Passive Control of Bridges

In the design of bridges with large spans, the significant values of the moments at the main deck-structure require very heavy members, either in the case of a beam or a truss deck-structure. In order to minimize the influence of bending moments, several applications of passive control of displacements using cable nets are herein proposed. The base for all the proposed systems is the cables supported beam nets with additional prestressing control on support cables to optimize the structural behavior of the system. The passive control design problem leads to an optimal control problem for structures governed by variational inequalities. In this presentation several bridge systems are proposed and studied as applications of this method

A newly developed life cycle inventory (LCI) database for commonly used structural steel components

The use of steel within the construction sector has enabled the delivery of larger-volume and more complex-shaped structures, while life cycle assessment (LCA) has been introduced as a pro-active design tool to ensure their sustainability. As LCA efficiency greatly depends on the life cycle inventory (LCI) data used, it is the purpose of the current research to present detailed structural steel LCI data and thus increase environmental benefits deriving from the effective use of LCA within construction. Hot-rolled structural steel members were chosen as the research starting point and the necessary information was provided by the leading structural steel manufacturer in Greece. Results include a list of environmental inputs and outputs, which can be used within relevant LCA studies and environmental impact assessment. Critical issues hindering the use of LCA were identified, along with the most environmentally damaging production stages and environmental categories mainly burdened. A new methodology for assessment results comparison was also applie

Active vibration suppression of smart beams

Summarization: In this paper an active vibration control technique for a smart beam is presented. The structure is made of two layers of piezoelectric material (PZT8) embedded on the surface of an aluminium beam. The active control is inserted into the finite element model by using programming tools of the general purpose code used herePresented on: PAM

Robust active control against wind-induced structural vibrations

Summarization: Slender flexible structures are vulnerable to vibrations under wind loads. The dynamic model of a frame-like structure is obtained by finite element approximation in this paper and used further for the design of an active control mechanism. The behavior of the structure is described by simplified linear equations. A linear quadratic regulator and an H2 optimal control method are used for the suppression of the extended vibration effects. Structured uncertainties are considered to reflect the errors between the model and the reality. To accommodate directly the plant uncertainties and to obtain a best possible performance in the face of uncertainties a robust H∞ optimal control for active control structure is used. The two latter robust controllers take into account as well incompleteness of the measured information, a fact that cannot be neglected in civil engineering, and lead to applicable designs of smart structures. The numerical simulation shows that vibrations can be suppressed by means of the proposed methods.Παρουσιάστηκε στο: Journal of wind engineering and industrial aerodynamic