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Condition assessment and retrofit of a historic steel-truss railway bridge
Abstract
This paper presents an experimental and analytical study to access the condition of a his-toric railway steel truss bridge still in use. The task is pursued through static and dynamic field measurements, as well as laboratory tests. A validated analytical model is employed to evaluate the capacity of the bridge to carry seismic and wind loads specified by current design codes, as well as the heavier trainloads set by the owner. Strengthening and replace-ment measures are proposed for bridge upgrade. An estimation of the remaining fatigue life of the bridge in its present condition and after the suggested strengthening is also made. # 2003 Published by Elsevier Ltd.
... Most literature that assess fatigue in historic metallic railway bridges considers fully fixed stringer-to-floor-beams and truss-girder-to-floorbeam connections, assuming, that this is a conservative, and therefore safe approximation of the real rotational stiffness between members [5,[10][11][12]. Members within the truss girder of these bridges have also been modelled has fully-fixed connections, and even riveted joints in old metallic lattice girders have been observed to exhibit a rigid behaviour regarding out-of-plane rotation [13]. ...
... To reduce computational effort, many studies use global FE numerical bridge models with frame elements [7,10,14]. Better results are shown through the use of shell elements [15], as they provide a more accurate stiffness distribution. Nonetheless, global models of riveted bridges do not consider the details of the riveted double-angle connections usually found in these historic bridges. ...
... To improve the live load-carrying capacity of these bridges and adapt their design to environmental loading conditions, such as wind and earthquake, different retrofitting solutions have been applied worldwide. The most common retrofitting technique for historic truss bridges involves adding locally more material (plates) to the more stressed members to enhance their load-carrying capacity [10,11,22]. Other retrofitting methods, aimed at a more global improvement of the structure, comprise replacing gusset plates and aged rivets to improve connection performance; adding new members (such as cross girders) or external prestressing of the truss to improve shear and bending capacity [22][23][24][25]. ...
Fatigue damage has been the most common reason for failure in riveted bridges, with the stringer-to-floor-beams connections being identified as the most prone-fatigue locations by several studies. When assessing fatigue damage of historic riveted railway bridges, the analysis usually considers the structure in its current configuration, disregarding any retrofitting the bridge has experienced during its lifetime. This paper presents a fatigue analysis of a one-century-old riveted through-truss railway bridge, part of the Chilean North-South railway line, considering all interventions made to the superstructure since its construction. To perform the analysis, a detailed train loading spectrum is defined considering historical and current data of freight trains and traffic to generate a realistic loading model for the bridge. FE models are generated for the bridge in all configurations (initial and after each retrofitting), and the fatigue damage is evaluated through S-N curves from the Eurocode. The accumulated fatigue damage obtained by this sequence is then compared with a fatigue analysis of the structure in its current configuration. The comparison shows that the fatigue damage is significantly underestimated when assessing the bridge considering only its current configuration and that the retrofitting can substantially change the structural response at the stringer-to-floor beam connections.
... Vibration-based dynamic system identification process has been performed in historical buildings and sufficient results and experiences have been obtained [8][9][10][11][12]. This process was also examined for bridges [13][14][15][16][17][18][19], buildings [11,[20][21][22][23][24][25] and tall towers [26][27][28][29][30][31][32]. ...
... For determination of the displacement time history response at the monitored pixel, it is necessary that four corrections are applied on the results of Eq. (9). These required corrections are described in the following. ...
... In which, U i is the horizontal or vertical component from Eq. (9). Ui is the corrected time history displacement response in the same direction under real-time measured ambient excitation. ...
A video-based indirect sensing procedure for dynamic identification purposes is presented. To overcome major limitations of video-based methods in real on-site measurements, a novel three step pre-modification, magnification, post-modification process is developed. This process includes revision of the initial input video record in order to delete disturbing objects, utilizing a magnification method to filter the frequency content of the monitored motion and using a revision step for elimination of noises generated during magnification process. Finally, a set of digital signal and image processing analyses are performed on the modified video using virtual visual sensor technology. Based on the results of this research, motion signals of the monitored object are detected. The proposed approach has been used for identification of dynamic characteristics of two historic masonry minarets in Istanbul. Results shows that the proposed procedure is able to assess the dynamic characteristics of the monitored structure with a high-level of accuracy.
... . Big Creek River Bridge: truss elevation and floor system plan viewsreproduced from Tobias et al. (1993) (Imam et al., 2004;Rakoczy, 2012;Spyrakos et al., 2004) they are still an essential component of any modern society. One of the key components of any railway system are bridges over which the trains travel and, in the United States, many of these bridges were steel trusses or plate girders constructed in the 19 th and early 20 th Centuries. ...
... Spyrakos (Spyrakos et al., 2004) also examined a RTB to assess bridge condition prior to strengthening via static and dynamic field measurements under special and actual train loads. The research found that stringer ends and main truss top and bottom chords were subjected to significant moments while insignificant moments were developed in main truss verticals and diagonals. ...
... Multiple investigators state that, for riveted steel railway bridges, one of the most fatigue prone details are the stringer-to-floor beam connections, which can be subjected to significant stress concentrations and reversals (Al-Emrani et al., 2004;Chotickai & Kanchanalai, 2010;Haghani et al., 2012;Imam et al., 2004). Field and numerical studies have demonstrated that these connections are more rigid than originally assumed and subjected to in-plane bending moment, which might result in high stress reversals and fatigue degradation in the connecting angles and rivets (Al-Emrani et al., 2004;Al-Emrani, 2005;Chotickai & Kanchanalai, 2010;Haghani et al., 2012;Imam et al., 2004;Imam et al., 2005;Spyrakos et al., 2004;Tobias et al., 1993). ...
Railway bridges are an essential component of any modern society and play a significant transportation role. During the 19th and early 20th centuries steel truss and plate girder bridges were commonly used railway designs, with most of the trusses constructed using pin and eyebar systems and most other load carrying members being riveted, built-up sections.
Many of these bridges are still in use and are subjected to increased railway traffic intensity, loads and speeds. The current practice for evaluating the integrity of bridges in the United States, irrespective of use, is primarily via visual inspection, with those inspections occurring at a maximum prescribed frequency of one calendar year for railway bridges (Agdas et al., 2015; AREMA, 2015; Hearn, 2007; ODOT, 2017; Roach et al., 2012).
Based on observed condition and structure importance, each railway bridge could be inspected one, two or four times annually. While this method has reliably maintained railway bridge condition, it is intermittent, costly, and subject to human interpretation. To improve how condition is assessed, some railway bridges have been outfitted with traditional, voltage based, sensors, such as strain gages and accelerometers that quantify their response. These projects have largely focused on isolated, large bridges, not on a group of bridges, and have involved an extensive array of these sensors, an approach that is also costly labor intensive.
The work discussed herein summarizes initial steps of a large-scale effort focused on developing a cost-effective, optimized, robust health monitoring system that takes advantage of repeatable patterns found on most, if not all, riveted steel railway bridges and, as a result, can be broadly utilized on a railway system. Initial work completed for this project encompassed analytical model validation, sensitivity analyses, field testing and model calibration for one truss and one plate girder segment of a large railway bridge over a river crossing. This research developed and assessed a computationally-based methodology to optimize structural health monitoring (SHM) plans for this and other, similar bridges.
Other secondary findings of this work that address riveted steel bridges key behaviors observed from field testing and/or computational data are: (i) truss flooring system members may experience a higher variation in axial forces which was not addressed during the construction phase; (ii) exterior stringers, adjacent to the truss bottom chords, experience high axial tension while interior stringers experience almost negligible axial compression forces; (iii) floor beams experience high lateral bending stresses, varying between 45 and 60% of their vertical bending stress, at exterior stringer intersections; (vi) loose truss bottom chords eyebars and bottom laterals were subjected to high frequency, low amplitude stress cycles; and (v) lateral bracing connection failures could be captured from the significant reduction in the recorded strains. These insights into behavior, together with the sensitivity of damage detection to sensor placement, led to the proposed SHM plans.
As a result of the research that was completed, three structural health monitoring plans with varying number of sensors were proposed to detect deficiencies reported by the owner of the bridge. One of those proposed plans is currently deployed on a riveted steel railway bridge for continuous monitoring and evaluation of its efficiency. The deployed plan was selected initially over the other two plans because sensitivity analyses showed significant change in the monitored responses at the instrumented locations of this plan due to damage. Evaluating the other plans which contained lower number of sensors is planned via monitoring the bridge continuously in the future.
... . Big Creek River Bridge: truss elevation and floor system plan viewsreproduced from Tobias et al. (1993) (Imam et al., 2004;Rakoczy, 2012;Spyrakos et al., 2004) they are still an essential component of any modern society. One of the key components of any railway system are bridges over which the trains travel and, in the United States, many of these bridges were steel trusses or plate girders constructed in the 19 th and early 20 th Centuries. ...
... Spyrakos (Spyrakos et al., 2004) also examined a RTB to assess bridge condition prior to strengthening via static and dynamic field measurements under special and actual train loads. The research found that stringer ends and main truss top and bottom chords were subjected to significant moments while insignificant moments were developed in main truss verticals and diagonals. ...
... Multiple investigators state that, for riveted steel railway bridges, one of the most fatigue prone details are the stringer-to-floor beam connections, which can be subjected to significant stress concentrations and reversals (Al-Emrani et al., 2004;Chotickai & Kanchanalai, 2010;Haghani et al., 2012;Imam et al., 2004). Field and numerical studies have demonstrated that these connections are more rigid than originally assumed and subjected to in-plane bending moment, which might result in high stress reversals and fatigue degradation in the connecting angles and rivets (Al-Emrani et al., 2004;Al-Emrani, 2005;Chotickai & Kanchanalai, 2010;Haghani et al., 2012;Imam et al., 2004;Imam et al., 2005;Spyrakos et al., 2004;Tobias et al., 1993). ...
Railway bridges are an essential component of any modern society and play a significant transportation role. During the 19th and early 20th centuries steel truss and plate girder bridges were commonly used railway designs, with most of the trusses constructed using pin and eyebar systems and most other load carrying members being riveted, built-up sections. Many of these bridges are still in use and are subjected to increased railway traffic intensity, loads and speeds. The current practice for evaluating the integrity of bridges in the United States, irrespective of use, is primarily via visual inspection, with those inspections occurring at a maximum prescribed frequency of one calendar year for railway bridges (Agdas et al., 2015; AREMA, 2015; Hearn, 2007; ODOT, 2017; Roach et al., 2012). Based on observed condition and structure importance, each railway bridge could be inspected one, two or four times annually. While this method has reliably maintained railway bridge condition, it is intermittent, costly, and subject to human interpretation. To improve how condition is assessed, some railway bridges have been outfitted with traditional, voltage based, sensors, such as strain gages and accelerometers that quantify their response. These projects have largely focused on isolated, large bridges, not on a group of bridges, and have involved an extensive array of these sensors, an approach that is also costly labor intensive. The work discussed herein summarizes initial steps of a large-scale effort focused on developing a cost-effective, optimized, robust health monitoring system that takes advantage of repeatable patterns found on most, if not all, riveted steel railway bridges and, as a result, can be broadly utilized on a railway system. Initial work completed for this project encompassed analytical model validation, sensitivity analyses, field testing and model calibration for one truss and one plate girder segment of a large railway bridge over a river crossing. This research developed and assessed a computationally-based methodology to optimize structural health monitoring (SHM) plans for this and other, similar bridges. Other secondary findings of this work that address riveted steel bridges key behaviors observed from field testing and/or computational data are: (i) truss flooring system members may experience a higher variation in axial forces which was not addressed during the construction phase; (ii) exterior stringers, adjacent to the truss bottom chords, experience high axial tension while interior stringers experience almost negligible axial compression forces; (iii) floor beams experience high lateral bending stresses, varying between 45 and 60% of their vertical bending stress, at exterior stringer intersections; (vi) loose truss bottom chords eyebars and bottom laterals were subjected to high frequency, low amplitude stress cycles; and (v) lateral bracing connection failures could be captured from the significant reduction in the recorded strains. These insights into behavior, together with the sensitivity of damage detection to sensor placement, led to the proposed SHM plans. As a result of the research that was completed, three structural health monitoring plans with varying number of sensors were proposed to detect deficiencies reported by the owner of the bridge. One of those proposed plans is currently deployed on a riveted steel railway bridge for continuous monitoring and evaluation of its efficiency. The deployed plan was selected initially over the other two plans because sensitivity analyses showed significant change in the monitored responses at the instrumented locations of this plan due to damage. Evaluating the other plans which contained lower number of sensors is planned via monitoring the bridge continuously in the future. Advisor: Daniel Linzell
... Consequently, the fatigue life of those components and their connections might be compromised. Published numerical and laboratory research concluded that stringer-tofloor beam connections are more rigid than they initially assumed and, as a result, large bending stress cycles and corresponding fatigue degradation in connecting angles and rivets may develop (34,(36)(37)(38)(39)(40)(41)(42). An analytical study focused on stringer end fixity ratio effects on fatigue damage accumulation found that stringer-to-floor beam connections experienced more severe damage than floor beam-to-main girder connections in steel riveted plate girder railway bridges (40). ...
... • Automated data cleansing prior to POM ( ) extraction was necessary to reduce discrepancies caused by nonstationary inputs; DL 11 13 46 15 Train ID 41 17 35 19 29 • The developed approach could accurately capture damage represented by DIs greater than 20%, with clearly improved accuracy for DIs higher than 40%; and ...
Visual inspection is often used to assess the condition of railway bridges at discrete points in time, an approach that can be subjective and possibly unsafe. Alternatively, certain bridges have their condition assessed via the installation of a large number of sensors. These sensors can be costly to place, power and maintain. Therefore, reducing their numbers and maximizing the extracted information is of utmost importance. In addition, evaluating bridge condition from measured response can be quite challenging due to loading and environmental variations, especially when a limited number of sensors are used. The focus of this research is to develop an automated hybrid experimental-numerical framework to detect and locate damage and estimate its intensity. The framework was developed analytically, based on Proper Orthogonal Modes (POMs) and Artificial Neural Networks (ANNs), and validated experimentally using 1 and 8 weeks of measured strains collected from a monitoring system placed onto an in-service, multi-span, railway bridge. The analytical work involved using three sensor instrumentation sets and investigated structural response for two bridge spans of different type and size. To generate training data for the ANNs, Modeling uncertainties that could lead to erroneous indication or omission of damage are incorporated into framework development via a systematic analyses. The procedure was based on synergizing POMs extracted from measured structural response and POMs calculated from the numerical model with a robust damage feature independent of level and location of modeling uncertainty. A hybrid experimental-numerical approach was developed and implemented to estimate damage scenario POMs from field measured strains. ANNs were trained and tested using these POMs with DL and DI being detected. These results show the promise of the POD-ANN method as a robust, real-time fatigue damage detection tool for steel railway bridges. Advisor: Daniel G. Linzell
... Experiences from engineering practices have indicated that fatigue analysis based on specification loads and distribution factors usually underestimates the remaining fatigue life of existing bridges by overestimating the live load stress ranges. In this context fatigue evaluation based on field measured stress range histograms under actual traffic load proves to be a more accurate and efficient method for existing bridges [3,4]. Most of the present day fatigue assessment approaches used for railway bridges are generally based on combination of measured stress histories, Miner's rule [5] and railway code provided fatigue curve (also referred to as S-N or Wohler curve). ...
... Therefore, it is required to know the stress cycles (stress histories) distributions of all the critical members for trains that are included in present and past timetables. Since fatigue evaluation based on field-measured stress range histograms under actual traffic loads of the bridge is a more accurate and efficient method for existing bridges [3,4], this section describes the evaluation methodology of real stresses in the bridge related to the current state. ...
The paper proposes an accurate methodology to estimate remaining fatigue lives of riveted railway bridges. The proposed method mainly consists of measured stress histories, recently developed sequential law and fully known Wohler curve. Here, it is essential to use the fully known Wohler curve as the related fatigue curve. Therefore the technique, which utilizes to transfer the partially known Wohler curve to fully known curve, is also discussed under this paper. Since most of the bridges do not have past strain measurements, this method describes reasonably accurate procedure to obtain the past stress histories from present day measured stress histograms. Initially paper describes the proposed method for remaining fatigue life estimation. Secondly remaining fatigue life of an existing railway bridge is estimated by performing a case study. Case study describes the details of the considered railway bridge and the appraisals related to condition evaluation, FE analysis, material testing, experimental static and dynamic load testing. Then the remaining fatigue lives of each critical components of the bridge are obtained. Hence validity and merits of proposed method is confirmed by comparing the results with previous method-based fatigue lives.
... A novel procedure proposed by [9] which integrates real measurements from sensor with FE analysis to predict hot spot stress at uninstrumented points. On the other hand, a laboratory tests and field measurements carried out to develop and validate an analytical model which is then used to assess the capacity of steel bridge to support heavier train loads [10,11]. In addition, a case study was presented for a steel railway bridge in which dynamic and quasi-static measurements were utilized to calibrate a FE model and propose a strengthening scheme [12]. ...
Structural health monitoring system (SHM) has an essential role in the prediction of steel bridges behavior and damage detection. Due to site difficulties and economic reasons, it is not possible to instrumenting all sensitive details within the structure. Finite element modelling is an effective tool for analyzing fatigue-sensitive details, as it enables the extension and interpretation of measured data. This study investigates the structural health monitoring (SHM) system of Southern Railway Danube bridge located in Budapest from fatigue sensitive details point of view. The research applies load testing data for the validation of finite elements models (FEM) which are to be used for specifying the sensitive details. Based on a detailed stress analysis, three fatigue-sensitive areas were identified in the bridge, as follows: 1. the cutout holes of cross girder, 2. the cope-holes, and 3. the transvers welding of bottom flange. Artificial cracks are applied in these details separately to investigate the efficiency of SHM system for crack detection. Stress values at the location of strain gauge points of the SHM system are calculated continuously as cracks size increased, simulating the propagation. The results show that the SHM strain gauges in the current placements not highly efficient to detect the cracks of the investigated details. The study extended to propose strain gauge positions to recognize the crack initiation and propagation in these details.
... The combination of a finite element model with in-situ strain measurements allows for accurate simulation of the global structural behavior, with a limited number of local measurements. An experimental study was performed by Spyrakos et al. [7] and Ermopoulos and Spyrakos [8] to develop a validated analytical model. Malm and Andersson [9] measured dynamic effects on a tied arch railway bridge and developed a 3D finite element model including dynamic vehicle-bridge interaction. ...
This work presents the development of a finite element model of a welded railway bridge constructed in 1955. This model will be used as the main tool for a structural health monitoring system of this ageing infrastructure. Such a system requires load monitoring for which the bridge was instrumented with fiber optic Bragg grating sensors spread over two longitudinal and two transverse girders. After the instrumentation, a series of passages using a locomotive with known axle loads and geometry was performed, during which strains were continuously recorded. A comparison between the experimental and numerical results showed excellent agreement for all sensors located remote from the bridge bearings. The comparison also showed that the influence of the bridge bearings on local deformations differs from the hypothesized design, especially at high load. It was found that deformation of structural elements is strongly constrained to the loaded sectors. The truss design efficiently transfers the loads on the longitudinal girders through the closest transverse girders onto the main trusses.
... Numerous studies have reviewed diagnostic load testing, repair techniques, and strengthening schemes based on field measurements and laboratory tests to address the issue of distortion-induced fatigue Ermopoulos and Spyrakos (2006). Hahin et al. (1993), De-Wolf et al. (2002), Chakraborty and DeWolf (2006), Ermopoulos and Spyrakos (2006), Moses et al. (1994), Spyrakos et al. (2004), and Alampalli and Lund (2006) to the field of fatigue evaluation of steel bridges, furthering our understanding and management of bridge infrastructure. ...
Engineering structures, including bridges, undergo fatigue loads over time,
leading to material degradation, reduced resistance, and increased risk of failure.
Regular local inspections or structural health monitoring (SHM) are crucial to
identify potential failures and predict fatigue life. However, challenges arise in
predicting the remaining useful life (RUL) of structures, such as limited data,
large structural dimensions, and estimating vehicle-induced loading. This study
addresses these challenges by employing Bayesian filtering-based SHM frameworks for fatigue life prediction. Two conditions are considered: structures
with visible fatigue cracks and those without visible cracks. Cost-efficient and
practical detection algorithms are developed for both conditions. In structures
without visible cracks, RUL estimation utilizes Miner’s rule and the S-N curve
of the material, using stress data obtained through SHM. For structures with
visible cracks, RUL estimation focuses on crack length prognosis based on crack
growth history. The updated Paris model is used to simulate fatigue crack propagation, with model parameters estimated using SHM data while accounting for
uncertainties.
For the structures with visible cracks and available crack growth history,
an online model-based approach is proposed to provide a probabilistic estimate
for fatigue life by jointly inferring fatigue parameters from available SHM data
using a Joint Extended Kalman Filter (JEKF). The effectiveness of the proposed
method is validated through numerical studies on two fracture scenarios: edge
and center cracks in a finite plate subjected to mechanical and thermal loading
conditions. Additionally, numerical simulations are performed to study the RUL
for a welded joint of a bridge based on its worst operational scenario. To validate
the accuracy of the proposed approach, an experimental study is conducted on
compact tension (CT) specimens, confirming its consistency in estimating fatigue
model parameters and subsequently predicting the RUL.
Further, to address the practical challenges in infrastructure fatigue monitoring, wherein the structures are high-dimensional enhancing computational
and instrumentation expenses, probabilistic substructure monitoring approaches
powered by interacting filtering algorithms, such as particle and ensemble Kalman
filters (IP-EnKF) are employed to focus on critical segments or members of the
structure, thereby reducing computational complexity and improving efficiency.
The efficiency of the algorithm in estimating substructural health is rigorouslydemonstrated through both numerical and experimental studies. Further, the
unknown substructure boundary forces, required for estimating the fatigue life
of the substructure, are also reconstructed through post-processing. Numerical
experiments conducted on a bridge structure modelled with vehicle-structure
interaction aspect validate the proposed method. Several real-life experiments
are also done wherein the damage is however required to be simulated in its
calibrated digital twin.
Moreover, a similar substructure algorithm is employed to estimate the RUL
of a crack-free bridge structure. Numerical experiments are conducted on a reinforced concrete box girder bridge, considering vehicle-bridge interaction. A
parametric analysis investigates the relationships between the FDI and factors
such as surface roughness, vehicle speed, weight, and category, with the aim
of identifying dominant stimuli. The results demonstrate an accurate estimation of health parameters and RUL. Additionally, a novel decomposed approach
for RUL estimation is developed, enabling the mapping of traffic information
to fatigue damage without the need for costly simulations. A case study is
presented, focusing on a reinforced concrete box girder bridge in Kamand, Himachal Pradesh, India, to highlight the practical applicability of the approach
in real-world scenarios.
... Due to aging, increased train/truck axle loads, vehicle collisions, and loss of structural members, structural rehabilitation or modification of the bridges may be required. Many experimental and analytical studies have been performed on assessment and rehabilitation of steel bridges (Farhey et al. 2000;Spyrakos et al. 2004;Ermopoulos and Spyrakos 2006;DelGrego et al. 2008;Brencich and Gambarotta 2009;Cavadas et al. 2013;Costa and Figueiras 2013) as well as reinforced concrete bridges (Sun et al. 2003;Jiang et al. 2017;Malomo et al. 2020). ...
Electrification of railway lines provides more economical, faster, safer, and quieter railway transportation as well as significant reductions in carbon emissions. To accomplish the electrification of railway lines, an electrical system needs to be installed on bridges. However, old existing railway bridges were not designed considering a vertical clearance (height) required for electrification. Thus, structural modifications are needed for some steel truss railway bridges. In this paper, a study on structural modifications of a 70-year-old two-span continuous steel truss railway bridge still giving service was presented to increase a safe clearance between the overhead line electrification equipment and rolling stock. Before beginning with modifications, it was firstly aimed to assess the actual bridge condition as well as the load-bearing capacity. For these goals, in situ field dynamic tests were conducted, and a three-dimensional (3D) finite-element (FE) model of the bridge was calibrated based on the field measurements captured. Then, rating factors and safety indices of the bridge were calculated using the calibrated 3D FE model. Finally, a modification procedure including replacement of portal bracing without reducing transversal rigidity and load-carrying capacity of the bridge was proposed.
... Unfortunately, all of these guidelines are meant for not-soold highway bridges and do not consider the specific aspects characteristic of old railway metallic bridges, including materials and constructive details (such as riveting joints). The literature on the matter, including studies on bridge parts made of old puddled iron (or wrought iron) [15][16][17][18] and old assembly elements (such as rivets) [19,20], was examined. ...
This work presented salient features of the steel behavior of seven metallic bridges close to, or over, 100 years old, among the Spanish conventional rail network as well as the results of a fatigue life expectancy study. A preliminary study of the properties of the constituent materials obtained from the bridges samples was carried out followed by dynamic fatigue tests under service representative loads. Due to the steelmaking techniques in the late 19th and early 20th centuries, disperse fatigue behavior results were obtained. However, the wide safety margins with which these bridges were designed, as well as the mechanical properties of the steel (relatively good mechanical resistance but with low ductility), seem to guarantee a long fatigue life. This estimate decreases sharply with increasing loads.
... The primary scope was to gain a better insight into the structural behaviour of such systems during construction activities, normal operation and extreme events (earthquakes, strong winds and oods), by tracking specic parameters suitable for the extraction of information regarding the structural response and for the identication of possible anomalous changes . In the context of SHM for historic structures, several applications of AVT and OMA, aimed at vulnerability assessment through calibration of Finite Element (FE) models, can be found in the literature in the case of historic bridges (Calcada et al. 2002;Spyrakos et al. 2004;Brencich and Sabia 2008;Limongelli et al. 2018;Gkoktsi et al. 2019;An et al. 2019), monumental buildings (Bartoli et al. 1996;Jaishi et al. 2003;Casarin and Modena 2008;Pau and Vestroni 2008;Ramos et al. 2010;Ramos et al. 2011;Aras et al. 2011;Formisano et al. 2012;Ramos et al. 2013;Clementi et al. 2017;Formisano et al. 2018a;Lorenzo et al. 2019) and historic towers (Bennati et al. 2005;Ivorra and Pallares 2006;Gentile and Saisi 2007;Pena et al. 2010;Oliveira et al. 2012;Foti et al. 2012;Pieraccini et al. 2014;Gentile et al. 2015;Pellegrini et al. 2018;Bru et al. 2019;Ivorra et al. 2019), including applications as tools for nondestructive evaluation of the severity of damages caused by earthquakes (Tashkov et al. 2010;Krstevska et al. 2010). ...
The present Ph.D. Thesis was developed within a collaboration between the Department of Civil and Environmental Engineering of the University of Perugia, Italy, and the Department of Civil Engineering of the University of Minho, Portugal.
The main objective of this research work concerned the development and validation of an innovative methodology aimed at the detection, localization and quantification of earthquake-induced damages in historic masonry structures. The high cultural, economic and political value set upon historic buildings spread out all over the world has made the earthquake-induced damage identification, as well as preservation and conservation of architectural heritage, a subject of outstanding importance. The proposed methodology, called DORI, is based on the combination of data-driven, as well as innovative model-based methods, addressing the Damage identification based on Operational Modal Analysis (OMA), Rapid surrogate modeling and Incremental Dynamic Analysis (IDA) for Cultural Heritage (CH) masonry buildings subjected to earthquakes. More in detail, the DORI methodology proposes the static-and-dynamic data fusion in the OMA-based damage detection method, and extends it through the introduction and implementation of two independent and complementary innovative model-based methods, for localization and quantification of earthquake-induced damage in permanently monitored historic masonry buildings: the former is a surrogate model-based method, a rapid tool which combines long-term vibration monitoring data (i.e. OMA) and numerical modeling, while the latter is based on non-linear seismic IDA.
The Thesis focuses on the validation of different aspects of the DORI methodology, through application to four case study structures: an internationally well-known laboratory masonry structure, called the Brick House, and three CH masonry buildings equipped with permanent Structural Health Monitoring systems, namely the Consoli Palace, the Sciri Tower and the San Pietro Bell Tower.
The adopted enhanced vibration-based SHM tool, by introducing crack amplitudes as predictors in the dynamic MLR model, was validated in the case of the Consoli Palace, enabling rapid and automated earthquake-induced damage detection, even for small structural damages at an early stage, conceivably caused by a moderate/light seismic event. Afterwards, the surrogate model-based procedure for earthquake-induced damage detection and localization was applied in the case of the Sciri Tower, using long-term vibration monitoring data and numerical modeling. In particular, a quadratic surrogate model is used, whose objective function considers not only experimentally identified and numerically predicted damage-induced decays in natural frequencies but also on changes in mode shapes. The procedure was validated by considering both simulated damage scenarios, as well as a slight change in structural behavior experimentally observed after a seismic event. Finally, the proposed seismic IDA-based method, introduced for the first time in this Thesis and aimed at localization and quantification of earthquake-induced damages in masonry structures, is applied to the Brick House and San Pietro Bell Tower. It relies on a priori IDA carried out from a numerical model and construction of multidimensional IDA curve sets relating meaningful local damage parameters to selected seismic intensity measures. The IDA-based procedure has demonstrated to correctly localize damage in specific parts of the structures and to quantify earthquake-induced damage with a good level of approximation. The results are particularly interesting in the case of the San Pietro Bell Tower due to the integration of the IDA-based damage identification with seismic SHM data recorded during the 2016 Central Italy seismic sequence, allowing the proposal and exploitation of some original response intensity measures.
In conclusion, the DORI methodology proposed in this Thesis for earthquake-induced damage detection, localization and quantification is a novel methodological approach, successfully applied and validated in historic masonry structures, constituting a promising tool for rapid post-earthquake damage assessment of CH structures under long-term SHM monitoring.
Keywords: Earthquake-induced damage identification; Structural Health Monitoring; Historic masonry structures; Cultural Heritage; Preventive conservation; Finite Element modeling; Long-term monitoring; Temperature effects; Surrogate modeling; Incremental Dynamic Analysis; Earthquake; Intensity measure; Damage measure; Masonry tower; Masonry bell tower; Masonry palace.
... Spyrakos et.al [44] employed a combination of experimental and analytical methods to study the performance of a historical truss bridge to seismic and wind loads. A number of measures were proposed for retrofitting the structure and the fatigue life expectancy of the bridge before and after the strengthening methods was estimated. ...
Relative displacements are introduced between steel bridges and continuously welded rail (CWR) tracks as the bridge girders expand and contract due to thermal effects. Depending on the fastening profile between the CWRs and steel bridge girders, additional forces are transmitted between the two, and when rail compression forces are introduced at the transition zones of the bridge, the risk of track buckling increases. The aim of this paper is to study CWR track buckling in the transition zones of open-deck steel bridges. In order to do so, a finite element model of a bridge is developed and calibrated based on the available literature. The model is then used to study the effects of a number of fastening profiles between the CWRs and steel bridge girders on track buckling in transition zone of the bridge. It is shown that girder temperature and location of lateral misalignment are the primary factors affecting the buckling temperature in the transition zone. Increasing the girder temperature by 45 °C can cause a drop of 11.5 °C in the track buckling temperature, a reduction of almost 19% compared to that of the open track. Furthermore, using zero toe load fasteners can reduce the risk of track buckling in the transition zone, yet there is little to resist the increasing gap size in case of a broken rail in winter.
... Spyrakos et.al [30] employed a combination of experimental and analytical methods to study the performance of a historical truss bridge to seismic and wind loads. A number of measures were proposed for retrofitting the structure and the fatigue life expectancy of the bridge before and after the strengthening methods was estimated. ...
Visual inspection of a steel truss railway bridge revealed multiple fatigue cracks on the top member of the truss, mainly attributed to the high impact loads of crossing wheels over the jointed tracks on the bridge. The proposal to replace the jointed track with continuously welded rails (CWR) raised a number of issues regarding the thermal interaction of track and bridge, as the bridge experiences extreme temperature variations. Incorporation of high longitudinal restraint between the track and the bridge may increase the risk of track buckling failure at bridge transition zones, since bridge thermal expansion during hot weather can add compressive forces to the rails transferred through the track fastening system. Reducing longitudinal restraining may increase the size of a rail gap resulting from cold weather rail fracture. An optimal longitudinal fastening profile between the bridge and the track therefore is required to mitigate thermal issues both in hot summers and cold winters. To do so, a numerical model of the track and the bridge is developed in Abaqus and calibrated based on the results of tests performed on the bridge and available literature. Three longitudinal fastening profiles between the bridge and the track are introduced in the numerical model and performance of each for mitigating buckling failure and cold weather rail fracture are analyzed. It is concluded that providing 50% resilient fasteners and 50% zero toe load fasteners on each span can be a sound approach to mitigating the thermal issues of CWR tracks on the bridge.
... Several numerical models that follow the characteristics described above were used for the particular case of studying the dynamic behavior of old bridges under rail tra±c. Spyrakos et al. 45 conducted both experimental and numerical dynamic studies using validated FE models from steel truss railway bridges located in Greece with the objective of assessing their structural capacities and their feasibility to support heavier tra±c. The studies concluded that, in some cases, it was necessary to strength some of the bridges' elements in view of the obtained results and of the normative provisions. ...
The present work focuses on the evaluation of the dynamic behavior of a centenary steel arch bridge, located in Portugal, under light railway traffic loads. This works aims to assess the dynamic behavior of the bridge subjected to an alternative type of railway vehicle, more specifically, a typical underground vehicle that is currently in service in the Lisbon Metro. The dynamic response of the system has been evaluated using two distinct methodologies, namely a moving loads model and a vehicle–bridge interaction model. To achieve this goal, finite element (FE) models from both the bridge and the vehicle have been developed and a comprehensive study has been carried to evaluate the influence of distinct factors in the dynamic response of the bridge–train system, namely the methodology used to assess the dynamic response, the location of the response reference point in the deck, the train speed and the vehicle configuration (single or double vehicle). Moreover, both the traffic safety, passenger comfort and pedestrian comfort have also been evaluated using normative criteria based on acceleration responses. The results shown that the normative limits related to traffic safety and passenger comfort were never exceeded in any condition analyzed in the study. However, the pedestrian comfort was jeopardized when the train speed exceeded 20km/h.
... The fatigue assessment of structures is mainly done by either deterministic or probabilistic approach. Most of deterministic fatigue assessment approaches of bridges are generally based on the combination of measured stress histories under actual traffic load [2,3], Miner's rule and railway code provided fatigue curve (also referred S-N or Wöhler curve). Although the mentioned deterministic approach predicts the fatigue behaviour, the uncertainties inherent in the fatigue evaluation process are not captured. ...
p>The objective of this paper is to compare the predictions of deterministic and probabilistic fatigue assessment methods. The paper focuses on the nominal stress method in the stress-life approach. Three different assessment methods are presented and compared, the traditional deterministic method, the closed form method and the probabilistic method. The traditional method is the one described in Eurocode. The closed form method involves using a Weibull distribution to represent the stress spectrum. The probabilistic method involves the use of Monte Carlo simulations to obtain the probability of failure, Pf . An alternative fatigue load model is newly proposed in this paper. The associated procedures of the three assessment methods were verified and then used for fatigue analysis of a road bridge. Finally, the limitations, shortcomings and recommendation are concluded based on the research and the obtained results.</p
... Earthquakes are not the only sources that cause dynamic loads on structures. One of the main dynamic effects that may lead to sudden or progressive collapses is wind [21][22][23][24]. The wind is a very significant factor that leads to lateral loads to which building structures are relatively more sensitive than they are to vertical loads [25]. ...
This study investigates the failure of a roof with steel truss construction of a factory building in Tekirdag in North-western part of Turkey. The failure occurred under hefty weather conditions including thunderbolt, lightning strikes, heavy rain and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof are checked. Therefore, finite element analysis is performed several times under different assumptions and considering different factors aiming to determine the dominant ones that are responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. Also, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure.
... Earthquakes are not the only sources that cause dynamic loads on structures. One of the main dynamic effects that may lead to sudden or progressive collapses is wind [21][22][23][24]. The wind is a very significant factor that leads to lateral loads to which building structures are relatively more sensitive than they are to vertical loads [25]. ...
This study investigated the failure of the roof, with steel truss construction, of a factory building in Tekirdag in the northwestern part of Turkey. The failure occurred under hefty weather conditions including lightning strikes, heavy rain, and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof were studied. Finite element analysis, using the commercial software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France), was performed several times under different assumptions and considering different factors with the aim of determining the dominant factors that were responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. In addition, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure.
... Therefore, numerical studies are conducted to predict the mechanical behaviour as well as predicting a plausible failure. For truss type of structures, finite element method is usually employed for trusses since it is one of the most powerful tools of engineering [14,22,57,58]. Pieraccini et al. studied the collapse of a spatial truss roof of a gym building in North Italy during a moderate snowfall by using finite element method [59]. ...
This study investigates the failure of a roof with steel truss construction of a factory
building in Tekirdag in North-western part of Turkey. The failure occurred under hefty weather
conditions including thunderbolt, lightning strikes, heavy rain and fierce winds. In order to
interpret the reason for the failure, the effects of different combinations of factors on the design and
dimensioning of the roof are checked. Therefore, finite element analysis is performed several times
under different assumptions and considering different factors aiming to determine the dominant
ones that are responsible for the failure using the commercial software Abaqus (Dassault Systèmes,
Vélizy-Villacoublay, France). Each loading condition gives out a characteristic form of failure. The
scenario with the most similar form of failure to the real collapse is considered as the most likely
scenario of failure. Also, the factors included in this scenario are expected to be the responsible
factors for the partial collapse of the steel truss structure.
... Consequently, the fatigue life of those components and their connections might be compromised. Published numerical and laboratory research concluded that stringer-to-floor beam connections are more rigid than they initially assumed and, as a result, large bending stress cycles and corresponding fatigue degradation in connecting angles and rivets may develop (4,(6)(7)(8)(9)(10)(11)(12). An analytical study focused on stringer end fixity ratio effects on fatigue damage accumulation found that stringer-tofloor beam connections experienced more severe damage than floor beam-to-main girder connections in steel riveted plate girder railway bridges (10). ...
Stringer-to-floor beam connections were reported as one of the most fatigue-prone details in riveted steel railway bridges. To detect stiffness degradation that results from the initiation and growth of fatigue cracks, an automated damage detection framework was proposed by the authors (Eftekhar Azam et al., 2019; Rageh et al., 2018). The proposed method relies on Proper Orthogonal Decomposition (POD) and Artificial Neural Networks (ANNs) to identify damage location and intensity under non-stationary, unknown train loads. Bridge computational models were used to simulate damage scenarios and for training the ANNs. Damage detection method efficiency and accuracy were shown to be significantly influenced by the level of modeling uncertainties (MUs). To investigate the applicability of the proposed framework to in-service bridges, a systematic analysis of the effect of MUs on the proposed POD-ANN framework was necessary. MU influence on the performance of the POD-ANN damage detection method was investigated and a new procedure for generating training data for ANNs was proposed. The procedure was based on synergizing Proper Orthogonal Modes (POMs) extracted from measured structural response and POMs calculated from the numerical model. The current study integrated numerical and field investigations. The main objective of the numerical investigation was to identify a robust damage feature independent of the level and location of assumed MUs. Results showed that Damage Location (DL) and Damage Intensity (DI) were detected with high accuracy for studied uncertainty cases; however, as expected, damage detection accuracy reduced as MU increased. A hybrid experimental-numerical approach was then implemented for the field investigation studies. This approach applied identified damage features from the numerical investigation to measurements from an in-service railway bridge to produce damage scenarios used to train the framework. MATLAB algorithms were developed that preprocessed field data and eliminated POM variations resulted from loading uncertainties. ANNs were trained and tested using the field strain estimated POMs from the hybrid approach and DL and DI results were obtained for the studied railway bridge under non-stationary, unknown train loads. These results show the promise of the POD-ANN method as a robust, real-time fatigue damage identification tool for steel railway bridges.
... This work presents herein is a condition survey and a linear moving load analysis for a wrought iron truss railway bridge built in 1880. Dynamic loading to bridge structures are treated by introducing a dynamic factor, a constant increment to static live loads (Spyrakos et al. 2004, Thambirathnam et al. 2000. This factor takes into account the effect of bridgevehicular interaction, impact loads, etc. Remaining fatigue life analysis was performed for critical members to predict their remaining lifetime for future anticipated loads. ...
A study for estimating load carrying capacity and remaining fatigue life of a wrought iron truss railway bridge is presented. The task is perused through static and dynamic field measurements and a numerical analysis. The dynamic factors obtained from the field testing were compared with those given by empirical formulae. For the numerical study, a three dimensional finite element model was prepared using SAP2000. Static responses obtained from the field load tests were used to validate the numerical model. A linear multi-step moving load case was introduced to the validated numerical model to determine member forces of the bridge under live loads. Based on the numerical solutions, along with dynamic and load factors for different type of engines and carriages, working stresses, factors of safety against yielding and fracture and remaining fatigue life were obtained and reported. The suitability of the bridge for anticipated increase of loading is verified. A bracing system for the bridge deck is suggested in order to reduce the lateral vibrations due to high speed trains.
... Tarihi bir demiryolu çelik köprüsünün durum tespiti için gerçekleştirilen deneysel ve analitik bir çalışmada ise tarihi bir köprünün sismik ve deprem yüklerini taşıma kapasitesi belirlenmiş ve köprü analitik modeli statik ve dinamik saha ölçümlerine göre güncellenmiştir [2]. Bir trenin geçişinden hemen sonra oluşan serbest titreşim verisinin kullanılabilirliğine ilişkin değerlendirmelerde bulunulmuştur [3]. ...
... Ermopoulos and Spyrakos (2006) and Schlune et al. (2009) are conduct a research to assessment of a railway steel truss bridge by using a validated computer model and use dynamic field measurement and laboratory test. In another study (Spyrakos et al., 2004) determine seismic and wind load carrying capacities of a historical railway bridge with static and dynamic field measurement. Existing bridges are including many deficiencies on load carrying capacity and unknown about corrosion, support condition, joint condition and many other structural parameters. ...
Steel truss bridges are frequently used in railway and roadway lines. There are lots of steel truss bridges that are still giving service in Turkish Railway lines. A large part of these bridges was built up at the beginning of the twentieth century. The increase in train loads and development of railway technology have made it possible to discuss the adequacy of the performance of existing railway bridges. Electrification of the railway lines helps to increase capacities as well as to improve the safety of the railway lines. To construct electrification system on these lines, portal upper beams of some truss bridges need to be changed. In this paper, due to the electrification system, different portal upper beam configurations of a simply supported steel truss railway bridge are studied. Firstly, FE model of the bridge is generated and is updated based on in-situ field tests. First three modes of the bridge obtained from the field test are adjusted to be very close to the modes of the analytical model. Then, for all bridge members, rating analyses based on the Allowable Stress Rating (ASR) method are performed. Finally, effect of portal upper beam configuration on the bridge rating is thoroughly investigated. The portal upper beams are the strongest member of a bridge top connection and have an important effect on lateral rigidity of the bridge. Removing portal upper beams of the bridge tremendously causes a decrease of the lateral rigidity. Lateral rigidities are calculated for the existing bridge, new portal beam configuration and removed portal beams, respectively. The rating results for the existing and new portal upper beam configuration are obtained close to each other.
... The detected ODS are normalized to the range of [-1 1] along the vibration direction. The normalized result shows similar result with mode shapes identified in previous studies [40,41] which validates the practicability of this method. Table 2 Means of mode shapes at S1 and S2 and the computed frequency bands for motion magnification 1 st mode (frequency band) 2 nd mode (frequency band) 3 rd mode (frequency band) S1 1.08 (0.6 -1. ...
Image-based vibration mode identification gained increased attentions in civil and construction communities. A recent video-based motion magnification method was developed to measure and visualize small structure motions. This new approach presents a potential for low-cost vibration measurement and mode shape identification. Pilot studies using this approach on simple rigid body structures was reported. Its validity on complex outdoor structures have not been investigated. The objective is to investigate the capacity of video-based motion magnification approach in measuring the modal frequency and visualizing the mode shapes of complex steel bridges. A novel method that increases the performance of the current motion magnification for efficient structure modal analysis is introduced. This method was tested in both indoor and outdoor environments for validation. The results of the investigation show that motion magnification can be an efficient tool for modal analysis on complex bridge structures. With the developed method, mode frequencies of multiple structures are simultaneously measured and mode shapes of each structure are automatically visualized.
... The most critical observed deficiencies were corrosion and deterioration due to aging. Spyrakos et al. [3] and Ermopoulos and Spyrakos [4] performed complete assessment of a nineteenth century railway bridge and suggested possible repair procedures. Bancila et al. [5] presented the Romanian methodology in assessment of failure and malfunction in steel bridges accompanied with some case studies. ...
Several metallic bridges are present in Egypt and form an important part of the transportation network. Many of these bridges exceeded the intended design life. Currently, deterioration of bridge conditions is pronounced and is leading to many problems. In addition, it is feared that lack of corrective procedures may lead to failure within a few years. Periodic maintenance and major repair activities during a structure service life are mandatory to sustain a satisfactory performance that preserves public safety and extends the service life. The current work is carried out to summarize the most frequent structural problems and defects faced during inspection campaign of a group of metallic bridges in Egypt. Reported problems include but are not limited to corrosion, fatigue cracks, and permanent deformations in structural elements. Data are collected through an extensive investigation of several metallic bridges in Egypt. The study included visual inspection, structural analysis under the action of loads imposed by latest design codes, fatigue assessment of different bridge components, and field tests. Observations include problems or defects related to steel superstructure, pedestrian side walkways, sleepers and rails system, bracing systems, in addition to reinforced concrete substructures. The study is meant to shed light upon the current conditions of vital structures and explore the available practical repair techniques.
... The fatigue assessment of structures mainly done by either deterministic or probabilistic approach. Most of the present day deterministic fatigue assessment approaches of railway bridges are generally based on the combination of measured stress histories under actual traffic load [12,13], Miner's rule [14] and railway code provided fatigue curve (also referred S-N or Wöhler curve). Although the mentioned deterministic approach predicts the remaining fatigue life, the uncertainties inherent in the fatigue evaluation process are not captured. ...
... At present, rail authorities all over the world are paying special attention to evaluate the remaining fatigue life of riveted railway bridges, since most of these bridges are nearing the end of their design fatigue lives [1]. Most of the present day fatigue assessment approaches of railway bridges are generally based on combination of primary stress histories under actual traffic load [2,3], Miner's rule [4] and railway code provided design fatigue curve (also referred to as S-N or Wohler curve). ...
... In recent years, bridge health monitoring has gradually become an important topic in bridge engineering. Monitoring data are obtained by properly arranging bridge monitoring devices, and the data can be used in evaluating the reliability of a structure, updating the numerical model, and examining safety conditions at observation points [3][4][5][6], thus offering comprehensive bridge information such as deformation and stress. Depending on the assessment requirements, different types of data acquisition devices such as accelerometers, smart total stations, velocity meters, and ground penetrating radars can be used. ...
In order to reduce the self-weight of Highway No. 4 in the Taichung living circle in Taiwan, a corrugated steel web, with a span of 145 m, is used to replace the conventional concrete web. To appraise the structural safety and operating conditions of a prestressed composite box-girder bridge with a corrugated steel web, which is the first bridge of its kind in Taiwan, a bridge monitoring system is developed based on in-situ experiments, numerical modeling, and long-term monitoring. In order to determine the initial static and dynamic behaviors of a real bridge, a series of experiments are first carried out on a newly-constructed bridge. Before entering service, a bridge is subjected to forced vibration experiments and static loading experiments to establish its initial condition. In this study, a numerical model of the bridge is constructed based on the finite element method. The results of the structural analysis are compared with experimental data, and the two sets of results are found to show good agreement. Moreover, thermometers, strain gages, displacement gages, and inclinometers are installed on the bridge to measure changes in the physical quantities, and the monitored temperature gradient profile over a year is fed back to the numerical model for further analysis. Results have indicated that the in-situ linear variable differential transformer (LVDT) and inclinometer monitoring data can be effectively simulated by the numerical model. Finally, based on the material properties, numerical model, and long-term monitoring data from inclinometers, the safety threshold of the bridge is determined to provide a useful reference for bridge management agencies. Prediction of the extreme inclination angles by the Generalized Extreme Value Distribution (GEVD) method for the 50-year life cycle of the monitored bridge also falls within the envelopes of the warning and critical thresholds, which support the long-term safety of bridges.
... The most critical observed deficiencies were corrosion and deterioration due to aging. Spyrakos et al. [5] and Ermopoulos and Spyrakos [6] assessed the structural condition of a 19 th century railway bridge and suggested possible repair procedures. Akgul and Frangopol [7] performed a correlation study linking bridge rating factor and reliability index of different bridge types. ...
Egyptian railway transportation network is one of the oldest networks worldwide. Recently, an extensive assessment campaign has been initiated for a group of railway steel bridges in Egypt. In many cases, major repair and rehabilitation activities were observed due to accidents that may have happened to the structure such as: fire, derailment, or collision. The strengthening and rehabilitation of the considered bridges usually include - but not limited to - adding steel plates or replacing damaged members. The current study focuses on evaluating the different repair procedures applied on several aging steel railway bridges in Egypt. Field tests and analytical models are used to deduce deviations from the expected behaviour and pinpoint possible defects. The previous performed strengthening and rehabilitation applications are determined. Hence, their effect on the steel bridge behaviour is assessed.
... A more widespread application of these technologies in the context of historic and even archaeological constructions is thus expected in the near future, also considering recent documented applications of ambient vibration testing (AVT) and OMA, mostly for complementing vulnerability assessment through calibration of finite element models. Relevant applications of such techniques concerned historic bridges [18][19][20] , monumental buildings [21][22][23][24][25][26] and historic towers [27][28][29][30][31][32][33] . These last, perhaps, represent the most suitable type of historic structure to be tested and monitored using operational dynamic responses, due to their higher amplitudes of vibration in comparison to low-rise buildings. ...
This article presents the development and the results of 1 year of implementation of a simple vibration-based structural health monitoring system for preventive conservation and condition-based maintenance of an Italian monumental masonry bell-tower. The system is based on the data recorded by a small number of high-sensitivity accelerometers, on remote automated frequency tracking and on a multivariate statistical analysis criterion for damage detection, combining data regression, principal component analysis, and novelty analysis. The analysis of monitoring data highlights the main characteristics of the response of the tower to wind, swinging bells, and low-return period earthquakes. Despite the low levels of vibration in operational conditions, the system is seen able to track the time evolution of five natural frequencies of the structure and successfully use such information for detecting anomalous deviations from normal conditions. More in general, the presented results show a promise toward a more widespread use of low-cost vibration-based monitoring systems for cultural heritage preservation.
... The fatigue assessment of structures is mainly done by either deterministic or probabilistic approach. Most of deterministic fatigue assessment approaches of railway bridges are generally based on the combination of measured stress histories under actual traffic load [12,13], Miner's rule [14] and railway code provided fatigue curve (also referred S-N or Wöhler curve). Although the mentioned deterministic approach predicts the remaining fatigue life, the uncertainties inherent in the fatigue evaluation process are not captured. ...
Rail authorities all over the world are paying attention to extend the service lives of railway bridges. The famous Miner’s rule employed deterministic or probabilistic fatigue assessment approaches are generally used to predict remaining fatigue life of ageing railway bridges. Under many variable amplitude loading conditions, life predictions have been found to be unreliable since Miner’s rule does not properly take account the loading sequence effect. Therefore, this paper presents a comparison of a new probabilistic fatigue assessment approach with deterministic approach consisting of a new damage indicator, which captures the loading sequence effect of variable amplitude loads more precisely than the Miner’s rule. The comparison is performed by applying both fatigue assessment approaches to predict the remaining fatigue life of an ageing railway bridge. This comparison intends to conclude the possibility of capturing uncertainty behind loading sequence effect by proposed probabilistic fatigue assessment approach. Initially the paper presents the both approaches. Then the proposed approaches are applied to predict the fatigue lives of an ageing railway bridge. Finally predicted fatigue lives are compared and rationality, significance and validity of the proposed approaches are discussed.
... Farhey et al., [17] and Farhey et al., [16] studied deterioration assessment and rehabilitation design of existing steel bridges. Bancila and Cristescu [3], Spyrakos et al. [29], and Brencich and Gambarotta [6] studied on the rehabilitation of steel bridges. Biezma and Schanack [4] investigated the collapse of steel bridges. ...
... Hai et al. (2004) and Hai (2006) explored the status of railway bridges in Vietnam and provided a general review of the observed deficiencies through site investigation and questionnaires. Different research efforts assessed old steel bridges through experimental and numerical studies of old bridges and investigated the influence of the performed strengthening works [Spyrakos et al. (2004), Costa and Figueiras (2013), Gentile and Saisi (2011), Ermopoulos and Sprakos (2006), and Brencich and Gambarotta (2009)]. In Egypt, an extensive assessment campaign has been initiated for the steel railway bridges. ...
Existing combined Railway and Roadway steel bridges constitutes a very important part of the railway transportation network in Egypt. Maintenance of the old steel bridges has an important economical impact. Hence, proper determination of the structural defects and accurate condition assessment is crucial. The current paper presents experimental and numerical investigation of two combined railway and roadway steel bridges still in use (Marazek and Zefta bridges) crossing the Nile River in Egypt. The two bridges represent two different structural systems including simple span truss bridge and continuous truss bridge with different span lengths. The investigation includes a series of extensive visual inspection, static load tests, dynamic modal properties tests, and non-destructive testing procedures. Moreover, a validated finite element model is used to check the different members and connections according to the Egyptian code provisions. Estimates for the remaining fatigue life of the structural elements are provided based on the available data records. Afterwards, the observed problems are classified and decision regarding recommending demolition, applying major repair procedures, or applying periodic maintenance procedures is provided. In addition, possible repair procedures are proposed and investigated. The current research provides insight into the performed steps in each evaluation item and discussions regarding the final conclusions are drawn.
... Hai et al. (2004) and Hai (2006) explored the status of railway bridges in Vietnam and provided a general review of the observed deficiencies through site investigation and questionnaires. Different research efforts assessed old steel bridges through experimental and numerical studies of old bridges and investigated the influence of the performed strengthening works [Spyrakos et al. (2004), Costa and Figueiras (2013), Gentile and Saisi (2011), Ermopoulos and Sprakos (2006), and Brencich and Gambarotta (2009)]. In Egypt, an extensive assessment campaign has been initiated for the steel railway bridges. ...
Existing combined Railway and Roadway steel bridges constitutes a very important part of the railway transportation network in Egypt. Maintenance of the old steel bridges has an important economical impact. Hence, proper determination of the structural defects and accurate condition assessment is crucial. The current paper presents experimental and numerical investigation of two combined railway and roadway steel bridges still in use (Marazek and Zefta bridges) crossing the Nile River in Egypt. The two bridges represent two different structural systems including simple span truss bridge and continuous truss bridge with different span lengths. The investigation includes a series of extensive visual inspection, static load tests, dynamic modal properties tests, and non-destructive testing procedures. Moreover, a validated finite element model is used to check the different members and connections according to the Egyptian code provisions. Estimates for the remaining fatigue life of the structural elements are provided based on the available data records. Afterwards, the observed problems are classified and decision regarding recommending demolition, applying major repair procedures, or applying periodic maintenance procedures is provided. In addition, possible repair procedures are proposed and investigated. The current research provides insight into the performed steps in each evaluation item and discussions regarding the final conclusions are drawn.
... As-built drawing and design data was not available. Hence an extensive investigative program was chalked out, comprising of preparation of as-built drawings at the site, development of analytical model to obtain the baseline structural parameter and conduct of field tests to obtain the present status of the bridge (Spyrakos et al. 2004). ...
This paper presents the status improvement of an old damaged deck type rural road steel truss bridge through the modal parametric study after partial retrofitting. The dynamic and static tests on bridge were carried out as in damaged state and after partial retrofitting. The dynamic testing on the steel bridge was carried out using accelerometers under similar environmental conditions with same speed of the moving vehicle. The comparison of the modal parameters i.e., frequency, mode shape mode shape curvature, modal strain energy, along with the deflection parameter are studied with respect to structural analytical model parameters. The status up gradation for the upper and downstream truss obtained was different due to differential level of damage in the bridge. Also after retrofitting the structural elemental behavior obtained was not same as desired. The damage level obtained through static tests carried out using total station indicated further retrofitting requirement.
... As-built drawing and design data were not available, an extensive investigative program was chalked out, comprising preparation of the as-built drawings at the site, development of analytical model to obtain the baseline structural parameter, and conduct of field tests to obtain the present status of the bridge [23]. ...
Signal-processing techniques have been widely used in structural health monitoring and non-destructive evaluation. Wavelet analysis, a relatively new mathematical and signal-processing tool, for damage detection in various civil and mechanical structures. It is a time–frequency analysis that provides more detailed information about nonstationary signals which traditional Fourier analysis miss. This paper aims to provide the damage identification in an existing 100-year-old deck-type steel truss bridge using-frequency and time–frequency-based approaches. The dynamic testing of steel bridge was carried out using accelerometers for the damaged state and after partial retrofitting under similar environmental conditions and instrumental set up. The comparison is carried out using power spectral density, short-time Fourier transform, and wavelet packet transform with respect to both the upstream and the downstream trusses of the bridge. Higher and uniform dissipation of energy at resonating-frequency of the respective node after retrofitting showed intactness of joints. The variations of power spectral density in the first mode of the upstream and the downstream trusses clearly revealed improvements in the bridge signifying the importance of generating a signature of bridge before and after retrofitting. The status upgradations for the upstream and the downstream trusses obtained were different due to differential levels of damage in the bridge. Also, after retrofitting, the structural elemental behavior obtained was not the same as desired.
... Ermopoulos and Spyrakos (2006) identified the structural components in need of strengthening or replacement for a 19th century railway bridge through static and dynamic field measurements as well as laboratory tests, and proposed the strengthening schemes and predicted the remaining fatigue life of the bridge in its present condition and after the suggested strengthening. Investigations into fatigue evaluation of steel bridges by use of NDE techniques were also reported by Moses et al. 1994, Roeder et al. (2000, Abdou et al. (2003), Lund and Alampalli (2004), Spyrakos et al. (2004), Wang et al. (2005), Alampalli and Lund (2006), and Malm and Andersson (2006). ...
Vermoeiing is één van de meest voorkomende schademechanismen bij grote gelaste constructies. Wereldwijd wordt men alsmaar vaker geconfronteerd met de gevolgen van verouderende infrastructuur. Om ervoor te zorgen dat deze constructies veilig in gebruik kunnen blijven, is er nood aan betrouwbare methodes om de resterende levensduur te berekenen met inachtneming van huidige en toekomstige eisen. Hierbij moet onderscheid gemaakt worden tussen structuren met én zonder scheuren. Voor gelaste verbindingen die (nog) geen scheuren vertonen werden algoritmes ontwikkeld die toelaten om een volautomatische levensduur analyse uit te voeren op basis van de zogenaamde 'hot spot' spanning. Dit voor plaat- en buis verbindingen. Hierbij werd ook een diepgaand numeriek en experimenteel onderzoek verricht naar schade accumulatie modellen. Deze zijn essentieel voor een schatting van de resterende levensduur. In het tweede deel van het proefschrift wordt de focus verlegd naar de vermoeiingsanalyse van constructies die één of meerdere scheuren bevatten. Een robuuste numerieke tool werd ontwikkeld die toelaat om de multi-axiale, niet-planaire vermoeiingsscheurgroei te simuleren in grootschalige driedimensionale modellen. In samenwerking met industriële partners werden drie stalen structuren (een kraanbaan, spoorwegbrug en offshore jacket) geïnstrumenteerd en gemodelleerd. Op basis van de experimentele data werden de numerieke modellen en ontwikkelde tools gevalideerd.
Purpose
This study aims to include the diagnosis of an old concrete deck steel truss rural road bridge in the damaged and retrofitted state through vibration response signals.
Design/methodology/approach
The analysis of the vibration response signals is performed in time and time-frequency domains using statistical features-root mean square, impulse factor, crest factor, kurtosis, peak2peak and Stockwell transform. The proposed methodology uses the Hilbert transform in combination with spectral kurtosis and bandpass filtering technique for obtaining robust outcomes of modal frequencies.
Findings
The absence or low amplitude of considered mode shape frequencies is observed both before and after retrofitting of bridge indicates the deficient nodes. The kurtosis feature among all statistical approaches is able to reflect significant variation in the amplitude of different nodes of the bridge. The Stockwell transform showed better resolution of present modal frequencies but due to the yield of additional frequency peaks in the vicinity of the first three analytical modal frequencies no decisive conclusions are achieved. The methodology shows promising outcomes in eliminating noise and visualizing distinct modal frequencies of a steel truss bridge.
Social implications
The findings of the present study help in analyzing noisy vibration signals obtained from various structures (civil or mechanical) and determine vulnerable locations of the structure using mode shape frequencies.
Originality/value
The literature review gave an insight into few experimental investigations related to the combined application of Hilbert transform with spectral kurtosis and bandpass filtering technique in determining mode frequencies of a steel truss bridge.
This paper proposes a conceptual framework for the essential maintenance of truss bridges based on an accurate remaining fatigue life estimation technique. The framework mainly consists of structural appraisal based critical members and connections identification, remaining fatigue lives estimation of critical connections and time dependent member replacement or strengthening scheme. In the stage of critical member identification, detailed structural appraisal has to be conducted giving priority to visual inspection for condition, FE analysis, and material testing, experimental static and dynamic load testing. Accurate fatigue life estimation techniques of both members and connections consist of measured stress histories and recently developed new fatigue models. A verification of the proposed framework is conducted by comparing the predicted replacement scheme with a sequence of experimental failure and fatigue life of selected test specimens. Finally, the proposed framework was applied to a case study railway bridge to obtain time dependent member replacement scheme and obtained results were compared with previous estimations. Hence, validity and merits of the proposed framework were confirmed.
Fatigue failure of steel connections is a well-known failure mechanism, especially for structures which sustain heavy cyclic loads like steel bridges. Great numbers of these bridges were constructed at the beginning and the middle of first half of the last century, where the most steel fabrication fashions were the riveted connections and the riveted built-up members. These bridge elements consist of steel plates and/or steel angles, which are connected with each other by hot driven rivets, which are subjected to shear stress, so that they can be simplified to single or double lapped joints.
This thesis is consisted of two parts, in the first part, single and double lapped joints were studied numerically. Load transfer, stress concentration, stress intensity, crack path and crack tip plasticity in the lapped joints under axial load were analyzed. Finite element method was adopted to simulate the static, and fatigue behaviors of these joints. A parametric study for different bolt/rivet diameters and numbers is developed, to show the behavior of these connections.
It was observed that for lapped joint the crack path is approximately perpendicular to the loading direction as found experimentally in the literature. Small deviation in the path was detected, which may be due to the bolt contact pressure, which has a component perpendicular to the loading direction. In the case of lapped joints, the crack emanated from bolted hole closed to the applied load has a high stress intensity factor (SIF). Therefore, the failure of the multiple bolted/riveted joint structures may be occurred at the first hole. This situation cannot be treated by the arrangement of more bolts/rivets in the plate, since the critical condition of the first hole will not be changed by increasing the number of bolts/rivets.
It was found that, the extents of both monotonic and cyclic plasticity accommodated at the tip of a crack artificially advancing from the bolted hole showed transition behavior from the bolted hole-affected short crack regime to the relatively long crack regime. This transition behavior of monotonic and cyclic crack tip plastic zones can explain the phenomenon of initiated but not propagating crack which occasionally found in the bolted/riveted steel connections.
The effects of clamping force and friction coefficient were presented and studied on the single and double lapped joints for cracked and un-cracked connections. Different parameters such as, clamping force (0, 10, 20, 100, 200 kN) and friction coefficient (0.0, 0.3, 0.5) were studied. It was observed that, high clamping force causes a decrease in stress concentration for un-cracked connection. For cracked lapped joint, a SIF range (∆KI) decreases i.e. increase in fatigue life.
The second part of this thesis is a partial fatigue evaluation for an existed steel roadway bridge (El-Ministerly Bridge) which still in service. El-Ministerly Bridge is a riveted steel bridge located in El-Sharkia governorate in Egypt. Field strain measurements and a numerical modeling were carried out for El-Ministerly Bridge. The experimental results are used to develop and validate the numerical finite element model. Evaluate the bridge is executed using the developed numerical model. Different design codes were presented to understand the fatigue evaluation. Further, the Egyptian code and S-N curves from literature were used to the evaluation of the bridge. It was observed that, all stress ranges for this bridge are less than the ECP limits (Fsr) and the remaining fatigue life is 22 years, if it is environmentally protected.
Continuously identified natural frequencies of vibration can provide unique information for low-cost automated condition assessment of civil constructions and infrastructures. However, the effects of changes in environmental parameters, such as temperature and humidity, need to be effectively investigated and accurately removed from identified frequency data for an effective performance assessment. This task is particularly challenging in the case of historical constructions that are typically massive and heterogeneous masonry structures characterized by complex variations of materials' properties with varying environmental parameters and by a differential heat conduction process where thermal capacity plays a major role.
In order to investigate the method of electromagnetic measurement of stress, an experimental research of the relation between stress and induction EMF (electromotive force) was performed for Q235A parallel-chord steel truss. Two types of magnetic core sensors, planar or arc, was put respectively in the surface of chord and vertical web member flange, I-shaped steel of 12#, or in the surface of diagonal in diameter 25 mm. The magnetic line of force was made to penetrate the partial area of member and EMF was induced at the point of measurement. When the load was acted on the truss, the data of induction EMF and strain were measured at the same time. The experiment indicates that the change law of stress and induction EMF hold unanimity, within the range of loading. With the compressive stress increasing, EMF of upper chord and vertical web member decreases. With the tensile stress increasing, EMF of bottom chord increases, and the algebraic value of negative EMF of diagonal rises. The experimental data-fitting result accords with the relation between load and EMF from the analysis of stress-magnetic moment deflection.
The railway transportation network in Egypt incorporates steel bridges crossing the Nile River in addition to several canals. The construction of such bridges employs different materials including cast iron, wrought iron, steel and reinforced concrete. Some of these bridges are constructed since over 100 years. Deterioration over the years combined with poor maintenance practices may lead to failure within a few years. In addition, the design of such bridges may not be able to support the currently expected heavier loads. The current paper investigates the most frequent structural problems and defects faced during the first phase of inspection campaign of 10 Nile railway bridges in Egypt. Such problems include but are not limited to corrosion, fatigue cracks, and permanent deformations in structural elements. Data are collected through an extensive investigation of several railway Nile bridges in Egypt. The study included visual inspection, structural analysis under the action of the expected loads, fatigue assessment of different bridge components, and field tests. The problems or defects are categorized into several groups including: steel superstructure, pedestrian walkways, and sleepers and rails system. In addition, practical repair techniques of the observed defects are explored.
To investigate the wind-resistant behavior of long-span steel truss bridge during construction of flexible arches, taking the world's longest steel truss bridge with flexible arches as an example, the influence of closure position on the wind-resistant behavior has been studied, and based on the analysis results, different wind-resistant measures are proposed and compared, and an innovative measure is proposed according to the mechanical characteristics of this bridge. The results show that the protection against wind damage should be placed in a prominent position especially during the erection of the flexible arches. The innovative measure is effective, and provides reference to similar projects.
When a structure was in insufficient condition, its material, and geometric properties, encompassing alters of boundaries’ status and system connectivity could also be different to as-designed original condition. In this research, a static loading field test was carried-out on
a bridge to evaluate its current status of hinges and bearings. The target bridge named Chousei Bridge for 77 in-service years is a steel cantilever through-truss bridge structured by suspended spans and cantilever spans connected via Gerber hinges. A series of sensors of strain and displacement
were established to measure the response to the test loads. The bridge is then simulated as 3D finite element model with differentiating the hinges’ condition considered as certain stiffness springs. Performing a comparison between the analytical results to the experimental results indicates
that each hinge’s current status is different to the others instead of the same stiffness parameter as original state.
When assessing the residual service life of old bridge structures, the question arises whether they can be still used after having exceeded the theoretical service life, or if they should be replaced by a new structure after having been newly classified, or if they are still usable after reinforcement or on the basis of shorter service intervals.
The determination of the residual service life of a bridge results in the difficulty of recording the exact history of the loads and the state of the bridge. Insufficient knowledge about the strength and fatigue behaviour of old steels and constructions applied aggravate the above decision.
This paper deals with experimental investigations on a complete bridge structure of the ‘museum railway’ of the community of Blumberg as well as with two developed bridge structures of the Federal Railways. The results of these component tests are compared with data known from literature as well as with other results of similar investigations performed at the institute.
In our days, fatigue steel structures, as for example railway bridges, are designed for a certain service life. Old railway bridges, for example those of the last century, are not calculated for fatigue loadings, because the adequate knowledge was missing. The assessment of the remaining service life is therefore one of the main problems for numerous existing railway bridges. When assessing the residual service life of old bridge structures, the question arises whether they can be still used after having exceeded the theoretical service life, or if they should be replaced by a new structure after having been newly classified, or if they are still usuable after reinforcement or on the basis of shorter service life. The determination of the loads and the state of the bridge face the difficulty of recording the exact history of the loads and the state of the bridge. Insufficient knowledge about the strength and fatigue behaviour of old steel grades as well as constructions aggravate the above decision. This paper deals with experimental investigations on complete bridge structures of the 'museum railway' of the community of Blumberg as well as with four bridge structures of the Federal Railways in Germany. The results of these component tests are compared with data known from literature as well as with other results of similar investigations performed at the institute, in Karlsruhe.
Remaining life of a suite of railway bridges. IABSE Workshop: Remaining Fatigue Life of Steel Structures
- P Grundy
- Chitty
Grundy P, Chitty G. Remaining life of a suite of railway bridges. IABSE Workshop: Remaining Fatigue Life of Steel Structures, Lausanne. 1990.
Steel and composite bridges in Greek
- J Ermopoulos
Ermopoulos J. Steel and composite bridges in Greek, Kleidarithmos Publ., Athens, 2000.
In-situ testing of two steel railway bridges
- P Karydis
- H Mouzakis
Karydis P, Mouzakis H. In-situ testing of two steel railway bridges, Earthquake Engineering Laboratory Report, September 2002.
Remaining life of a suite of railway bridges
- Grundy