Papers by Keyword: Analytical Model

Abstract: In this paper is presented a new mathematical model which is intended to simulate the hysteretic phenomenon of SERB-C Romanian friction device for damping and dissipation of earthquake energy used for buildings. These devices have unusual shape of force-displacement loop which can be simulated with our new model which represents a specific adaptation of the well known Bouc-Wen hysteretic model. The purpose of this analytical simulation is to determine a relation for the hysteretic loop which was obtained by experimental tests performed by the authors. The mathematical model presented in this paper can be used in computational simulation of a building protected with these types of devices, in order to determine the anti-seismic performances of a Romanian friction building protection system.

Abstract: Planetary transmissions used as speed amplifiers in wind/hydro conversion systems typically rely on the conventional concept of mechanism with one input and one output. This concept is found in the most of the high power wind turbines; however, the need to implement in the built environment smaller wind turbines with speed amplifiers led to new turbine concepts such as counter-rotating rotors and classical generator. The paper presents a comparative analysis of two wind turbines with one rotor and respectively two counter-rotating rotors, which contain identical electrical generators and the same type of mechanical amplifier used as a 1 DOF mechanism and differential one respectively. With the assumption of maintaining the same electrical generator running point for both wind turbines, the steady-state behaviour of the considered turbines is identified and a comparative kinematic and static performance analysis is performed, aiming at highlighting the impact on efficiency and on constructive design and development of the two turbines.

Abstract: This study presents an analytical model for assessing reinforced simply supported beams based on recommendations of the Brazilian Concrete Norm (NBR-6118) and a study published by the International Federation of Concrete (fib). Rectangular and “T” sections are only considered in this study. The beam’s deformation depicted the diagram of moment curvature in regard with the limits of materials deformation in the elastic state is also explored. The results obtained by both Norms were complement with each other, revealing great similarity. Furthermore, destructive tests of reinforced beams made in the laboratory were compared with those obtained by the analytical model, showing excellent performance of the proposed model. The objective of this publication is the presentation of the analytical model. Analysis of comparing the results between the analytical model and from field tests were presented in another publication that will be mentioned in this study.

Abstract: Ovalization (or flattening) of tubes in cold bending operations causes dimensional inaccuracy that may lead to loss of fit-up and function of the formed product. The particular distortion mechanism is governed by radial bending stress components forcing the extremities of the tube section towards the neutral layer of the cross-section. Thus, the magnitude of distortions is limited by the instantaneous stiffness of the tube section upon plastic bending. In order to proactively consider tube ovalization in the product design process, it is necessary to develop a practical methodology that takes into account the impact of governing parameters such as material, tool and section geometries. In the present work, an analytical model of the ovalization problem has been developed using the deformation theory of plasticity. The results show that the diameter of the tube is the most important parameter with respect to tube ovalization, while the thickness of the tube section and the bending radius are of the same relative importance. The developed model indicates that strain hardening is the most important material parameter, whereas tube ovalization is nearly unaffected by the initial yield stress. The present model shows good correlation with a number of experiments.

Abstract: Cases of tunneling adjacent to existing structures are common nowadays in urban construction. The interaction between newly constructed tunnels and existing underground structures is an important issue, while the previous works mainly focused on the effect that constructing a new tunnel would have on existing structures. In this article, the effect that existing structures would have on newly constructed tunnels was come up with, and a model was proposed to analyze the confinement of existing structures to the tunnel surrounding rock. Discussions were carried out theoretically and numerically.

Abstract: Anti-blast wall can effectively reduce blast load and, therefore protect human and structures from external explosion. A new kind of anti-blast wall, HESCO Bastion wall (HB wall), was designed by the QIAOSHI(China) International Trade Limite. The research about the HB wall was mainly focus on the construction of rotation model and the anti-overturn stability of the wall, but no research could be found on the blast wave pressure distribution law behind the HB wall, the anti-penetration capability and the assembling mode of the HB wall. In this paper, research progress of the HB wall has been presented, research ideas about the HB wall have been put forward.

Abstract: In the full power wind power system, the cage induction wind generator-rectifier system can be regarded as a independent part if the DC voltage could be always controlled constant by inverter part. The prospective AC voltage and frequency of induction generator is dependent on the specific speed and input power, which is obtained by use of SPWM. All rectifier switching state and the alternating moments can be calculated by switching function given by SPWM control. This paper focuses on how to use analytical methods to calculate the process of alternately switching the state of the system. Furthermore, the dynamic mathematical model of induction generator is studied and derived under different states, which is suitable for analytical method on base of Laplace transform.

Abstract: An analytical model based on some solutions in the context of a two-layered fluid was developed to estimate the occurrence of northeasterly wind-driven coastal upwelling associated with “Aoshio” on the northeast shore of Tokyo Bay, and its validity was verified by comparing with observation data [1]. In this study, influences of all of the factors incorporated into this analytical model (including densities and thicknesses of the upper and lower layers, the parameter expressing the influences of interfacial friction and bottom friction) on the model are analyzed. The analytical model is found to express the competition between the wind-shear effect and the stratification effect: when the former dominates over the latter, Aoshio will occur on the northeast shore of the bay. The parameter that can be used to characterize the stratification effect can be simply expressed in terms of the product of density contrast and the square of thickness of the upper layer. Using different values of this parameter corresponding to different months in the model can simply estimate in which months it is easy for Aoshio phenomenon to happen on the northeast shore of the bay, and the result is roughly consistent with an observation phenomenon that Aoshio was frequently observed on the northeast shore of the bay in September and May and relatively less observed in June and July during 1978-2010.

Abstract: Design provisions for the repair, retrofitting, and rehabilitation of existing masonry structures are not always available and included in International and National Building Codes. Due to the extremely large variability in masonry performances, equations of general validity cannot be provided, namely relationships suitable for confinement of every masonry type, as it is done for concrete. Large amount of results obtained for concrete led to consolidated design guidelines. Despite the great research effort in the experimental field on masonry, considerable theoretical work is still needed to fully outline a definitive analytical model to predict the behavior of FRP confined masonry. In this study, a mechanically based confinement model is proposed based on mechanical parameters able to differentiate similar masonry types and to highlight that they present different confinement performance. The most relevant parameters are the compressive and tensile strength of unconfined masonry and they are discussed in the framework of solid mechanic based models based on triaxial plasticity and calibrated experimentally. The proposed approach can then be extended to other masonry types.

Abstract: This paper supposes a S-shape low yield steel damper. Based on the mechanical behaviors of the damper, its analytical model is established. Meanwhile, the damper’s hysteretic characteristics are numerically simulated by the FEM ABAQUS to obtain the main mechanical parameters of this damper. These parameters are compared with the results from the established analytical model. Results indicate that the analytical model is a-greeable to the FEM analysis. In addition, Analytical results also show that the S-shape low yield damper pos-sesses superior mechanical behaviors and hysteretic characteristics to fit extremely for mitigating the vibrationof engineering structures.