Application Of Passive Control Research Articles

Application of 3D Laser Scanning for Digitization, Design and Analysis of Multistoried Building

Laser scanning is a fast-developing technology, which collects millions of points and creates a framework within a few minutes, generating a 'point cloud' of the structure. Laser scanning is a quite new but rapidly evolving technology that has been reviewed. this research study has used most modern models of laser scanners and their accompanying software that are capable of accurate capture and alignment of point clouds. Consequently, the laser scans have precisely captured the current geometry of each structure, which is irregular in many cases due to inherently complex geometry, anomalies during the original construction, aging, deterioration, and structural damage. As both the exterior and interior of the structure have been scanned, the point cloud became a digital 3D image of the historical building, which can be virtually toured from inside and outside. A 4-story public building was scanned using a 3D laser scanner to determine the architectural and structural drawings of the response to an earthquake. The application of passive control using a damper with the laser scanner has been modelled in this study. The results corroborate that this technique provides the best outcomes for reducing seismic damage collapses.

A case study on the application of passive control and seismic isolation techniques to cable-stayed bridges: A comparative investigation through non-linear dynamic analyses

This paper investigates the seismic performance of an existing steel cable-stayed bridge located in a high seismic zone. In 1988 the structure experienced the failure of one of its anchorage plates needing closure and structural repair as a consequence of seismic activity. In this study, the possibility of retrofitting the original bridge with different passive supplemental damping and seismic isolation systems is proposed and assessed, in order to improve the response of the structure in its longitudinal direction. To this end a Finite Element model of the bridge is developed and the structural response is evaluated through non-linear dynamic response analyses under a set of historical ground motions of different intensities, including a near field record. Strength degradation capabilities are introduced in the model, allowing the occurrence of brittle failure in all the members. Seismic performance indices referred to the dynamic response of the unretrofitted structure and to the results of a pushover analysis are defined and used to compare the proposed innovative solutions. The major improvement on the overall response of the bridge is shown and conclusions regarding the most appropriate retrofit alternative for the particular case study are determined.

A passive control device with SMA components: from the prototype to the model

The use of shape memory alloy (SMA) components in passive structural control devices was repeatedly proposed in the last decade by several research groups. Among these proposals, an efficient coupling of SMA bars with a sliding system was recently introduced by the authors. It was studied at a prototype level to implement a base isolator with displacement limitations. This paper addresses first the issue of an accurate quality control on the alloy. Indeed an undesired creep effect has been experimentally detected in some specimens: it should be systematically avoided in passive control applications. The further step covers the transition from the prototype results to an accurate modelling of the device. Copyright © 2009 John Wiley & Sons, Ltd.

DISTORTION PROPERTIES OF GaN SWITCHES AT HIGH-TEMPERATURES

The origins of HEMT distortion in passive control applications as SPST switch are presented in this paper. Also, this paper describes the change of the AlGaN/GaN HEMT switch distortion properties (second-and third distortion intercept points) over a wide range of temperature. The results indicate that the change in second-and third-order distortion intercept points is smaller (about 2dBm) over a wide range of temperature from −50 to +300°C. A comparison of the GaN-based HEMT switch with InP-and GaAs-HEMT switches shows that the GaN technology generates lower distortion than its InP and GaAs technologies counterpart.

A basic experimental investigation of passive control applied to a transonic interaction

Passive control applied to a turbulent shock wave/boundary layer interaction has been investigated by considering a two-dimensional channel flow. The field resulting from application of passive control has been probed in great detail by using a two-component laser Doppler velocimetry system to execute mean velocity and turbulence measurements. Four different perforated plates have been considered, as also the solid wall reference case. The performed measurements have shown that passive control deeply modifies the inviscid flowfield structure, the unique strong shock being replaced by a lambda shock system. This fractionning of the compression induces a substantial reduction of the wave drag associated with the interaction. On the other hand, the combined injection-suction effect taking place in the control region provokes an important thickening of the boundary layer. There results an increase of the friction drag which nearly outbalances the gain in wave drag. A determination of the total drag in the control region was made. It was found that passive control induced a modest decrease of this drag compared to the solid wall case. Also, the rugosity of the holes is an important source of drag (excrescence drag) which contributes to compromise the potential benefit of the passive control technique.