Advanced Dynamics and Control of Structures

Mission

Our main objectives are forged by the needs of modern civil and mechanical engineering that are continuously asked to do their substantial share in the call for productivity, competitiveness and renewal. In detail, predefined levels of structural reliability and optimization are sought for both structural components and systems subjected to natural or anthropic hazards by means of conceptual analyses, design techniques and control. In order to reach these objectives, enhanced high strength steel materials, magnetorheological fluids and mechanical devices with controllable damping and/or stiffness properties are exploited. These goals encompass the disciplines of advanced smart materials and devices, seismic engineering, non-linear structural dynamics, system identification, structural health monitoring and control assisted by modern dynamic testing techniques exploited both in structural laboratories and in situ.

Research areas

Research activities encompass the following research areas:

  • i) advanced material and devices for the dynamic control of structures;
  • ii) system identification and structural health monitoring;
  • iii) seismic analysis and design of structural components and systems;
  • iv) modern dynamic testing techniques for characterization of substructures, non-linear devices and systems.

To reduce complexity, continuous structural components and systems are modelled as finite-dimensional systems by means of the Finite Element (FE) technique; hence, their time evolution can be described by systems of ordinary differential equations typically integrated by means of linear multistep methods applied to the Euler-Lagrange form of equations of motion.

 

The goal of the activity that employs advanced material and devices for dynamic structural control, derives on one hand, from the trend toward taller, longer and more flexible structures characterized by weight and costs savings and, on the other hand, from more stringent performance requirements and reliability. Along these lines, we investigate in depth both modern control and structural control theories, to be able to develop and apply: i) passive devices that do not require external power sources; ii) semi-active devices, for which the external energy requirements are orders of magnitude smaller than those typical of active control systems. In both cases bounded-input bounded-output stability is guaranteed.

Our research activities in system identification and structural health monitoring are motivated by the reason that complex or aging engineering structures in developed countries require cost effective and timely inspection and maintenance. Therefore, the ability to detect damage at an early stage can reduce the costs and down-time associated with repairs of critical systems. Therefore, we developed techniques based on forced and ambient vibration measurements that, through the identification of properties both in time and frequency domains, are able to detect, localize and quantify member-level damage.

The activity focussed on seismic analysis and design of structural components and systems is driven by two needs. On one hand, we aim at utilizing high strength steel circular hollow sections that are still limited in the construction industry, despite of their excellent properties with regard to load-bearing capacity, their attractive shapes in appearance and the fast development of relevant manufacturing processes; on the other hand, we intend to exploit performance-based earthquake engineering design methodologies, in order to safeguard the integrity of industrial equipment steel structures like liquid storage tanks, pressure vessels and piping systems under seismic loadings.

The research area on modern dynamic testing techniques for characterization of non-linear devices and systems comes at a time when the complexity of structures are escalating considerably, leading to higher demands on the analysis, conceptual design and testing techniques. Although significant savings can be achieved by using increasingly powerful and scalable numerical simulations, experimental testing cannot be obviated entirely. Instead, modern testing techniques need to be more targeted, faster, and more closely integrated with numerical techniques. Therefore, the principal aim of this research is to investigate new developments in the area of structural testing, particularly those based upon the principle of fusing numerical and experimental methods, such as real-time dynamic substructuring and hardware-in-the-loop testing. In this context, we propose to integrate ordinary differential equations by means of real-time compatible linearly implicit Rosenbrock-based methods applied to the Hamilton form of equations of motion.

Application areas

The application area of advanced material and devices for the dynamic control of structures regards buildings, foot-cycle bridges and falling rock protection kits, respectively. Buckling restrained braces based on yielding of metals can be utilized for the protection of braced steel structures, combining high strength and regular steel or employing cold-formed profiles. Studies are on going by means of the project NOMI-PAT, in order to reduce energy dissipation demands on primary foot-cycle bridges. Therefore, proper control laws are under development for adaptive tuned mass dampers. Anew, the adoption of tubular dissipative devices made of steel or aluminium, within the project ROCKFALL PROTECTION-IGOR seems to be very promising to enhance the performance of falling rock protection kits, together with friction energy dissipated by ropes and nets. Fig. 1 highlights relevant components and systems.

The application area of system identification and structural health monitoring involves the research projects HITUBES. We want to make a contribution to the progress of vibration-based structural health monitoring and to encourage its application to civil infrastructures, with special regard to complex footbridges endowed with passive vibration control systems. In detail, a recent curved twin-deck cable-stayed footbridge was analysed, see Fig. 2a, whose structural complexity required wind tunnel tests and a specific design for vibration reduction. A passive control system was deemed necessary in order to: i) meet wind safety requirements owing to premature aeroelastic instability; ii) mitigate pedestrian vibrations. Uncertainties in finite element modelling, see Fig. 2b, and changes during its construction suggested a modal testing campaign in order to check the effectiveness of the vibration absorption system. Different excitation sources related to output-only techniques were exploited, see Fig. 3, including ambient noise and free-decay oscillations through released masses. Several sensor set-ups were deemed necessary in view of the structure complexity that exhibited numerous close modes and modal couplings between the two decks. The effect of the dampers, including the one shown in Fig. 4, was analysed by means of testing campaigns.

The application area of seismic analysis and design of structural components and systems considers the conceptual analysis and design of structural components, mainly subjected to exceptional loadings. It also comprises analysis techniques both based on first principles and advanced finite element software, in order to optimize the performance of structural components. In a greater detail, through the ATTEL project we intend to develop high strength steel-based approaches, where the capacity design methodology routinely used in seismic engineering to avoid brittle failure modes and favour ductile modes will be combined with the higher strength of tubular columns, to face exceptional loadings like earthquake and fire. A typical outcome conceived at DIMS is shown in Fig. 5, i.e. a moment resisting beam-to-column joint. With regard to the development of guidelines for the seismic design of industrial equipments, compatible with the Eurocode 8 framework, we are actively involved in the INDUSE project. Its primary objective is to provide performance-based methodologies for the seismic design of industrial piping systems towards safer construction and operation, that are very often subjected to phenomena of the type illustrated in Fig. 6.

The application area of modern dynamic testing techniques regards the characterization of substructures, non-linear devices and structural systems. These objectives are pursued by means of the projects SERIES and RELUIS. Through the use of advanced sensing and control techniques for transfer systems, it is possible to experimentally test substructures of steel-concrete composite decks under dynamic loadings. In addition, advanced computational techniques for the simulation of monolithic and heterogeneous structural dynamic systems will allow fluid viscous damping devices to be tested in cable-stayed bridges numerically simulated as illustrated in Fig. 7. Moreover, through a common communication platform developed in the SERIES project, we intend to carry out geographically distributed testing as part of a very large virtual European research laboratory. This entails a wide sharing of data and knowledge through web portals and distributed databases via the concept sketched in Fig. 8.

 

Funded research grants and projects

Both European grants and National grants/projects are listed here.

European grants
Research Grant: ATTEL – 01/07/2008-2012, 42 months. "Performance-based approaches for high strength tubular columns and connections under earthquake and fire loadings". Principal Investigator (PI): Oreste S. Bursi.
Research Grant: HITUBES – 01/07/2008-2012, 42 months. "Design and integrity assessment of high strength tubular structures for extreme loading condition". Co-ordinator and PI: Oreste S. Bursi.
Research Grant: INDUSE – 01/07/2009-2012, 36 months. "Structural safety of industrial steel tanks, pressure vessels and piping systems under seismic loading ". PI: Oreste S. Bursi.
Research Grant: SERIES – 01/03/2009-2013, 48 months. " Seismic Engineering Research Infrastructures for European Synergies". PI: Oreste S. Bursi.

National grants/projects
Research Grant: RELUIS - Theme AT-3 - 01/07/2010-2013, 36 months. “Technologies for monitoring and emergency management”. PI: Oreste S. Bursi.
Research contract: NOMI-PAT - 01/07/2009-2011, 24 months. "Design of devices for vibration reduction and structural health monitoring of a foot- cycle-bridge on the Adige river. PI: Oreste S. Bursi.
Research contract: ROCKFALL PROTECTION-IGOR - 01/11/2009-2011, 15 months "Design of dissipating devices and measurement systems for large falling rock protection kits. PI: Oreste S. Bursi.

Highlights

We actively collaborate and grateful acknowledge research support provided by the:

People

Faculty:

Postdoctoral researchers

Doctoral students

Selected publications

  • Erlicher, S. and BURSI, O.S., "Bouc-Wen-type models with stiffness degradation: thermodynamic analysis and application", Journal of Engineering Mechanics, ASCE, 347, 2008, 331-338.
  • Pipinato A., Pellegrino, C., BURSI O.S., Modena, C., "High-cycle fatigue behavior of riveted connections for railway metal bridges", Journal of Constructional Steel Research, 65(12), 2009, 2167-2175.
  • BURSI, O.S. He L., Lamarche C.P. and Bonelli A., "Linearly implicit time integration methods for real-time dynamic substructure testing", Journal of Engineering Mechanics, ASCE, 136, 11, 2010, 1380-1389.

Selected PhD theses

  • He L. “Development of Partitioned Time Integration Schemes for Parallel Simulation of Heterogeneous Systems”, 2008.
  • Savadkoohi A. “Inverse Modelling of a Steel-Concrete Composite Moment Resisting Structure Subjected to Severe Cyclic Loads and Forced Vibration Tests”, 2008.
  • Tondini N. Performance-based analysis of concrete and steel-concrete composite box-girder bridges. 2009.

Contacts

Oreste S. Bursi, Ph.D., P.E., MASCE
Professor of Structural Dynamics and Control
e-mail: Oreste.Bursi@ing.unitn.it
snail mail: Department of Structural and Mechanical Eng.
Via Mesiano 77 - 38123
University of Trento - ITALY
Fax number   +39-0461-282505/282599
Phone number +39-0461-282521.