1,630 research outputs found
An overview of the most advanced frameworks for bridge asset management
During this paper it will be discussed some important novelties related to the topic of bridge
asset management. In a first step, it will be covered the problematic of bridge assessment through the
use of Key Performance Indicators. An emphasis will be made to the outcomes from the COST Action
TU 1406 (www.tu1406.eu). Then, it will be discussed how these indicators can be used in the
management of existing bridge stock. It will be introduced the problematic of performance predictive
models and how maintainability could be integrated for the Life Cycle Cost analysis. At the end it will
be discussed the difference between the management of a single and a network of bridges, what type
of optimization models and decision-support algorithms can be used. An example is shown through the
main results from the research and development project SustIMS – Sustainable Infrastructure
Management Systems. The main objective is to show operators how the standardization of this
procedure, and how these frameworks would contribute for a more sustainable and efficient
management of their bridge stock.This article is based upon the work from COST Action TU1406, Quality specifications for roadway bridges,
standardization at a European level (BridgeSpec), supported by COST (European Cooperation in Science and
Technology).info:eu-repo/semantics/publishedVersio
An Alternative Interpretation for the Moduli Fields of the Cosmology Associated to Type IIB Supergravity with Fluxes
We start with a particular cosmological model derived from type IIB
supergravity theory with fluxes, where usually the dilaton is interpreted as a
Quintessence field. Instead of that, in this letter we interpret the dilaton as
the dark matter of the universe. With this alternative interpretation we find
that in this supergravity model gives a similar evolution and structure
formation of the universe compared with the CDM model in the linear
regime of fluctuations of the structure formation. Some free parameters of the
theory are fixed using the present cosmological observations. In the non-linear
regimen there are some differences between the type IIB supergravity theory
with the traditional CDM paradigm. The supergravity theory predicts the
formation of galaxies earlier than the CDM and there is no density cusp in the
center of galaxies. These differences can distinguish both models and can give
a distinctive feature to the phenomenology of the cosmology coming from
superstring theory with fluxes.Comment: 7 pages, 5 figures, references added, minor modifications, typos
corrected. Version accepted for publication in IJMP
Industry energy optimization: A case study in a biodiesel production site
This paper presents a case study of heat exchanger network (HEN) retrofit with the objective to reduce the utilities consumption in a biodiesel production process. Pinch analysis studies allow determining the minimum duty utilities as well the maximum of heat recovery. The existence of heat exchangers for heat recovery already running in the process causes a serious restriction for the implementation of grassroot HEN design based on pinch studies. Maintaining the existing HEN, a set of alternatives with additional heat exchangers was created and analysed using some industrial advice and selection criteria. The final proposed solution allows to increase the actual 18 % of recovery heat of the all heating needs of the process to 23 %, with an estimated annual saving in hot utility of 35 k(sic)/y
COST Action TU 1406 quality specifications for roadway bridges (BridgeSpec)
Roadway bridges, being one of the most critical road infrastructures components, require regular maintenance actions. Therefore, it becomes important to define strategies to maximize societal benefits, derived from the investment made in these assets. Consequently, this investment should be planned, effectively managed and technically supported by appropriate management systems, supported in quality control plans. For this purpose, authorities need to produce an asset management plan which should, not only define the goals to be achieved by exploiting the roadway bridge network, but also identify the investment needs and priorities based on a life cycle cost criteria. Additionally, a proper condition assessment of these assets must be conducted to support the decision-making process regarding their preservation. A COST Action recently started in Europe with the aim of standardizing the establishment of quality control plans for roadway bridges. This paper describes this Action and, particularly, its most recent developments.
MaintenanceThis article is based upon work from COST Action TU-1406, Quality specifications for roadway bridges, standardization at a European level (BridgeSpec), supported by COST (European Cooperation in Science and Technology)
Análise experimental do comportamento até à rotura de vigas de betão armado
O presente artigo incide sobre a análise experimental do comportamento de um conjunto de
vigas de betão armado, ensaiadas até rotura no Laboratório de Estruturas da Universidade
do Minho (LEST-UM). Estas foram construídas e betonadas em simultâneo, apresentando
diferentes distribuições de armadura longitudinal, recobrimento e espaçamento de armadura
transversal. Procedeu-se ao ensaio de um total de 36 vigas simplesmente apoiadas, e 32
vigas apoiadas num dos extremos e encastradas no outro. O carregamento aplicado
correspondeu a duas cargas concentradas, aplicadas a 1/3 e 2/3 do vão. Algumas das vigas
apresentaram roturas típicas de flexão e, outras, de corte. Apresentam-se os principais
resultados experimentais e os resultados obtidos com uma análise de sensibilidade, que
permitiu aferir a relação existente entre armaduras utilizadas, valores de recobrimento e
condições de apoio, com os diferentes modos de rotura.Fundação para a Ciência e a Tecnologia (FCT
Uncertainty evaluation of civil engineering structures behavior
All decisions that concern the development and
management of existent infrastructure are of extremely
importance for society. However, it is verified that these
decisions are influenced by a huge source of
uncertainties that must be taken into account. A
methodology that consider this, and, which objective, is
to support such decisions, is developed within this
research. In order to support such methodology, a
numerical model is developed. Such model is then
calibrated using backanalysis procedures, so that, given
results, could best fit obtained experimental data. The
developed model is continuously updated with collected
data, by using inference processes. Then, a full
probabilistic analysis is performed in order to evaluate
the respective structure behavior. This paper describes
such methodology, and the respective application with a
batch of reinforced concrete beams, tested at laboratory,
till failure. The developed methodology is applied with
success and obtained results revealed the respective
importance in future decisions concerning the societal
infrastructure. Further steps consider the application of
such methodology with a real structure.Fundação para a Ciência e a Tecnologia (FCT
Uncertainty evaluation of reinforced concrete structures behavior
The evaluation of reinforced concrete structures behavior is doted of uncertainty as parameters,
like used materials and geometry, are not deterministic. This article presents experimental tests and respective
numerical study of a series of simply and mixed supported reinforced concrete beams, which were loaded till
rupture. Those beams were executed at same time, presenting different longitudinal reinforcement, distance
between transversal reinforcement and concrete covering. Such beams were first analyzed using a calibrated
deterministic non-linear numerical model. In order to take into account the uncertainty, a probabilistic nonlinear
analysis was then executed. The results from numerical analysis were defined by random distributions.
Experimental data was grouped by beam typologies and characterized by a random distribution, also. An index,
which relates the proximity of both random distributions, was then defined. Such index will characterize,
in a more rigorous and consistent way, if the structural behavior is, or not, within the expected one.Fundação para a Ciência e a Tecnologia (FCT
Non linear probabilistic analysis of reinforced concrete structures
The behaviour of reinforced concrete bridges is doted of uncertainty as main parameters, like the
ones related to material properties, are variable and not deterministic. In order to take this into
consideration, a non linear probabilistic analysis should be developed. This paper presents an
application of it on the evaluation of the structural behaviour of two batches of reinforced concrete
beams, which were loaded, in laboratory, up to failure. However, when performing it, a previous
attention must be paid to the intervenient parameters. In fact, on the one hand it is important to
consider the highest number of parameters as possible but, on the other hand, this implies higher
computational costs. In order to avoid this, it is essential to identify, by developing a sensitivity
analysis, all critical parameters. A comparison of numerical results with obtained experimental data
is executed, being, the advantages of such kind of analysis, pointed out.Fundação para a Ciência e a Tecnologia (FCT
An overview of COST Action TU1406, quality specifications for roadway bridges (BridgeSpec)
Publicado em "Life-cycle of engineering systems: emphasis on sustainable civil infrastructure: proceedings of the Fifth International Symposium on Life-Cycle Civil Engineering (IALCCE 2016), ISBN 978-1-138-02847-0"Life-cycle analyses are used in condition assessment of new and existing bridges as well as for evaluation of
maintenance strategies. During the implementation of asset management strategies, maintenance actions are required to keep assets at desired performance levels. In case of roadway bridges, performance indicators, which can be obtained by inspections, non-destructive tests or monitoring systems, are established for components.
These indicators, along with the definition of standardized performance goals, allow to assess the accomplishment of quality control plans. In Europe there is a large disparity regarding the way performance indicators are quantified and goals specified. Therefore, a discussion at a European networking level, seeking to achieve a standardized approach in this subject, will bring significant benefits. COST Action TU1406 aims to bring together research and practicing communities in order to establish a European guideline in this issue, based on the existing practices across the involved European countries.COST (European Cooperation in Science and Technology
Advanced evaluation of civil engineering structures behaviour
The development, maintenance and operation of infrastructures are central tasks on continued success of society. The decision processes involved in these tasks concern all aspects of managing. The main objective from a societal perspective is to improve the quality of life of individuals both for present and future generations. On the other hand, from the owner point of view, the main objective is to maximize the economic return of investments.
If all aspects of decision problem would be known with certainty, the identification of optimal decisions would be straightforward by means of traditional cost-benefit analysis. However, our understanding of problems involved in decision analysis is often far less than perfect. In fact, the decision problem in engineering is subject to significant uncertainty.
Infrastructures are constituted by civil engineering structures disposed in a series system. Accordingly, in any time instant, to decide about the optimal decision, the operator should evaluate each structural behavior. A structural analysis based in a probabilistic model is always preferable than in a deterministic one, as all possibilities of structural behavior are considered. Accordingly, within this research project, a methodology for advanced civil engineering structures evaluation, was developed.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/10705/2002
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