1,720,989 research outputs found
A NUMERICAL MODEL FOR SIMULATING UNILATERAL RESPONSE IN CROSS-TIES DURING FREE VIBRATION OF “CABLE-CROSS-TIE SYSTEMS
No full textGENERALIZED STIFFNESS MODEL FOR THE SIMULATION OF NONLINEAR FREE-VIBRATION IN “CABLE-CROSS-TIE SYSTEMS
No full textOSSERVAZIONI SUL COMPORTAMENTO DINAMICO NON-LINEARE NEI SISTEMI STRALLI-CONNETTORI PER IL CONTROLLO DELLE VIBRAZIONI INDOTTE DAL VENTO
No full textEffects of modeling nonlinearity in cross-ties on the dynamics of simplified in-plane cable networks
No full textCross-ties are often employed as passive devices for the mitigation of stay-cable vibrations, which have been observed in the field under the excitation of wind and windrain. In-plane cable networks are structural systems derived by interconnecting several stays through transverse cross-ties. This study was motivated by a recent research activity aimed at the study of the free-vibration dynamics for in-plane cable networks.
Even though dynamic models for the analysis of the network vibration had been proposed by one of the writers in previous studies, a linear dynamic modeling of the system had been utilized. In this paper, the use of a nonlinear element was introduced to describe the nonlinear behavior of the cross-tie and to account for an 'imperfect' transfer of the restoring force mechanism at the anchorages (collars) between the cross-tie and the stay. The goal of this model is to simulate, perhaps more realistically, failure onset at the anchorages, sometimes experienced on some bridges.
The solution to the free-vibration problem for two simplified cable networks was determined by energy-based 'equivalent linearization' (EL), which simulates the nonlinear response in the restrainer through an equivalent linear restoring force component (amplitude-dependent). The first system consists of one stay with one cross-tie, anchoring the cable to the deck; the second system is a double-cable network with nonlinear cross-tie. Performance of both systems was analyzed. Investigation was restricted to the fundamental mode and some of the higher ones. A time-domain lumped-mass algorithm was utilized for the validation of the EL method
Examination of experimental errors in Scanlan derivatives of a closed-box bridge deck
No full textThe objective of the investigation is the analysis of wind-tunnel experimental errors, associated with the measurement of aeroelastic coefficients of bridge decks (Scanlan flutter derivatives). A two-degree-of-freedom experimental apparatus is used for the measurement of flutter derivatives. A section model of a closed-box bridge deck is considered in this investigation. Identification is based on free-vibration aeroelastic tests and the Iterative Least Squares method. Experimental error investigation is carried out by repeating the measurements and acquisitions thirty times for each wind tunnel speed and configuration of the model. This operational procedure is proposed for analyzing the experimental variability of flutter derivatives. Several statistical quantities are examined; these quantities incline the standard deviation and the empirical probability density function of the flutter derivatives at each wind speed. Moreover, the critical flutter speed of the setup is evaluated according to standard flutter theory by accounting for experimental variability. Since the probability distribution of flutter derivatives and critical flutter speed does not seem to obey a standard theoretical model, polynomial chaos expansion is proposed and used to represent the experimental variability
Examination of experimental errors in Scanlan derivatives of a closed-box bridge deck
No full textThe objective of the investigation is the analysis of wind-tunnel experimental errors, associated with the measurement of aeroelastic coefficients of bridge decks (Scanlan flutter derivatives). A two-degree-of-freedom experimental apparatus is used for the measurement of flutter derivatives. A section model of a closed-box bridge deck is considered in this investigation. Identification is based on free-vibration aeroelastic tests and the Iterative Least Squares method. Experimental error investigation is carried out by repeating the measurements and acquisitions thirty times for each wind tunnel speed and configuration of the model. This operational procedure is proposed for analyzing the experimental variability of flutter derivatives. Several statistical quantities are examined; these quantities include the standard deviation and the empirical probability density function of the flutter derivatives at each wind speed. Moreover, the critical flutter speed of the setup is evaluated according to standard flutter theory by accounting for experimental variability. Since the probability distribution of flutter derivatives and critical flutter speed does not seem to obey a standard theoretical model, polynomial chaos expansion is proposed and used to represent the experimental variability
EFFECTS OF MODELING NONLINEARITY IN CROSS-TIES ON THE DYNAMICS OF A SIMPLIFIED IN-PLANE CABLE NETWORK
No full textEFFECTS OF MODELING NONLINEARITY IN CROSS-TIES ON THE DYNAMICS OF SIMPLIFIED IN-PLANE CABLE NETWORKS
No full textA gyroscopic stabilizer to improve flutter performance of long-span cable-supported bridges
No full textLong-span cable-supported bridges are gaining considerable importance in the world. It is generally recognized that long-span cable-supported bridges can be very sensitive to wind effects due to their aerodynamic properties and deck flexibility. Flutter is usually a major concern because it can lead to structural deck failure. This communication introduces a prototype of gyroscopic device as an active stabilizer for improving flutter performance. A mathematical model of the gyroscopic device, installed at the bridge deck level, was studied and implemented to assess its effectiveness in increasing the critical wind speed. A preliminary study was conducted to evaluate the stabilizer's performance on a benchmark long-span cable-supported bridge as a function of its gyricity. The results demonstrate that the gyroscopic stabilizer is very successful and bridge flutter threshold increases with the gyricity of the gyroscopic device, within a practical operational range
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