Showing papers in "Structure and Infrastructure Engineering in 2022"

Effect of pinching on structural resilience: performance of reinforced concrete and timber structures under repeated cycles

Abstract: This article attempts to define pinching of two structural joints, reinforced concrete (RC) and wood ones. In particular, the research outlines differences and analogies between pinching of an RC portal and a Light Timber Frame (LTF) wall. This is done by focusing on the concavity of pinching in their response under repeated cycles, which produces differences in the energy dissipation. The response of the two structural archetypes under pseudo-static and dynamic simulations is analysed using the Atan hysteresis model modification. The truncated incremental dynamic analysis (TIDA) of the two systems modelled as single-degree-of-freedom (SDOF) oscillators yielded the fragility curves, approximated by a lognormal cumulative distribution (CDF). The stability of RC under repeated cycles reveals its significant resilience compared to LTF structures. The examination of the fragility functions supports a discussion about the relation between the pinching concavity and the notion of structural resilience by introducing a robustness index ranging from 0 to 1. Ultimately, a parametric analysis of a fictitious structural system derived from the timber one by varying the concavity of the pinching path leads to the estimation of the robustness index as a function of the pinching concavity.

Multi-objective optimisation of in-service asphalt pavement maintenance schedule considering system reliability estimated via LSTM neural networks

Abstract: Abstract This article presents a novel system reliability-based framework for multi-objective optimisation of preventive maintenance (PM) management of in-service asphalt pavement. To accurately predict the international roughness index (IRI) sequence of pavement sections, a long short-term memory (LSTM) neural network that considers the spatiotemporal correlations between IRI sequences is trained with data retrieved from the long-term pavement performance (LTPP) program. Based on time-dependent limit-state functions (LSFs) incorporating the uncertainty associated with LSTM neural network prediction and the observational error involved in IRI measurement, Monte Carlo simulation (MCS) with importance sampling (IS) is adopted to calculate the reliability of pavement sections. Pavement sections located in New Mexico and Montana are selected as illustrative examples. Tri-objective optimisation processes are investigated by maximising user benefits (i.e. improved system reliability) and agency benefits (i.e. extended service life) while minimising the associated life-cycle cost (LCC) (i.e. user and agency costs) with multi-objective genetic algorithms (GAs). The obtained Pareto solution sets may assist decision-makers in the selection of well-balanced solutions to identify the optimal timing for applying PM treatments to in-service asphalt pavement.

Monitoring structural responses during load testing of reinforced concrete bridges: a review

Abstract: Abstract Nowadays, with the aging of the bridges and the advancements in technology, load testing has emerged as an effective method to assess existing concrete bridges with missing information, or where analytical methods do not provide an accurate assessment. Two types of load tests are identified: diagnostic load tests and proof load tests. Both rely on field measurements of parameters or structural responses of the bridge during the test. A diagnostic load test measures the response of the bridge so that analytical models can be calibrated and evaluated. In a proof load test, the bridge directly demonstrates that it can carry a certain load. Since large loads are applied, the bridge needs to be carefully monitored. In this case, monitoring the measurements provide a warning to avoid damage. This paper reviews the literature on reported load tests and the measurement techniques used during these tests. It also includes a review of traditional and recently developed sensing technologies. Finally, the measurement requirements for diagnostic and proof load tests are given as well as a flow chart to guide engineers in the selection process of appropriate monitoring and measurement techniques during load tests. This paper can serve engineers during the preparation of a load test.

Quantifying disaster resilience of a community with interdependent civil infrastructure systems

Abstract: Disaster resilient civil infrastructure systems are essential for disaster resilient communities. Measuring the resilience of these systems is the first step towards their improvement. This, however, is not easy: civil infrastructure systems are highly complex, operate in different ways, and are affected differently in different disasters. Adding to the complexity are the dynamic interdependencies among components of such systems, that change as the community is recovering. The Re-CoDeS framework for quantifying disaster resilience measures the lack of resilience of a system (e.g., a community) as the amount of the system’s unmet demand for a considered resource or service over the resilience assessment interval. This paper presents a novel demand/supply-based method to consider dynamic component interdependencies by extending the Re-CoDeS framework: whenever the demand of a component is not met by the currently available supply capacity of the system, that component ceases to operate and its supply capacity decreases. The proposed iRe-CoDeS framework is demonstrated on a virtual community served by three interdependent civil infrastructure systems producing five types of resources and services. Step-by-step instructions for defining a community model within the iRe-CoDeS framework are presented to facilitate the use of the proposed framework.

On the vertical coupling effect of ballasted tracks in multi–span simply–supported railway bridges under operating conditions

Abstract: This contribution investigates the vertical coupling exerted by ballasted tracks on the vertical response of bridges composed either of (i) several successive simply-supported spans with weak coupling between them due to the continuous track; or (ii) adjacent single-track decks conforming a double-track bridge, in which interaction effects are induced due to the transverse continuity of the ballast layer. To this end, 2 D and 3 D track-bridge interaction Finite Element models are implemented, which consider a three-layer discrete and explicit idealization of the track. The 2 D track-bridge interaction model is used to perform sensitivity analyses on the track parameters, which have revealed that the ballast shear mechanisms along the track may significantly affect the train-induced vibrations under resonant conditions. Then, the influence of the ballast coupling on the response of twin adjacent decks is investigated with a 3 D track-bridge interaction model. To this end, this model is updated based on the results of an experimental campaign performed on a real bridge composed of two SS spans and two single track twin adjacent decks. The numerical-experimental comparison shows an evident dynamic vertical coupling between the bridge decks and reveals the importance of including the ballasted track in the modelling process of these structures.

A comparison of the UK and Italian national risk-based guidelines for assessing hydraulic actions on bridges

Abstract: This paper compares the application of two recently published guidance documents for risk-based assessment of hydraulic actions on bridges, namely the UK Design Manual for Roads and Bridges and the Italian Ministry of Infrastructure and Transport’s Guidelines, to two case study bridges (Staverton Bridge, UK; Borgoforte Bridge, Italy). This work is one of the first to illustrate how to apply these guidelines. Both documents present risk-based methods for the assessment of hydraulic actions, while exhibiting fundamental differences. For example, the UK method prescribes calculations for local and constriction scour, water depth, and velocity at several cross-sections; by comparison, the Italian method does not prescribe calculations to assess the risk level. For the case studies in this paper, the hydraulic risk obtained for Staverton Bridge resulted as ‘High’ using both methods. The scour score for the Borgoforte Bridge resulted higher using the Italian method (Medium-High), as compared to the UK approach (Medium). This difference is due to how the guidelines assess the vulnerability associated with the minimum clearance. The comparison of these two risk-based approaches and the resulting discussion may serve as a useful resource for those wishing to develop new risk-based methods for assessing hydraulic actions on bridges.

Experimental and numerical investigation on wave impacts on box-girder bridges

Abstract: Abstract Climate change could result in more extreme weather events and induce increasing challenges to the low-lying coastal bridges. The structural performance of box-girder bridges under wave impacts was seldom investigated. In this paper, a three-dimensional (3D) computational fluid dynamics (CFD) model is established to simulate the wave-bridge interactions, and laboratory experiments are conducted to investigate wave impacts on a bridge. The experiments and 3D CFD simulations are unique as compared with other relevant studies since they provide the complex wave-bridge interactions through dynamic and spatial analyses. Specifically, time histories of vertical and horizontal wave forces are measured through experiments. The time-dependent pressure distributions, wave-induced forces, and overturning moments on the bridge model are computed with the CFD model. The effects of different parameters on the maximum wave forces are discussed. Also, comparisons of the differences between two-dimensional (2D) and 3D CFD models are conducted. Then, the results are converted to a prototype scale to explore the effects of wave impacts, and prediction formulas are proposed accordingly. This study combining experimental and 3D numerical investigations could help improve understanding of the wave-bridge interaction mechanism, and further aid the optimal and robust designs of coastal bridges.

Life-cycle connectivity-based maintenance strategy for bridge networks subjected to corrosion considering correlation of bridge resistances

Abstract: Abstract The safety of road networks is crucial for the well-being of the society. Corrosion is a common problem facing bridges. Traditionally, the reliability analysis is performed on individual bridges and maintenance strategies are laid out based on the reliability profiles resulting from this analysis. This paper aims to investigate how to allocate maintenance resources for a group of bridges in a transportation network. Performance indicators associated with connectivity between different nodes in the bridge network are selected as the objectives of the optimization associated with this allocation. Correlation profiles associated with resistances of bridges subjected to corrosion are taken into account in the optimization process. Two approaches to determine life-cycle maintenance strategies are considered: (a) ranking the importance of bridges in terms of their contribution to connectivity; (b) performing optimization to obtain optimal maintenance strategies associated with objectives related to connectivity and maintenance cost. For each approach, the strategies associated with different O (origin)-D (destination) pairs as well as a performance indicator illustrating the overall connectivity within the bridge network are investigated. The results show that different O-D pairs may have different optimal maintenance strategies under the same maintenance budget to maximize the probability of network connectivity. The correlation of bridge resistances has a significant influence on the probability of network connectivity, and as a result, needs to be accounted for.

An overview on finite element-modelling techniques for structural capacity assessment of corroded reinforced concrete structures

Abstract: About 80% of the observed damage in existing reinforced concrete structures is related to corrosion. Typical corrosion-associated phenomena that affect structural capacity concern: (i) cross-section and ductility reduction of steel, (ii) concrete cracking, (iii) concrete area reduction due to spalling and (iv) modification of the bond properties. A number of models have been presented in recent years addressing these issues. The paper presents a critical review of such models and their application to the analysis of corroded reinforced concrete members using nonlinear finite element analysis. The accuracy of different modelling approaches is assessed through comparison with experimental results on corroded beams subjected to monotonic and cyclic loading. Specimens showing different failure modes were selected, such as flexure, combined flexure-shear and bond failure. Sensitivity studies are performed in order to gain better understanding of the contribution of each degradation phenomenon. Finally, recommendations are given for reliable capacity assessment of existing concrete structures affected by corrosion.

Challenges in the application of digital transformation to inspection and maintenance of bridges

Abstract: Abstract Bridges constitute an important part of the infrastructure and are subjected to damage and deterioration of materials and support conditions, as well as exposure to adverse environmental conditions. Continuous or repeated monitoring of structural responses may add important information for decision-making regarding their maintenance, repair and reinforcement. The use of these data, in conjunction with techniques of structural reliability for the treatment of the uncertainties, allows a better understanding of the structural behaviour and integrity. Modern Information and Communication Technologies can greatly contribute to the improvement of the maintenance capacity and, consequently, to the reliability of the assets and to their operational availability. New wireless communication technologies, such as 5 G networks, are considered as the enabling technologies of the digital transformation, integrated with the concept of the Internet of Things. High connectivity capacity and intensive automation enable, for example, changes in inspection paradigms and asset maintenance, by transferring the product focus to service platforms, bringing gains to productivity, comfort, operational safety and costs. New predictive maintenance approaches, which make use of a large amount of data available, can improve the efficiency of maintenance processes, producing more accurate and reliable anticipated diagnostics. The Digital Twins incorporate all these tools and allow a real-time view of the evolution of the asset behaviour. This concept applied to a railway bridge is presented and discussed in detail in this paper.

Residual performance and damage mechanism of prestressed concrete box girder bridge subjected to falling heavy object impact

Abstract: Extreme vertical impact loading from dropped heavy cargo or falling rocks threatens the safety of bridge structures. The impact behavior and post-impact performance of a multi-piece prestressed concrete (PC) box girder bridge were investigated through numerical simulation. The moment-curvature analysis was performed to explain the damage mechanism and to predict the residual capacity of the girder under impact. The results demonstrate that the impacted girder suffers the most severe flexural failure whereas the other un-impacted girders exhibit flexural-torsional combined damage type. The impacted girder suffers from flexural failure to shear failure if the impact position on the girder transfers from mid-span to support. The increased impact energy deteriorates the damage of impacted girder while has little influence on the un-impacted girder. When the impact area decreases due to the varying impact angle, the displacement and impact force of the impacted girder reduce whereas local damage becomes more severe. The residual stiffness and resistance decrease significantly as the impact energy raises. It is concluded that severe concrete damage of top plate diminishes the flexural capacity of impacted girder.

Inspection and maintenance planning for offshore wind structural components: integrating fatigue failure criteria with Bayesian networks and Markov decision processes

Abstract: Abstract Exposed to the cyclic action of wind and waves, offshore wind structures are subject to fatigue deterioration processes throughout their operational life, therefore constituting a structural failure risk. In order to control the risk of adverse events, physics-based deterioration models, which often contain significant uncertainties, can be updated with information collected from inspections, thus enabling decision-makers to dictate more optimal and informed maintenance interventions. The identified decision rules are, however, influenced by the deterioration model and failure criterion specified in the formulation of the pre-posterior decision-making problem. In this paper, fatigue failure criteria are integrated with Bayesian networks and Markov decision processes. The proposed methodology is implemented in the numerical experiments, specified with various crack growth models and failure criteria, for the optimal management of an offshore wind structural detail under fatigue deterioration. Within the experiments, the crack propagation, structural reliability estimates, and the optimal policies derived through heuristics and partially observable Markov decision processes (POMDPs) are thoroughly analysed, demonstrating the capability of failure assessment diagram to model the structural redundancy in offshore wind substructures, as well as the adaptability of POMDP policies.

Seismic performance of earthquake-damaged corroded reinforced concrete beam-column joints retrofitted with basalt fiber-reinforced polymer sheets

Abstract: This present research conducted an experimental study on the influence of different earthquake damages on the seismic performances of aged reinforced concrete (RC) beam-column joints retrofitted with basalt fiber-reinforced polymer (BFRP) sheets under cyclic loadings. Six beam-column joints included one benchmark specimen, one uncorroded specimen retrofitted with BFRP sheets, and four earthquake-damaged corroded specimens with the corrosion rates of 0% and 9% retrofitted with BFRP sheets. Test results demonstrated that the seismic performances of earthquake-damaged corroded specimens effectually improved after retrofitting with BFRP sheets, and the retrofitting effectiveness was significantly affected by the earthquake-damaged levels. The bucking of stirrups, spalling and crushing of concrete of retrofitted specimens were effectually postponed, while the ductility of corroded and uncorroded specimens under the earthquake damages increased after retrofitting with BFRP sheets. The total cumulative energy dissipation and final stiffness of retrofitted specimens considerably improved with the maximum increase of 22.3% and 14.3% comparing to those of benchmark specimen, respectively. Besides, the models for predicting the shear strength of RC beam-column joint cores considering the influences of earthquake damage, reinforcement corrosion, and FRP retrofitting were proposed.

Flexibility and adaptability within the context of decision-making in infrastructure management

Abstract: Abstract Worldwide, large infrastructure projects almost invariably have major delays, cost over-runs, benefit shortfalls, and generally fail to perform up to expectations. This questions the results of many models as tools for decision-making. The design and management of infrastructure systems requires making assumptions and decisions about aspects of the project that change over the project’s lifetime. Thus, for real projects to meet performance objectives, it is necessary to combine short and long-term predictions with an understanding of the stakeholder’s interests and decisions, which unravel as the project evolves with time. In practice, successful projects are those that better adapt to new circumstances as they materialize. Within this context, this paper discusses key elements of the decision-making process and examines the value of incorporating flexibility in the design and management of large infrastructure. It discusses the nature of flexibility, the complexities of integrating it within a project, and the gains of adopting this approach for both stakeholders and users. The ideas presented in this paper builds off of former published literature, including that by the author. At the end, the proposed approach for incorporating flexibility in infrastructure design and management is illustrated with the case of an airport design and expansion.

Stochastic analysis of railway embankment with uncertain soil parameters using polynomial chaos expansion

Abstract: Abstract This paper focuses on the stochastic response of railway embankments considering the uncertainties in soil cohesion and friction angle. The non-sampling stochastic method concerning generalised polynomial chaos (gPC) expansion was employed for the dynamic numerical simulation. The uncertain parameters, including soil cohesion and friction angle, were defined by the truncated gPC expansions. Furthermore, the system’s response, namely, the displacement and acceleration of different embankment sections, was presented by the gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection was used to calculate a set of deterministic equations. The unknown gPC coefficients of the system’s response were determined by a non-intrusive solution as a set of collocation points. In addition, the results of these analyses were compared with classical Monte Carlo simulations. It is essential to note that although only a few collocation points have been used, the results are in good agreement with the MC sampling method. One of the main objectives of this study is to demonstrate the accuracy of the results and the time efficiency of the proposed non-sampling method in quantifying the uncertainty of stochastic systems compared to the sampling procedure (e.g. Monte Carlo simulation).

Creep effects on elastomeric and ball rubber bearings under sustained lateral loads

Abstract: Abstract Base isolation applications are becoming popular in the seismic design of resilient structures and infrastructures. Even though the response of the bearings is widely studied under cyclic displacements, limited information is available for bearing response under sustained lateral loads. These types of loads can develop sustained lateral displacement in the bearing. During the holding time under sustained lateral displacement, the creep or stress relaxation may significantly change the properties of the bearings and may affect the response in the reloading stage. This research paper aims at assessing the influence of short-term lateral creep on the hysteretic response of rubber bearings, and ball rubber bearings. To this end, experimental testing on different elastomeric bearings under imposed lateral displacement is performed. For each device, the lateral response is measured, and the advantages and disadvantages are discussed in terms of strength, stiffness, energy dissipation and equivalent damping. The loss of load under sustained lateral displacement is experimentally assessed and the effects of creep in the design procedure of a base isolated system are discussed.

An efficient simplified model for high-speed railway simply supported bridge under earthquakes

Abstract: An efficient model of high-speed railway simply supported bridge with China Railway Track Structure II (CRTS II) ballastless track structure, setup on ANSYS platform, is proposed in this article. The goal is to improve the low computational efficiency and reduce the high computer memory consumption caused by complex bridge models of numerous spans. Programming language and modeling procedures are utilized to ensure that all spans in the proposed model of a large multispan simply supported railway bridge have consistent boundary conditions. Hence, only the middle span is simulated. The comparison of the first longitudinal vibration modes and first natural frequencies of the proposed model and the conventional simply supported bridge model preliminarily validates the feasibility of the model. It also confirms the range of the span number that the proposed model can simulate with accuracy. Taking into account eight different seismic excitations, the results further prove that the proposed model can significantly improve the computational efficiency of the seismic analyses, and can decrease the modeling complexity and calculation time cost without loss of accuracy. The design verification of three different heights of pier groups and the consideration of nonlinear springs enables the proposed model to be utilized in a wide range of applications. As a conclusion, for seismic simulation of high-speed railway simply supported bridges, the proposed model is a reliable alternative for practical engineering simulation.

Challenges of integrated multi-infrastructure asset management: a review of pavement, sewer, and water distribution networks

Abstract: The prosperity of urban life is dependent on its infrastructure. Urban underground infrastructure components (assets) are aging and need regular monitoring, maintenance and rehabilitation. These assets are often placed under pavements and in close vicinity to each other. Managing them in a coordinated way is rational considering costs and disruption of services and communities caused by each intervention on the different assets. Recently, interest in practice as well as in research has grown to manage urban infrastructures in a coordinated way. This article reviews journal articles and grey literature to evaluate managing these infrastructures in an integrated way (i.e. the highest level of coordination) and describe possible obstacles for doing so. This article identifies seven main challenges of integrated multi-infrastructure asset management (IMAM) that need to be addressed by practitioners and researchers. These challenges are related to: (i) dependencies and interdependencies, (ii) data quality, availability and interoperability, (iii) uncertainties in modelling and decision-making, (iv) comparability, (v) problems of scale, (vi) problems of fit and (vii) problems of interplay. This article provides details on these challenges and discusses future research and practical directions.

Numerical simulation of root-deck crack propagation of orthotropic steel bridge deck

Abstract: Abstract The fatigue crack at the rib-to-deck joint that initiated at the weld root and propagated through the deck plate is one of the most common and unfavorable crack types on orthotropic steel deck (OSD). To evaluate the fatigue performance of OSD during its life-cycle in a more accurate way, a numerical simulation method to reproducing the behavior of this type of crack was established based on linear elastic fracture mechanics (LEFM) in this paper. Firstly, the crack growth at the weld root was provided by the fatigue test using the beach marking method. Then, by adopting the proposed crack propagation simulation method, the crack growth in the test was simulated and the fatigue cracks growth life was predicted. Finally, some factors that may have a great influence on crack propagation behaviors were analyzed, including the lack of penetration defects (LOP) at the weld root, the angle between the crack surface and the deck plate, initial crack depth as well as crack aspect ratio. Accordingly, a practical approach was put forward to estimate the fatigue life based on the test, which can be applied to actual structures that are manufactured by the same process of the specimens, and the inspection and maintnenance works can be benefitted.

An integrated damage modeling and assessment framework for overhead power distribution systems considering tree-failure risks

Abstract: The overhead power distribution system (OPDS) is vulnerable to strong winds, such as hurricanes. Due to the challenges of including tree damage risks to the OPDS, tree failures are usually ignored in the risk assessment of the OPDS against strong winds. In the present study, an integrated damage modeling and assessment framework for the OPDS is proposed considering tree failure risks. The geographical information of trees surrounding the OPDS is extracted from satellite images using computer vision techniques, including CNN-based (convolutional neural network) image classifier and sliding window approach. The tree failure risk models are developed using tree geographical information in conjunction with tree height data, tree allometry and finite element analysis. With further integration of the conditional probability failure of poles under fallen tree impacts, the pole’s failure probability considering the combined wind and fallen trees is obtained using series system reliability analysis. The failure probability of the pole is obtained using physics-based modeling facilitated by Bayesian regularisation neural network (BRNN) algorithm. The poles and wires are connected for system reliability assessment using connectivity-based theory. When the wind direction is 300° counterclockwise from the east and the wind speed is 57 m/s, tree-failure can introduce 68.6% differences in OPDS’ failure probabilities compared with that without consideration of fallen trees.

Experimental investigation on the flexural behaviour of stainless steel reinforced concrete beams

Abstract: The durability of reinforced concrete (RC) structures and infrastructure has been the subject of significant attention from the engineering research community in recent years, mainly owing to the deterioration of RC elements due to corrosion of the embedded steel reinforcement. In this context, stainless steel reinforcement can provide an efficient solution to enhance the expected lifetime of concrete structures, reducing the damage due to corrosion of the reinforcement and carbonation and deterioration of the concrete. However, current international design standards for reinforced concrete structures do not include appropriate guidance for stainless steel reinforced concrete (SSRC). In order to investigate the behaviour of stainless steel RC beams, a series of six beam tests was conducted and is discussed herein. The key performance measures for RC beams such as load-deflection response, cracking behaviour and deflections at service load are assessed. The validity and applicability of existing design rules, which were developed for carbon steel RC, are also examined for stainless steel reinforced concrete members. Other recently developed design procedures, based on the Continuous Strength Method and including an accurate material model for the stainless steel bars, are also examined.

Numerical analysis-based structural behavior assessment of a cable-stayed bridge under tanker fire

Abstract: Recently, preparation and preventive measures against disasters that can affect the public infrastructure have emerged as a major issue worldwide. Cable-stayed bridges are one of the important infrastructures, damage to which may lead to significant casualties and economic loss in the event of a disaster. Fire accidents involving cable-stayed bridges can cause considerable damage to the structures. In this study, numerical analysis was performed to evaluate the effects of fire on cable-stayed bridges. In previous studies, a fire intensity model (FIM) was proposed to simulate cable-stayed bridges’ fire that is an open environment. Heat transfer analysis (HTA) and structural analysis were performed using the proposed model. Although the results of HTA presented that higher temperature rises were observed in cables with smaller cross-sections, the structural behavior of the bridge demonstrated vulnerability when a fire occurred near any cable locations that would greatly affect the behavior of the bridge in the event of damage. Based on fire analysis conducted in this study, it is expected that the findings will enable indirect evaluations of fire damage to cable-stayed bridges.

Fatigue life updating of embedded miter gate anchorages of navigation locks using full-scale laboratory testing

Abstract: Abstract Locks and dams facilitate the transportation of billions of dollars in goods through inland waterways annually. Miter gates are lock components that are supported by steel anchorage frames embedded in the concrete lock wall. In the US, many of these anchorages have been subjected to over 80 years of cyclic loads. The typical analysis approach for anchorages treats the steel frame as a freestanding truss, ignoring the embedding concrete. This approach predicts that some anchorages may imminently fail in fatigue. Thus, there is a push to excavate and replace these anchorages at a cost of nearly $10 million USD per site. Previous numerical modelling of an embedded miter gate anchorage, considering the effects of concrete, shows that the stress in most of the anchorage is below the endurance limit of steel. To verify these modelling results, a full-scale laboratory test is performed wherein a representative anchorage is instrumented and loaded under typical gate loads. The testing is performed in three phases: the first phase represents the freestanding truss; the second and third phases represent the fully embedded anchorage in two typical orientations. Results of the test support the numerical modelling results, suggesting that planned anchorage replacements are not required.

Dynamic performance-based assessment for tied-arch bridges subjected to heavy multi-axial tractor-trailers

Abstract: With rapid industrial development, the overloading of bridges caused by heavy multi-axle vehicles has become a critical problem worldwide. This work conducts a performance-based evaluation for tied-arch bridges subjected to heavy multi-axle vehicles, and a prediction function of the dynamic impact factor (DIF) for tied-arch bridges is proposed considering the bridge frequency, vehicle speeds, and road quality level. Specifically, the main parameters affecting the bridge response were first identified theoretically using a simplified multi-axle vehicle-bridge model. A tractor-trailer mechanical model and a tied-arch bridge model were subsequently constructed and coupled using displacement coordination conditions to explore the characteristics of the bridge response under heavy multi-axle tractor-trailers. Additionally, based on the identified factors, a detailed investigation of DIF was performed using the developed special vehicle-bridge interaction model. Finally, a suggested computational method for predicting DIF of tied-arch bridges was proposed. The results obtained indicate the impact effect of special tractor-trailers on bridges should not be ignored, even at low operating speeds and in good road conditions. Moreover, additional monitoring measures should be placed on the structural components that are sensitive to dynamic responses to regulate responses within an acceptable range.

Verifying the suitability of uncoupled numerical methods for solving vehicle-bridge interaction problems

Abstract: Abstract The response of a structure subjected to a moving load can be obtained using coupled or uncoupled methods. The uncoupled method is often preferred since modal superposition is applicable, which implies computational efficiency and ease of implementation. However, the uncoupled method ignores the changes in the dynamic features of the combined structural system due to the time-varying location of the load. This paper analyses the extent to which the accuracy of the uncoupled method is affected by these changes. First, a parametric study is conducted on two discretized beam models traversed by a sprung mass at a constant speed. The error associated with the uncoupled method is calculated using the coupled solution as a reference. The influence of the load to structure mass and frequency ratios and the speed of the vehicle on the error is quantified. Heavier loads travelling at higher speeds are found to increase the inaccuracy of the uncoupled method. Then, the analysis is extended to a half-car travelling on a rough profile. Although errors from the uncoupled simulation remain low for the range of parameters under investigation, they may not be acceptable in some applications, i.e., the training of an algorithm for early damage detection.