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The science of a bridge collapse
\"This book discusses the science behind bridge collapses and their effects. The chapters examine historical bridge collapses, explain how bridges are designed and built, and show how scientists and engineers are working to prevent future collapses. Diagrams, charts, and photos provide opportunities to evaluate and understand the scientific concepts involved.\"--Publisher's website.
Book
Data-driven assessment of Apulian road network resilience: Bridge unavailability and inner municipality isolation impact
Road networks are crucial for the movement of resources, passenger transportation, and supply chains. In seismically active areas like Italy, earthquakes can compromise road infrastructure, leading to structural failures and connectivity disruptions. Bridges, vital for travel and emergency response, are especially vulnerable to these extreme events, making their maintenance and recovery crucial for preserving transport efficiency. This study examines the resilience of the Apulian road network against bridge failures by assessing seismic hazards, the structural vulnerability of each bridge to seismic actions, and the systemic consequences of its disruption. A bridge criticality score is defined to support data-driven decision-making for bridge maintenance and recovery. This novel quantitative metric integrates seismic hazard data at each bridge site, fragility curves, and topological complex network analysis to provide a comprehensive evaluation of bridge criticality. Additionally, the risk of isolation for inner municipalities due to bridge disruptions is assessed using centrality metrics. By combining the bridge criticality score with an emphasis on inner municipalities, this approach offers valuable insights to improve road network resilience, mitigate isolation risks, and promote territorial sustainability in earthquake-prone zones.
Journal Article
Alternative Methods for Failure Prediction in Twin-Cell Box-Girder Bridges
Intense research works on twin-cell box-girder bridges are limited when compared to single-cell box-girder bridges and hence, not many sources are available to study the simultaneous effect of bending and torsion in them. The estimation of ultimate load in a twin-cell box-girder bridge under different modes of failure using the two existing simplified methods--namely, the space truss analogy and collapse mechanism--demands more research attention. The primary objective of this paper is to develop simplified equations for twin-cell box-girder bridges using the principles of collapse mechanism. The second main objective is to check the suitability of using space truss analogy and collapse mechanism in different modes of failure. Experimental work for studying the effects of various structural actions due to an eccentric loading on a simply supported twin-cell concrete box-girder bridge is conducted and numerical analyses are presented to understand the effect of load positions and reinforcement ratios in the failure modes. Keywords: collapse mechanism; failure modes; space truss analogy; twin-cell box-girder bridges.
Journal Article
Strength and Serviceability of Shear-Critical Post-Tensioned Girders (Open Source)
The results of an experimental program conducted to evaluate the performance of shear-critical post-tensioned I-girders with grouted and ungrouted ducts are presented. The experimental program involved the design, construction, and testing to failure of six full-scale specimens with different duct layouts (straight, parabolic, or hybrid) and using both grouted or ungrouted ducts. All tests resulted in similar failure modes, such as localized web crushing in the vicinity of the duct, regardless of the duct condition or layout. Furthermore, the normalized shear stresses at ultimate were similar for the grouted and ungrouted specimens. The current shear design provisions in the AASHTO LRFD Bridge Design Specifications (AASHTO LRFD) were reviewed, and updated shear-strength reduction factors to account for the presence of the duct in the web and its condition (that is, grouted or ungrouted) were proposed. The data generated from these tests served as the foundation for updated shear-strength reduction factors proposed for implementation in AASHTO LRFD. Keywords: AASHTO LRFD; flexible filler; post-tensioned concrete member; post-tensioning; prestressed I-girder; shear; spliced precast girder.
Journal Article
Scour Reduction around Bridge Pier Using the Airfoil-Shaped Collar
Scouring around the bridge pier is a natural and complex phenomenon that results in bridge failure. Failure of bridges have potential devastation and public safety and economic loss, which lead to political consequences and environmental impacts. Therefore, it is essential to countermeasure the scour around the bridge pier. This paper studies the effects of four different airfoil-shaped collars (i.e., bc1 = 1.5b, bc2 = 2.0b, bc3 = 2.5b and bc4 = 3.0b, where bc and b are the diameter of the airfoil-shaped collar and pier, respectively) as a scour countermeasure. All the experiments are conducted under clear water conditions with uniform sediment and a constant water depth (y) of 10 cm. Airfoil-shaped collar is placed at four elevations, i.e., bed level, y/4, y/2 and 3y/4 above the sediment bed level. It is observed that the maximum percentages of scour reduction of 86, 100 and 100% occurred due to protection provided by the collar bc2, bc3 and bc4, respectively, at sediment bed level. So, collars bc2, bc3 and bc4 are efficient at the sediment bed level. The profiles of scour hole show that the length of the transverse scour hole is greater than that of the longitudinal one. Numerical investigation of the morphological changes in sediment bed and scour depth contours is developed using the FLOW-3D for the pier with and without the airfoil-shaped collar.
Journal Article
Cascade effect of rock bridge failure in planar rock slides: numerical test with a distinct element code
Plane failure along inclined joints is a classical mechanism involved in rock slope movements. It is known that the number, size and position of rock bridges along the potential failure plane are of prime importance when assessing slope stability. However, the rock bridge failure phenomenology itself has not been comprehensively understood up to now. In this study, the propagation cascade effect of rock bridge failure leading to catastrophic block sliding is studied and the influence of rock bridge position in regard to the rockfall failure mode (shear or tension) is highlighted. Numerical modelling using the distinct element method (UDEC, Itasca) is undertaken in order to assess the stability of a 10 m3 rock block lying on an inclined joint with a dip angle of 40 or 80∘. The progressive failure of rock bridges is simulated assuming a Mohr–Coulomb failure criterion and considering stress transfers from a failed bridge to the surrounding ones. Two phases of the failure process are described: (1) a stable propagation of the rock bridge failures along the joint and (2) an unstable propagation (cascade effect) of rock bridge failures until the block slides down. Additionally, the most critical position of rock bridges has been identified. It corresponds to the top of the rock block for a dip angle of 40∘ and to its bottom for an angle of 80∘.
Journal Article
Service Life Evaluation of Curved Intercity Rail Bridges Based on Fatigue Failure
There are curved bridge structures in the intercity rail line. During the operation of bridges, they are subjected to train loads, resulting in stress amplitudes of the construction materials; during operation, when the train interval is short, the fatigue performance of the bridge should be emphasized. Unlike straight bridges, when a train travels on a curved bridge, it tends to move in the original direction, which undoubtedly causes the train to deviate from the track. Therefore, it is necessary to set the track deflection to limit this movement trend, which will also impart radial forces on the track structure, and the reaction force of this force is called centripetal force. Under the action of centripetal force, the train generates a virtual force called centrifugal force. The material stress amplitude caused by centrifugal force and the vertical force both need to be considered. Therefore, a curved train–bridge coupled system was established to simulate the dynamic stress of the train passing through a curved bridge, and the stress amplitude and cycle number of the dynamic stress time–history curve were analyzed based on the rain-flow method. The cumulative damage of the bridge under different curve radii, different train speeds, different lengths of span, and different operation interval times was analyzed, and the fatigue life was calculated. The results show that the influence of centrifugal force at a small curve radius cannot be ignored. In addition, the cumulative damage and service life are greatly affected by the train speed and bridge span; especially when the train speed is close to the resonance speed, the service life is significantly reduced. Finally, the recommended values for the train passing speed for curved bridges with different spans are given. It was suggested that the design speed of a curved bridge with a span of 25 m, 30 m, and 35 m should be set in the range of 70 to 106 km/h, 78 to 86 km/h, and about 75 km/h, respectively.
Journal Article
A Deep Learning Approach to Detect Failures in Bridges Based on the Coherence of Signals
Structural health monitoring of civil infrastructure, such as bridges and buildings, has become a trending topic in the last few years. The key factor is the technological push given by new technologies that permit the acquisition, storage, processing and visualisation of data in real time, thus assessing a structure’s health condition. However, data related to anomaly conditions are difficult to retrieve, and, by the time those conditions are met, in general, it is too late. For this reason, the problem becomes unsupervised, since no labelled data are available, and anomaly detection algorithms are usually adopted in this context. This research proposes a novel algorithm that transforms the intrinsically unsupervised problem into a supervised one for condition monitoring purposes. Considering a bridge equipped with N sensors, which measure static structural quantities (rotations of the piers) and environmental parameters, exploiting the relationships between different physical variables and determining how these relationships change over time can indicate the bridge’s health status. In particular, this algorithm involves the training of N models, each of them able to estimate the quantity measured via a sensor by using the others’ N−1 measurements. Hence, the system can be represented by the ensemble of the N models. In this way, for each sensor, it is possible to compare the real measurement with the predicted one and evaluate the residual between the two; this difference can be addressed as a symptom of changes in the structure with respect to the condition regarded as nominal. This approach is applied to a real test case, i.e., Candia Bridge in Italy, and it is compared with a state-of-the-art anomaly detector (namely an autoencoder) in order to validate its robustness.
Journal Article
Development of fragility curves for road bridges exposed to volcanic lahars
One of the main volcanic processes affecting road bridges are lahars, which are flows of water and volcanic material running down the slopes of a volcano and river valleys. Several studies have evidenced the effects of other volcanic processes on road infrastructure; however, limited information is available about the effects of lahars on bridges. In this paper, bridge failure models due to lahars are proposed and, based on these, fragility curves are developed. Failure models consider the limit state of pier and abutment overturning, and deck sliding caused by lahars. Existing physical models are used to stochastically characterize lahar loads and overturning momentum on bridges. Monte Carlo simulations are applied to quantify the probability of bridge failure given by different lahar depths. Fragility curves of bridges are finally parameterized by maximum likelihood estimation, assuming a cumulative log-normal distribution. Bridge failure models are empirically evaluated using data on 15 bridges that were affected by lahars in the last 50 years. Developed models suggest that decks fail mainly due to pier and/or abutment overturning, rather than deck-sliding forces. Moreover, it is concluded that bridges with piers are more vulnerable to lahars than bridges without piers. Further research is being conducted to develop an application tool to simulate the effects of expected lahars on exposed bridges of a road network.
Journal Article