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Koo K.Y.,University of Sheffield | Brownjohn J.M.W.,University of Sheffield | Carden P.,Lloyd's Register | List D.I.,Tamar Bridge and Torpoint Ferry Joint Committee | And 2 more authors.
Bridge Maintenance, Safety, Management and Life-Cycle Optimization - Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Management | Year: 2010

For structural health monitoring purposes, it has become extremely important to understand, model, and compensate for the environmental variations on both of static and dynamic characteristics of structures under ambient operation conditions. This paper presents a long-term structural health monitoring on Tamar Suspension Bridge to understand the environmental effects of temperature, wind speed and traffic volume. The monitoring system consists of two parts: a static monitoring system for cable tensions, wind, temperature measurements and a dynamic monitoring system for deck and cable accelerations. The data-driven stochastic subspace identification (SSI) method was implemented for modal parameter identification of the lower 5 natural frequencies. Environmental effects were investigated for a record of over 6 month and it was found that cable tensions appeared to be dominated by the temperature change while the frequency variations were appeared to be affected by all of the wind, the temperature and the traffic loading with different contributions in each mode. Input-output modeling using quadratic polynomials was tried in a purely mathematical perspective and it was found the quadratic polynomial model reasonably fits the frequency time history. Analytical validation for the observations and identification of a feasible FE model are underway. © 2010 Taylor & Francis Group, London.


Brownjohn J.M.W.,University of Exeter | Koo K.-Y.,University of Exeter | Scullion A.,Humber Bridge Board | List D.,Tamar Bridge and Torpoint Ferry Joint Committee
Structure and Infrastructure Engineering | Year: 2015

Long-span bridges deform quasi-statically and dynamically under a range of operational conditions including wind, traffic and thermal loads, in varying patterns, at different timescales and with different amplitudes. While external loads and internal forces can only rarely be measured, there are well-developed technologies for measuring deformations and their time and space derivatives. Performance data can be checked against design limits and used for validating conceptual and numerical models which can in turn be used to estimate the external loads and internal forces. Changes in performance patterns and load–response relationships can also be used directly as a diagnostic tool, but excessive deformations themselves are also a concern in terms of serviceability. This paper describes application of a range of measurement technologies, focusing on response to extreme loads, for suspension bridges over the River Tamar (with 335 m main span) and Humber (with 1410 m man span). The effects of vehicular, thermal and wind loads on these very different structures are compared, showing that apart from rare extreme traffic and wind loads, temporal and spatial temperature variations dominate quasi-static response. Observations of deformation data and sensor performance for the two bridges are used to highlight limitations and redundancies in the instrumentation. © 2014, © 2014 Taylor & Francis.


Koo K.Y.,University of Sheffield | Brownjohn J.M.W.,University of Sheffield | List D.I.,Tamar Bridge and Torpoint Ferry Joint Committee | Cole R.,Tamar Bridge and Torpoint Ferry Joint Committee
Structural Control and Health Monitoring | Year: 2013

This paper presents experiences and lessons from the structural health monitoring practice on the Tamar Bridge in Plymouth, UK, a 335-m span suspension bridge opened in 1961. After 40 years of operations, the bridge was strengthened and widened in 2001 to meet a European Union Directive to carry heavy goods vehicles up to 40 tonnes by a process in which additional stay cables and cantilever decks were added and the composite deck was replaced with a lightweight orthotropic steel deck. At that time, a structural monitoring system comprising wind, temperature, cable tension and deck level sensors was installed to monitor the bridge behaviour during and after the upgrading. In 2006 and 2009, respectively, a dynamic response monitoring system with real-time modal parameter identification and a robotic total station were added to provide a more complete picture of the bridge behaviour, and in 2006 a one-day ambient vibration survey of the bridge was carried out to characterize low-frequency vibration modes of the suspended structure. Practical aspects of the instrumentation, data processing and data management are discussed, and some key response observations are presented. The bridge is a surprisingly complex structure with a number of inter-linked load-response mechanisms evident, all of which have to be characterized as part of a long-term structural health monitoring exercise. Structural temperature leading to thermal expansion of the deck, main cables and additional stays is a major factor on global deformation, whereas vehicle loading and wind are usually secondary factors. Dynamic response levels and modal parameters show apparently complex relationships among themselves and with the quasi-static load and response. As well as the challenges of fusing and managing data from three distinct but parallel monitoring systems, there is a significant challenge in interpreting the load and response data firstly to diagnose the normal service behaviour and secondly to identify performance anomalies. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.


Brownjohn J.M.W.,North Park University | Koo K.-Y.,North Park University | Scullion A.,Humber Bridge Board | List D.,Tamar Bridge and Torpoint Ferry Joint Committee
Structure and Infrastructure Engineering | Year: 2014

Long-span bridges deform quasi-statically and dynamically under a range of operational conditions including wind, traffic and thermal loads, in varying patterns, at different timescales and with different amplitudes. While external loads and internal forces can only rarely be measured, there are well-developed technologies for measuring deformations and their time and space derivatives. Performance data can be checked against design limits and used for validating conceptual and numerical models which can in turn be used to estimate the external loads and internal forces. Changes in performance patterns and load-response relationships can also be used directly as a diagnostic tool, but excessive deformations themselves are also a concern in terms of serviceability. This paper describes application of a range of measurement technologies, focusing on response to extreme loads, for suspension bridges over the River Tamar (with 335 m main span) and Humber (with 1410 m man span). The effects of vehicular, thermal and wind loads on these very different structures are compared, showing that apart from rare extreme traffic and wind loads, temporal and spatial temperature variations dominate quasi-static response. Observations of deformation data and sensor performance for the two bridges are used to highlight limitations and redundancies in the instrumentation. © 2014 © 2014 Taylor & Francis.


Koo K.Y.,University of Sheffield | Brownjohn J.M.W.,University of Sheffield | List D.,Tamar Bridge and Torpoint Ferry Joint Committee | Cole R.,Tamar Bridge and Torpoint Ferry Joint Committee | Wood T.,Cornwall Country Council
Bridge Maintenance, Safety, Management and Life-Cycle Optimization - Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Management | Year: 2010

This paper presents an innovative structural health monitoring system using an automated Total Positioning System (TPS) and its application to Tamar Suspension Bridge. Conventional TPS also known as Total Station used for surveying have evolved to have a functionality of automated and unmanned operations. For SHM purposes, an automated TPS can be utilized for monitoring 3D deflections of a structure. Tamar Bridge, Plymouth, UK has been equipped by an automated TPS on the roof of the bridge office for monitoring of the bridge deck and tower to understand complex behavior of the suspension bridge system under environmental loadings such as temperature, wind and traffic loads. From Sept 2009, 15 points around the bridge deck and towers have been monitored and the global deflections were recorded. Based on the three months monitoring records, temperature change was found to be the dominant contributor of bridge deflections in the longitudinal and vertical directions while the transverse deflections are not understood yet. Further analysis on the deflections is underway. Limitations of the current technology were discussed. © 2010 Taylor & Francis Group, London.

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