Strategies of structural health monitoring for bridges based on cloud computing Abstract The collapse of the Polcevera bridge in Italy represents a serious event which seems to be a direct result of cumulated local damages due to the aggressive environment of the construction site. Recently, evidence of corrosion of both ordinary and post-tension steel reinforcements were detected, in addition to concrete carbonation. Such phenomena generally lead to an increase in the deformation of all the elements of the bridge structure, which start to increase in time, leading to a progressive deterioration of the overall system. As a consequence, a proper structural monitoring layout would provide an extremely useful tool, for a correct plan of maintenance for all the elements of the considered infrastructure. In this work, strategies for the definition of structural health monitoring systems for bridges are discussed, from both software and hardware points of view. More specifically, a Cloud computing interface is considered, to make recorded data available for further analyses and post-processing procedures. The presented definition of the monitoring architecture could lead to the proper maintenance of all the structural elements, preventing the unexpected collapse of the structure.

Behavioural study of surface Rayleigh waves in concrete structure containing delamination Abstract Delamination is one of the defects that cause concrete structures to fail in structural integrity. For this reason, the assessment of concrete delamination without affecting the serviceability and functionality of concrete structure is essential. Non-destructive tests (NDT) are developed and applied to serve this purpose without damaging the structure components. In this study, Rayleigh wave (R-wave) is proposed to determine the extent of delamination in concrete. Numerical simulations were carried out to examine the behaviour of R-waves propagated through the concrete medium with different concrete delamination conditions, i.e., top delamination and bottom delamination. The relationships between the changes of R-wave group velocity and peak frequency with the existence of delamination were established. The established data were then verified with experimental measurements. It is found that the R-wave group velocity is reduced in the presence of delamination. Furthermore, the group velocity of R-wave is relatively faster while propagating through the delamination layer which is closer to the testing surface. In addition, the peak frequency retrieved from R-wave power spectrum also reduced in the presence of delamination. Owing to these observed changes, the potential of utilising R-wave group velocity and peak frequency in the assessment of concrete delamination is high.

Implementation of real-time seismic diagnostic system on emergency management center buildings: system introduction and operational status on municipal government office buildings Abstract In preparation for a major earthquake in the Nankai Trough, the authors plan to introduce a real-time seismic diagnostic system for emergency management center building clusters in the Aichi prefecture eastern region in Japan. The system involves installing seismometers (three-axis accelerometers) in the buildings and storing observation records in a cloud-based internet system (the Cloud) in real time. Immediately after an earthquake, a simple diagnosis of the building’s residual seismic performance is performed using a lumped-mass model and emergency management officials are notified of the results by email. Also, a detailed analysis of the damaged condition using a three-dimensional frame model is performed for several hours after the event to try to assess the specific building parts that are damaged. This paper describes the proposed system and then presents the results of setting up the system and conducting trial operations in municipal government office buildings as a test case prior to actual system implementation.

Dynamic monitoring and evaluation of bell ringing effects for the structural assessment of a masonry bell tower Abstract The paper presents a rational procedure for the structural assessment of bell towers with respect to the dynamic actions induced by the bell ringing, based on structural monitoring and data processing. This methodology is tested on the bell tower of Saint Prospero (Reggio Emilia, Northern Italy), a masonry tower of great historical interest. The procedure includes an accurate geometrical survey for a deep knowledge of the structural geometry, which is the base for the structural modelling. A finite element model of the tower is calibrated with respect to the modal properties evaluated from the structural response measured in operational conditions. The structural response of the tower was also measured during a famous cultural event held in the city centre of Reggio Emilia, when skilled bell ringers played traditional melodies. The tower displacements are evaluated applying a double integration technique and a detrending procedure based on the empirical mode decomposition to the acquired accelerations. To simulate the structural response to the bell ringing, the tower and the bell are modelled as a single degree of freedom system and an unforced and undamped simple pendulum, respectively. For safety assessment purposes, the structural response of the tower is evaluated considering different oscillation angles in order to identify the one causing the maximum displacement. Finally, the stress pattern of the masonry caused by the bell-induced displacement is estimated thanks to the calibrated finite element model of the tower. Results show that the bell ringing causes a stress pattern lower than the allowable masonry strength for the serviceability conditions.

Structural and health assessment of historic timber roofs from the Convent of Christ in Tomar Abstract Before coming up with any important decision of intervention in the restoration process of existing buildings, the assessment of the conservation state is required as regards heritage timber structures and especially for those that suffered a lack of maintenance in their service life. In that context, three timber roof structures from the Convent of Christ in Tomar, Portugal, were selected and investigated. To this end, a research methodology was introduced and applied to these case studies into four main steps: (1) visual inspection; (2) non-destructive wood diagnosis; (3) structural safety evaluation; (4) prevention and intervention measures. For the visual inspection, every element and joint constituting the roof structures received scrutiny through assessing the wood species, the different construction stages and, last but not least, their respective geometry. As regards the encountered pathologies, structural disorders (e.g. accidental failure, serviceability defects…) and wood deteriorations due to biological agents (e.g. wood-destroying fungi or insects), which ineluctably leads to a likely decrease of the mechanical performances of the roof structure, were reported. To estimate the residual element cross section and elastic modulus, wood diagnosis was carried out using three relevant non-destructive tests: (1) ultrasonic pulse velocity; (2) drilling resistance; (3) impact penetration. From the collected data, the three timber roof structures were modelled on a commercial software to check their safety and integrity. Based on those outcomes, some prevention and intervention measures haves been lastly proposed case by case.

Data-based models for fatigue reliability assessment and life prediction of orthotropic steel deck details considering pavement temperature and traffic loads Abstract Considering the effects of long-term moving vehicle loads and ambient temperature on the fatigue life of details in orthotropic steel decks in cable-stayed bridges, a novel fatigue damage regression analysis model was developed and then used with reliability profiles to predict fatigue life. The regression model can characterize the normal correlation pattern between the daily averaged pavement temperatures, the annual average hourly aggregated traffic volume (AAHTV) or annual average hourly traffic weight (AAHTW) and a stress-based performance indicator. Prediction models based on the monitoring outcomes from the structural health monitoring systems installed on a Yangtze River cable-stayed bridge were first developed and used to describe and predict the time-series of the long-term moving vehicle loads and asphalt concrete (AC) pavement temperatures. An exponential regression model was then developed to quantify the relationship between daily averaged pavement temperatures, moving vehicle loads and the stress-based indicator, which is derived using S–N principles from strain measurements. Further, a limit equation based on the exponential regression model mentioned above for the fatigue life prediction, which considers both the traffic conditions and pavement temperature, has been developed. Finally, this methodology was employed to predict the fatigue life of details in orthotropic steel decks.

Data-driven method of damage detection using sparse sensors installation by SEREPa Abstract This paper presents a model-based method of damage detection and severity identification in structural elements. The model-based method is performed with a finite element model. One of the important challenges in damage identification problems is lack of measured degrees of freedom and limitations of installed sensors on the structures. The new approach of this study is the use of expanded mode shapes data to train artificial neural network (ANN). In this study, the measured mode shapes are expanded by SEREPa. SEREPa expansion is developed based on the System-Equivalent Reduction and Expansion Process (SEREP), which is a non-smooth method and protects the measured data. ANN was then trained through the expanded data as inputs, location and severity of damage as outputs. The algorithm used to train ANN is scaled conjugate gradient. The advantage of this algorithm is that less data storage space is used and lower computation costs are needed. To show SEREPa’s efficiency in estimating unmeasured mode shapes, an experimental example containing a truss tower was presented. Two numerical examples including a plane truss and a space truss were presented to illustrate efficiency of damage detection method. Finally, the proposed method was verified by an experimental example. Damage prediction results for both numerical and experimental examples indicated an acceptable accuracy of the proposed method.

Analytical study on damage detection method using displacement influence lines of road bridge slab Abstract Structural health monitoring has garnered attention as a method to quantitatively evaluate damage to road bridges, and various dynamic and static damage detection methods have been proposed recently. However, few damage detection methods focus on the displacement shapes of road bridge decks. In this study, a damage detection approach is proposed using Displacement-Based Index (DBI) and Grey Relational Coefficient (GRC), in which displacement influence lines of deck slabs are used as inputs in the evaluation procedures. Parametric studies were performed by changing the damaged positions and boundary conditions of a full-scale bridge model to examine their possible effects on the performance of the proposed method. The results indicated that either approach could properly detect damage in the simulation model. In addition, because the proposed method was insensitive to damage away from the measurement position, it was clarified that damage detection could be performed accurately by installing multiple displacement meters at appropriate intervals.

Scour at river bridge piers: real-time vulnerability assessment through the continuous monitoring of a bridge over the river Po, Italy Abstract Bridge failures are not uncommon during floods. Therefore, the assessment of bridge vulnerability is crucial to help a bridge’s administration take the best decisions during emergencies (i.e. closing the bridge). The first step to achieve this is to implement a monitoring system providing needed information to develop scenarios based on administration response time. The proposed system seeks a real-time evaluation of the loads acting on the bridge. Wind and water contributions, debris accumulation upstream of piers and river bed level are evaluated by specific devices. The most difficult measurement is the identification of the riverbed position in close proximity to piers. Scour model predictions are still far from robust and accurate and no standard devices are available to measure it. Unfortunately, the main reason for bridge failure is scour around bridge piers, called local scour. A monitoring system was developed for this purpose and installed on a critical bridge over the river Po in Italy, as a result of the cooperation between the Politecnico di Milano and the Province of Mantova. The aim was to measure the main parameters for a proper evaluation of the bridge’s vulnerability. The paper’s focus is twofold: to show long-term data and all the phases needed to assess bridge safety. The first aspect, not so common in the literature, is useful to understand the temporal evolution of the environment around the bridge. The second one provides a roadmap for risk assessment and management decisions relying on the widely available database. With regard to this second topic, another paper describing the overall strategy has already been published. The main focus here is on potential implementation, with an emphasis on the available data.

In-service bridge SHM point arrangement with consideration of structural robustness Abstract To date, structural health monitoring (SHM) has been used in several long-span bridges and even some middle-span bridges. Many monitoring sensors are usually arranged based on traditional structural mechanical analysis, such as load tests and engineering experiences. Moreover, several studies have also been carried out to reduce the number of monitoring sensor deployments and improve the pertinence of monitoring sensor arrangements. One example is structural robustness analysis, which can be used to locate the vulnerable and weak parts of a bridge to determine the arrangement of SHM sensors. In this paper, a strain energy index is first proposed to evaluate structural robustness. The universal applicability of the evaluation index is also verified by energy principle, and then this index can be widely accepted for engineering applications. A theoretical numerical simulation of the structural robustness of a simply supported beam subjected to different damage effects is then carried out. Different damage locations, different damage degrees and different moving speeds are considered. With the consideration of the same structural type, an in-service simply supported girder bridge is also presented as the verification case study. The bridge once experienced an explosion caused by a moving fireworks vehicle. The monitoring point arrangement based on load tests and engineering experiences can be verified to be highly consistent with the theoretical numerical simulation result. This study provides a method for the SHM point arrangement of this kind of bridge. The structural robustness strain energy evaluation index is also acceptable for other kinds of bridges. The inconvenience caused by traditional structural analysis, such as the temporary closing of road traffic, can also be greatly reduced.