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RESTRICTION OF SUSPENDED BRIDGES’ VIBRATIONS BY USING INCLINED PYLONS
Last modified: 2017-05-26
Abstract
Over the last 100 years, many researchers have studied the dynamic response of railway bridges under the influence of moving loads and later the response of highway bridges.
During the last decades, cable bridges have received great attention because of their ability in relation to other long span bridges, as well as reduced erection costs and an improved utilization of the materials. As a consequence, several applications have been proposed in the framework of both suspension and cable stayed bridge types.
Long span bridges, based on cable stayed or suspension bridge systems, have been used in different frameworks. The use of the cable system types is strictly connected to structural, economic and practical reasons.
For the suspension bridges the dynamic interaction vehicle-bridge has been discussed, mainly, for traffic loads of single or multi-span systems.
A serious problem of the long-span cable bridges is the lateral instability caused by dynamic loadings, as for example earthquake or wind pressure or buffeting forces. The usual classical confrontation of the problem is the deck’s strengthening, but it is proved as a non-economic one. In some cases, mainly in foot-bridges, a system of external cables was applied, that had an slight inclination to the horizontal, in order to minimize the lateral motion produced by crowd loading.
Until today long-span suspension bridges with inclined cable systems are not erected.
At the end of the 1960’s, Nervi was amongst engineers, who were asked to propose a design for a bridge across the Messina Straits, between Italy and Sicily. The depth of water in the Straits meant that the bridge had to cross about 3km in a single span.
Nervi’s compatriot Sergio Musmeci proposed a peculiar suspension bridge, where the suspension cables are hung not directly from towers, but from cable stays which are in turn suspended from super-towers beyond the ends of the main bridge. Musmeci’s idea included lateral cables on either side of the deck to provide it with transverse stability.
Although this was an odd design, the proposal by Nervi was even stranger.
Authors do not find either notable research studies on this field or other communications related to constructional or other objects that set on thinking designers or constructors, except papers dealing with footbridges and using cables in order to minimize its oscillations caused by human crowd.
The present paper deals with the influence of the inclination of cables’ system on the decrease of the lateral-torsional motion because of dynamic loadings. For this goal a mathematical model is proposed.
A 3-D analysis is performed for the solution of the bridge model. The theoretical formulation is based on a continuum approach, which has been widely used in the literature to analyze bridges. The resulting equations of the uncoupled motion are solved by using the Laplace Transformation, while the case of the coupled motion is solved through the use of the potential energy. Finally characteristic examples are presented and useful results are obtained.
During the last decades, cable bridges have received great attention because of their ability in relation to other long span bridges, as well as reduced erection costs and an improved utilization of the materials. As a consequence, several applications have been proposed in the framework of both suspension and cable stayed bridge types.
Long span bridges, based on cable stayed or suspension bridge systems, have been used in different frameworks. The use of the cable system types is strictly connected to structural, economic and practical reasons.
For the suspension bridges the dynamic interaction vehicle-bridge has been discussed, mainly, for traffic loads of single or multi-span systems.
A serious problem of the long-span cable bridges is the lateral instability caused by dynamic loadings, as for example earthquake or wind pressure or buffeting forces. The usual classical confrontation of the problem is the deck’s strengthening, but it is proved as a non-economic one. In some cases, mainly in foot-bridges, a system of external cables was applied, that had an slight inclination to the horizontal, in order to minimize the lateral motion produced by crowd loading.
Until today long-span suspension bridges with inclined cable systems are not erected.
At the end of the 1960’s, Nervi was amongst engineers, who were asked to propose a design for a bridge across the Messina Straits, between Italy and Sicily. The depth of water in the Straits meant that the bridge had to cross about 3km in a single span.
Nervi’s compatriot Sergio Musmeci proposed a peculiar suspension bridge, where the suspension cables are hung not directly from towers, but from cable stays which are in turn suspended from super-towers beyond the ends of the main bridge. Musmeci’s idea included lateral cables on either side of the deck to provide it with transverse stability.
Although this was an odd design, the proposal by Nervi was even stranger.
Authors do not find either notable research studies on this field or other communications related to constructional or other objects that set on thinking designers or constructors, except papers dealing with footbridges and using cables in order to minimize its oscillations caused by human crowd.
The present paper deals with the influence of the inclination of cables’ system on the decrease of the lateral-torsional motion because of dynamic loadings. For this goal a mathematical model is proposed.
A 3-D analysis is performed for the solution of the bridge model. The theoretical formulation is based on a continuum approach, which has been widely used in the literature to analyze bridges. The resulting equations of the uncoupled motion are solved by using the Laplace Transformation, while the case of the coupled motion is solved through the use of the potential energy. Finally characteristic examples are presented and useful results are obtained.