Bridges

Damper Retrofit of the London millennium footbridge-A case study in Biodynamic design

ABSTRACT

The Millennium Footbridge was opened to the public on June10, 2000-the first new bridge across the River Thames in historic London in more than a century. Nearly 100,000 people used the new bridge in its first day of o Abstract

On June 12, 2000, the Millennium Bridge was ordered closed, due to hazard deck motions. Seemingly random pedestrian footfalls were causing resonance of the bridge deck, with lateral accelerations measuring up to 0.25 g.

The selected method of retrofit was to add fluid damping to the bridge- and test the structure with groups of up to 2,000 people.

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ENERGY DISSIPATION DEVICES IN BRIDGES USING HYDRAULIC DAMPERS

ABSTRACT

Specially designed energy dissipation systems are well known for improving seismic performance of structures by absorbing earthquake induced energy. In this paper, the use of linear and nonlinear hydraulic dampers is investigated in a bridge application. A two-span, skewed, cast-in-place pre stressed concrete bridge with an outrigger bent is examined. The bridge is located in a highly seismic area of Southern California. It is observed that dampers alleviate the torsional movement and reduce the transverse and longitudinal movements of the superstructure.

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Shock control of bridges in china using Taylor devices’ fluid viscous damper devices

ABSTRACT

Fluid Viscous Devices are a successful structural protective system for bridge vibration. The structural protective technique and the dampers have been introduced to China since 1999. The Taylor Devices’ damper system has already been successfully installed or will be installed in large or the super large bridges in China for protection from earthquake, wind. vehicle and other vibration. Seventeen different bridge projects introduced here include the Sutong Yangtze River Bridge, the longest cable stayed bridge in the world, the Nanjing 3rd Yangtze River Bridge, the fifth longest suspension bridge in the world, and the Xihoumen Across Sea Bridge, the second longest suspension bridge in the world. The performance of the bridges and dampers have been reported as “very good” during the May 12, 2008 Wenchuan earthquake. All of the dampers produced have been subjected to rigorous static and dynamic testing, which show the dampers will perform well for the next 50 years and possibly a lot longer.

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STRUCTURAL CONTROL USING HYBRID SPRING-DAMPER ISOLATOR WITH INTEGRAL GAPPING FUNCTION

ABSTRACT

The design of a component to provide combined spring and damping output is strongly driven by scaling issues for the discrete mechanical elements used to provide the required output forces. Multiple design concepts and technologies are available to provide damping and/or spring forces. However, consideration of the relative force requirements, life cycle, operative environment, and space envelope available usually will result in a specific type of damper and a specific type of spring being optimum. The spring-damper isolator described was designed and manufactured for use on the world’s largest cable stayed bridge – the Sutong Bridge over China’s Yangtze River, completed in 2008.

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Fluid viscous dampers: an effective way to suppress Pedestrian-induced motions in footbridges

ABSTRACT

In the civil engineering field, fluid viscous dampers, used extensively in military applications, have found commercial applications on buildings and bridges subjected to seismic and/or wind storm inputs. Because fluid damping technology was proven thoroughly reliable and robust, implementation on footbridges to suppress undesirable pedestrian-induced vibrations is taking place. This presentation provides a brief overview of fluid damping technology with specific case studies being provided from pedestrian bridges now equipped with fluid viscous dampers. The viscous dampers are used to completely suppress the feedback between the pedestrians and the bridge and/or wind-induced vibrations. Design requirements of viscous damping devices for footbridge are discussed. The tested performance of structures with fluid viscous dampers show that tremendous gains in performance can be realized at relatively low cost.

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FLUID LOCK-UP DEVICES – A ROBUST MEANS TO CONTROL MULTIPLE MASS STRUCTURAL SYSTEMS SUBJECTED TO SEISMIC OR WIND INPUTS

ABSTRACT

Fluid Lock-up Devices have recently become quite popular for passive control of large structures subjected to earthquake or wind storm effects. The Lock-up Device, a variation of the Fluid Viscous Damper, allows unrestricted motion at low translational speeds. Yet, when a transient event occurs, the Lock-up Device activates, dynamically forming, in effect, a rigid brace connection between masses. After the transient event ends, the Lock-up Device reverts to low force output, permitting structural sections to thermally expand or contract without added stress. The operation of the device is completely passive, yet enables multi-mass structures to be dynamically braced, without resorting to the cost and complexity of an active.

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