrians depending on the comfort level experienced. For this purpose, the recommendations established by the French standards have been considered. The integration of the three levels in an overall model is achieved by the implementation of a predictive– corrective method. The performance of the proposed model is validated correlating the numerical and experimental dynamic response of the Pedro e Inês footbridge during the development of a lateral lock-in pedestrian test. As the first lateral natural frequency of the footbridge is inside the range that characterizes the walking pedestrian step frequency in lateral direction, numerical and experimental studies were performed to analyse its behaviour under pedestrian action. The agreement between the numerical and experimental results is adequate. However, further studies are recommended in order to generalize the proposed approach and facilitate its use during the design project of future footbridges.Ministerio de Ciencia DPI2014-53947-

Effect of Vinyl Flooring on the Modal Properties of a Steel Footbridge

Damping ratios associated with non structural elements play an important role in mitigating the pedestrian-induced vibrations of slender footbridges. In particular, this paper analyses the effect of vinyl flooring on the modal parameters of steel footbridges. Motivated by the unexpected high experimental damping ratios of the first vibration modes of a real footbridge, whose deck was covered by a vinyl flooring, this paper aims at assessing more accurately the experimental damping ratios generated by this non-structural element on steel footbridges. For this purpose, a laboratory footbridge was built and vinyl flooring was installed on it. Its numerical and experimental modal parameters without and with the vinyl flooring were determined. The operational modal analysis method was used to estimate experimentally the modal parameters of the structure. The damping ratios associated with the vinyl flooring were obtained via the substraction between the experimental damping ratios of the laboratory footbridge with and without the vinyl flooring. An average increase of the damping ratios of 2.069% was observed due to the vinyl flooring installed. According to this result, this type of pavement may be a useful tool to significantly increase the damping ratios of steel footbridges in order to reduce pedestrian-induced vibrationsMinisterio de Economía y Competitividad DPI2014-53947-RFondo Europeo de Desarrollo Regional DPI2014-53947-

Estimating robust optimum parameters of tuned mass dampers using multiobjective genetic algorithms

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.Tuned mass dampers (TMD) are a well-known control device widely used to control the vibratory problem originated by the pedestrian action on footbridges. The main purpose of this study is the robust multi-objective optimization design of a TMD using genetic algorithms to control the structural vibrations of a footbridge due to the pedestrian action. The performance of the TMD has been improved designing optimally its parameters, including, mass, stiffness and damping ratio using multiobjective genetic algorithms. Moreover, in order to take into account the uncertainties existing in the system, a robust design optimization procedure has been performed. As an example, a slender steel footbridge, modelled by 3-D frame elements, is used to assess numerically the performance and accuracy of the proposed method. The pedestrian action has been simulated by an equivalent harmonic force. The proposed approach is compared with the classical Den Hartog's proposal. This comparison shows that this approach is more effective than the classica l reported method and more feasible due to the smaller TMD parameters

Problemas antiplanos de mecánica de la fractura en materiales anisótropos

XV Congreso nacional de Ingeniería Mecánica, celebrado en Cádiz en 2002Se presenta la formulación mixta del Método de los Elementos de Contorno (MEC) para problemas de mecánica de fractura antiplanos en medios anisótropos. Se implementan las ecuaciones integrales (El) en desplazamientos y en tracciones. Las integrales hipersingulares asociadas a la El en tracciones se evalúan mediante un cambio de variable que permite su descomposición en integrales singulares con solución analítica conocida e integrales regulares de fácil integración numérica. Se consideran las soluciones fundamentales para plano completo y para semiplano.Ministerio de Ciencia y Tecnología DPI2000-12 l 7-C02-0

Análisis y diagnóstico de la Iglesia de Santiago en Jerez de la Frontera (España)

The church of Santiago (Jerez de la Frontera, Spain) has its origin in a small chapel built in the XIII century. Three naves added in the XV century gave rise to the current temple. The church has been modified along the history due to two main reasons: (i) the interest for its enlargement and embellishment and (ii) to solve some structural problems documented since the XVII century. The most relevant problems that have affected the structure can be summarized in two partial collapses (1695 and 1956) and the substitution of two columns (1902 and 1928) to prevent new catastrophes. However, at the beginning of the XXI century important damage in columns and walls caused to close the temple and initiate an ample investigation on the church and its structural behaviour. The conclusions of this analysis, together with a preliminary proposal for restoration, are the main goal of this paper.La Iglesia de Santiago (Jerez de la Frontera, España) tiene su origen en una pequeña capilla del siglo XIII. En el siglo XV se le añadieron tres naves, dando como resultado el templo actual. La Iglesia se ha modificado en determinadas ocasiones debido principalmente a: (i) el interés por ampliarla y embellecerla y (ii) solucionar algunos problemas estructurales documentados desde el siglo XVII. De estos últimos, los más relevantes en relación a la estructura pueden resumirse en dos colapsos parciales (1695 y 1956) y la sustitución de dos pilares (1902 y 1928) para evitar otras dos catástrofes. Al inicio del siglo XXI, la nueva aparición de daños en pilares y muros condujo al cierre del templo y al inicio de una investigación sobre el comportamiento estructural de la iglesia. Las conclusiones de este análisis, junto a una propuesta preliminar para su reparación, constituyen el objetivo principal de este artícul

Unified Model of Linear and Nonlinear Crosstalk in Multi-Core Fiber

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.In this paper, the theoretical unification of linear and nonlinear inter-core crosstalk (IC-XT) in step-index single-mode multicore fiber (MCF) media is reported and validated experimentally. In order to estimate the IC-XT when operating in linear and nonlinear regimes, the coupled-mode theory (CMT) and the coupled-power theory (CPT) have been unified in both power regimes. The theoretical analysis of the CMT indicates that in coupled MCFs with reduced core-to-core distance (core pitch) the nonlinear self-coupling and cross-coupling effects should be considered when operating with high optical powers. However, considering a core pitch value higher than three times the core radius only the self-coupling effect should be taken into account for estimating the nonlinear IC-XT. Considering these results, the CPT is also extended to nonlinear regime including the dominant nonlinear coupling effect. Using both CMT and CPT, the statistical model of nonlinear IC-XT is completed with the closed-form expressions for estimating the cumulative distribution function, the probability density function and the crosstalk mean and variance as a function of the power level launched into a single-core of the MCF. The crosstalkmodel presented is additionally extended when multiple cores are simultaneously excited. Finally, the theoretical model is experimentally validated in a homogeneous four-core fiber considering different bending radius configurations.This work was supported by Spain the National Plan Project TEC2015-70858-C2-1-R XCORE and RTC-2014-2232-3 HIDRASENSE. The work of A. Macho was supported by BES-2013-062952 F.P.I. Grant. M. Morant was partly supported by UPV postdoc PAID-10-14 program.Macho-Ortiz, A.; Morant Pérez, M.; Llorente Sáez, R. (2016). Unified Model of Linear and Nonlinear Crosstalk in Multi-Core Fiber. Journal of Lightwave Technology. 34(13):3035-3046. https://doi.org/10.1109/JLT.2016.2552958S30353046341

Next-Generation Optical Fronthaul Systems Using Multicore Fiber Media

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.This paper proposes and investigates the use of multicore fiber (MCF) media performing space-division multiplexed transmission for next-generation optical fronthaul systems. We report the experimental demonstration of combined radio-over-fiber (RoF) transmission of full-standard LTE-Advanced (LTE-A) and WiMAX signals providing fronthaul connectivity in 150m of 4-core fiber (4CF), transmitting simultaneously fully independent wireless services. Operating in linear and nonlinear optical power regimes, the experimental evaluation verifies that the error vector magnitude (EVM) is not degraded when intercore and intracore Kerr nonlinearities are excited in MCF with high input power levels. As a result, nonlinear regime is proposed as a key factor to reduce the temporal EVM fluctuation induced by the random nature of the intercore crosstalk in MCF. In addition, MCF fronthaul applied to converged fiber-wireless polarization multiplexed passive optical networks is demonstrated to transmit LTE-A and WiMAX signals over two orthogonal optical polarizations. The polarization-multiplexed signal is transmitted in RoF over 25.2 km of standard single-mode fiber and then demultiplexed and injected in different cores of the 4CF to provide fronthaul connectivity. Finally, the extension of multicore optical fronthaul capacity is proposed using MIMO LTE-A signals. The tolerance of the MIMO LTE-A RoF transmissions to in-band crosstalk is reported and compared to single-input single-output (SISO) configuration. The experimental results indicate that MIMO configuration is more tolerant than SISO to in-band crosstalk considering both internal and external interferences. MIMO and SISO configurations are compared when transmitted in RoF over a 4CF operating in linear and nonlinear regimes and core interleaving nonlinear stimulation is proposed to reduce the temporal and spectral EVM fluctuation when the same wireless standard is propagated in each core.This work was supported in part by Spain the National Plan Project XCORE TEC2015-70858-C2-1-R and RTC-2014-2232-3 HIDRASENSE. The work of A. Macho was supported by BES-2013-062952 F.P.I. Grant. The work of M. Morant was supported in part by UPV postdoc PAID-10-14 program.Macho-Ortiz, A.; Morant Pérez, M.; Llorente Sáez, R. (2016). Next-Generation Optical Fronthaul Systems Using Multicore Fiber Media. Journal of Lightwave Technology. 34(20):4819-4827. https://doi.org/10.1109/JLT.2016.2573038S48194827342