Showing papers in "Structure and Infrastructure Engineering in 2017"

Bridge life-cycle performance and cost: analysis, prediction, optimisation and decision-making

Abstract: The development of a generalised framework for assessing bridge life-cycle performance and cost, with emphasis on analysis, prediction, optimisation and decision-making under uncertainty, is briefly addressed. The central issue underlying the importance of the life-cycle approach to bridge engineering is the need for a rational basis for making informed decisions regarding design, construction, inspection, monitoring, maintenance, repair, rehabilitation, replacement and management of bridges under uncertainty which is carried out by using multi-objective optimisation procedures that balance conflicting criteria such as performance and cost. A number of significant developments are summarised, including time-variant reliability, risk, resilience, and sustainability of bridges, bridge transportation networks and interdependent infrastructure systems. Furthermore, the effects of climate change on the probabilistic life-cycle performance assessment of highway bridges are addressed. Moreover, integrati...

Resilience-based post-disaster recovery strategies for road-bridge networks

Abstract: This paper presents a novel resilience-based framework to optimise the scheduling of the post-disaster recovery actions for road-bridge transportation networks. The methodology systematically incor...

Recent developments of high-speed railway bridges in China

Abstract: China’s high-speed railway (HSR) construction industry has been experiencing a golden period of opportunities in the recent decades. Due to the necessity of protecting arable lands and the advantage of rapid construction, bridges (elevated structures) are predominantly used in China’s HSRs, which must meet the critical small settlement requirement. This article first reviews the main technical standards of small- to medium-span HSR bridges, where their comparison with the Japanese standard and International Union of Railway standards is highlighted. Then, the long-span HSR steel bridges are described and discussed case by case. Based on the engineering practice of HSRs, the main achievements and key technologies of HSR bridges in China are provided, followed by the opportunities and challenges of the current and future developments of HSR bridges.

Computer vision-based displacement and vibration monitoring without using physical target on structures

Abstract: Although vision-based methods for displacement and vibration monitoring have been used in civil engineering for more than a decade, most of these techniques require physical targets attached to the structures. This requirement makes computer vision-based monitoring for real-life structures cumbersome due to need to access certain critical locations. In this study, a non-target computer vision-based method for displacement and vibration measurement is proposed by exploring a new type of virtual markers instead of physical targets. The key points of measurement positions obtained using a robust computer vision technique named scale-invariant feature transform show a potential ability to take the place of classical targets. To calculate the converting ratio between pixel-based displacement and engineering unit (millimetre), a practical camera calibration method is developed to convert pixel-based displacements to engineering unit since a calibration standard (a target) is not available. Methods and a...

Deformational responses of operated shield tunnel to extreme surcharge: a case study

Abstract: A field case of operated shield tunnel disrupted by unexpected extreme surcharge in Shanghai is reported in this paper. The deformational responses of segmental lining, in terms of convergences, settlements and joint open width, are highlighted. The surcharge caused by unexpected dumped soils with a maximum height of 7 m is six times larger than the design value of surcharge. Three hundred and sixty segmental lining rings of the operated metro shield tunnel below this surcharge are severely affected. The measured horizontal convergence to outer-diameter ratio (ΔD/Dout) ranges from 16.6 to 35.7‰, which is far beyond the averaged value for normal condition, i.e. 5.1‰. The trend of tunnel deformation (e.g. horizontal convergence and settlement) varying with surcharge level is found to be significantly non-linear. Correspondingly, the longitudinal joints are also severely disrupted and have large open widths. The rubber packer for joint near-tunnel springline loses its function of waterproof due to th...

Target reliability for existing structures considering economic and societal aspects

Abstract: Specification of target reliability levels is one of the key issues of the assessment of existing structures. ISO 13822:2010 and ISO 2394:2015 indicate procedures for specification of target reliability levels by optimisation of the total cost related to an assumed remaining working life of a structure. These approaches are critically compared with human safety criteria, with target levels based on a marginal life-saving costs principle, and with recommendations of present standards. Optimal target reliability levels are then derived in the representative case study for an existing structural member. It appears that the requirement to reach the same target reliability levels for existing and new structures is uneconomical. Decisions made in the assessment can result in the acceptance of the actual state or in the upgrade of an existing structure. Two reliability levels are thus needed – the minimum level below which the structure is unreliable and should be upgraded, and the target level indicatin...

Novel vibration-based technique for detecting water pipeline leakage

Abstract: Exacerbating the imbalance between demand for freshwater and available water resources is the sub-optimal performance of water distribution systems, which are plagued with leaks that cause significant losses of treated freshwater. This paper presents an approach for leak detection that involves continuous monitoring of the changes in the correlation between surface acceleration measured at discrete locations along the pipeline length. A metric called leak detection index is formulated based on cross-spectral density of measured pipe surface accelerations for detecting the onset and assessing the severity of leaks. The proposed non-invasive approach requires minimal human intervention and works under normal operating conditions of the pipeline system without causing any operational disturbances. The approach is demonstrated on a 76 mm diameter polyvinyl chloride pipeline test system considering varying leak severities. The preliminary results presented in this paper seem promising and lead to sever...

Vibration monitoring via spectro-temporal compressive sensing for wireless sensor networks

Abstract: The reliable extraction of structural characteristics, such as modal information, from operating structural systems allows for the formation of indicators tied to structural performance and condition. Within this context, reliable monitoring systems and associated processing algorithms need be developed for a robust, yet cost-effective, extraction. Wireless Sensor Networks (WSNs) have in recent years surfaced as a promising technology to this end. Currently operating WSNs are however bounded by a number of restrictions relating to energy self-sustainability and energy data transmission costs, especially when applied within the context for vibration monitoring. The work presented herein proposes a remedy to heavy transmission costs by optimally combining the spectro-temporal information, which is already present in the signal, with a recently surfaced compressive sensing paradigm resulting in a robust signal reconstruction technique, which allows for reliable identification of modal shapes. To this end, th...

Post-quake urban road network functionality assessment for seismic emergency management in historical centres

Abstract: In this paper, a procedure for the evaluation of the interaction between existing buildings and urban roadway networks after a seismic event is proposed. This question is relevant in historical urban centres, where urbanisation typology has evidenced, in the past, lack of road networks’ residual connectivity in post-earthquake conditions. The present study proposes a method for the evaluation of the residual functionality in urban context, moving from the execution of building surveys, the application of probabilistic concepts and fuzzy logic with the aim to define probable urban road network damage scenarios. The methodology is applied to the Municipality of Conegliano (northeastern Italy) evaluating the potential seismic damage scenario to the historical urban centre and highlighting criticisms in the post-earthquake rescue operations.

Devices for protecting bridge superstructure from pounding and unseating damages: an overview

Abstract: Previous earthquakes have highlighted the seismic vulnerability of bridges due to excessive movements at expansion joints. This movement could lead to the catastrophic unseating failure if the provided seat width is inadequate. Moreover, seismic pounding is inevitable during a strong earthquake due to the limited gap size normally provided at the expansion joints. Various types of restrainers, dampers and other devices have been proposed to limit the joint movement or to accommodate the joint movement so that the damages caused by excessive relative displacements could be mitigated. To select and design appropriate devices to mitigate the relative displacement-induced damages to bridge structures during earthquake shaking, it is important that results from the previous studies are well understood. This paper presents an overview on various pounding and unseating mitigation devices that have been proposed by various researchers. Based on an extensive review of up-to-date literatures, the merits and...

Maintenance management of offshore structures using Markov process model with random transition probabilities

Abstract: The robustness of an offshore engineering design is highly dependent on the maintenance management, where the latter needs a full knowledge of engineering analysis and predictions. An accurate estimation of offshore structural performance with time-varying effect is a keen technical issue. The traditional Markov chain model used for structural strength predictions suffers from the difficulty that some of the measurements or inspection data are largely different from the predicted damage condition. This paper presents a deterioration prediction method for maintenance planning in offshore engineering using the Markov models. Instead of traditional deterministic approaches, the Markov chain model is refined by expressing the transition probabilities as random variables. Through such development, the proposed model is able to estimate an interval for the deterioration of an offshore structure. An existing offshore structure located in South China Sea is used in this study for the demonstration purpose. The selection of transition periods of the Markov chain model is investigated. The use of the stochastic model in the prediction of maintenance timing is also discussed. The results show that the proposed approach can provide more reliable information on structural integrity compared to the conventional method.

Simplified structural deterioration model for reinforced concrete bridge piers under cyclic loading1

Abstract: Deterioration due to reinforcement corrosion represents a significant cause of damage to reinforced concrete bridges all over the world. Although numerous studies have identified the substantial influence that corrosion can have on the failure of concrete structures under seismic loads, there has been comparatively less work done on the modelling of structural vulnerability due to corrosion. Accurate and computationally efficient structural modelling of corrosion deterioration is an essential prerequisite for structural reliability or fragility prediction, or life cycle cost and impact estimation. In this paper, a simplified approach for modelling reinforced concrete bridge columns that have undergone deterioration due to chloride-induced reinforcement corrosion is presented. While several models of increasing complexity are evaluated, a simplified non-linear analytical model that accounts primarily for the reduction in the steel cross-section due to corrosion is the central focus of the paper. Th...

Long-term performance assessment of the Telegraph Road Bridge using a permanent wireless monitoring system and automated statistical process control analytics

Abstract: The purpose of this study is to advance wireless sensing technology for permanent installation in operational highway bridges for long-term automated health assessment The work advances the design of a solar-powered wireless sensor network architecture that can be permanently deployed in harsh winter climates where limited solar energy and cold temperatures are normal operational conditions To demonstrate the performance of the solar-powered wireless sensor network, it is installed on the multi-steel girder bridge carrying northbound I-275 traffic over Telegraph Road (Monroe, Michigan) in 2011; a unique design feature of the bridge is the use of pin and hanger connections to support the bridge main span A dense network of strain gauges, accelerometers and thermometers are installed to acquire bridge responses of interest to the bridge manager including responses that would be affected by long-term bridge deterioration The wireless monitoring system collects sensor data on a daily schedule and

Experimental investigation of the spatial variability of the steel weight loss and corrosion cracking of reinforced concrete members: novel X-ray and digital image processing techniques

Abstract: The material properties of concrete structures and their structural dimensions are known to be random due to the spatial variability associated with workmanship and various other factors. This randomness produces spatially variable corrosion damages, such as steel weight loss and corrosion cracks. The structural capacity of reinforced concrete (RC) members strongly depends on the local conditions of their reinforcements. Modelling the spatial variability of steel corrosion is important, but steel corrosion in RC members can only be observed after severely damaging the concrete members. To understand the steel corrosion growth process and the change in the spatial variability of steel corrosion with time, continuous monitoring is necessary. In this study, X-ray photography is applied to observe steel corrosion in RC beams. The steel weight loss is estimated by the digital image processing of the X-ray photograms. The non-uniform distribution of steel weight loss along rebars inside RC beams determi...

First-order reliability method-based system reliability analyses of corroding pipelines considering multiple defects and failure modes

Abstract: A methodology that employs the first-order reliability method is proposed to evaluate the time-dependent system reliability of a segment of a pressurised steel pipeline containing multiple active corrosion defects. The methodology considers the leak and burst failure modes of the pipe segment and takes into account the correlations among limit state functions at different corrosion defects. The methodology involves first constructing two linearised equivalent limit state functions for the pipe segment in the standard normal space and then evaluating the probabilities of leak and burst of the segment incrementally over time based on the equivalent limit state functions. The applicability and accuracy of the proposed methodology is illustrated through system reliability analyses of three pipeline examples, each containing ten active corrosion defects whose growth over time is characterised by the linear, nonlinear and homogeneous gamma process-based models.

Investigating correlations between crack width, corrosion level and anchorage capacity

Abstract: In assessing existing structures, inspection results need to be linked to the effects on load-carrying capacity; to provide such information, this study has investigated the correlation between splitting crack width, corrosion level and anchorage capacity. The study was based on 13 reinforced concrete beams that had been exposed to natural corrosion for 32 years, eleven beams with splitting cracks and two without. The crack pattern and widths were documented before undergoing structur-al testing of anchorage capacity. Thereafter, the reinforcement bars were extracted and their corro-sion levels measured using two methods, gravimetric weight loss and 3D scanning. The corrosion level from the weight loss method was approximately twice as large; possible reasons are horizon-tal or subsurface corrosion pits, and the cleaning method. Further, for the same corrosion level, the specimens in this study had much larger crack widths and slightly lower bond capacity than the artificially corroded tests in the literature; a possible reason is that these specimens had been sub-jected to combined corrosion and freezing. However, the corrosion level and reduction in bond ca-pacity related to crack width were both lower in the present than in previous studies in the litera-ture. Thus, by formulating a damage indicator from the damage visible in the form of crack widths from artificial test data, the structural capacity is estimated to be on the safe side.

Inspection and maintenance of oil & gas pipelines: a review of policies

Abstract: Oil and gas (O&G) pipelines are expensive assets that cross through both the ecologically sensitive and densely populated urban areas. The pipeline failure may have potentially significant conseque...

Optimal seismic upgrading of a reinforced concrete school building with metal-based devices using an efficient multi-criteria decision-making method

Abstract: In the paper, the seismic retrofitting of an existing reinforced concrete school building located in the district of Naples has been examined. The school, which was designed to sustain gravity load only, is composed of seven constructions separated with seismic joints. One of these constructions has been retrofitted with different intervention techniques, namely reinforced concrete walls, steel concentric, eccentric and buckling restrained braces and steel shear panels, whose non-linear behaviour under seismic actions in terms of performance point detection have been evaluated and compared using Capacity Spectrum Method. Finally, the choice of the best intervention technique from economic, structural and environmental point of view has been done utilising an efficient multi-criteria decision-making (MCDM) method, the so-called TOPSIS method. From the performed analyses it was found that buckling restrained braces provide optimal solution for the seismic upgrading of the examined reinforced concret...

Numerical prediction of solitary wave forces on a typical coastal bridge deck with girders

Abstract: In this study, a numerical method for predicting solitary wave forces on a typical coastal bridge deck with girders is utilised in order to obtain an alternative way to assess solitary wave forces on coastal bridge decks with sufficient accuracy. Firstly, a wave model based on the solitary wave theory representing the incident wave of tsunamis is applied through a computational fluid dynamics computer program, where the shear stress transport k-ω model is adopted as the turbulent closure for the Reynolds Averaged Navier–Stokes model equations. Then, the numerical wave profiles and the predicted wave forces are compared with the analytical solutions and the reported laboratory measurements, respectively. These verifications assure the results in the following parametric study reliable. Finally, comparisons between the numerical results and those acquired through the empirical methods are conducted in order to examine the appropriateness of these empirical procedures regarding this specific case. Fu...

Probabilistic assessment of an interdependent healthcare–bridge network system under seismic hazard

Abstract: Strong earthquakes can destroy infrastructure systems and cause injuries and/or fatalities. Therefore, it is important to investigate seismic performance of interdependent infrastructure systems and guarantee their abilities to cope with earthquakes. This paper presents an integrated probabilistic framework for the healthcare–bridge network system performance analysis considering spatial seismic hazard, vulnerability of bridges and links in the network, and damage condition of a hospital at component and system levels. The system level performance is evaluated considering travel and waiting time based on the damage conditions of the components. The effects of correlation among the seismic intensities at different locations are investigated. Additionally, the correlations associated with damage of the investigated structures are also incorporated within the probabilistic assessment process. The conditional seismic performance of the hospital given the damage conditions of the bridge network and the...

Seismic performance assessment of highway bridge networks considering post-disaster traffic demand of a transportation system in emergency conditions

Abstract: Highway bridge networks (HBN) are one of the critical components of a transportation system that supports the operation of modern society. The traffic-carrying capacity of a transportation system is essential for emergency responses in a catastrophic seismic hazard. In this article, a methodology is proposed to assess the regional seismic performance of HBN considering the post-disaster traffic demand of a transportation system in emergency conditions. First, the framework of the methodology is introduced. Then, topological properties and vulnerability analyses are conducted to understand the connectivity of the HBN and the traffic-carrying capacity of the damaged bridge networks. In addition, traffic flow analysis is employed to consider the traffic situation in an emergency condition. Then, the entropy-right method is adopted to integrate these factors and to assess the importance of each bridge link in an emergency condition. Last, the seismic performance of HBN is also evaluated considering th...

A life-cycle framework for integrating green building and hazard-resistant design: examining the seismic impacts of buildings with green roofs

Abstract: Building design and performance are increasingly being scrutinised from perspectives of both sustainability and hazard resistance. However, the approaches taken to consider these perspectives are disconnected; green building rating systems do not consider hazard resistance in their assessments, while performance-based engineering methods have tended to neglect consideration of environmental impacts. This study presents a framework to assess a building’s life-cycle performance in terms of social, environmental and economic impacts using probabilistic approaches, considering the possible occurrence of an earthquake or other extreme event. The framework is illustrated through a case study of an office building in Los Angeles, designed with and without different types of vegetated (green) roofs, and at risk from varying earthquake hazard scenarios. The case study results demonstrate trade-offs between upfront building costs, material choices, hazard resistance and environmental impact.

Study of ground vibrations induced by railway traffic in a 3D FEM model formulated in the time domain: experimental validation

Abstract: In this paper, a three-dimensional numerical model is applied for studying railway vibrations. The numerical model is based on finite element method formulated in the time domain with an implicit scheme of integration. In the first part of the paper the numerical approach is briefly described. An uncoupled scheme is applied: (i) firstly the train loads are calculated taking into account dynamic excitation with a 2D vehicle-track model; (ii) the computed loads on each sleeper are introduced into a 3D numerical model, developed in the commercial code Plaxis, which is used to simulate the wave propagation in the ground. In the second part of the paper a real case study, located in Portugal, is presented, being used for the experimental validation of the proposed model. The numerical results of ground vibrations show an acceptable agreement with real measurements. Therefore, the proposed approach can be used as a reliable prediction tool based on PLAXIS software, which allows simulating railway vibrat...

Modelling processes related to corrosion of reinforcement in concrete: coupled 3D finite element model

Abstract: Aggressive environmental conditions, such as exposure to the sea climate or use of de-icing salts, have a strong influence on durability of reinforced concrete (RC) structures due to reinforcement corrosion-induced damage. In the present paper, a recently developed three-dimensional (3D) chemo-hygro-thermo-mechanical model for concrete is briefly discussed. The model was implemented into a 3D finite element code and its application is illustrated through numerical analysis of a RC beam-end specimen with stirrups, exposed to aggressive environmental conditions. Damage of concrete cover due to expansion of corrosion products and transport of rust through concrete pores and cracks are computed. Subsequently, the influence of corrosion-induced damage of concrete cover on pull-out resistance of deformed reinforcement is investigated. The comparison between numerical results and experimental evidence shows that the complex coupled mathematical model is able to realistically predict the phenomena related...

Design and construction of UHPC-filled duct connections for precast bridge columns in high seismic zones

Abstract: One of the column connection types that has been recently emphasised for accelerated bridge construction (ABC) in high seismic zones is grout-filled duct connections. Experimental results have shown that the seismic behaviour of reinforced concrete columns connected to precast cap beams using this connection type is emulative of conventional columns. However, an alternative ABC connection is required to connect precast columns to shallow cap beams and footings due to insufficient anchorage length in those elements. Ultra-high-performance concrete (UHPC) was proposed in this study to be used instead of conventional grout in the connection to reduce the anchorage length. First, fourteen large-scale pullout tests were performed to investigate the bond strength of UHPC-filled duct connections. The test results showed that the incorporation of UHPC instead of normal grout as duct filler can reduce the bar embedment length by 50% or more. Second, design equations were developed based on the pullout test...

Fundamental period of infilled reinforced concrete frame structures

Abstract: The fundamental period of vibration appears to be one of the most critical parameters for the seismic design and assessment of structures. In the present paper, the results of a large-scale analytical investigation on the parameters that affect the fundamental period of reinforced concrete structures are presented. The influence of the number of storeys, the number of spans, the span length, the infill wall panel stiffness and the percentage of openings within the infill panel on the fundamental period of infilled RC frames was investigated. Based on these results, a regression analysis is applied in order to propose a new empirical equation for the estimation of the fundamental period. The derived equation is shown to have better predictive power compared with equations available in the literature.

A Petri-Net-based modelling approach to railway bridge asset management

Abstract: Management of a large portfolio of infrastructure assets is a complex and demanding task for transport agencies. Although extensive research has been conducted on probabilistic models for asset management, in particular bridges, focus has been almost exclusively on deterioration modelling. The model being presented in this study tries to reunite a disjointed system by combining deterioration, inspection and maintenance models. A Petri-Net modelling approach is employed and the resulting model consists of a number of different modules each with its own source of data, calibration methodology and functionality. The modules interconnect providing a robust framework. The interaction between the modules can be used to provide meaningful outputs useful to railway bridge portfolio managers.

Effects of stirrup corrosion on shear behaviour of reinforced concrete beams

Abstract: Corrosion of stirrups is always more severe than longitudinal steel bars, leading to possible shear failure instead of bending failure. This paper covers the authors’ investigation on the effects o...

Experimental investigation of the ultimate bearing capacity of deformed segmental tunnel linings strengthened by epoxy-bonded filament wound profiles

Abstract: A new strengthening method employing epoxy-bonded filament wound profiles (FWPs) has been applied to shield tunnels subject to large deformation. Full-scale tests were conducted on the ultimate bearing capacity of linings strengthened by the new method. With consideration for secondary loading, the strengthening measures were applied when the lining deformation reached 120 mm (0.02D). The failure phenomena are described, and the main loading process results were obtained, including load-displacement curves, cracking, and joint openings. The failure mechanisms, the key performance points, and bearing capacities of the tested strengthened linings are discussed and analysed. In addition, a comparison was made between two FWP strengthening methods as well as with epoxy-bonded steel plate strengthening methods. The results show that the epoxy-bonded FWP method is effective and practical for strengthening segmental tunnel linings, which can improve both the ultimate bearing capacity and overall stiffnes...

Development of time-dependent fragility functions for deteriorating reinforced concrete bridge piers1

Abstract: This is the second article of an effort to develop a time-dependent framework for earthquake risk assessment. In this paper, a model is developed for estimating fragility functions that depend on the degree of structural deterioration. The deterioration model presented in the first paper is used to model the change in the structure over time and due to exposure to different environmental conditions. The effect of deterioration on structural demand and capacities is considered in the evaluation of the fragility functions. Three reinforced concrete columns are designed to correspond to seismic design criteria in place in 1960, 1980 and 2000. Fragility functions are developed for non-deteriorating and deteriorating columns based on their age and environmental exposure. It is shown that the time of construction, which reflects the seismic design criteria, and the environmental conditions dictate the amount of structural deterioration. Older columns in highly corrosive environments show the highest vul...