ABSTRACT
Fire protection of bridge cable systems has been identified as an important mitigating action with respect to operational risk as well as the safety of existing and new bridges. In ...particular, cable supported bridges have been demonstrated to be vulnerable to vehicle fires.
With the design of fire protection concepts for New Little Belt Bridge and Great Belt East Bridge, a process with development of fire protection of cable systems has been started. The project is based on the development of a fire protection concept for main cables based on insulation mats and currently a concept is being developed with use of intumescent coatings.
The R&D project and handling of the design challenges on cable systems on suspension bridges is presented, and it includes details about the main cable, cable clamps and suspenders based on numerical modelling and testing of the steel performance during fires up to 1100°C.
The fire protection relies on use of insulation mats and intumescent coatings and in developing the concept, one of the main challenges is to document the performance of the design concepts unique to each bridge. Furthermore, it is difficult to get access to information on material performance in such particular applications. Hence, in the current project, it has not been possible solely to rely on the supplier information and it has been necessary to carry out numerical modelling of performance during fire as well as use of laboratory testing.
In summary, the objective is to investigate the combined performance of the steel cable and the applied insulation concept. For solutions, design has not only to consider the fire protection of steel but also to address issues regarding cable durability and allowance for operation and maintenance.
Although the friction pendulum bearing system (FPS) has been widely used in the construction of buildings, bridges, and other structures to enhance their seismic performance, the FPS was adopted in ...bridge construction in Japan for the first time in 2020 on the Tokai-Hokuriku expressway. To validate the design hypotheses of the real bridge with FPS, a series of static and dynamic tests were performed, and the parameters of the FPSs were estimated. The girder of the bridge supported by four FPSs was pushed to various specified displacements considered in a maximum considered earthquake event in a quasi-static manner by hydraulic jacks equipped with large-caliber valves to enable quick pressure release. The load of the jacks was then suddenly released so that the bridge entered free vibration. The bearings in the site static tests are found to undergo a noncontinuous sliding motion (stick - slip) because a small loading rate of jacks is applied. This stick - slip phenomenon is confirmed in both the site and laboratory tests in cases where the sliding velocity either approached 0 or departed from 0, i.e. at every velocity reversal. The friction coefficient is estimated from the force and displacement data at the sliding points, and good agreement is observed between the site static tests and the laboratory tests. The friction coefficient model for dynamic analysis, accounting for the stick - slip effect and several dependencies, is calibrated by these test results. The free-vibration test results, including measured displacements and accelerations, show agreement with the simulation results based on a simplified model of the bridge with the FPSs. Finally, the unscented Kalman filter and its adaptive variant are applied to estimate the design parameters of the FPSs.
This paper discusses the seismic behavior of reinforced concrete (RC) bridge structures, focusing on the shear–flexure interaction phenomena. The assessment of reinforced concrete bridges under ...seismic action needs the ability to model the effective non-linear response in order to identify the relevant failure modes of the structure. Existing RC bridges have been conceived according to old engineering practices and codes, lacking the implementation of capacity design principles, and therefore can exhibit premature shear failures with a reduction of available strength and ductility. In particular, recent studies have shown that the shear strength can decrease with the increase of flexural damage after the development of plastic hinges and, in some cases, this can cause unexpected shear failures in the plastic branch with a consequent reduction of ductility. The aim of the research is to implement those phenomena in a finite-element analysis. The proposed model consists of a flexure fiber element coupled with a shear and a rotational slip spring. The model has been implemented in the OpenSEES framework and calibrated against experimental data, showing a good ability to capture the overall response.
Bridge structures face a critical threat from localized scour-induced damage, prompting urgent attention to civil infrastructure resilience. Prior research has primarily focused on the influence of ...pier shapes on scour patterns. However, the exploration of the combined effects of various debris shapes, each possessing distinct properties, on predictive scour depth models around the non-cylindrical pier has hitherto remained less researched. This study explored the complex dynamics governing local scour around bridge piers, focusing on the influence of surface and near-surface debris. This research shed light on changes in scour depth by investigating factors like pier geometries, debris arrangements, and submersion depths. The experiments and analysis revealed the effects of various pier shapes—cylindrical, square, rectangular, oblong, oval, and lenticular—on scour patterns. Different geometries influenced primary scour zones and affected areas, with square piers causing the deepest scour and lenticular ones showing shallower instances. Scour depths typically peaked upstream across geometries, but ogival and lenticular shapes exhibited unique patterns. The research also introduced a formula that integrated debris attributes into predictive scour depth modeling, validated with favorable accuracy. Ultimately, this predictive model advances scour prediction, particularly in debris-laden flows, offering valuable insights for engineering and management practices in understanding real-world scour mechanisms and hydraulic dynamics.
This study proposed the vision-based system which remotely measures dynamic displacement of bridges in real-time using digital image processing techniques. This system has a number of innovative ...features including a high resolution in dynamic measurement, remote sensing, cost-effectiveness, real-time measurement and visualization, ease of installation and operation and no electro-magnetic interference. The digital video camera combined with a telescopic device takes a motion picture of the target installed on a measurement location. Meanwhile, the displacement of the target is calculated using an image processing technique, which requires a target recognition algorithm, projection of the captured image, and calculation of the actual displacement using target geometry and number of pixels moved. For the purpose of verification, a laboratory test using shaking table test and field application on a bridge with open-box girders were carried out. The test results gave sufficient dynamic resolution in frequency as well as the amplitude.
The purpose of this work is to investigate the structure and mechanism of long‐range electronic contacts which are formed by wet mixing and their interaction and relationship with the structure ...responsible for ion transfer within the conductive binder domain of next‐generation LiNi
0.6
Mn
0.2
Co
0.2
O
2
lithium‐ion batteries. This article introduces a novel concept involving an efficient adapted structure model, which includes a bridge structure with two “nested” small and large pore systems, and an effective electrode conduction mechanism involving two “nested” percolation systems. The article also highlights a limitation in the improvement of the battery performance by percolation systems for electron transfer, which is restricted by pore systems for ion transfer through the ratio of electrical conductivity (
σ
) and ionic conductivity (
κ
) as
σ
/
κ
= 10. The findings of this article may provide valuable insight for formulation design and manufacturing of an optimal structure of the conductive binder domain for next‐generation lithium‐ion batteries.
The fatigue strength of structural steel components subjected to cyclic loading is often characterized in terms of S-N curves derived under constant amplitude (CA) loading. However, these are often ...subjected to load histories of variable amplitude and mean stress, i.e. variable amplitude (VA) loading. To take into account this loading condition for the design or the verification of structural components, damage accumulation models and modification of S-N curves have been proposed in the literature. However, these models require experimental characterization to verify or eventually calibrate some model parameters, e.g. the critical value of the Palmgren-Miner damage, among others.
This paper investigates the CA fatigue behavior of transverse welded steel attachments by reporting on an experimental characterization. Fatigue cracks have been monitored and fracture surfaces analyzed to obtain information about nucleation sites and growth rates. Moreover, the paper reports on the design of VA fatigue tests using a load history obtained from traffic measurements from a Swiss road bridge. As a design tool, the preliminary study using advanced probabilistic fatigue prediction models calibrated on similar welded details is presented. This model can also be used to define other load spectra to be applied in future VA experimental studies.
Durch den schlechten Zustand vieler älterer Brücken und Änderungen in den Regelwerken ergeben sich häufig Defizite bei der Nachrechnung von Bestandsbrücken nach Nachrechnungsrichtlinie. Für den Fall, ...dass die erforderliche Bauwerkssicherheit nicht nachgewiesen werden kann, können Bauwerksmessungen zeitlich begrenzt oder als Dauermonitoring durchgeführt werden, um Erkenntnisse über die zeitlich veränderliche Beanspruchung zu gewinnen. Zentral hierfür ist die Ableitung von Zustandsindikatoren für das Bauwerk, die letztendlich den Handlungsbedarf für Betreiber und Ingenieure anzeigen. Im einfachsten Fall wird hierfür z. B. ein Ausnutzungsgrad ermittelt, der allerdings keinen Rückschluss auf das Risiko ermöglicht und streng genommen nur eine binäre Bewertung zulässt. In diesem Beitrag wird daher eine Vorgehensweise erläutert und am Beispiel der Hamburger Köhlbrandbrücke umgesetzt, die es erlaubt, einen Zuverlässigkeitsindex als zeitlich veränderlichen Zustandsindikator bezogen auf den Beulnachweis aus den dynamischen Monitoringdaten abzuleiten.
Structural reliability assessment by structural monitoring – probabilistic buckling check of the Hamburg Köhlbrand bridge
The bad condition of many older bridges and changes in the code provisions often result in deficits after recalculation according to the recalculation guidelines. In case the necessary structural safety is not provided, temporary or permanent structural monitoring can be employed in order to gain knowledge about the time variant actions. For this, the derivation of condition indicators is key, since they indicate a need for action for the owners and the engineers. In the simplest case, a utilization will be derived which, however, does not allow for an assessment of the risk and strictly speaking only enables a binary assessment. In this paper, a method is described and demonstrated on the Hamburg Köhlbrand bridge which allows for the calculation of a reliability index as a time variant condition indicator on the basis of the dynamic monitoring data with regard to the buckling check.
•The theory for calculation lateral eigen frequencies of damaged multi-span bridge is developed.•The model of crack in the box-like concrete beam is developed.•The ratios of eigen frequencies for ...various mode shapes are proposed as ambient factors insensitive indicator of damage.•Verification of the proposed indicator of damage is carried out based on the operational database for the Z24.
Vibration based damage detection usually faces two fundamental problems, namely thelow sensitivity to the relatively small but potentially dangerous damage, and the dependence of vibration characteristics of structures on ambient factors (primarily temperature). Indeed, the effect of ambient factors on the vibration characteristics may be more significant than the influence of damage. In such situations, the reliable detection of damage is practically impossible. To solve this problem, the ratios of the natural frequencies for various mode shapes have been used. As the presented investigation reveals, these ratios are independent of the ambient factors and hence canimprovesubstantiallythe sensitivity and reliability of damage detection. To illustrate the higher efficiency of the proposed ratios applied to damage detection, the analytical model of the reinforced Z24 concrete bridge with the damage of crack type was developed. The natural frequencies of bending vibrations in vertical and horizontal planes at different crack depths and locations were calculated and compared with those measured on the Z24 bridge, demonstrating that the sensitivity of the natural frequencies change and ratios of frequencies for various mode shapes with respect to the size of damage is of the same order. At the same time, as opposed to the change of natural frequencies, the frequency ratios are dependent only on the parameters of damage, which makes them a much more efficient tool for health monitoring of structures operating in variable ambient conditions.
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