Stefan Hurlebaus

Bio: Stefan Hurlebaus is an academic researcher from Texas A&M University. The author has contributed to research in topics: Damper & Control theory. The author has an hindex of 35, co-authored 160 publications receiving 3659 citations. Previous affiliations of Stefan Hurlebaus include Georgia Institute of Technology & Texas A&M Transportation Institute.

Seismic Response Control Using Shape Memory Alloys: A Review

Abstract: Shape memory alloys (SMAs) are a class of alloys that possess numerous unique characteristics. They offer complete shape recovery after experiencing large strains, energy dissipation through hysteresis of response, excellent resistance to corrosion, high fatigue resistance, and high strength. These features of SMAs, which can be exploited for the use in control of civil structures subjected to seismic events, have attracted the interest of many researchers in structural engineering over the past decades. This article presents an extensive review of seismic applications of SMAs. First, a basic description of two unique effects of SMAs, namely shape memory and superelastic effect, is provided. Then, the mechanical characteristics of the most commonly used SMAs are discussed. Next, the material models proposed to capture the response of SMAs in seismic applications are briefly introduced. Finally, applications of SMAs to buildings and bridges to improve seismic response are thoroughly reviewed.

Smart structure dynamics

Abstract: This paper gives an overview of research in the area of smart structure dynamics. A general description of smart material systems is given. Particular focus is given to the following fields of application: semi-passive concepts, energy harvesting, semi-active concepts, active vibration control, and active structural acoustic control. The use of smart structures in structural health monitoring applications is also considered.

Performance-based response evaluation of reinforced concrete columns subject to vehicle impact

Abstract: Structures are often subject to vehicle collision. A collision can be accidental, in the case of a vehicle going astray, or intentional, as in a terrorist attack. Bridge columns, building columns, traffic signal structures, and electric poles are the most vulnerable structural members to vehicle collisions. Columns are typically constructed from reinforced concrete (RC); therefore design and protection of RC columns against vehicle impact is an important consideration. The current analysis methods and experimental procedures to estimate the capacity of and demand on RC columns do not capture the complex mechanism of an impact event. Current code specifications have only provisions for collapse prevention and do not take into account different performance levels. The categorization of the different damage states and defining appropriate performance levels during various vehicle impacts is important to minimize damage and provide an economical design. The estimation of the dynamic shear force capacity and demand at different performance levels becomes key factor for design and protection of the structure. This research aims to develop a framework for estimation of the dynamic shear force capacity of and demand on an RC column subject to vehicle impact for different performance levels. The performance levels are related with the different impact levels of the vehicle for design. The proposed methodology is an improvement over the existing static or quasi-static analysis to the dynamic analysis which is a more realistic representation of the vehicle impact with structures. The proposed procedure can be used for the design of RC columns to minimize damage and meet a set of performance objectives during different vehicle impact scenarios. The current work can be extended to estimate the capacity of and demand on other members such as prestressed columns, steel columns, and beams and other hazards such as high velocity impacts due to blasts or missiles impact.

Identification of the impact location on a plate using wavelets

Abstract: This paper presents an experimental method that has been developed for detecting flexural waves in plates by the use of piezoelectric films. The recorded signals are analysed by a ‘wavelet transform’ to determine arrival times of waves at different frequencies. These arrival times are used in conjunction with an optimisation to identify the location of the impact (i.e. the x - and y -coordinate of the source location). Also, the time lag between the instant of the impact and the recording of the signals together with the group velocity of the dispersive waves are specified. Close agreement is observed between the experimentally determined results and the exact solutions. This technique is a valuable method for identification of source locations that may be applied to problems related to in-service impact loading of structures, seismic data from earthquakes, and to acoustic emission signals from propagating cracks.

Semiactive nonlinear control of a building with a magnetorheological damper system

Abstract: This paper proposes a linear matrix inequality (LMI)-based systematic design methodology for nonlinear control of building structures equipped with a magnetorheological (MR) damper. This approach considers stability performance as well as transient characteristics in a unified framework. First, multiple Lyapunov-based controllers are designed via LMIs such that global asymptotical stability of the building structure is guaranteed and the performance on transient responses is also satisfied. Such Lyapunov-based state feedback controllers are converted into output feedback regulators using a set of Kalman estimators. Then, these Lyapunov-based controllers and Kalman observers are integrated into a global nonlinear control system via fuzzy logic. To demonstrate the effectiveness of the proposed approach, a three-story building structure employing an MR damper is studied. The performance of the nonlinear control system is compared with that of a traditional linear optimal controller, i.e., H2/linear quadratic Gaussian (LQG), while the uncontrolled system response is used as the baseline. It is demonstrated from comparison of the uncontrolled and semiactive controlled responses that the proposed nonlinear control system design framework is effective in reducing the vibration of a seismically excited building structure equipped with an MR damper. Furthermore, the newly developed controller is more effective in mitigating responses of the structure than the H2/LQG controller.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

Abstract: to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Guided Lamb waves for identification of damage in composite structures: A review

Abstract: The guided Lamb wave is widely acknowledged as one of the most encouraging tools for quantitative identification of damage in composite structures, and relevant research has been conducted intensively since the 1980s. The main aim of this paper is to provide a comprehensive review on the state of the art of Lamb wave-based damage identification approaches for composite structures, addressing the advances and achievements in these techniques in the past decades. Major emphasis is placed on the unique characteristics and mechanisms of Lamb waves in laminated composites; approaches in wave mode selection, generation and collection; modelling and numerical simulation techniques; signal processing and identification algorithms; and sensor network technology for practical utility. Representative case studies are also briefly described in terms of various experimental validations and applications.

Unmanned surface vehicles: An overview of developments and challenges

Abstract: With growing worldwide interest in commercial, scientific, and military issues associated with both oceans and shallow waters, there has been a corresponding growth in demand for the development of unmanned surface vehicles (USVs) with advanced guidance, navigation and control (GNC) capabilities. This paper presents a comprehensive literature review of recent progress in USVs development. The paper first provides an overview of both historical and recent USVs development, along with some fundamental definitions. Next, existing USVs GNC approaches are outlined and classified according to various criteria, such as their applications, methodologies, and challenges. Finally, more general challenges and future directions of USVs towards more practical GNC capabilities are highlighted.

Corrosion of steel by concrete

Abstract: The author details the reactions of various concretes on steel reinforcement. Although portland cements, slag cements and high alumina cements are all hydraulic binders, each possess special properties which are examined. The discussion of causes and methods of preventing the corrosion of steel reinforcement covers such aspects as galvanised steel reinforcement, effects of concrete composition, corrosion of steel reinforcments in concrete and prestressed reinforcement. It is concluded that the most significant influences on the corrosion of prestressing wire in concrete are: the presence of chloride; the presence of nitrates; the composition of the concrete; the degree of carbonation of the concrete; concrete compaction and, chlorides and sulphates should be used as far as possible when steel is embedded. (TRRL)