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Frontiers in Built Environment
Number of Followers: 1

This is an Open Access Journal

Open Access journal
ISSN (Print) 2297-3362
Published by Frontiers Media

[86 journals]

Continuous Prestress in Launched Extradosed Bridges
- Authors: Philippe Van Bogaert, Hans De Backer
  Abstract: The original concept of extradosed posttensioning in bridges is to obtain larger eccentricity of the tendons and thus to generate larger bending moments, opposing the external loading. This concept has been modified to constitute hybrid extradosed-cable supported bridges. However, the initial idea has the advantage to allow continuous prestressing, the number of costly anchors being minimized. On the basis of a set of geometrical equations and equalizing the live loads to a set of external forces, the conditions for concrete compression and tension are verified. In addition, the compliance with conditions for launching as a whole structure of extradosed bridges is examined. Some clarifying conclusions have been found, such as that extradosed prestress must be supplemented by additional centred prestress, an optimum deviator height can be derived and the amount of required prestress is a relatively stable fraction of the bridge girders. As the main span length increases, the extradosed prestress becomes more effective, although the auxiliary centred prestress takes the largest part in the total amount, thus confirming the character of this type of structures, which remains principally a prestressed concrete girder system The feasibility of launching as a whole has been demonstrated, provided the main span length does not exceed 60m.
  PubDate: 2019-06-19T00:00:00Z
Passenger Car Equivalents for Heavy Vehicles at Roundabouts. a Synthesis
Review
- Authors: Orazio Giuffrè, Anna Granà, Tullio Giuffrè, Maria Luisa Tumminello, Francesco Acuto
  Abstract: Passenger Car Equivalents (PCEs) are used to convert a mixed traffic flow into an equivalent passenger car flow and to analyze capacity and level-of-service of roads and intersections.Most roundabouts guidelines propose constant values for PCEs but a single PCE value can result improper under heterogeneous traffic conditions. PCEs should be vary with traffic and road conditions so that PCEs used under undersaturated conditions may underestimate the effect of heavy vehicles or be not sensitive to the traffic level or characteristics of heavy vehicles.Compared to other at-grade intersections, the interaction between the operational performances of the heavy vehicles and the geometric features at roundabouts can produce significant impacts on the heavy vehicle paths and traffic operations due to the curvilinear nature of the roundabout design.Literature presents various estimation methods to obtain PCE values for heavy vehicles. The focus of this paper is to review statistical methods and traffic simulation studies based on microscopic approaches used to calculate PCEs for heavy vehicles driving roundabouts. Effects on capacity and PCE estimations based on models currently employed in roundabout analysis are also compared. The results obtained in this study aim at providing an overview of the existing knowledge concerning the estimation of PCEs at roundabouts and can represent a guideline for transportation engineers in the design and capacity analysis of roundabouts where mixed traffic conditions occur.
  PubDate: 2019-06-18T00:00:00Z
Lessons Learnt From the 2009 Padang Indonesia, 2011 Tōhoku Japan and 2016
Muisne Ecuador Earthquakes
- Authors: S. C. Chian, S. M. Wilkinson, J. K. Whittle, R. Mulyani, J. E. Alarcon, A. Pomonis, K. Saito, S. Fraser, K. Goda, J. Macabuag, M. Offord, A. C. Hunt-Raby, P. Sammonds, G. Franco, H. Stone, B. Ahmed, F. E. Hughes, N. K. Jirouskova, S. Kaminski, J. Lopez
  Abstract: This paper presents the observations during EEFIT’s post-earthquake reconnaissance missions to the September 20, 2009 Padang (Mw7.6), March 11, 2011 Tōhoku (Mw9.0) and April 16, 2016 Muisne (Mw7.8) earthquakes. The performance of buildings and geotechnical structures within the affected regions were investigated to gain insights on their design and construction deficiencies. Findings on these damage observed are compared along with the characteristics of the earthquake and nature of building codes in these countries. They include building damage caused by resonance, deficiencies in reinforcement detailing, vulnerability to soft storey collapse, ground settlement, soil liquefaction and landslides. It was demonstrated that buildings which were severely damaged had natural building frequencies coinciding with the dominant frequencies of the ground shaking. The locations of damage of several such buildings showed insufficient confining reinforcements and lapping of stirrup links. Soft storey collapses were also observed in the three earthquakes, although many were attributed to old building codes that were less effective. In areas affected by the Muisne earthquake, soft storey collapses were mainly found at mid height of the building rather than at the ground floor as observed in the Padang and Tōhoku earthquakes, likely due to extension of building long after the bottom floors were completed. In the aspect of geotechnical failure, foundations of buildings found on piles performed reasonably well, except for areas affected by soil liquefaction. Landslides occurred following these earthquakes led to large concentration of casualties and property losses, motivating the EEFIT teams to invest efforts in hazard mapping and ground-truthing exercises using satellite images at Padang and Muisne earthquakes respectively. Such geospatial tools applied in these three earthquakes were reviewed and demonstrated to be capable of identifying landslide sites and producing reliable landslide hazard map.
  PubDate: 2019-06-18T00:00:00Z
The Restorative Health Benefits of a Tactical Urban Intervention: An Urban
Waterfront Study
- Authors: Jenny Roe, Laura Barnes, Nicholas J. Napoli, Jarrett Thibodeaux
  Abstract: Increasing access to urban waterfronts hold much promise for promoting healthy behaviors. While many US cities are revitalising their waterfronts, the health and well-being benefits associated with these urban design initiatives are largely unknown. Tactical urban interventions (such as parklets and pop-ups) are short-term projects that experiment with and gather input on potential urban design changes. To date, the effect of these projects on individual health outcomes has not been measured. This study reports a pilot quasi-experimental study which compares real-time exposure to an urban waterfront that was manipulated to provide a control versus an intervention ‘treatment’ condition that increased levels of comfort and fascination in the setting. Our study utilized a repeated-measures crossover randomized design and captured measures of stress and well-being whilst participants walked in each condition (n=23). First, real-time stress was captured using a smart watch to capture heart rate variability (HRV) during the walk, including for a resting baseline period of measurement pre-walk. Second, subjective mood (i.e. stress, arousal and hedonic tone) was assessed pre and post walk using the UWIST MACL Mood Scale (Matthews et al., 1990). Third, two measures of perceived restorativeness (i.e. fascination and being away) were captured pre and post walk using the PRS Scale (Hartig et al., 1997), together with two indicators of social well-being (i.e. place belonging and social trust). Results showed a statistically significant reduction in perceived stress from walking in the intervention, as compared to the control condition (p
  PubDate: 2019-06-14T00:00:00Z
Estimating Passenger Car Equivalent of Heavy Vehicles at Roundabout Entry
Using Micro-Traffic Simulation
- Authors: Robert Pajecki, Faisal Ahmed, Xiaobo Qu, Xinyi Zheng, Yanqun Yang, Said Easa
  Abstract: Passenger Car Equivalent (PCE) is a unit used to represent the impact of a larger vehicle on a road by expressing it as the number of equivalent passenger vehicles. This paper focuses on estimating the PCE of various sized heavy vehicles in roundabouts with respect to different entry flow rates. A single-lane roundabout was tested under predefined mixed traffic and demand scenarios in VISSIM micro-simulation environments. The individual and group behaviour of four separate heavy-vehicle types were tested: single-unit trucks, buses, small semitrailers, and large semitrailers. The obtained PCE values were found to be on average lower than those suggested in the United States guidelines for roundabouts. The estimated PCE values for heavy vehicles in mixed traffic conditions are 1.30 for single unit trucks, 1.40 for small semitrailers, 1.60 for buses, and 1.70 for large semitrailers. Additional factors such as varying inflow (balanced, unbalanced, and congested traffic) show direct influences on the PCE values. The PCE value under these conditions ranged from 1.25 to 1.75 for smaller vehicles (single-unit trucks, buses, and small semitrailers) and 1.45 - 2.10 for larger heavy vehicles (large semitrailers). A general equation was developed based on the data to relate vehicle proportions and heavy-vehicle reduction factors that would be useful for professionals to analyze the operational performance of roundabouts with better accuracy.
  PubDate: 2019-06-12T00:00:00Z
Multi-Span Steel–Concrete Bridges With Anti-seismic Devices: A Case
Study
- Authors: Raffaele Pucinotti, Giovanni Fiordaliso
  Abstract: Seismic protection of structures in general, and bridges in particular, is very complex. In particular, the analysis of bridges with fluid viscous dampers and shock transmitting devices must be done on the best possible analytical model. Indeed a large number of factors must be treated accurately in order to be even more efficient in preserving human life. For complex structures, as is the case of the viaduct under examination, which contains numerous devices, consistent of fluid-viscous dampers and shock transmitters integrated with bearings, design assisted by testing is an almost necessary procedure. In this respect, the FE modelling of the viaduct have required a model updating procedure for its optimization. In fact, the viaducts built within the "Caltagirone Project", can be fully defined as works of great interest due both to the construction methods adopted and to the techniques of stress control in the seismic stage. The design process allowed to solve seismic issues deriving from structural irregularities (altimetric and planimetric) as well as from the high seismicity of the area. The analyses have been carried out by a Capacity Design approach, using non-linear seismic dissipative devices integrated to supports and checking that the substructures maintain substantially elastic. For this reason the piers have been modelled upon their non-linear behaviour under Takeda's hysteretic model. Furthermore, fluid viscous dampers and shock transmitters integrated with bearings, have been designed in accordance with the different stiffness by the substructures, this allowing to limit and partially dissipating stresses induced by earthquakes, in order to keep the deck and the substructures substantially elastic for Life-Safety Limit state condition (at the Ultimate Limit State). The verifications carried out have demonstrated the capability of structures to withstand the stresses under the Collapse Limit State condition without damage, plus ensuring the curvature capability by piers. The comparisons between experimental and numerical results together with the demanding qualification tests carried out in this study, demonstrates that the hydraulic devices are an efficient solution to control the seismic stresses induced on the viaduct and in its substructures, confirming the reliability of the aforesaid devices, that ensure a better structural safety.
  PubDate: 2019-06-12T00:00:00Z
Smart Desks to Promote Comfort, Health, and Productivity in Offices: A
Vision for Future Workplaces
- Authors: Ashrant Aryal, Burcin Becerik-Gerber, Francesco Anselmo, Shawn C. Roll, Gale M. Lucas
  Abstract: : People spend most of their day in buildings, and a large portion of the energy in buildings is used to control the indoor environment for creating acceptable conditions for occupants. However, majority of the building systems are controlled based on a ‘one size fits all’ scheme which cannot account for individual occupant preferences. This leads to discomfort, low satisfaction and negative impacts on occupants’ productivity, health and well-being. In this paper, we describe our vision of how recent advances in Internet of Things (IoT) and machine learning can be used to add intelligence to an office desk to personalize the environment around the user. The smart desk can learn individual user preferences for the indoor environment, personalize the environment based on user preferences, and act as an intelligent support system for improving user comfort, health and productivity. We briefly describe the recent advances made in different domains that can be leveraged to enhance occupant experience in buildings and describe the overall framework for the smart desk. We conclude the paper with a discussion of possible avenues for further research.
  PubDate: 2019-06-12T00:00:00Z
Seismic Vulnerability of Buildings in Historic Centers: From the
“Urban” to the “Aggregate” Scale
- Authors: Giulia Cocco, Andrea D'Aloisio, Enrico Spacone, Giuseppe Brando
  Abstract: Seismic vulnerability assessment of urban centers is a challenging issue that needs to be faced accurately for the earthquake risk of large territorial areas.The selection of suitable methods is a crucial aspect that must be treated according to different evaluation processes, depending on the size of the problem and on the available calculation capacities. A possible strategy consists in analyzing large stocks of buildings, so to include in the analyses all those structural parameters that characterize their response and to involve the variability of the considered features. This would require a high computational effort that should be addressed to the investigation of the response of a large number of models. For this reason, simplified procedures based on engineeristic judgements, are commonly considered a viable way to be undertaken in order to predict damage scenarios.Alternatively, the attention could be focused on a limited number of buildings that are judged to be representative of the whole stock. In this case, more sophisticated analyses could be carried out and the obtained results could be extended to the whole urban center.Based on this premise, this paper presents the results obtained through the application of two different seismic vulnerability methodologies on the historic center of Campotosto, in Italy, which was hit by the last 2016 Central Italy earthquake. The first is an empirical method, applied considering a large stock of 130 buildings, which was calibrated by the authors after the 2009 L’Aquila earthquake for historical centers that are similar to the one studied in this paper. The latter, is a method based on analytical formulations dealt with by the Vulnus software, developed at the University of Padua in Italy, which was used for evaluating the seismic vulnerability of an aggregate building, which has been considered representative of the historic center.The final aim is to compare, also in the light of the damage observed after the 2016 earthquake, the damage scenarios, expressed in terms of fragility curves, derived from the two applied methodologies, in order to prove their reliability and to stress the possible issues related to their implementation at different scales.
  PubDate: 2019-06-11T00:00:00Z
Capacity Evaluation of a Railway Terminal Using Microsimulation: Case
Study of a Freight Village in Turin
- Authors: Vasco Reis, Ana Almeida
  Abstract: Increasingly significant freight transport had led to larger and more complex transport chains. More specifically, intermodal transport has arisen as a desirable alternative to long-haul road transport, as it creates opportunities for cost reduction and to decrease both polluting emissions and road congestion. Hence, achieving good levels of service in intermodal dedicated structures is of paramount importance for the success of this transport option. The global objective of this research is to determine the capacity of the Freight Village of Turin. This is motivated by future changes in traffic demand, related with the neighboring Port of Savona-Vado. The role of freight villages and other logistics centers is becoming progressively more substantial with saturating sea ports focusing on handling operations. Existing literature shows success in intermodal transport highly depends on terminal performance.To fulfil the already mentioned objective, a simulation model was developed, based on discrete-event methodology, which simulates rail and handling operation inside the freight village. The model is then used to test several scenarios with the purpose of investigating variation in operation techniques and resources and the respective impact it has on comprehensive capacity.Confronting the tested scenarios allowed to comprehend the inefficiencies of both rail and handling processes, hence concluding that locomotive operation presents the most limiting factor. Furthermore, by combining different operation conditions and resources, it was possible to conclude how these affect final capacity and overall performance.
  PubDate: 2019-06-06T00:00:00Z
Frictional Heating in Double Curved Surface Sliders and Its Effects on the
Hysteretic Behavior: An Experimental Study
- Authors: Dario De Domenico, Giuseppe Ricciardi, Samuele Infanti, Gianmario Benzoni
  Abstract: The hysteretic behavior of friction isolators is affected by the variability of the friction coefficient caused by heating phenomena at the sliding interface. The aim of this paper is to investigate such heating phenomena through a series of full-scale experimental tests on a double curved surface slider. The prototype isolator is equipped with eight thermocouples placed in different points of the isolator, which are embedded in the sliding plate. The probes of the thermocouples are in contact with the stainless steel sheet covering the sliding plate, in such a manner that their measurements are representative of the temperature rise occurring at the sliding interface. By investigating different axial loads and sliding velocities, we discuss the measured temperature rise and its implications on the hysteretic behavior of the prototype isolator. Friction variation is observed in the cyclic response of the isolator, which reduces the energy dissipated per cycle and, consequently, may lead to some underestimations of the displacements occurring during real seismic events if a constant friction coefficient is assumed. The proposed data can be helpful to calibrate sophisticated thermo-mechanical finite element models, which is the object of ongoing research.
  PubDate: 2019-06-04T00:00:00Z
Seismic Vulnerability Analysis and Retrofitting of the SS. Rosario Church
Bell Tower in Finale Emilia (Modena, Italy)
- Authors: Antonio Formisano, Gabriele Milani
  Abstract: The Italian territory is rich of constructions belonging to the architectural heritage which deserve to be protected against earthquakes. In seismic prone areas ecclesiastic complexes, including churches, bell towers, monasteries, basilicas, synagogues, cathedrals and so on, have shown to be very susceptible at damage, even with partial or total collapses, when undergoing earthquakes. Indeed, these constructions, which are usually designed to withstand gravity loads only, are characterised by slender walls, lack of horizontal floors, bad quality of the masonry apparatus, ineffective connections among walls and between roof and walls and absence of tie-beams able to absorb the thrusts of arches and vaults. All these issues are responsible of the damages suffered by these structures, as detected after the last Italia earthquakes, such as those occurred in L’Aquila (2009), Emilia-Romagna (2012), Central Italy (2016) and Ischia (2017). In the current paper the seismic vulnerability assessment of the bell tower of the SS. Rosario ecclesiastic complex in Finale Emilia (district of Modena, Italy) is presented and discussed. After the geometrical and structural surveys of the whole masonry structure have been performed, the global seismic analysis of the bell tower by the 3Muri analysis software has been done. In particular, the behavioural differences between the isolated condition of the tower and the case within the ecclesiastic complex have been highlighted, showing the aggregate beneficial effect. Finally, proper retrofitting interventions have been designed and applied to the masonry bell tower, considered both as isolated construction and aggregate one, and the different benefits deriving from these interventions in the two inspected cases have been emphasised.
  PubDate: 2019-05-28T00:00:00Z
Cross Laminated Timber (CLT) Beams Loaded in Plane: Testing Stiffness and
Shear Strength
- Authors: Francesco Boggian, Mauro Andreolli, Roberto Tomasi
  Abstract: Cross Laminated Timber (CLT) is a relatively new timber product used in constructions that gained lots of popularity over the last decade. The product itself is constituted by multiple glued layers of juxtaposed boards, usually arranged in an opposite direction between one layer and the adjacent ones. This particular structure brings several benefits, i.e. the possibility to use the same product both for walls and slabs, since it can bear in plane and out of plane loads. However, the mechanical behavior differs from usual timber products, and research is still ongoing to achieve common agreement on standard procedures for testing and theories for evaluating stresses for safety verifications. This paper proposes to investigate the behavior of CLT beams loaded in plane by testing several specimen with a four point bending test setup according to the EN 408 procedure \cite{EN408}. The main goal is to analyze the shear behavior of these beams hence the particular geometry is specifically chosen to obtain in plane shear failure. First the matter is analyzed by a literature review to study the existing theories for the calculation of in plan shear stresses in CLT elements. Then the experimental campaign is reported, the first part regarding elastic range test for Modulus of Elasticity measurement and the second main part regarding the failure tests to investigate shear behavior with regard to different mechanisms. Last conclusions are made and results are compared with other existing tests and proposed values in literature.
  PubDate: 2019-05-28T00:00:00Z
The Vulnerability of Buildings From the Osijek Database
- Authors: Gordana Pavić, Borko Bulajić, Marijana Hadzima-Nyarko
  Abstract: Estimating of buildings vulnerability is based on a well-organized and detailed database of buildings and their characteristics.Creation of the buildings database of the city Osijek is in progress. This database contains, for each building, information regarding its location, geometric and structural characteristics, materials which were used for structural elements, and other relevant data. This paper presents numerical and statistic values of some characteristics of the buildings from the database.Different methods can be applied for the prediction of damage probability in the field of earthquake risk assessment. With the empirical Macroseismic method and the analytical Capacity Spectrum Method, the vulnerability of the few blocks of buildings, typical for the city Osijek, is estimated.For unreinforced masonry structures with flexible floors, the probability of reaching a certain degree of damage is estimated by the two selected methods, and the obtained results are compared.
  PubDate: 2019-05-24T00:00:00Z
Finite Element Modeling of Ballasted Rail Track Capturing Effects of
Geosynthetic Inclusions
- Authors: Yajun Jiang, Sanjay Nimbalkar
  Abstract: This paper presents a two dimensional finite element (FE) approach to investigating beneficial aspects of geogrids in the railway track. The influences of different factors including the subgrade strength, the geogrid stiffness, the placement depth of geogrid, the effective width of geogrid, the strength of ballast-geogrid interface and the combination of double geogrid layers were investigated under the monotonic loading. The results indicated the role of geogrid reinforcement is more pronounced over the weak compressible subgrade. A stiffer geogrid reduces ballast settlement and produces a more uniform stress distribution along a track. The placement location of a geogrid is suggested at the ballast-sub-ballast interface to achieve better reinforcement results. Although the width of a geogrid layer should be sufficient to cover an entire loaded area, excessive width does not guarantee additional benefits. Higher interface strength between a ballast and a geogrid is beneficial for effective reinforcement. Increasing the number of geogrid layers is an effective way to reinforce the ballast over weak subgrades. The results of the limited cyclic FE simulations revealed the consistency of the reinforcement effect of the geogrids under monotonic and cyclic loads.
  PubDate: 2019-05-22T00:00:00Z
The Passenger Car Equivalent Factors for Heavy Vehicles on Turbo
Roundabouts
- Authors: Elżbieta Macioszek
  Abstract: The presence of heavy and slower vehicles within the traffic stream significantly reduces traffic capacity. This reduction increases with the higher participation of heavy vehicles in the stream, which, compared to passenger cars, move at a lower speed. Furthermore, they occupy more space on the road, are characterized by a longer reaction time to the road traffic situations, and put greater pressure on the surface structure, etc. In order to conduct analyses related to determination of the conditions in the traffic stream, the traffic stream mixed in terms of composition is converted from real vehicles into passenger car equivalents. For this purpose, the passenger car equivalent factors (Ei) appropriate for a given group of vehicles are used. The paper presents the results of a study aimed to determine the numerical values of passenger car equivalent factors for heavy vehicles (trucks, buses, trucks with trailers, articulated buses) on turbo roundabouts. The research was carried out on turbo roundabouts located in Poland.
  PubDate: 2019-05-22T00:00:00Z
Ambient Vibration Measurement Data of a Four-Story Mass Timber Building
- Authors: Ignace Mugabo, Andre R. Barbosa, Mariapaola Riggio, James Batti
  PubDate: 2019-05-22T00:00:00Z
Fatigue Assessment and Deterioration Effects on Masonry Elements: A Review
of Numerical Models and Their Application to a Case Study
- Authors: Vito Michele Casamassima, Michele D'Amato
  Abstract: Safety assessment with respect to seismic and vertical loads of existing and very old masonry structures is currently a central topic of engineering scientific community. In particular, there are many ancient bridges still in service subjected, respect to the past, to higher and more frequent cyclic loads. For these structures it is really important to determine, rather than the ultimate carrying capacity, the actual fatigue strength. In this way the remaining service life, with also possible traffic load limitations, may be estimated.This paper reports an updated review of state of the art about the recent fatigue models published in the literature, taking also into account deterioration effects under cyclic loads. In addition, some results related to the fatigue performance of a case study are shown and commented. The numerical comparisons reveal that the application of the available fatigue model is particular problematic in the case of ancient masonry elements, where appropriate stress-life curves are required.
  PubDate: 2019-05-21T00:00:00Z
Model-Based Occupant Tracking Using Slab-Vibration Measurements
- Authors: Slah Drira, Yves Reuland, Sai G. S. Pai, Hae Young Noh, Ian F. C. Smith
  Abstract: Sensor-based occupant tracking has the potential to enhance knowledge of the utilization of buildings. Occupancy-tracking strategies using footstep-induced floor vibrations may be beneficial for thermal-load prediction, security enhancement and care-giving without undermining privacy. Current floor-vibration-based occupant-tracking methodologies are based on data-driven techniques that do not include a physics-based model of the structural behavior of the floor slab. These techniques suffer from ambiguous interpretations when signals are affected by complex configurations of structural and non-structural elements such as beams and walls. Using a physics-based model for data-interpretation enables deployment of sparse number of sensors in contexts of non-uniform structural configurations. In this paper, an application of physics-based data interpretation using error-domain model falsification (EDMF) is presented to track an occupant within an office environment through footstep-induced floor vibrations. EDMF is a population-based approach that incorporates various sources of uncertainty, including bias, arising from measurements and modeling. EDMF involves the rejection of simulated model responses that contradict footstep-induced floor vibration measurements. Thus, EDMF provides a set of candidate locations from an initial population of possible occupant locations. A sequential analysis that accommodates information from previous footsteps is then used to enhance candidate locations and identify trajectories among candidates. In this way, incorporating structural behavior in interpreting vibration measurements induced by occupant footsteps has the potential to identify accurately the trajectory of an occupant in buildings with complex configurations, thereby providing tracking information without undermining privacy.
  PubDate: 2019-05-16T00:00:00Z
Technology Leveraging for Infrastructure Asset Management: Challenges and
Opportunities
- Authors: A. Emin Aktan, Ivan Bartoli, S. Gokhan Karaman
  Abstract: Transportation and other infrastructure systems, particularly in dense urban regions, are intertwined, interdependent, multi-scale, multi-domain and complex, and their behavior cannot be predicted even when element behaviors are known. Such systems should be managed just like financial assets, leveraging measurement-based, objective and reliable metrics for documenting their value, performance and condition, and based on their lifecycle and disutility risk for each distinct limit-states of performance as discussed in the following. In this paper writers attempt to offer a perspective for asset management of civil infrastructures with a focus on highway bridges and describe the tools that are considered necessary for rectifying the current shortcomings mainly arising from subjective and incomplete performance and condition evaluation practice. The adoption of sensing systems, which allows measurements of displacement, acceleration, strain, tilt and that can be collected wirelessly, has the potential of providing objective metrics needed for optimal asset management. The authors however caution that such a transition (from asset management based on visual inspection to data-driven asset management based on objective metrics) could be truly achieved only if combined with the proper training of a new generation of infrastructure inspectors and stakeholders. The paper attempts to provide a roadmap to achieve such a transition in asset management and describes the critical concepts that should be incorporated in training a new generation of civil engineers in charge of maintaining our transportation assets.
  PubDate: 2019-05-16T00:00:00Z
Shunt Piezoelectric Systems for Noise and Vibration Control: A Review
- Authors: Konstantinos Marakakis, Georgios K. Tairidis, Panagiotis Koutsianitis, Georgios E. Stavroulakis
  Abstract: In this paper, the current state of the art on shunt piezoelectric systems for noise and vibration control is reviewed. The core idea behind the operation of electronic shunt piezoelectric circuits is based on their capability of transforming the dynamic strain energy of the host structure, i.e. a smart beam or plate, into electric energy, using the properties of the direct piezoelectric phenomenon and sending this energy into the electronic circuit where it can be partially consumed and transformed into heat. For this purpose, transducers which are made by piezoelectric materials are used, since such materials present excellent electromechanical coupling properties, along with very good frequency response. Shunt piezoelectric systems consist of an electric impedance, which in turn consists of a resistance, an inductance or a capacitance in every possible combination. Several types of such systems have been proposed in the literature for noise or vibration control for both single-mode and multi-mode systems. The different types of shunt circuits provide results comparable to other types of control methods, as for example with tuned mass-dampers, with certain viscoelastic materials, etc. As for the hosting structure, several studies on beams and plates connected with shunt circuits have been proposed in recent literature. The optimization of such systems can be performed either on the design and placement of the piezoelectric transducers or on the improvement and fine-tuning of the characteristics of the system, i.e. the values of the resistance, the inductance, the capacitance and so on and so forth. There are several applications of shunt systems including among others, structural noise control, vibration control, application on hard drives, on smart panels etc. Last but not least, shunt circuits can be also used for energy harvesting in order to collect the small amount of energy which is necessary in order to make the system self-sustained.
  PubDate: 2019-05-15T00:00:00Z