Parametric study on a Bouc-Wen model with degradation features for the study of cyclic behavior of a reinforced concrete frame

Non-linear behavior in building frame structures is inevitable and expected in moderate to severe seismic events. This behavior tends to be concentrated at the ends of beams and columns of moment-resisting frames. These critical regions, where plastic hinges form, are important for the global stability of the structural system. Depending on the available ductility, these mechanisms are responsible for the permanent deformations that the structure undergoes, leaving the remaining parts of the structural elements in the elastic regime, and hence in the safe zone. The importance of these mechanisms led to the search for an adequate model capable of well-capturing the non-linearity phenomena involved. The development of versatile hysteresis models with degradation features has been the aim of different studies. Hence, this paper presents a parametric study based on a smooth hysteresis model, a further modification to the well-known Bouc-Wen model, developed by Sivaselvan and Reinhorn, with a physical interpretation appropriate to the study of the non-linear behavior of civil engineering structures, particularly, building structures. Furthermore, an optimization procedure is implemented to calibrate the mentioned model’s parameters, attempting to replicate the actual cyclic response of a reinforced concrete frame structure. The effect of each parameter in the hysteresis response will help on the understanding and on the possibilities of this kind of model in simulating different types of structural systems or different materials.This paper is within the scope of the first author’s Ph.D. degree in progress, financially supported by the Portuguese Foundation for Science and Technology (FCT) through the PhD grant reference SFRH/BD/139570/2018 under the programme POCH (N2020-P2020) and subsidized by the European Social Fund (FSE) and national funds from MCTES. This work was financially supported by: Base Funding- UIDB/04708/2020 of the CONSTRUCT-Instituto de I&D em Estruturas e Construções-funded by national funds through the FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Cyclic response of a reinforced concrete frame: comparison of experimental results with different hysteretic models

An accurate hysteresis model is fundamental to well capture the non-linearity phenomena occurring in structural and non-structural elements in building structures, that are usually made of reinforced concrete or steel materials. In this sense, this paper aims to numerically estimate through simplified non-linear analyses, the cyclic response of a reinforced concrete frame using different hysteretic models present in the literature. A commercial Finite Element Method package is used to carry out most of the simulations using polygonal hysteretic models and a fiber model, and additionally, a MATLAB script is developed to use a smooth hysteresis model. The experimental data is based on the experiments carried out in the Laboratório Nacional de Engenharia Civil, Portugal. The numerical outcomes are further compared with the experimental result to evaluate the accuracy of the simplified analysis based on the lumped plasticity or plastic hinge method for the reinforced concrete bare frame. Results show that the tetralinear Takeda’s model fits closely the experimental hysteresis loops. The fiber model can well capture the hysteresis behavior, though it requires knowledge and expertise on parameter calibration. Sivaselvan and Reinhorn’s smooth hysteresis model was able to satisfactorily reproduce the actual non-linear cyclic behavior of the RC frame structure in a global way.This paper is within the scope of the first author’s Ph.D. degree in progress, financially supported by the Portuguese Foundation for Science and Technology (FCT) through the PhD grant reference SFRH/BD/139570/2018 under the programme POCH (N2020-P2020) and subsidized by the European Social Fund (FSE) and national funds from MCTES. This work was financially supported by: Base Funding- UIDB/04708/2020 of the CONSTRUCT-Instituto de I&D em Estruturas e Construções-funded by national funds through the FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Mechanical analysis of PDMS material using biaxial test

Polydimethylsiloxane (PDMS) materials are classified as a silicone and commonly present a hyperelastic behaviour. Many researchers have studied PDMS in recent years, motivated by its applications in the biomedical field. In the present manuscript, a biaxial tensile test performed at different speeds is described. The displacement field for the different experimental test conditions is measured using the digital image correlation technique. Numerical studies were also carried out using the most popular constitutive models, namely Mooney-Rivlin, Yeoh and Ogden, for comparison with the experimental measurements. From the experimental displacement profile taken along the central section of each sample, that this tensile test presents linear behaviour; it is an independent speed test. The same conclusion can be found from the numerical results. The results of the numerical simulation show that they are strongly dependent on the constitutive model of the material. The numerical simulations with the Yeoh model presented the most accurate results for PDMS behaviour. Another important conclusion is that the digital image correlation technique is well suited for the analysis of hyperelastic materials.info:eu-repo/semantics/publishedVersio

Fuzzy controller optimization using a genetic algorithm for non-collocated semi-active MR based control of a three-DOF framed struture

This paper aims to explore the usefulness of a simple genetic algorithm (GA) optimized Fuzzy Logic Controller (FLC) to reduce the response of a three-DOF framed structure equipped with a MagnetoRheological (MR) damper. These actuators can be controlled in bi-state control mode and/or in a semi-active configuration by continuously adjusting the amount of damping according to the actual response. Generally, model based controllers are designed to determine the actuator output. In recent years, soft computing techniques have been implemented to deal with the highly non-linear nature of structural systems. Among others, fuzzy based controllers seem to be adequate approach for these cases due to the inherent ability to deal with uncertain systems. However, a FLC design requires a wide experience in operating the system. This can be very difficult to implement in complex systems and several optimization techniques have been suggested to enhance the design process of fuzzy controllers. In this paper, a genetic algorithm (GA) optimized semi-active fuzzy based controller is proposed to reduce the seismic response of a three degree-offreedom (DOF) structure using a MR damper at the first DOF. The uncontrolled and controlled structural responses are compared to evaluate the effectiveness of the semi-active fuzzy based controller.info:eu-repo/semantics/publishedVersio

Numerical simulation of torsional response control of a plan-eccentric mass distribution building by using magnetorheological dampers

Wind and earthquake loads can cause coupled lateral-torsional deformations in building structures due to stiffness and/or mass eccentricities. Simple and regular structural configurations are usually recommended in designing seismic resistant systems to ensure optimal distribution of mass and stiffness in order to reduce torsional effects. However, these structures generally present irregular geometry due to other design requirements resulting in a complex three-dimensional dynamic behavior. In this regard, structural control has become a novel approach to reduce torsional seismic effects in asymmetric-plan building systems. Smart structures based on semi-active control systems are capable to improve significantly the seismic response of these structures with low power requirements, which represent a significant advantage over active systems. This paper presents a numerical simulation of a semi-active based control system using MagnetoRheological (MR) dampers to minimize the coupled lateral-torsional seismic response of a two-story framed building. A parametric study is carried out to evaluate the seismic behavior of the structure taking into account the effect of different mass eccentricities. The results show that it is possible to evaluate and validate the effectiveness of the semi-active control approach to reduce the structural seismic response for planeccentric or irregular mass distributions.info:eu-repo/semantics/publishedVersio

Influence of stiffness and stregth degradation of an infill wall upon the performance of a TMD

The present work presents an investigation about the influence of an infill wall on the dynamic behavior of a tuned mass damper (TMD) designed to control lateral displacements of a framed building structure under seismic excitation. A Macro-Simulink model is used to simulate the hysteretic behavior of the infill wall under cyclic loading assuming two hysteretic models: stiffness degradation and strength degradation. A MATLAB/Simulink code was implemented to evaluate the influence of each model on the structural response of the controlled structure. Finally, the numerical results are presented and discussed for comparison and further studies.info:eu-repo/semantics/publishedVersio

Structural control of a sdoff frame with non-linear hysteric behavior using a tuned a mass damper

This paper presents a parametric study on the control parameters of a Tuned Mass Damper (TMD) to reduce the seismic response of a simple framed structure with non-linear hysteretic behavior. A numerical model was implemented in MATLAB/Simulink to obtain the structural response and evaluate the contribution of each control parameter to the system. Based on the results, it can be concluded that the appropriate definition of some control parameters are crucial to reach rapidly and consistently the optimal TMD performance.info:eu-repo/semantics/publishedVersio

Convergence of vector bundles with metrics of Sasaki-type

If a sequence of Riemannian manifolds, $X_i$, converges in the pointed Gromov-Hausdorff sense to a limit space, $X_\infty$, and if $E_i$ are vector bundles over $X_i$ endowed with metrics of Sasaki-type with a uniform upper bound on rank, then a subsequence of the $E_i$ converges in the pointed Gromov-Hausdorff sense to a metric space, $E_\infty$. The projection maps $\pi_i$ converge to a limit submetry $\pi_\infty$ and the fibers converge to its fibers; the latter may no longer be vector spaces but are homeomorphic to $\R^k/G$, where $G$ is a closed subgroup of $O(k)$ ---called the {\em wane group}--- that depends on the basepoint and that is defined using the holonomy groups on the vector bundles. The norms $\mu_i=\|\cdot\|_i$ converges to a map $\mu_{\infty}$ compatible with the re-scaling in $\R^k/G$ and the $\R$-action on $E_i$ converges to an $\R-$action on $E_{\infty}$ compatible with the limiting norm. In the special case when the sequence of vector bundles has a uniform lower bound on holonomy radius (as in a sequence of collapsing flat tori to a circle), the limit fibers are vector spaces. Under the opposite extreme, e.g. when a single compact $n$-dimensional manifold is re-scaled to a point, the limit fiber is $\R^n/H$ where $H$ is the closure of the holonomy group of the compact manifold considered. An appropriate notion of parallelism is given to the limiting spaces by considering curves whose length is unchanged under the projection. The class of such curves is invariant under the $\R$-action and each such curve preserves norms. The existence of parallel translation along rectifiable curves with arbitrary initial conditions is also exhibited. Uniqueness is not true in general, but a necessary condition is given in terms of the aforementioned wane groups $G$.Comment: 44 pages, 1 figure, in V.2 added Theorem E and Section 4 on parallelism in the limit space

Exploitation of washing products of granitic tin-bearing sands from Conquista (Córdoba)

Se estudia un material arcilloso con alto contenido en caolinita, procedente del lavado de arenas graníticas de la formación de Los Pedroches (Córdoba). Se han realizado las siguientes determinaciones: análisis granulométrico, químico y mediante difracción de rayos X, estudio térmico por ATD-TG y dilatométrico, así como estudio de las propiedades cerámicas del material en probetas prensadas y cocidas durante dos horas hasta la temperatura de 1.300°C, obteniéndose los correspondientes diagramas de gresificación. El análisis mineralógico del material crudo lo señala,como altamente caolinítico, con variable contenido eh cuarzo, ilita, feldespatos (potásicos) y óxidos de hierro (~5% F2O3), en estado de gel en su mayor parte. Mediante cocción hasta 1.300°C de las probetas prensadas, el estudio mediante difracción de rayos X permite observar la aparición y desarrollo de nuevas fases, entre las que destaca la mullita, junto con abundante formación de fase vítrea. La situación y gran potencia del yacimiento, así como las buenas propiedades cerámicas de este material natural, permiten su empleo en la industria de pavimentos y revestimientos cerámicos gresificados de pasta roja dado su contenido en óxidos de hierro que preparados adecuadamente pueden modelarse por prensado, extrusión y colaje.An argillaceous material, high in kaolinite, from washing products of granitic sands of Pedroches (Córdoba) formation, is studied. The following determinations were carried out: mechanical analysis, chemical analysis. X-ray diffraction study, DTA-TG and dilatometric analysis, as well as a ceramic study of pressed and fîred bodies for two hours up to 1.300°C, to obttain the sintering diagrams. Through mineralogical analysis, it is concluded that the raw material is very high in kaolinite with variable contents of quartz, illite, feldspars (potassic), an iron oxides (~5% F2O3) mainly as gel. Through firing up to 1.300°C of presssed bodies, we can observe by the X-ray study the appearance and development of new phases among which mullite stands out, together with great vitreous phase formation. The location and great potential of the deposit, as well as the good ceramic properties of this material, permit their use in the good ceramic properties of this material, permit their use in the floor and tile industry due to its iron oxide content, being possible the processing by pressing, extrusion and slip casting