pinecone/core-2020-05-10-deduplication huggingface dataset:
Distributed sensing of a masonry vault during nearby piling

Piles were constructed inside historic brick barrel vaults during the London Bridge Station redevelopment. In order to ensure safe operation of the tracks above, movements of the vaults were monitored regularly by total stations. Concurrently, two distributed sensing technologies, fibre optic cables and laser scanners, were used to investigate the vault response to settlements. This paper discusses the monitoring data retrieved from these ‘point’ and ‘distributed’ sensing technologies, and evaluates their use in structural assessment. The total station data is examined first. It is characterised by high precision and limited spatial coverage due to the use of optical targets. As a result, the total station data is useful for threshold detection but does not provide a detailed understanding of structural response or damage. In contrast, by utilizing distributed fibre optic sensors based on Brillouin Optical Domain Reflectometry, the strain development in the structure during piling is quantified. The location and width of resulting crack openings are also determined, providing useful indicators for damage evaluation. The comparison of point clouds from laser scanners obtained at different stages of pile construction further expands the spatial coverage by detecting global movement of the structure on all visible surfaces. Using this data, the two hinge response mechanism of the vault is revealed. The rich distributed data enables the calibration of the 2D mechanism and the finite element models, elucidating the contribution of arch stiffness, arch and backfill interaction, potential lateral movements and inter-ring sliding to the response.The work carried out was funded by EPSRC and Innovate UK, through the Cambridge Centre for Smart Infrastructure and Construction. The research materials supporting this publication can be accessed at https://www.repository.cam.ac.uk/handle/1810/254826. The authors are grateful to Tim Embley of Costain and Jim Woodhams of Topcon for making this project possible. They’d like to thank Network Rail for allowing them to publish this data. Help from a number of individuals requires special mention; Vincent Auzel of Soldata, Dean Bain of Costain and Andy Evans of Topcon provided useful information that enabled this study. CSIC colleagues Peter Knott, Jason Shardelow and Emanuele Giglio assisted in site work and discussions with Matthew DeJong helped improve the manuscript.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/stc.187
Transducer placement optimisation scheme for a delay and sum damage detection algorithm

In this work, a transducer placement scheme based on wave propagation is proposed, which enhances damage localisation. The method was tailored to seek an optimal transducer network placement for a delay and sum damage detection algorithm. The proposed method determines a coverage index map and utilises a genetic algorithm to determine an optimal transducer network. It can also minimise the impact of faulty transducers, incorporate the effect of stiffeners and different damage types. The method is initially verified using numerically simulated signals. The optimal network outperformed the suboptimal for detection of holes and debonding in a stiffened panel. It is also shown that the coverage index reflected the localisation accuracy. The method is then validated with experimental results and the generated optimal transducer network compared with a suboptimal arrangement. The optimal network is shown to locate an actual crack with significantly higher accuracy than the suboptimal arrangement
Acceleration-based fault-tolerant control design of offshore fixed wind turbines

Wind turbines (WTs) are basically controlled by varying the generator load torque (with the so-called torque control) and the blade pitch angles (with the so-called pitch control) based on measurement of the generator shaft speed. These two controllers unitedly work to satisfy the control objectives, and it is crucial that they are tolerant to possible faults in the WT system. Passive fault-tolerant control comprises the design of robust controllers against disturbances and uncertainties. This enables the controller to counteract the effect of a fault without requiring reconfiguration or fault detection. In this regard, the main contribution of this paper is to propose new control techniques that not only provide fault tolerance capabilities to the WT system but also improve the overall performance of the system in both fault-free and faulty conditions. Coupling nonlinear aero-hydro-servo-elastic simulations of an offshore WT with jacket platform is carried out for several pitch actuator faults. The jacket platform motions and structural loads caused by fault events with the proposed controllers are compared with loads encountered during normal operation and with respect to a well-known baseline controller in the literature. The proposed controllers are based in the super-twisting algorithm by using feedback of the generator shaft speed as well as the fore-aft and side-to-side acceleration signals of the WT tower.Preprin
Monitoring of masonry historical constructions: 10 years of static monitoring of the world's largest oval dome

This paper presents the analyses conducted on the data acquired by the monitoring system of the “Regina Montis Regalis” Basilica of Vicoforte (Italy) in the decade 2004–2014. The Basilica is a building of great historical, architectural, and structural significance, owing its fame to its impressive masonry oval dome, the world's largest of this shape (internal axes of 37.23 by 24.89 m).

The dome-drum system of the Basilica has suffered over the years of significant structural problems, partly due to the settlements of the building induced progressively by newly built masses and also to the sliding of the underground. In 1983, concerns over the severe settlements and cracking phenomena affecting the structure prompted the decision to undertake strengthening interventions. A special hooping system, consisting of 56 tie bars, placed around the oval perimeter of the dome, was thus conceived to limit the crack opening.

The monitoring system of the Basilica installed in the early 1980s underwent several renovations, and in 2004, its acquisition procedure was automatized. One hundred twelve instruments, consisting of temperature sensors, crackmeters, load cells, pressure cells, wire gauges, hygrometer, piezometers, and hydrometer, are currently installed on the Basilica.

This study is primarily focused on data acquired by the crackmeters, the extensometers along the main axes of dome, and the load cells placed at the ends of the tie bars. The main aim of the reported analysis is to evaluate the possible progression of the cracks on the Basilica, and the structural performance of the strengthening interventions put in place in 1985–1987
Proof of Concept of Wireless TERS Monitoring

Temporary earth retaining structures (TERS) help prevent collapse during
construction excavation. To ensure that these structures are operating within
design specifications, load forces on supports must be monitored. Current
monitoring approaches are expensive, sparse, off-line, and thus difficult to
integrate into predictive models. This work aims to show that wirelessly
connected battery powered sensors are feasible, practical, and have similar
accuracy to existing sensor systems. We present the design and validation of
ReStructure, an end-to-end prototype wireless sensor network for collection,
communication, and aggregation of strain data. ReStructure was validated
through a six months deployment on a real-life excavation site with all but one
node producing valid and accurate strain measurements at higher frequency than
existing ones. These results and the lessons learnt provide the basis for
future widespread wireless TERS monitoring that increase measurement density
and integrate closely with predictive models to provide timely alerts of damage
or potential failure
Phase II benchmark control problem for seismic response of cable-stayed bridges

This paper presents the problem definition for the second generation of benchmark structural control problems for cable-stayed bridges. The goal of this study is to provide a testbed for the development of strategies for the control of cable stayed-bridges. Based on detailed drawings of the Bill Emerson Memorial Bridge, a three-dimensional evaluation model has been developed to represent the complex behavior of the full-scale benchmark bridge. Phase II considers more complex structural behavior than phase I, including multi-support and transverse excitations. Evaluation criteria are presented for the design problem that are consistent with the goals of seismic response control of a cable-stayed bridge. Control constraints are also provided to ensure that the benchmark results are representative of a control implementation on the physical structure. Each participant in this benchmark bridge control study is given the task of denning, evaluating and reporting on their proposed control strategies. Participants should also evaluate the robust stability and performance of their resulting designs through simulation with an evaluation model which includes additional mass due to snow loads. The problem and a sample control design have been made available in the form of a set of MATLAB equations.National Science Foundation Grant CMS 97-3327
A nonlinear damping control for the vibration mitigation of the benchmark highway bridge

Active, passive and semi-active controls have been extensively considered to improve the protection of structures against earthquakes. In this paper, we present a new nonlinear damper, which is then applied to a three-dimensional benchmark structural control problem for seismically excited highway bridge. The main feature of the proposed controller is the simplicity in formulation, design and implementation. It is based on using a passive static hyperbolic function depending only on the base velocity. This function ensures energy dissipation capability with always bounded control force. The performance indices show that the proposed controller behaves satisfactorily and with a reasonable control effort. Copyrightr2009\ud
John Wiley & Sons, Ltd.Postprint (published version
Application of the damage index method for plate-like structures to timber bridges

The paper presents a research recently completed by the authors utilizing a method of damage evaluation for identifying damage in timber bridges, numerically and experimentally. The method utilizes changes in modal strain energy between the undamaged and damaged states of plate-like structures. A finite element model of a laboratory timber bridge was developed to investigate the capabilities and limitations of the method to detect damage. A simple four-girder bridge was fabricated and tested in a laboratory to verify the method. The numerical studies showed that the method can correctly identify single and multiple damage locations within the bridge. The experimental studies also showed promising results for detecting severe damage, but less effective for light and medium damage
Crack detection in simply supported beams using stationary wavelet transform of modal data

A new approach, using stationary wavelet transform (SWT), is proposed for crack detection in beam-like structures. SWT is a redundant transform that doubles the number of input samples at each iteration, which can provide a more accurate estimation of the variances and facilitate the identification of salient features in a signal, especially for recognizing noise or signal rupture. The mode shape of a cracked beam with a small crack depth, while apparently a single smooth curve, actually exhibits a local peak or discontinuity in the region of damage. The mode shape ‘signal’ can be approximately considered as that of the intact beam contaminated by ‘noise’ which consists of response noise and the additional response due to the crack. The signal can be decomposed by SWT into a smooth curve, called approximation coefficient, and a detail coefficient curve, which includes crack information, respectively. In this paper, the modal responses of damaged simply supported beams are computed using the finite element method in conjunction with some experimental tests. The effect of noise on the proposed method is also studied. It is shown that SWT of the modal data of cracked simply supported beams provides a better crack indication than conventional discrete wavelet transform. The relationship between SWT detail coefficient and crack size (depth and width) are also discussed. A new method based on the average difference of the SWT detail coefficient of vibration bending modes of a cracked beam and an intact beam is proposed as a damage index and verified
Control of flapwise vibrations in wind turbine blades using semi-active tuned mass dampers

The increased size and flexibility of modern multi-Megawatt wind turbines has resulted in the dynamic behaviour of these structures becoming an important design consideration. The aim of this paper is to study the variation in natural frequency of wind turbine blades due to centrifugal stiffening and the potential use of semi-active tuned mass dampers (STMDs) in reducing vibrations in the flapwise direction with changing parameters in the turbine. The parameters considered were the rotational speed of the blades and the stiffness of the blades and nacelle. Two techniques have been employed to determine the natural frequency of a rotating blade. The first employs the Frobenius method to a rotating Bernoulli-Euler beam. These results are compared with the natural frequencies determined from an eigenvalue analysis of the dynamic model of the turbine including nacelle motion, which is developed in this paper. The model derived considers the structural dynamics of the turbine and includes the dynamic coupling between the blades and tower. The semi-active control system developed employs a frequency-tracking algorithm based on the short-time Fourier transform technique. This is used to continually tune the dampers to the dominant frequencies of the system. Numerical simulations have been carried out to study the effectiveness of the STMDs in  reducing flapwise vibrations in the system when variations occur in certain parameters ofthe turbine. Steady and turbulent wind loading has been considered
A Damage Identification procedure based on Hilbert transform: experimental validation

This paper aims at validating the feasibility of an identification procedure, based on the use of the Hilbert\ud
transform, by means of experimental tests for shear-type multi-degree-of-freedom systems. Particularly,\ud
a three-degree-of-freedom frame will be studied either numerically or experimentally by means of\ud
a laboratory scale model built at the laboratory of the Structural, Aerospace and Geotechnical Engineering\ud
Department (DISAG) of University of Palermo. Several damage scenarios have been considered to prove\ud
the effectiveness of the procedure. Moreover, the experimental tests have been conducted by considering\ud
two different input loads: pulse forces, simulated by means of an instrumental hammer, and wide band\ud
noise base inputs, by a shake table.\ud
In the first section the damage identification procedure, proposed in recent works, is presented. The\ud
procedure is based on the minimization of an objective function mathematically based on the properties of\ud
the analytical signal and the Hilbert transform. Second section reports the experimental model geometrical\ud
data and the data acquisition set-up as built in the DISAG laboratory. In Section 3, the results of the\ud
experimental campaigns are presented and discussed having considered three damage scenarios. The\ud
validated procedure has been proved to be able to not only detect damage even at early stage but it also needs\ud
processing of only few samples of the structural respons
A note on predetermined earthquake damage scenarios for structural health monitoring

It is shown that the damage scenarios for site-specific building models, responding in highly nonlinear manner to strong earthquake ground-motion pulses, can be used in real-time health-monitoring systems. When it can be shown that such predictions produce robust results and are not sensitive to the details of the complete time history of strong ground motion, the predetermined earthquake damage scenarios (PEDS) method can produce reliable predictions of the location(s) and the degree(s) of structural damage in essentially real time. It is shown that for a full-scale building, damaged during the 1994 Northridge earthquake in California, PEDS based on one-dimensional wave propagation in the layered building model would have produced accurate and realistic predictions of damage. In contrast to the vibrational health-monitoring methods that track changes in the frequency and stiffness of the characteristic functions, PEDS methods provide invaluable information for spatial and temporal identification of damage
Experimental and numerical investigations of a thermoplastic composite (carbon/PPS) thermoforming

For lightweight structural components, continuous fibre-reinforced thermoplastic composites have demonstrated success in aerospace and defence applications. Their mechanical behaviour is a result of the possible sliding and interactions between the fibres, but the complex deformation mechanisms of this sheet are a main problem in the practical thermoforming process. In this context, a large experimental work was developed to analyse the behaviour of a 5-harness satin weave carbon–polyphenylenesulfide (PPS) composite. Firstly, we started this work with a microscope observation of the sheet cross section and a thermo-gravimetric analysis of carbon/PPS to understand the thermal condition in the forming process, the reinforcement (fibre and yarn) geometry and dimensions and the textile reinforcement architectures. Secondly, in high temperature conditions (at 320�C), static uniaxial and biaxial tensile tests were carried out. During these mechanical tests, we used a digital image stereo-correlation technique to get full field displacement measurements and an infrared camera to measure the temperature in the surface of sample.\ud
The results of the experimental investigation were used with the commercial software ABAQUS to develop a numerical model of stamp thermoforming operation. The stamp thermoforming part was developed using a hemispherical punch and compared with an experimental result. In the deformed part obtained by thermoforming of the carbon/PPS sheet, we analysed the instability phenomena such as wrinkling
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
Recent research on the design and behaviour of drive-in steel storage racking systems

This paper summarizes a recently completed research programme carried out at the University of Sydney on drive-in steel storage racks subjected to horizontal impact loads. Impact loads develop frequently during the normal operation of drive-in racks when the forklift truck strikes an upright on entering or leaving a bay, and may lead to local or global collapse. The collapse follows the bowing of the upright which may cause a pallet to drop off the supporting beam rails and initiate progressive collapse down through the bay and possibly into adjacent bays as well.    The research programme comprised full-scale tests on assemblies of a four-bay-wide racking system, tests on system components, the development of finite element models capable of predicting the behaviour of the system accurately, parametric studies of the strengths and stiffnesses of steel storage racks, the development of a simple mechanical model for understanding the dynamic behaviour of the system during impact and a reliability analysis for deriving equations for the design impact loads and associated load factors.    The purpose of the paper is to give an overview of the methodology adapted for the research programme and to present the main findings and final outcome of the research.Griffith Sciences, Griffith School of EngineeringFull Tex
Torsion and its interaction with other internal forces in EN 1993-1-1: a new approach

This is the accepted version of the following article: [Real, E., Bordallo, J. and Real, E. (2016), Torsion and its interaction with other internal forces in EN 1993-1-1 – a new approach. Steel Construction, 9: 240–248. doi:10.1002/stco.201500005], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/stco.201500005/abstractThis paper presents and clarifies the treatments included in EN 1993-1-1, relating to checking the resistance of the steel cross-sections under torsion and its interaction with other internal forces. Specifically, the origin of the formulations for shear-torsion interaction, which was not found in the literature, is presented. Furthermore, a very simple formulation based on the expressions used for shear-torsion interaction is developed, in order to take into account bending-warping torsion interaction for symmetrical double T cross-sections (IP and HE steel profiles). Such formulation overcomes the overly conservative approach stated in EN 1993-1-1, for Class 1 and Class 2 cross-sections (plastic and compact cross-sections). Finally, a rigorous method for the determination of the bending resistance of cross-sections is proposed, considering the interaction with shear and torsion. The proposal is well suited to the concept of cross-sectional class and it is perfectly consistent with the approaches set out to consider the bending-shear and bending-warping torsion interactions.Peer ReviewedPostprint (author's final draft