Service loads, environmental and accidental actions may cause damage to constructions. Regular inspection and condition assessment of engineering structures are necessary so that early detection of any defect can be made and structure’s remaining safety and reliability can be determined. When the structural damage is small or it is in the interior of the system, its detection cannot be done visually. A useful more elaborate nondestructive evaluation tool is vibration monitoring. It relies on the fact that occurrence of damage or loss of integrity in a structural system leads to changes in the dynamic properties of the structure. In this paper, different techniques will be presented and compared to derive from experimentally determined modal characteristics of a reinforced concrete beam its dynamic bending stiffness. The degradation of stiffness, due to the cracking of the reinforced concrete, gives information on the position and intensity of the occurred damage.

A need exists to bridge the gap between innovation in the bituminous materials sector and adoption of the new technologies by national road administrations (NRAs). The Evaluation and Decision process for Greener Asphalt Roads (EDGAR) enables NRAs to do this by providing an assessment methodology which makes sustainability information on new technologies readily accessible to the decision-making process, and therefore facilitates quick adoption of the technologies that offer the greatest sustainability benefits for the highways sector and society as a whole. EDGAR commenced with a wide-ranging review of the range of ‘green’ technologies in the bituminous materials sector and the sustainability benefits that they offer. Two methodologies to assist NRAs were then devised. The first acknowledged that the ability to recycle asphalt is its foremost environmental attribute, and devised a quick, qualitative method for the assessment of recyclability. The second devised a methodology for a more detailed assessment of the sustainability of any bituminous technology, considering all three facets of sustainability: environmental, social and economic, with particular attention given to how the information might be used in the decision process by NRAs, and the common challenges they might encounter when assessing a ‘novel’ technology.

In October 2015 the city of Antwerp has, as part of their traffic noise action plan, constructed two test sites in an urban environment where five different thin noise reducing asphalt layers (TAL) and a poroelastic road surface (PERS) are compared to the standard Stone Mastic Asphalt 10 (SMA - 10). The mechanical and acoustical characteristics of all these test tracks will be monitored twice a year for at least three years. Furthermore, the objective noise reduction is compared to the subjective perception of the residents living nearby using a pre- and post-survey.In this paper the objective noise reduction is compared with self-reported physical complaints, which were assessed in the pre- and post-survey. From the objective results a noticeable reduction in road traffic noise can be observed, ranging from 3.8 to 5.2 dB(A). No clear changes could be found in the self-reported physical complaints, although the overall disturbance from road traffic noise has been reduced.

Increasing attention being paid to the environmental impact of construction activities has led to the adoption of Environmental Product Declarations (EPD) for the purpose of producing standardized assessments. Facilitating the comparison of the environmental performance of construction products, EPDs represent an excellent tool for the decision making process.The development of EPDs for building construction products is based on Product Category Rules (PCRs), which define a wide set of environmental indicators relevant for the whole sector. Because of the large range of products covered by the PCRs, the resulting EPDs appear to be mainly addressed to generic products without considering individual material's specific characteristics. The highway industry in particular necessitates the use of specifically customized sets of rules to encourage and improve the environmental performance of the products.It is a prerogative of the national road administrations (NRAs) to favor the introduction of green solutions. This can be facilitated by adopting appropriate rules for sustainability assessment. While on one side, some of the recommended PCRs for construction products, such as ozone depletion potential and formation potential of tropospheric ozone, have little relevance for asphalt technologies, on the other side they do not fully embrace the specific necessities of the NRAs. An appropriate tool to inform the decision making process of the NRAs should not be limited to environmental criteria but should include an indication of the social and economic impact of the asphalt, all considered from a life cycle perspective. Until now, PCRs with potential relevance to asphalt technologies have been autonomously introduced in few countries, but do not fully satisfy the scope being limited to the production stage.With the purpose of developing a methodology for the assessment of the overall sustainability of bituminous mixtures produced with novel materials and technologies the Evaluation and Decision Process for Greener Asphalt Roads (EDGAR) project started by creating a reduced set of rules specifically designed for asphalt materials and directly relevant to NRAs. Both environmental and socio-economic indicators are considered from a life cycle perspective to describe the impact of innovative asphalt materials on sustainability. A methodology will be proposed for NRAs to determine these indicators, using either existing or new tools, and to implement them in the decision making process. In the final stage of the two year project, which will end in April 2016, the EDGAR methodology will be demonstrated through application in practical test cases. (C) 2016 The Authors. Published by Elsevier B.V.

As part of the Brite-EuRam project BE96-3157 SIMCES (System Identification to Monitor Civil Engineering Structures) the three span box bridge Z24 in Switzerland was monitored during almost one year before it was artificially damaged. In the preceding monitoring period the influence of environmental conditions, such as humidity, wind and especially temperature, on the bridge eigenfrequencies was studied. The goal of the subsequent damage tests, corresponding to realistic and relevant cases, was to prove that damage could be detected, localised and quantified by considering changes in eigenfrequencies and modeshapes. Some of the main conclusions are that ambient vibrations treated by proper system identifications algorithms can provide accurate results for eigenfrequencies and modeshapes, that it is mandatory to filter beforehand the influence of environmental conditions and that small, stiffness degradation producing damage can be detected if the corresponding eigenfrequency diminutions surpass 1%.

The project New Road Construction Concepts (NR2C) is an innovation project of FEHRL supported by the European Commission under the Sixth Framework Programme. NR2C develops long-term perspectives and physical trial projects, in which long-term visions and ideas are linked to short-term action. One of the ideas towards sustainable road construction concerns the development of high performance underlayers with high percentages of re-use materials. High stiffness underlayers are largely used in Europe, but re-use is often very restricted or not used at all because of fear for limited durability. This project aims to optimize the design of such mixes so as to guarantee their long-term performance, even with high percentages of reclaimed asphalt (RA) (including mixes containing 25 per cent and 40 per cent of RA). The mix designs are made and optimized using BRRC's PradoWin-software. An extensive laboratory testing program is carried out, with the aim to evaluate, compare and optimize the performance of these mixes, which is related to stiffness, fatigue cracking, durability/adhesion and permanent deformation. After this laboratory testing phase, three mix designs will be selected and further studied in the full-scale accelerated loading testing (ALT) facility of LAVOC. The sections will be loaded with a heavy traffic simulator, and assessed at subsequent thermal cycles. This study will permit to evaluate the behaviour of the selected solutions in an accelerated way and close to field conditions. The instrumentation (gauges to measure horizontal as well as vertical deformations) in the structure will provide data that are necessary for the assessment of the structural design. Based on the performance characteristics of the mixtures determined in the laboratory study and on the results of the accelerated loading, the impact on the structural design of the road and on the lifetime of the pavement will be investigated. New construction as well as different repair situations with these solutions will be considered, for different climatic and traffic conditions, representative for Europe (A). For the covering abstract of the conference see ITRD E212343.

The project "New Road Construction Concepts" (NR2C) is an innovation project of FEHRL supported by the European Commission under the Sixth Framework Programme. NR2C develops long-term perspectives and physical trial projects, in which long-term visions and ideas are linked to short-term action. One of the ideas towards sustainable road construction concerns the development of high performance underlayers with high percentages of re-use materials. High stiffness underlayers are largely used in Europe, but re-use is often very restricted or not used at all because of fear for limited durability. This project aims to optimize the design of such mixes so as to guarantee their long-term performance, even with high percentages of reclaimed asphalt (RA) (including mixes containing 25% and 40% of RA). The mix designs are made and optimized using BRRC's PradoWin-software. An extensive laboratory testing program is carried out, with the aim to evaluate, compare and optimize the performance of these mixes, which is related to stiffness, fatigue cracking, durability/adhesion and permanent deformation. After this laboratory testing phase, three mix designs will be selected and further studied in the full-scale accelerated loading testing (ALT) facility of LAVOC. The sections will be loaded with a heavy traffic simulator, and assessed at subsequent thermal cycles. This study will permit to evaluate the behaviour of the selected solutions in an accelerated way and close to field conditions. The instrumentation (gauges to measure horizontal as well as vertical deformations) in the structure will provide data that are necessary for the assessment of the structural design. Based on the performance characteristics of the mixtures determined in the laboratory study and on the results of the accelerated loading, the impact on the structural design of the road and on the lifetime of the pavement will be investigated. New construction as well as different repair situations with these solutions will be considered, for different climatic and traffic conditions, representative for Europe.

Because of the importance of predicting the resistance to permanent deformation of a mix in the design phase, BBRC previously proposed a semi-empirical law based on cyclic triaxial compression testing. This law contained a limited number of mix properties (voids and dynamic modulus) and test conditions (deviatoric stress). Recently, BRRC has acquired a new test set-up for performing cyclic triaxial compression tests. With this test set-up, it is possible to verify the law of permanent deformation for a wider range of asphalt mixtures and test conditions. This demonstrated some of the limitations of the law, but it also indicated how the law could be improved to obtain a more reliable prediction of the permanent deformation under repeated loading. This paper describes the experimental work that is going on at BRRC using the new cyclic triaxial compression test and the conclusions that already follow from this work with respect to the law of permanent deformation. A first part of the paper is dedicated to the description of the triaxial test set-up and the selection of the test conditions. The effect of sample preparation on the test results and the repeatability is also discussed. Secondly, the experiments are described that give a closer insight into the effect of the material properties on permanent deformation.

In this paper dynamic experiments on the Antoing Bridge located on the high-speed railway line between Paris and Brussels are reported. The experiments were co-operatively carried out by the Northern Jiaotong University from China, the Catholic University of Leuven, the Free University of Brussels and the Belgium Railway Company NMBS-SNCB from Belgium. The bridge is composed of multi-span simply supported PC girders with spans of 50m and U-shaped sections. The loads are the high-speed Thalys trains with articulated vehicles. The speeds of the Thalys trains were between 265 and 310km/h. In the experiments, the dynamic responses of the bridge such as the deflections, the accelerations and the strains that were measured by a laser velocity displacement transducer accelerometers and strain gauges, respectively. Many useful results have been obtained from the analysis of the recorded data. The tests and the measured results can be a reference for the study and the design of high-speed railway bridges.

Large scale tests with progressive damage on a prestressed concrete highway bridge have been performed to investigate the sensitivity of several damage detection, localization, and quantification methods based on modal parameters. To investigate the quality of modal parameters, the data set of one damage step was analyzed by several output-only identification techniques. Although the bridge was severely cracked, natural frequencies as well as mode shapes display only minor changes. However, the relative changes of mode shapes are larger than those observed for natural frequencies. A novel damage indicator, called mode shape area index, based on changes of mode shapes, has been developed and found as the most sensitive damage detection approach. Damage detection or localization via changes of the flexibility matrix performed better than natural frequencies or mode shapes alone. The application of the direct stiffness calculation and a sensitivity-based model update technique showed results having a high level of ambiguity about the location and quantification of damage also at the highest damage level. Evaluating the information collected in this study the test results indicate that an early stage damage identification in prestressed concrete bridges is hardly possible because of the nearly complete recovery of stiffness after closing of cracks in prestressed concrete and the effect of environmental parameters on modal data.

Vibration monitoring is a useful evaluation tool in the development of a non-destructive damage-identification technique, and relies on the fact that occurrence of damage in a structural system leads to changes in its dynamic properties. It can give global information of a structure, and the location of the damage has not to be known in advance. The damage-identification technique is based on the observed shifts in eigenfrequencies and modeshapes and relate the dynamic characteristics to a damage pattern of the structure. The presented technique makes use of the calculation of modal bending moments and curvatures to derive the bending stiffness at each location. The basic assumption is that damage can be directly related to a decrease of stiffness in the structure. Damage-assessment techniques are validated on the progressively damaged prestressed concrete bridge Z24 in Switzerland, tested in the framework of the Brite Euram project SIMCES. A series of full modal surveys are carried out on the bridge before and after applying a number of damage scenarios.

Vibration monitoring is a useful evaluation tool in the development of a non-destructive damage-identification technique, and relies on the fact that occurrence of damage in a structural system leads to changes in its dynamic properties. It can give global information of a structure, and the location of the damage has not to be known in advance. Damage-assessment techniques are validated on the progressively damaged prestressed concrete bridge Z24 in Switzerland, tested in the framework of the Brite Euram project SIMCES. A series of full modal surveys are carried out on the bridge before and after applying a number of damage scenarios.

SUMMARY: A sensitivity-based Finite Element Model (FEM) Updating method using experimental modal data is presented. Such a procedure aims to adjust the uncertain properties of the FE model by minimising iteratively the differences between the measured modal parameters (natural frequencies and mode shapes) and the correspon- ding analytical predictions. In the paper the FEM Updating method is applied for damage assessment (damage localisation and quantification). In this application the structural damage is represented by a reduction factor on the element bending stiffness. But in order to reduce the number of unknown variables and to obtain a physically meaningful result, a limited set of damage functions is used to determine the bending stiffness distribution over the FE model. The updating parameters are the multiplication factors of the damage functions. The procedure is illustrated with a laboratory tested reinforced concrete beam on which a modal test has been carried out before and after damage is applied. FEM updating can be applied as damage detection method. An initial FE model is updated by minimising an objective function which is defined in terms of the discrepancies between the vibration data identified by modal testing and those computed with the numerical model (1, 2). The damage identification procedure is performed in two updating steps. In the first step the initial FE model is tuned to a reference state of the structure, using the measured vibration data of the undamaged structure. In the second step the reference FE model is updated to obtain a model which can reproduce the measured vibration data of the damaged state. The damage is identified by comparing the differences between the reference and the damaged FE model. Structural damage is typically related with the changes in the structural stiffness parameters. Instead of adjusting the stiffness properties of all the elements separately, the stiffness distribution is determined by means of damage functions, which have to be multiplied with the appropriate factors. This approach results in a reduced number of unknowns (the multiplication factors) and ensures a physically significant solution. The paper contains the basic theory of FEM Updating. Next, the use of damage functions within the updating procedure is presented. The method is illustrated with a laboratory tested reinforced concrete beam on which a modal test with a free-free set up has been carried out, before and after damage is applied. The identified damage pattern corresponds well with the results obtained through a direct stiffness derivation technique (3). The results of a FEM Updating process without the use of damage functions are given for comparison.

This paper is concerned with the results from the COST Action F3 Working Group Two benchmarking exercise in Structural Health Monitoring. Data from two large-scale structures were modelled for the purposes of damage detection, location and quantification. Several analysis papers have been submitted for a special issue of Mechanical Systems and Signal Processing and the conclusions of each are summarised here, together with more general conclusions arising from the concerted effort.

A construction can be identified by vibration measurements, from which are derived the intrinsic properties of the structure like eigenfrequencies and modeshapes. Heavy structures like bridges, buildings and dams, having very low natural frequencies, are difficult to put into vibration. In this case ambient vibrations, caused by wind, traffic, microtremors,... are generally used. One of the advantages is that normal operation is not disturbed by the measurement. Substantial damage will affect these properties: so their use for health monitoring is an interesting and intensively explored research topic. However, the measured values do not necessarily return the exact properties of the bridge. Under the influence of environmental factors, like e.g. temperature and humidity variations, the dynamic properties will undergo changes. In this paper the influence of traffic loads on the identified modal parameters will be investigated. For this purpose, finite element simulations are used, in which a vehicle moves over a bridge model. Different vehicle-models are considered. Using the simulated bridge response, the eigenfrequencies and modeshapes of the bridge vehicle system are determined by the stochastic subspace identification method and afterwards compared with those of the original, unloaded structure.