Lessons from monitoring the performance of highway bridges

This is the peer reviewed version of the following article :Brownjohn, J. M. W., Moyo, P., Omenzetter, P. and Chakraborty, S. (2005), Lessons from monitoring the performance of highway bridges. Struct. Control Health Monit., 12: 227–244. doi: 10.1002/stc.67, which has been published in final form at doi: 10.1002/stc.67.Monitoring programs on four very different highway bridges originating from a range of requirements related to calibration of numerical models, assessment of load capacity and long term tracking of performance are summarized in order to draw out lessons relevant to the future development of structural health monitoring ‘systems’. These lessons concern validation of structural models, appropriate methods for instrumentation, communication, data management and system identification. The paper presents experience obtained by collaboration in a form intended to educate, by example, bridge operators about potential and limitations of SHM systems

Lessons from monitoring the performance of highway bridges

Peer reviewedPreprin

Interpreting data from bridge performance and health monitoring systems

startedmonth: OctoberPaper presented at 2nd International Conference on Bridge Maintenance, Safety and Management, Kyoto, JapanStructural health monitoring (SHM), particular for highway bridges, is a fertile research area for academics and a potentially very useful tool for bridge management authorities. The academic approach often focuses on sensor technology, data collection, detecting visible and invisible damage and areas that may not be of immediate use to the practical operators who need condensed information for decision making. The steps in the process such as data management, data mining, conversion to knowledge of structural behaviour and integrity are frequently absent, and even the most operationally successful SHM systems may lack the component where deep understanding on the nature of the bridge performance is obtained. This paper presents experience gained in a number of bridge monitoring exercises where static and dynamic response data have been interpreted, with or without the aid of calibrated structural models, in order to characterise the mechanisms at work and the experiences of the structure. Hence, while considerable experience has been gained in pure signal analysis, we are also merging the SHM data with dynamically calibrated FE models in an approach which we believe to be the way forward for future SHM systems

Vibration stability of Orion laser facility

This is the author accepted manuscript. The final version is available from Thomas Telford (ICE Publishing) via the DOI in this record.In 2005 the UK Ministry of Defence awarded a contract for construction of the Orion laser facility at the Atomic Weapons Establishment (AWE). Orion delivers a power density of 1021W/cm2 on a 5 µm target, making it a world class facility for the study of high energy density physics. The ability to target to such high precision depends on ‘stability’ of the building and internal structures with respect to thermal expansion and vibrations. This paper concerns experimental activities supporting prediction and evaluation of the minute vibrations against a ‘budget’ comprising effects of all vibration sources, internal and external, and the sequence of experimental campaigns and signal evaluation that fed into this process. This involved a sequence of dynamics-based measurements of: • foundation pile stiffness • vibration propagation from both controlled and uncontrolled sources at stages during the construction and finally • evaluation of vibration levels in the as-built facility due to internal machinery and the few external vibration sources passing through the sophisticated vibration barrier. The approach focused on time series of vibrations in the design phase, and on evaluation of statistical properties of displacement power spectral density functions

Effect of sensory stimuli on dynamic loading induced by people bouncing

Prediction of dynamic loads induced by groups and crowds of people bouncing is a hot topic among designers of grandstands and floors in entertaining venues. Using motion capture technology transferred and adapted from biomedical research, this study aims to investigate effect of visual, auditory and tactile cues on the ability of people to coordinate or synchronise their bouncing movements in groups of two. The numerical results showed a great significance of such stimuli on people's mutual interaction during bouncing, signifying that their effect should be considered in developing much-needed models of crowd dynamic loading of structures due to coordinated rhythmic activities. © The Society for Experimental Mechanics, Inc. 2013

Floor vibration serviceability in a multistory factory building

ArticleExperimental and analytical modal analysis and in-operation vibration measurements were performed on the massive concrete structural floors of several structurally connected ‘units’ of a six-level, multitenant industrial complex with total floor usable area exceeding 0.1 km2. The aim of the systematic study was to characterize vibration sources and factors that affect vibration serviceability, which is a major concern when changing usage patterns lead to conflicting requirements for vibration generation and tolerance for different types of industrial/ commercial user. This was a rare investigation aiming to provide information on specific performance and relevant technologies for occupancy decisions by tenants and building management of similar structures. Floors evaluated were within different types of industrial singleoccupant unit stacked up to six levels and having multibay floors with spans up to 12 m with first vibration mode frequencies greater than 8 Hz. These “high-frequency floors” display typical transient response behavior to footfalls, with response levels controlled by modal mass. Units were studied in typical operational conditions including warehousing, instrument assembly and testing, light electronic/mechanical manufacturing, and machining. Vibration sources included internal and external vehicles, human footfalls, and machinery. The study showed the most onerous form of loading to be forklift trucks and that higher level floors of the same type were least serviceable. Experimental modal analysis showed a surprising range of modal properties for nominally identical floors of the same type and the relevance to performance of modal mass

Bayesian operational modal analysis of offshore rock lighthouses for SHM

This is the author accepted manuscript. the final version is available from the British Institute of Non-Destructive Testing via the link in this recordDuring 2016 and 2017 a program of field vibration measurements was made on a set of Victorian era granite lighthouse towers around the British Isles. The field tests were designed for structural identification to enable condition assessment and identification of extreme wave loads through long term monitoring. The primary test method was forced vibration, and ambient vibration measurements was used as a backup. The best operational modal analysis (OMA) results were obtained using Bayesian OMA, which provide a clear picture of the directionality of the mode shapes which appeared at very close frequencies due to the symmetry of the towers. The paper describes measurements and sample analysis illustrating difficulties and achievements.Engineering and Physical Sciences Research Council (EPSRC

Tumour necrosis factor induces increased production of extracellular amyloid-β- and α-synuclein-containing aggregates by human Alzheimer's disease neurons

In addition to increased aberrant protein aggregation, inflammation has been proposed as a key element in the pathogenesis and progression of Alzheimer’s disease. How inflammation interacts with other disease pathways and how protein aggregation increases during disease are not clear. We used single-molecule imaging approaches and membrane permeabilization assays to determine the effect of chronic exposure to tumour necrosis factor, a master proinflammatory cytokine, on protein aggregation in human-induced pluripotent stem cell-derived neurons harbouring monogenic Alzheimer’s disease mutations. We report that exposure of Alzheimer’s disease neurons, but not control neurons, to tumour necrosis factor induces substantial production of extracellular protein aggregates. Aggregates from Alzheimer’s disease neurons are composed of amyloid-β and α-synuclein and induce significant permeabilization of lipid membranes in an assay of pathogenicity. These findings provide support for a causal relationship between two crucial processes in Alzheimer’s disease pathogenesis and suggest that targeting inflammation, particularly tumour necrosis factor, may have beneficial downstream effects on ameliorating aberrant protein aggregation and accumulation

Bayesian operational modal analysis with buried modes

This is the author accepted manuscript. The final version is available form Elsevier via the DOI in this recordIn full-scale ambient vibration tests, challenging situations exist where in the frequency domain the measured data is dominated by other modes that ‘bury’ the subject mode of interest. In this case, conventional modal identification methods are either not applicable or inefficient to apply. This paper proposes a Bayesian frequency domain method for identifying the modal properties of such buried modes. The buried-mode situation is modelled and computation difficulties are addressed, leading to an efficient algorithm for modal identification in such challenging situation. The proposed method is validated by synthetic data examples. The associated uncertainty of the identified modal parameters are investigated. The method is also applied to identifying the buried modes of a long-span suspension bridge, demonstrating its utility with challenging modes encountered in field test data.Engineering and Physical Sciences Research Council (EPSRC

Vibration serviceability assessment of floors in a multi-use, multi-storey industrial complex

Structures Congress 2014, Boston, Massachusetts, United States, 3 - 5 April 2014Vibration serviceability assessments were carried out on the floors of several 'units' of an industrial complex in Singapore. Floors tested were within large, two-level, structural units described as detached, semi-detached and terraced and having usable single floor areas up to 2100 m2. All floors were constructed from hollow core slabs with spans up to 12 m and all nominally behaved as high frequency floors. Occupancy conditions ranged from empty and untenanted to usage for warehousing, instrument assembly and testing, electronic equipment manufacture to light manufacturing and machining of metal structures. Forms of loading included internal and external vehicles, human footfalls and excitation by machinery. The study identified the most onerous form of loading and provides guidance for facility owners with mixed vibration serviceability requirements