Search results for "Linear"

On the reliability of ASHRAE conduction transfer function coefficients of walls

2000

The transfer function method recommended by the ASHRAE can be considered the most modern tool currently available for the thermal analysis of a building. It is particularly well suited for use with a computer as it makes it possible to describe with great accuracy the internal heat gain of walls using a small set of coefficients. The present paper shows how to calculate sets of coefficients diverse from that proposed by Mitalas who first developed the method and on the basis of an unequivocal criterion, to prove the advantages in using them. The authors also investigated some of the paramount mathematical and physical aspects which affect the approximation degree of the ASHRAE method and, w…

Seismic response of braced frames with and without friction dampers

1995

Abstract The dynamic response of friction damped bracing systems and ordinary cross-bracing systems inserted into surrounding frames without lateral stiffness is analysed in order to compare the typical behaviour of the two different bracing systems. The cyclic force-displacement relationship in the two cases is accurately modelled on the basis of experimental and related numerical models which are available in the literature, and the structural dimensionless parameters defining the shapes of the cycles are stressed. Systems having the same average period of vibration in the elastic phase of the response are assumed to be comparable with one another, which leads to a relationship linking th…

Modeling traffic safety at urban four leg-signalized intersections

2013

According to the state-of-the-art of the methodologies, the development of safety performance functions (SPFs) for road sections and intersections requires the employment of statistical models to predict expected crash frequencies on the basis of traffic volumes and site characteristics to be surveyed and used as input to models. Nevertheless, literature reports several studies on issues deriving from data features or methodological approaches that may invalidate the efficiency of the models and the accuracy of the estimates. Drawing inspiration from the above mentioned considerations, the objective of this study is to develop safety performance functions for a sample of urban four leg-sign…

Investigation of thick sheet AHSS springback in combined bending under tension

2012

In this paper, we investigate the springback behavior of several advanced high-strength sheet steels (TRIP, Dual-Phase, ferrite-bainite) with thicknesses up to 4 mm. Samples were tested by means of the bending-under-tension (BUT) test. The BUT has been extensively applied, in the literature, to relatively thin (1 mm and thinner) sheet metals for automotive applications; the applicability of several guidelines from the literature was investigated in this work in the context of thick advanced high strength steel (AHSS) sheets and using a sample width of 12 mm. The monotonic decrease of springback as back force increased was confirmed for this category of sheet steels, and a general trend for …

Semiactive Control Methodologies for Suspension Control With Magnetorheological Dampers

2012

Authors version of an article published in the journal: IEEE/ASME Transactions on Mechatronics. Also available from the publisher at: http://dx.doi.org/10.1109/TMECH.2011.2107331 Suspension systems are one of the most critical components of transportation vehicles. They are designed to provide comfort to the passengers to protect the chassis and the freight. Suspension systems are normally provided with dampers that mitigate these harmful and uncomfortable vibrations. In this paper, we explore two control methodologies (in time and frequency domain) used to design semiactive controllers for suspension systems that make use of magnetorheological dampers. These dampers are known because of th…

2014

The problem of robust decentralized adaptive neural stabilization control is investigated for a class of nonaffine nonlinear interconnected large-scale systems with unknown dead zones. In the controller design procedure, radical basis function (RBF) neural networks are applied to approximate packaged unknown nonlinearities and then an adaptive neural decentralized controller is systematically derived without requiring any information on the boundedness of dead zone parameters (slopes and break points). It is proven that the developed control scheme can ensure that all the signals in the closed-loop system are semiglobally uniformly ultimately bounded in the sense of mean square. Simulation …

Modeling of out-of-plane behavior of masonry walls

2009

The flexural behavior of rectangular masonry sections is investigated by considering nonlinear stress-strain in compression and limited-tension material. A preliminary analysis shows that, with variation in the parameters specializing with the adopted conventional constitutive law, the experimentally observed behavior of different kinds of masonry materials can be approximated. Subsequently, moment-curvature dimensionless curves are derived numerically by satisfying the equilibrium equations of the section. In the case of negligible tensile strength these curves exhibit a typical shape that can be approximated by analytical expressions; consequently, suitable functions are proposed that are…

A state-space approach to mathematical modeling and parameters identification of vehicle frontal crash

2014

In this paper a state-space estimation procedure that relies on the time-domain analysis of input and output signals is used for mathematical modeling of vehicle frontal crash. The model is a double-spring–mass–damper system, whereby the front mass and real mass represent the chassis and the passenger compartment, respectively. It is observed that the dynamic crash of the model is closer to the dynamic crash from experimental when the mass of the chassis is greater than the mass of the passenger compartment. The dynamic crash depends on pole placement and the estimated parameters. It is noted that when the poles of the model are closer to zero, the dynamic crash of the model is far from the…

Composite nonlinear feedback control for path following of four-wheel independently actuated autonomous ground vehicles

2015

This paper studies the path following control problem for four-wheel independently actuated (FWIA) autonomous ground vehicles (AGVs) through integrated control of active front-wheel steering (AFS) and direct yaw-moment control (DYC). A modified composite nonlinear feedback (CNF) strategy is proposed to improve the transient performance and eliminate the steady-state errors in the path following control considering the tire force saturations, in the presence of the time-varying road curvature for the desired path. The path following is achieved through vehicle lateral and yaw control, i.e., the lateral velocity and yaw rate are simultaneously controlled to track their respective desired valu…

Stochastic seismic analysis of MDOF structures with nonlinear viscous dampers

2009

Fluid damper devices in civil structures such as buildings or bridges are commonly used as energy absorbers for seismic protection. The problem in the response analysis of structures with filled dampers mainly consists in the fact that, due to the strongly nonlinear behavior of such equipments, the response spectrum (RS) technique fails. In this paper by using the concept of power spectral density function compatible with the elastic RS and the statistical linearization technique, the equivalent damping ratio is obtained. It is shown that once the system is linearized, results obtained by Monte Carlo simulation and those obtained by stochastic analysis are in good agreement. Copyright © 200…