Single-span Bridge Research Articles

Case study of adjacent integral bridges supported on continuous secant piled walls

Integral bridges are often the preferred way of construction for short and medium span bridges in the UK. However, the behaviour of integral bridges is influenced by complex soil-structure interaction behaviour that may be cumbersome to predict and analyse when dealing with unusual structural arrangements. This paper presents a case study for the design of two single span bridges carrying a roundabout over a dual carriageway, supported on continuous secant piled walls. One of the bridges is fully integral while the adjacent structure is articulated at one end due to its skew. An alternative detail for the articulated end is proposed, to eliminate soil pressures and settlements at the back of the abutments as well as reduce the risk of water ingress to the bearings. The complex nature of the structural arrangement presented analytical challenges, that were solved by developing an advanced modelling approach, exploring two proposals. The first is to evaluate the geotechnical model for a range of imposed top of abutment displacements from the onset. The second, using unique non-linear springs and derived P-Y curves describes the more realistic variable nature of soil-structure interaction over the length of the walls leading to reduced soil pressures enhancing design feasibility.

Intrados FRCM-strengthening of a masonry bridge: Experimental and analytical investigations

This paper will present the results of an experimental campaign aimed to study the structural behavior of solid clay brick masonry arch models strengthened at the intrados with Fiber Reinforced Cementitious Matrix (FRCM). The arch models’ peculiarities are: i) the presence of the haunching made of hydraulic lime mortar-based conglomerate, and ii) the geometry that reproduces a 1:2 scaled longitudinal section of a typical Italian railway single span bridge. The arch models are tested, imposing loading-unloading cycles to analyze the effectiveness of the strengthening system. The results are expressed in terms of failure mode, load carrying capacity and ductility, which shows the increase in the strength and displacement capacity of the strengthened model. Finally, limit analysis was performed to validate the experimental results and to assess the maximum fiber strain and the corresponding stress at the peak load.

Analytical model analysis of suspension bridges with tower-girder-connected dampers

Recently the tower-girder-connected damper has been utilized to suppress multi-mode vertical vortex-induced vibration (VIV) of long-span suspension bridges. In this paper, an analytical solution is proposed for the damping ratio of vertical bending modes of a single-span suspension bridge, with a vertical or/and a rotational damper mounted near the end of the stiffening girder, which significantly simplifies the design procedure for tower-girder-connected dampers on suspension bridges. The damping effect and the accuracy of the analytical solution are validated for Humen Bridge. It is found that both the vertical and rotational damper with an appropriate parameter selected can supply significantly additional damping ratio to multiple bending modes of the suspension bridge. The rotational and vertical dampers work in a similar way and provide nearly the same maximum additional damping ratio for each mode. In particular, for the first two symmetric modes, regions of reduced motion near the ends of the stiffening girder are developed due to the effects of cable geometry and elasticity, and this reduces the effect of the tower-girder-connected damper. Excluding these modes, the damper effect on a suspension bridge is similar to that on a tension beam with the same beam stiffness and horizontal tension forces.

Comparison of Different Modeling Approaches and Their Influence on the Dynamic Calculation of Four Single-Span Railway Bridges

Various approaches to mechanical modeling are available in practice to calculate the dynamic response of railway bridges under high-speed traffic, differing significantly in their complexity and accuracy. Very simple models often overestimate the vibrations occurring in reality but are much more computationally efficient and dependent on only a few input parameters than more complex and accurate models. Modeling the high-speed train as a multi-body system can represent the beneficial vehicle-bridge interaction, but it requires knowledge of numerous vehicle parameters, which manufacturers rarely disclose. In contrast, the track-bridge interaction can also be depicted by a simple coupling beam modeling of the structure, requiring only a few input parameters representing the dynamic stiffness and damping of the track. Several calculations on different single-span steel girder bridges demonstrate the influence of different model variants and input parameters on the acceleration results of the structure. Additionally, an approach for determining a dynamic distribution of the train axle loads affecting the bridge depending on the assumed vertical track stiffness is presented.

Analytical solutions for static longitudinal displacements of suspension bridges under a moving vertical concentrated load

The longitudinal displacement at the girder ends of long-span suspension bridges is a crucial issue that affects structural safety, durability, as well as traffic safety and ride comfort. The primary cause of these reciprocating displacements is the action of moving live loads, which induces quasi-static displacements in the longitudinal direction. This paper theoretically investigates the static longitudinal displacements of suspension bridges under a moving vertical concentrated load and elucidates the underlying deformation mechanisms. Considering geometrical nonlinearity, analytical equations are established for the longitudinal deformations of the main cable and stiffening girder under a vertical concentrated load. By analyzing the geometrical deformation conditions of the suspenders, the relationship between the longitudinal displacements of the stiffening girder and the main cable is derived. Due to the coupling between longitudinal and vertical displacements, the vertical displacement of the stiffening girder must be solved to obtain its longitudinal displacement. Based on deflection theory and considering the bending stiffness of the stiffening girder, this paper derives the vertical deformations of the stiffening girder for single-span suspension bridges and those with short continuous side spans under a vertical concentrated load, which is then used to calculate the longitudinal displacement. Finite element models are used to verify the accuracy of the analytical solutions. Differences between the proposed solutions and previous solutions neglecting the bending stiffness of the stiffening girder are compared and analyzed. The effects of neglecting the longitudinal displacement at the bridge tower top and the presence of short continuous side spans on the longitudinal displacement of stiffening girder are also investigated. The results demonstrate the high accuracy of the proposed analytical solution for the longitudinal displacement at the girder ends of suspension bridges. Importantly, the bending stiffness of the stiffening girder cannot be neglected in calculating the longitudinal displacement. The longitudinal displacement at the girder ends is primarily caused by the longitudinal deformation of the main cable, while the contribution from the flexural deformation of the girder is negligible. Furthermore, the longitudinal displacement at the bridge tower top has a negligible effect on the longitudinal displacement of the girder, and the presence of short continuous side spans is beneficial for reducing the longitudinal displacement of the stiffening girder. The proposed analytical solution method provides a rapid approach for calculating the static longitudinal displacement at the girder ends of suspension bridges under passing live loads and reveals the deformation mechanism. This is beneficial for preliminary design and structural optimization, as it avoids the complex finite element modeling and solution process.

Track vertical irregularity estimation for railway bridges using a novel and lightweight deep-learning architecture

A comprehensive methodology is presented for the estimation of track vertical irregularities of railway bridges from vehicle responses, based on a novel and lightweight multi-layer-perceptron (MLP) deep learning architecture. Firstly, a vehicle–track–bridge interaction (VTBI) model is established for the generation of the datasets of deep learning networks. Secondly, the lightweight deep learning architecture is meticulously designed to identify the track's vertical irregularities. Then, the effectiveness of the proposed technique is validated through examples of a single-span simple bridge and a three-span bridge. Further, the sensitivity of the present method against various factors is investigated, including different combinations of vehicle responses, measurement noise, vehicle speed and different classes of track irregularity. It is confirmed that the identified track irregularities of the railway bridges, regardless of irregularity class and noise level, are in excellent agreement with the ground-truth ones. The increase in vehicle speed to some extent reduces the estimation accuracy of the irregularity. The proposed method has higher identification accuracy and efficiency for longer irregularity sequences of multi-span railway bridges.

Smartphone-Based Vibration Monitoring Studies of a Pedestrian Link Bridge

Vibration-based structural health monitoring has gained a new pace with the rise of emerging consumer-grade sensor technologies. Accelerometers embedded in smartphones are among those which provide ubiquitous data potential with minimal burden to administrators. This research presents the preliminary findings of modal identification results obtained from smartphone sensors positioned on a single-span pedestrian link bridge. While a good number of modal identification studies are available in the literature, most of them correspond to short-term tests which are unlikely to capture seasonal features impacting identification results. In this study, the authors summarise a large vibration dataset from the testbed bridge with repetitive measurements taken over a month. The identification results presented herein are early representations of the daily and monthly temporal behaviour of modal frequencies observed throughout the tests.

Hybrid vehicle scanning techniques for detection of damaged hangers in tied-arch railway bridges

Regular monitoring of the hanger system is essential for preserving structural integrity in tied-arch bridges. This proactive monitoring enables preventive maintenance and early detection of hanger damage. To confront this issue, we propose a novel scanning method for assessing the impact of damaged hangers on the dynamic behaviour of single-span tied-arch railway bridges. Using each hanger as a positional reference, this method employs an instrumented vehicle as a mobile scanner to indirectly acquire vibration data from the traversed bridge deck. The hybrid approach integrates vehicle-bridge interaction (VBI) dynamics, vehicle scanning method (VSM), and moving windowed Fourier transform (mw-FT) technique to generate time–frequency spectrograms from the collected signals. In this representation, the time axis indicates the duration of the inspection vehicle traversing the bridge deck. By analysing frequency shifts within the spectrogram, we can identify damaged hangers through observed variations in frequency content over time. Numerical studies demonstrate the efficacy of the proposed hybrid vehicle scanning technique in detecting potential hanger damage in tied-arch railway bridges.

Modal effects of span-layout types on coupled flutter of long-span suspension bridges

This study provides a theoretical explanation for a perplexing experimental phenomenon observed frequently in suspension bridge flutter testing, where the flutter critical wind speed (Ucr) predicted by two-dimensional (2D) section model testing is higher than that predicted by three-dimensional (3D) full aeroelastic model testing. Six long-span suspension bridges with either a single simply supported span or multiple continuously supported spans were taken as research examples, then the comparative studies on the flutter critical wind speeds, flutter frequencies, modal energy ratios and aerodynamic damping corresponding to 2D and 3D coupled flutter states were carried out to illustrate the flutter modal effects. The research findings indicate that the Ucr of 2D testing being higher than that of 3D testing is an inherent characteristic for single-span simply-supported suspension bridges, which can be attributed to the prominent aerodynamic negative damping associated with 2nd-order vertical bending mode. However, due to the aerodynamic positive damping associated with 3rd-order vertical bending mode, the Ucr of 2D testing is consistently lower than that of 3D testing in the cases of multi-spans continuously-supported suspension bridges. Additionally, to eliminate unsafe 2D evaluations, a reasonable modal matching principle is recommended for section model testing of single-span simply-supported suspension bridges.

Centrifuge model tests on vertical stress distribution of geosynthetics reinforced soil (GRS) abutment

Geosynthetics reinforced soil (GRS) abutment has been widely used in the construction of small to medium single-span bridges and shows good service performance in engineering projects. Vertical stress distribution plays an important role for engineering design of the GRS abutments. Three centrifugal model tests of GRS abutments were carried out to investigate the vertical stress distribution underneath the centreline of beam seat, considering the setback distance (i.e., the distance from the beam seat to the inner of the facing) and beam seat width as influencing factors. Test results indicated the measured incremental vertical stresses under the beam seat increased with increasing loads uniformly and presented “larger on the upside and smaller on the downside” along the elevation. There existed the phenomenon of stress concentration near the top of the abutment and with the increasing beam seat width, the phenomenon of stress concentration presented more obvious. However, the setback distance had little effect on the vertical stress distribution. A comparison between measured and theoretical vertical stress showed that the AASHTO method provided a better prediction of the incremental vertical stress distribution than the FHWA method under the load of 200 kPa, but with the increasing loads, these two methods significantly underestimated the incremental vertical stress.

Numerical evaluation of Hybrid Deck Bulb Tee (HDBT) as a solution to improve durability of single-span bridges

To address the shortcomings of traditional prestressed concrete girders, a new hybrid beam element, the Hybrid Deck Bulb Tee (HDBT) is proposed. The HDBT utilizes staged fabrication. First, the bottom flange is cast with Ultra-high Performance Concrete (UHPC) and prestressed prior to casting the web and top flange with High-Performance Concrete (HPC). The purpose of this study is to analytically evaluate the structural performance of HDBT beams for bridge structures. Multiple HDBT bridges were designed following the state-of-the-art criteria in regard to UHPC bridge design. The performance was evaluated using the following criteria: 1) the deflections under live load and dead load, 2) design checks for temporary stresses before losses, 3) stresses at serviceability limit states after losses, and 4) demand-to-capacity ratios under the American Association of State Highway and Transportation Officials (AASHTO) Strength I load combination. To obtain more refined results for the serviceability limit state, the bridges were modeled using a commercial finite element software. The model captured the time dependent material properties such as strength gain, creep, and shrinkage, as well as the stages of fabrication. The analysis demonstrates that the innovative design and fabrication processes of HDBTs are capable of resolving the current limitations of prestressed concrete elements.

REMOVED: Optimization of linear multiple-tuned mass damper to control nonlinear vibrations of high-speed railway PRC bridges

The structural health monitoring (SHM) survey of prestressed reinforced concrete (PRC) bridges of Japan’s high-speed railway revealed that some of these bridges are showing excessive vibrations under the live load of train passages. The detailed investigations demonstrated that the vibration frequency of these bridges decreases nonlinearly with the increase in the vibration amplitude. This paper clarifies this nonlinear vibration behavior using finite element (FE) model in which a single-span bridge is modeled as a beam-shell element, and the train is modeled as a moving load. To overcome this excessive vibration, a set of five tuned-mass dampers (TMD) having a particular natural frequency range, called multiple-TMD, is designed with the optimized parameters i.e., damping ratio of 6%, frequency range of 0.44 Hz, and total mass ratio of 1% of the modal mass of the bridge considering not only the displacement limitations of bridges but also the limitations of stroke length of the dampers. Furthermore, this study also validates the effectiveness and practicality of using a numerical simulation-based approach to design linear multi-TMDs instead of single-TMD to suppress the nonlinear vibrations of the bridges.

Mode Shape-Based Damage Detection of Twin Skewed Bridges Based on OMA and FE Model Updating

A comparative study of the dynamic behavior of twin single-span bridges was carried out based on operational modal analysis and a linear finite element model updating with the aim of finding a potential damage indicator. The bridges are skewed, 30 m long and with prestressed concrete girders as the main support structure, but one of them were collided and suffered damage in two of its I-shape girders. Ambient vibration tests were conducted by deploying 14 uniaxial accelerometers along the sidewalks, experimental modal parameters were identified using the COVariance-driven Stochastic Subspace Identification method (SSI-COV). Six vertical modes were clearly identified for each structure. Additionally, some extra modes with non-proportional damping were identified. It was found that the modal frequencies are sensitive to the support conditions and the overall stiffness of the bridge but not to the localized girder damage, which, on the contrary, is reflected in the discrepancy in the fundamental bending mode shape amplitude between the lateral sides of the bridge, and a so-called Continuous Symmetry Measure adopted as a symmetry index seems to be a good damage indicator for this type of straight-alignment simply supported bridges, given the symmetric nature of the bending mode shapes and the asymmetric nature of the damage.

Numerical Simulation of Single-Span T-Shaped Bridge Under Explosion Load

Numerical Simulation of Single-Span T-Shaped Bridge Under Explosion Load

Axial live load distribution among single row of piles of integral bridges

This study investigates the axial live load distribution among steel H-piles in single-span integral bridges. To achieve this, two- and three-dimensional finite-element models for various integral bridges are conducted and analysed using the structural analysis software SAP2000, to determine the maximum axial loads in steel H-piles within two- and three-dimensional models. Subsequently, axial live load distribution factors from the ratio of axial loads calculated from these models are derived. The parametric study reveals that girder spacing and pile spacing exert notable influences on the axial live load distribution among the steel H-piles in integral bridges. Then, non-linear regression analysis is employed to formulate practical equations as functions of these two parameters. These equations can effectively calculate the live load distribution factors for the piles in integral bridges. To validate the accuracy of the live load distribution factors calculated from the proposed formulae, a comparative analysis is performed with results obtained from structural analysis. The standard deviations of the ratios between these two results are found to be a mere 2%. This clearly demonstrates that the developed formulae yield highly precise estimates of axial live load effects in integral bridge piles.

A non-linear static analysis for the seismic design of single-span integral abutment bridges

Integral abutment bridges are characterised by a monolithic connection between the deck and the abutments. Because of this connection, the seismic behaviour of the entire structure tends to be controlled by its interaction with the surrounding soil, and especially with the approach embankments. To date, methods for the seismic design of this type of bridges are still characterised by substantial uncertainties, mostly because of insufficient understanding of the dynamic response of the soil–structure system. This paper provides a contribution to the interpretation of the seismic behaviour of integral abutment bridges, focusing on a single-span structural scheme that has been receiving significant attention in recent years. The dynamic interaction between the bridge and the soil is studied with global numerical models of the soil–bridge system developed in OpenSees and subjected to a variety of ground motions. The results of the dynamic simulations, interpreted also with the aid of a modal analysis of the system, are used to develop and finally validate a simplified design procedure. This procedure is based on the capacity spectrum method, aimed at evaluating the maximum deformation and internal forces in the structure produced by the longitudinal component of the seismic motion that typically dominates the design of integral bridges.

The impact of pier height on the construction costs of integral road bridges: An application of artificial intelligence

There are multiple definitions for integral road bridges. One of them explains that these are single-span bridges without expansion joints or bearings at the discontinuity locations. In terms of durability and maintenance, discontinuity locations are considered to be construction parts most exposed to damage in this type of structure. Engineers' efforts to lower maintenance costs and extend the durability of structures have led to the emergence of integral bridges. Early assessment of construction costs is crucial in determining the justification for constructing such structures, as it allows both the investor and the contractor to gauge their involvement in the project's implementation. The construction costs can be determined based on the structure characteristics. One of the major characteristics of integral bridges is the height of their piers. This paper examines how the pier height affects the construction costs of integral road bridges. The prognostic model in the Python 3.7.6 software package applies neural networks to determine the impact of pier height. According to the research, the pier height accounts for up to 20% of the total construction costs of integral road bridges.

Evaluation of strengthening efficiency based on combined global and sectional response of masonry arch bridges

The paper is focused on the numerical analysis of the efficiency of strengthening solutions dedicated to masonry arch bridges. An overview of common strengthening methods is described covering the most frequent techniques and their influence on the bridge’s structural behaviour. The numerical study concentrates on the longitudinal behaviour of the arch of single-span bridges. The applied methods are related to the addition of specific structural components on both sides of the arch – extrados and intrados. Two basic solutions are studied based on a rigid or flexible layer corresponding to the most common techniques being applied to these bridges around the world. A comparison of the selected strengthening techniques is given considering their impact on the bridge’s structural behaviour under incremental static loadings. Structural details of the solutions are given as well as their efficiency is evaluated through analytical and numerical analyses. Advanced nonlinear Finite Element models using a meso-modelling technique are presented and selected results showing the mechanical performance of the structure before and after strengthening are provided. The interpretation of the bridge model response parameters, representing the increment of resistance given by the addition of each reinforcement solution, is based on the analysis of the evolution of the structural failure modes up to the maximum load capacity of the bridges, namely in terms of the interaction of internal resistant forces M-N in representative arch cross-sections determined also analytically. Conclusions are formulated to identify optimal reinforcement solutions through the ratios of the maximum load capacity of strengthened and unstrengthened bridge cases, and the ratios between the areas of the M-N interaction diagrams of strengthened and unstrengthened solutions.

3D Numerical and Experimental Investigation on Thermal Behavior of Single-Span Masonry Bridges Considering Monthly and Yearly Temperature Changes

3D Numerical and Experimental Investigation on Thermal Behavior of Single-Span Masonry Bridges Considering Monthly and Yearly Temperature Changes

Fragility of bridge decks exposed to hydraulic and driftwood actions

A resilient bridge network is vital to a community recovery after natural disasters. Floods are the main cause of bridge collapses, but there is little research on the combined fragility of single-span bridge decks to hydrodynamic forces and driftwood clogging. Moreover, most studies concentrate on multi-span bridges and piers. By using HEC-RAS software and in-house developed Python scripts, this work proposes a method to obtain fragility curves for single-span bridges accounting for hydrodynamic actions and driftwood. Due to the lack of indications from standards concerning uplift and overturning of bridge decks, these limit states are included in the formulation together with slippage. Results revealed that all three limit states must be taken into account and showed that driftwood clogging can have a severe impact on the failure probability of the bridge, with even a minor decrease in clearance causing a significant safety reduction. Additionally, this work discusses the influence of hydrologic model recalibration on the failure probability of a structure.