Krzysztof Wilde

Base isolation system with shape memory alloy device for elevated highway bridges

Base isolation provides a very effective passive method of protecting bridges from the hazard of earthquakes. The proposed smart isolation system combines a laminated rubber bearing with a device made of shape memory alloy (SMA). The smart base isolation utilizes the different responses of the SMA at different levels of strain to control the displacements of the rubber bearing at various excitation levels. At the same time the hysteresis of the alloy is used to increase the energy dissipation capacity.

Pounding of superstructure segments in isolated elevated bridge during earthquakes

Past severe earthquakes indicate that pounding may cause considerable damage or even lead to collapse of colliding structures. The aim of this paper is to present an analysis of pounding between superstructure segments of an isolated elevated bridge induced by the propagating seismic wave. High-damping rubber bearings (HDRBs), used as isolation devices, are modelled by proposed non-linear formulation and the significance of the bearings model for pounding is indicated. The results of the study show that pounding leads to the increase or decrease of the forces acting on piers, depending on the gap size between superstructure segments.

Reduction of pounding effects in elevated bridges during earthquakes

Pounding of adjacent superstructure segments in elevated bridges during severe earthquakes can result in significant structural damage. The aim of this paper is to analyse several methods of reduction of the negative effects of collisions induced by the seismic wave propagation effect. The analysis is conducted on a detailed three-dimensional structural component model of an isolated highway bridge. The results show that the influence of pounding on the structural response is significant in the longitudinal direction of the bridge and significantly depends on the gap size between superstructure segments. The smallest response can be obtained for very small gap sizes and for gap sizes large enough to prevent pounding. Further analysis indicates that the bridge behaviour can be effectively improved by placing hard rubber bumpers between segments and by stiff linking the segments one with another. The experimental results show that, for the practical application of such connectors, shock transmission units can be used. Copyright

Analytical and experimental study on passive aerodynamic control of flutter of a bridge deck

Abstract Considerable attention has been paid to the research of passive and active structural control for wind-induced self-excited vibration of long-span bridges in recent years. In this paper a passive aerodynamic control of bridge flutter is proposed. The system consists of two additional surfaces to generate stabilizing forces. The torsional motion of the surfaces is governed by the additional pendulum attached to the bridge deck. The state-space equation of the flutter control system is derived through the rational function approximation of the unsteady aerodynamics of the bridge section. The performance of the control system is evaluated for various parameters of the pendulum and the potential improvement of flutter wind speed is demonstrated through numerical examples. The experimental study showed very good agreement with the theoretical prediction for small amplitude motion of the control surfaces.

Simple model of rain-wind-induced vibrations of stayed cables

Abstract This paper proposes a single-degree-of-freedom model of rain-wind-induced vibrations in stayed cables. It is assumed that the frequency of the circumferential motion of the upper rivulet is equal to that of cable and the rivulet amplitude is set constant for a given wind speed. The obtained results are verified with the existing experimental data showing that these assumptions capture the qualitative properties of the phenomenon. The explicit, analytical expressions are derived for the aerodynamic damping and exciting force. Finally, a linear SDOF model is derived for simple estimation of the amplitude of cable vibrations induced by wind and rain.

A simple method of conditional random field simulation of ground motions for long structures

Abstract The recently developed theoretical framework of conditional random fields is not widely used for engineering purposes due to its complexity and the difficulty of estimating the spatial correlation of fields. This paper presents a simple method of conditional simulation of space–time variation of a ground motion. The frequency dependence of the spatial correlation function is simplified so that only the correlation of the predominant frequency of the earthquake is taken into account. Numerical simulations of ground motion fields for long structures conditioned by the El Centro (1940) and Kobe (1995) earthquake records are presented. The simulations are performed in the time domain and three simplified procedures such as: simulation conditioned by one specified record, cumulative and successive simulation, are compared.

Suppression of wind-induced instabilities of a long span bridge by a passive deck-flaps control system

Abstract A passive aerodynamic control method for suppression of the wind-induced instabilities of a very long-span bridge is presented. The control system consists of additional control flaps attached to the edges of the bridge deck. Rotational motion of the control flaps is governed by prestressed springs and additional cables connecting the flaps to an auxiliary transverse beam supported by the main cables of the bridge. The rotational movement of the flaps is used to modify the aerodynamic forces acting on the deck, as well as to provide aerodynamic forces on the flaps, used to stabilize the bridge. A time domain formulation of self-excited and buffeting forces is obtained through the rational function approximation of the generalized Theodorsen and Kusner functions, respectively. Performance indices assessing improvement in critical wind speed and degree of stability of the system are proposed to find the optimal configuration of the deck–flaps system. This paper lays the theoretical groundwork for the one that follows.

System of monitoring of the Forest Opera in Sopot structure and roofing

The authors present a solution realized in Forest Opera (name in Polish: Opera Leśna) in Sopot (Poland) in connection with the modernization and construction of a new roof. The complicated structure of the roof of the facility and the used covering in form of membrane made of technical fabric required (for security reasons) to install the unit of devices allowing for the continuous geodetic monitoring of the facility. Monitoring of relocations in case of engineering structures of a complex design allows for the extended safety of their use. Realized (for this purpose) geodetic measurements require (to be useful) a high accuracy, full automation making the assessment independent from the human factor and the use of reference points. The main element of the presented system is a motorized total station used for the determination of roof cover relocations, whereas the complementary elements are vibration and temperature sensors and weather conditions monitoring station. Data recorders from the entire facility are connected to the computer central unit, providing automation of measurements and archiving of results along with their analysis. The problem occurring in the analyzed object is relatively unstable (subject to vibration) total station. Therefore, the solution implemented for Opera Leśna in Sopot assumes, that it is required to carry out measurements against reference points before every measurement of controlled points. On the basis of these measurements, for each measurement epoch the coordinates and relocation vectors for the tachymeter station are checked as well as analyses of an accuracy suitable for this process. The solution of this problem is useful for monitoring in other movable or subject to relocation engineering facilities. The article signalizes the problem of accuracy of surveying. For this purpose, the preliminary analyses of an accuracy were carried out. They made it possible to determine the expected errors of the reference points location in the designed network geometry and position of the total station for two variants: with and without taking into account the erroneous of reference points location. To summarize, we can say that the automatic measurement systems are an appropriate method for the continuous observation of the construction condition, however, they must be based on accurate, repeatable (for each measurement epoch) analyses of the observation of both monitored elements as well as their spatial references.

Technical Monitoring System for a New Part of Gdańsk Deepwater Container Terminal

Abstract Development strategy for the port of Gdańsk assumes that , up to 2027, it will become the main transport centre in the Baltic Sea region. To this end , for many years work has been carried out to facilitate access to the port both by sea and land. One of the elements of extension of the port is the building of another terminal of Deepwater Container Terminal, Gdańsk. In this task, geotechnical operations aimed at appropriate preparation of subgrade for storage of containers and operation of cranes, have been especially important. Effectiveness of the assumed design solution of land-side girder for gantry crane has been verified by means of a technical monitoring system. This paper presents main elements of design the land-side girder of a new quay of the container terminal in Gdańsk, together with its computational analysis, as well as the results collected during a few months of observation, which have revealed real work of monitored elements.

Variable-gain control applied to aerodynamic control of bridge deck flutter

A method of suppressing flutter of a very long span bridge is presented in this paper. The control system consists of actively controlled surfaces which by torsional movement generate stabilizing aerodynamic forces. The unsteady aerodynamic forces, acting on the bridge deck, are approximated by the rational function approximation and the frequency independent equation of motion is derived. The dependence of the system on mean wind speed limits the efficiency of application of the conventional constant gain optimal feedback control. The improvement in control effectiveness is obtained by proposed variable-gain concept. The output variable-gain approach is formulated in terms of mathematical optimization problem and necessary conditions are derived.