Journal of Bridge Engineering

A methodology will be presented to predict the complete history of flexural deformations in composite prestressed concrete and steel beams from inception to the end of service life, which will include a prediction of beam rebound and subsequent deformations when the deck is replaced. The methodology will use distinct creep curves for each loading event and will provide an efficient framework to account for the effects of differential creep, differential shrinkage, shrinkage-induced creep, loading time, concrete aging, prestress losses, and temperature gradients on composite and noncomposite beam flexural deformation history. The method will be based on a time-dependent strain compatibility analysis, which will provide curvatures at various points along the span as a function of time to obtain the history of the deflected shape of the beam. Measured discrete and periodic flexural deformation data will be used to validate the methodology. The presented method will be used to quantify the influence of creep, shrinkage, modulus of elasticity models, temperature gradients, deck placement and replacement time, and time step generation method on the beam flexural deformation history. The results show that steel beams can rebound to their original position after the deck has been removed, the rebound in the prestressed concrete beams varied from 51% to 92%. In addition, the influence of the initial deck placement time had a marked effect on the short-term beam flexural deformations at service, and its influence diminished after 200 days for the cases that were considered in this study. In addition, the selection of models for creep, shrinkage, and modulus of elasticity at prestress release and 28 days had a marked effect on the beam deformation history, and the considered models for the variation in modulus with time resulted in similar predictions.

Time-dependent flexural deformations for composite and noncomposite prestressed concrete beams and steel–concrete composite beams, which are subject to various loading and unloading events, are predicted based on several methods with varying levels of complexity. The considered prediction methods range from computational methods that provide curvatures at various points along the span as a function of time to widely used multiplier-based methods. The impact of various levels of analytical simplification on beam flexural deformation history is quantified. Pre-erection camber predictions based on various methods are compared with measured pre-erection camber values for 105 noncomposite prestressed concrete beams. Similarly, predictions for the full flexural deformation history of six composite prestressed concrete and six steel beams are compared with test data reported in the literature. All computational methods considered result in similar predictions of pre-erection camber in prestressed concrete beams despite fundamental differences in the methods and despite gross simplifications in creep behavior used in some methods. However, when long-term flexural deformations at service and prediction of beam rebound are considered, the effect of simplifying assumptions for creep behavior becomes more significant. The quantification of such differences in predictions may inform decisions during the design phase regarding which method should be employed for a particular application.

The plate-truss composite girder (PTCG) has commonly been used in the design of long-span bridges in recent years. However, most studies regarding flutter stability and related mitigation measures primarily focus on traditional plate-truss separated girders (PTSGs). In this paper, a comparative study is performed to investigate the differences between the flutter characteristics of the PTCG and PTSG via wind tunnel tests and computational fluid dynamic simulations. Upper and lower central vertical stabilizers are applied to the PTCG and PTSG to examine their flutter mitigation effects. The flutter and its mitigation mechanisms are preliminarily explored based on the time-averaged streamlines and flow structures around the truss girder sections. The results show that the PTCG has a better flutter performance at the most unfavorable attack angle of +3° compared with the PTSGs in their service state. The flutter mitigation effect of the upper central vertical stabilizers is much more significant than that of the lower central vertical stabilizers for the investigated truss sections. Moreover, both the upper and the lower central vertical stabilizers have better mitigation effects on the flutter of the PTSG compared with that of the PTCG.

The fatigue of orthotropic steel bridge decks (OSBDs) is a bottleneck for its application, especially the fatigue of rib-to-floor beam (RF) junction. Thus, it is necessary to optimize the RF junction to improve its fatigue performance. In this study, the effect of equipping a separate inner stiffener (SIS) on the fatigue performance of an RF junction was investigated. The growth of fatigue cracks in the weld toe of the rib at the RF junction tip (RT) was examined through static and fatigue tests of a full-scale OSBD. Moreover, the influence of crack growth on other details was also studied. Subsequently, the fatigue strengths of two cracked details and the minimum fatigue strengths of four uncracked details were evaluated considering the results of a finite-element analysis. Finally, the verified finite-element model was used to analyze the influence of the form and size of the inner stiffener on the fatigue performance of RF junction. The SIS was found to be the most optimal inner stiffener, and its recommended size was obtained. When the recommended RF junction was adopted, the most unfavorable stress of the RT detail most prone to fatigue cracking could be reduced by 51.3%.

Probabilistic Damage Control Application (PDCA) has been developed to apply the performance-based earthquake engineering (PBEE) to the seismic design of highway bridge structures. The main component of the PDCA is the total risk that enables designers to conduct a life-cycle cost analysis and to answer the owner’s cost-related questions such as how to optimize the design by balancing two primary decision-making parameters: performance and cost. This paper introduces an enhanced total risk model adopting the backbone formula used for calculating the annual rate of exceeding intensity measure (IM) level in Probabilistic Seismic Hazard Analysis (PSHA). The life-cycle cost analysis is a function of initial construction cost, repair costs, and economic loss. The inclusion of expected repair costs and economic consideration results in a comprehensive life-cycle cost analysis that makes the PDCA methodology unique. A detailed case study using a multispan bridge is presented as an example to show how to apply the PDCA framework into the bridge design practice with an emphasis on the life-cycle cost analysis that is computed using the total risks. Bridge column is the main seismic critical member in the bridge system that has nonlinear performance under seismic events. The total risk model and loss analysis of the PDCA addressed in this paper is based on the seismic performance of the bridge columns only. Other components such as abutment and in-span hinge seat widths that will have some contribution to the total risk may be considered in the future.

Studying the failure or collapse mechanism of an entire bridge under vehicle–pier collision has engineering demand and practical meaning, while the existing damage assessment work mainly focuses on the impacted pier. This study aims to numerically clarify the collapse mechanism and evaluate the damage level of the entire bridge. First, the previously validated finite-element (FE) model of a simply supported RC bridge with double-pier bent when impacted head-on by a heavy truck. The model improved by incorporating the nonlinear behaviors and damage of the bridge superstructure. According to the truck mass and impact velocity involved in the actual collision accidents, 20 truck–pier collision scenarios are designed and numerically simulated by adopting the nonlinear FE program LS-DYNA. The damage/failure or collapse mechanism of the entire bridge, as well as the vehicular impact force and bridge structural dynamic behaviors, are examined. It shows that (i) the overall collapse of the bridge structure is an impact-successive and damage-accumulative process, which is not completely coincident with the failure of impacted pier; and (ii) the cargo-induced internal forces of the impacted pier have two peaks attributed to the initial contact and the following pushing–drag effect of cargo, respectively. Then, based on the damaged area of concrete and effective plastic strain of reinforcement, the damage levels of the main bridge components, including the pier, bent cap, tie beam, pile, girder, and deck, are qualitatively assessed and classified, followed by the clarifications of their corresponding inner correlations. Furthermore, by proposing two quantitative damage indexes, a feasible on-site approach for assessing the post-collision damage of the bridge structure is established and validated by eight additional collision scenarios, and the dependency of bridge damage level on both the vehicular impact velocity and mass is graphically presented. The proposed approach can be practically generalized to on-site damage evaluation of a bridge structure after actual accidents and can provide useful reference in design and restoration of RC bridges.

The buckling–anchorage system (BAS) is critical in the construction of cantilever casting concrete arch bridges. However, due to the limitations of the anchor positions, the BAS always needs a trade-off between material cost and construction safety. This paper proposes a cost optimization method for BAS while considering the safety requirements of the structure during the erection process. The proposed framework couples particle swarm optimization with the numerical simulation of the erection process. The optimization model considers the height of the pylon and the anchorage interval of the buckle cables as design variables with constructional safety constraints. The internal force balanced method is utilized to determine the anchorage–buckling cable forces to reduce the structural analysis cost of the optimization. The numerical investigation based on a real arch bridge demonstrates the feasibility of the proposed approach and shows valuable suggestions to the design of BAS for similar applications.

Bridge weigh-in-motion (B-WIM) systems are employed for monitoring traffic weights, providing useful information for management decisions. Many applications were proposed based on the information collected, such as calculation of influence lines and damage detection. In this work, an additional application is addressed, to perform model updating of structural parameters from information collected during the calibration of B-WIM systems. The goal of model updating techniques is to adjust the model parameters in order to achieve better agreement between predicted and experimental responses. Therefore, the resulting updated model is able to provide valuable information for decision makers. For many civil engineering applications, the updated parameters may have an inherent variability during the execution of the experimental procedure, since some external effects, such as environmental conditions, may change considerably along the process. To account for this inherent variability properly, a hierarchical Bayesian strategy is adopted. Results for both numerically simulated signals and a real engineering calibration procedure indicate that the proposed hierarchical Bayesian model updating approach is able to perform suitable estimates.

A novel composite connection, the steel–concrete composite connection with notched perfobond connectors (NPCs), is proposed for bridge pier–pile cap joint in this paper. In the steel–concrete composite connection with NPCs (SCCN), connection steel plates pre-embedded at the bottom of the pier column are bolted to the pile cap. The load from the pier column to the pile cap is transferred through a steel–steel connection rather than a traditional concrete–concrete connection. To investigate the failure modes and the hysteretic behaviors of precast piers with SCCN, pseudostatic capacity tests of two half-scale specimens have been conducted, with the axial compression ratio (n) of 0.17 and 0.06, respectively. The results show that the precast piers with SCCN present typical flexural failure, the same as cast-in-place (CIP) piers. Concrete cracking, longitudinal rebar yielding, concrete spalling and crushing, and longitudinal rebar fracture are successively observed. Concrete cracking and crushing both appear at the bottom of the pier columns but above the steel jacket. The hysteretic curves of the precast piers have a large shape with a slight pinching. The ductility and equivalent damping coefficient of the specimens are close to CIP piers. Compared to a specimen with n = 0.06, the flexural capacity and initial stiffness of a specimen with n = 0.17 increase by 44% and 37%, respectively. Furthermore, the residual drift ratios of the specimens with n = 0.17 and n = 0.06 are 1/4–1/2 to CIP piers, as 1.28% and 1.00%, respectively. Consequently, the proposed connection can significantly improve elastic deformation and self-centering ability.

A fixed base is generally assumed in various dynamic response analyses and the design of bridges. However, soil–foundation flexibility and energy absorption and radiation by the soil system can alter the response of bridges to dynamic loads. This interaction between the structure, foundation, and soil, which in some cases may even change the dynamic load transmitted through the ground, is, in general, referred to as dynamic soil–structure interaction (DSSI). DSSI can either have detrimental or beneficial effects on a bridge response, particularly forces and displacements. These effects depend on several factors such as the rigidity ratio (ratio of the stiffness of the structure to the same of the soil–foundation system), slenderness ratio (height of the structure to the base width ratio), the foundation type, and the mass of the structure relative to the mass of the engaged soil–foundation system. In this paper, the dynamic characteristics of an actual bridge are inferred via an experimental study and numerical simulations. The research concentrated on the evaluation of the significance of DSSI effects under operational live load levels. The bridge was shaken using T-Rex, a large-amplitude mobile shaker from the National Hazards Engineering Research Infrastructure (NHERI) facilities. Two finite-element models were created to assess the DSSI effects on the dynamic response of the bridge. One model included elements that incorporate the DSSI effects, while the other had fixed-base boundary conditions. The response from the DSSI FEM model matched the field results better than that from the fixed-base model, in terms of the peak response amplitudes and identified natural frequencies and modes. In addition, the model incorporating the DSSI effects led to a reduction in stress levels in various bridge components, compared with that of the fixed-base model. The results of this study are applicable to bridges with similar features and site conditions.

Precast segmental concrete beams (PSCBs) are being increasingly applied in bridges worldwide benefitting from the advantages of accelerated bridge construction. It is of importance to accurately predict the direct shear strength (DSS) of precast concrete joints (PCJs) for ensuring the safe structural design of PSCBs. However, existing prediction models of PCJs’ DSS are deemed inaccurate and unreliable when numerous parameters are varied in wide ranges. This study aims to establish an accurate and reliable prediction model for PCJs’ DSS using a machine learning algorithm called support vector regression (SVR). A PCJs’ DSS database of 304 test results with 23 input parameters was assembled from the literature. A model training procedure was conducted through stratified train-test split, feature scaling, feature selection, and two-step grid-search hyperparameter tuning. A new correlation matrix–based feature selection method was proposed, and three SVR models with different feature combinations were trained for validating the selection method. The trained SVR models were experimentally validated and compared with six existing mechanical models through two groups of performance indicators. A reasonable interpretation for the SVR model with the selected features in the proposed selection method was done using the combination of partial dependence (PD) and individual conditional expectation (ICE) plots. The results show that the SVR algorithm can be deemed feasible to accurately and reliably predict the DSS of PCJs. The proposed feature selection method is beneficial to the prediction performance of the SVR model. It is impossible for the typical mechanical models to achieve a similar prediction performance of the SVR model. The influence of each input parameter on the DSS of PCJs is recognized and depicted, which can offer useful information for further developing new mechanical models for predicting the DSS of PCJs with higher prediction performance in future research.

Pin joints are widely used connections for hanger assembly in suspension bridges. Significant rotary motions have been observed between pin rods and the connected members for long-span bridges subjected to traffic and environmental vibrations. Besides, the pin rods are under complex loading conditions and harsh environments, so they are prone to multitype damages. According to the investigations on the pin rods of suspenders at the midspan of the Jiangyin Yangtze Bridge, three main damaging mechanisms were found in the most damaged section covered by the lubricating bushing. It is observed that the half of the pin rod tightly contacted with the gusset plate was severely worn due to the galling seizure, while pitting corrosion was the predominant damage in the other half of the pin rod. Between the two zones, a small transition area was found damaged in the form of oxidational wear, indicating that it is affected by both friction and corrosion. It was found that the shear stress and bending stress are not threatening to the safety of the pin rods due to the appropriate material selection and sufficient load-bearing capability. However, stress concentration increased significantly due to the sharp step planes at the joint of the fork socket and the gusset plate, which is potentially risky to promote fracture of the pin rod.

Compared with those of other bridge types, the structural system of through tied-arch bridges is particularly susceptible to failure owing to the deterioration and fracturing of tie-bars as well as a lack of structural robustness, which are the main internal and external causes of progressive collapse accidents, respectively. In particular, low structural robustness strongly influences the severity of accidents induced by tie-bar breakage. To objectively reflect the possible failure mode induced by tie-bar failure and to provide improved structural robustness in through tied-arch bridges, within which the suspended deck system is relatively independent, a robustness assessment framework considering tie-bar failure is proposed in this study, by considering the design and maintenance essentials. First, the main analysis parameters for the extreme-event limit state considering tie-bar failure are put forward, including the critical tie-bar failure rate, partial factor for load effects, transverse reduction factor of multilane loading, dynamic magnification factor of material strength, and reduction factors of residual strength. Second, the quantitative assessment index of structural robustness I_T,rob is proposed based on the safety redundancy of the remaining structural members, and robustness assessment rules are put forward in accordance with the different calculation results of I_T,rob and horizontal displacement. A typical rigid-framed through tied-arch bridges is assessed using the proposed framework. The assessment results reveal that multiple fortifications against extreme events of tie-bar failure can be established by designing the tie-bars and the piers with sufficient safety features to form the first and final line of defense against the tie-bar breakage effect. Moreover, proper maintenance should be conducted to guarantee the structural robustness of bridges in use. The methodology is well suited for the design of new through tied-arch bridges and to access the robustness of existing bridges to ensure the safety of transportation services.

Postflutter limit cycle oscillations (LCOs) are typical nonlinear aeroelastic phenomena for bridge girders. An H-shaped section with a roughly 5:1 aspect ratio, treated as a simplified section of the Old Tacoma Narrows Bridge, was chosen for wind-induced instability re-evaluation, considering its vibration amplitude-dependent aerodynamics characteristics and nonlinear structural damping effects from the energy perspective of aerodynamic work. Forced vibrations at large torsional amplitudes in a wind tunnel were realized with the help of an improved forced motion apparatus (FMA), and synchronous measurements of forces and displacements on the FMA were achieved. Self-excited forces (SEFs) were extracted, and an energy map showing quantitative relationships between vibration amplitude, reduced velocity, and aerodynamic work acting on the section were established. Furthermore, the postflutter LCOs phenomena originating from the energy balance between nonlinear aerodynamic work input and energy consumption by structural damping effects were reillustrated, and nonlinear structural damping effects of prototype bridges are therefore discussed. Moreover, the instability paths of the bridge were investigated by the energy map, considering its vibration amplitude-dependent aerodynamics and structural damping effects from an aerodynamic work perspective. The results show that LCO velocity basically increases with vibration amplitude at different structural damping ratios in torsional degree of freedom, characterizing postflutter LCOs phenomena. The structural damping ratio at the bridge’s collapse is also re-estimated as about 0.0115 with better coincidence of on-the-spot observation and theoretical analysis. In addition, both the aerodynamic damping ratio considering nonlinear characteristics of the SEFs and the structural damping ratio basically increasing with vibration amplitude contribute to postflutter LCOs phenomena of the Tacoma Bridge. The instability paths of the bridge essentially rely on the competitive relationships between structural damping ratios, structural stiffness degeneration, and oncoming wind velocities in the process of collapse.

Because repetitive high strain caused by complicated deformation due to traffic load leads to fatigue damage in an orthotropic steel deck, reinforcement methods that suppress deformation are effective as a countermeasure. In Japan, a steel fiber–reinforced concrete (SFRC) pavement is often used as reinforcement to suppress deformation by improving the stiffness of the deck plate of the orthotropic steel deck. To appropriately evaluate the suppression of deformation, it is important to compare the deformation before and after reinforcement. In this study, the reinforcement effects of an SFRC pavement were verified based on visualizations of the deformation of a trough rib of an in-service orthotropic steel deck bridge before and after reinforcement by such a pavement. The visualization results showed that the deformation of the trough rib midway between the transverse ribs decreased after reinforcement, and the strain ranges at the weld joints between the deck plate and the trough rib decreased by approximately 18.5%–31.1%. On the other hand, at the intersection of the transverse rib, it was confirmed that the rotations of the lower flange of the trough rib increased after reinforcement. Accordingly, as inferred from the visualization results for the trough rib, the strain range of the web of the trough rib on the left side at the upper slit and that of the deck plate on the right side at the upper slit after reinforcement increased by approximately 10.6% and 47.5%, respectively.

This study proposes a type of bioinspired box-girder bridge with a trabecular-honeycomb steel web (THSW) inspired by beetle elytra (hardened forewings), and the buckling and shear properties of the THSW are investigated via the finite-element method under transverse loading. The results are as follows: (1) When η (the ratio of the trabecular radius to the distance between the center points of two trabeculae) is larger than 0.2, the buckling stability of the THSW is significantly better than that of a conventional corrugated steel web (CSW); however, considering the buckling mode, the achieved increases in the properties, and economic factors, the parameter η is recommended to be 0.2 or 0.25. (2) The stress level in the trabeculae is approximately only half of that in the CSW, but the THSW still bears most of the shear force, which is similar to a CSW bridge. (3) Under a shear load, the THSW is dominated by an S-type shear deformation. Importantly, the corresponding synergistic shear mechanism makes the trabecula and honeycomb wall yield in an obvious sequential order, leading to a significant improvement in the ductility of the structure. These results provide a foundation for further research and applications of this new bioinspired bridge and a solution for improving the buckling and shear performance of conventional CSWs.

Temporary supports, as mechanical devices that bear reaction forces transmitted from jacks, play an important role in bearing replacement. Compared with medium- and small-span highway bridges, temporary support for bearing replacement in large-tonnage high-speed railway (HSR) bridges always has higher performance requirements, due to the higher stability requirements for the operation of trains, larger jacking reaction forces, and long construction period. Research and development efforts for temporary supports for bearing replacement in large-tonnage HSR bridges are imminent. In this paper, a modular temporary support with a continuous height adjustment (20 mm) is initially designed based on the principle of self-locking, followed by the investigation of the bearing capacity and stability of the designed temporary support through laboratory experiments. Finally, a case of bearing replacement of a three-span continuous box girder bridge under operating HSRs using the designed temporary support is implemented. The experiments and application suggest that the bearing capacity of the designed temporary support can reach 30,000 kN, and it has the advantages of high efficiency, labor savings, and stable bearing performance, enabling it to be popularized and applied in similar projects.

Investigating the seismic behavior and safety of structures subjected to near-fault ground motions is vital. Cases involving damages to or failure of structures during earthquakes provide valuable opportunities to achieve the aforementioned goal, as these are the actual results of in situ tests of full-scale structures. The Baihua Bridge, a concrete continuous-curved girder bridge, was located at the epicenter area of the 2008 Wenchuan earthquake in China, and it collapsed partially in the quake. This study focuses on exploring the collapse mechanism of curved multispan continuous bridges subjected to near-fault strong ground motions. A refined multiscale finite-element model was used for analysis of the seismic response and simulation of the collapse process of the bridge, and the seismograms recorded by the local observation station during the Wenchuan earthquake were employed. The results show multiple cases of failure mechanism-induced serious damage to the main bearing components of the bridge structure, resulting in the progressive collapse of a unit consisting of curved girders. The redistribution of the internal forces after unseating, swinging of the girders, and collisions between the falling girders and piers were the main reasons for the progressive collapse of the bridge. The collapse could have been avoided by increasing the seating length of the girders or their resistance to negative bending moments. Configuring the stirrups according to the new code could improve the shear capacities of most piers by 62%–89%, which would meet the shear demands. However, configuring the longitudinal reinforcements according to the new code could increase the flexural capacities by 37%–39%, which would remain insufficient for ensuring the safety of the piers. The longitudinal reinforcement ratio of high pier columns should be individually designed, especially in curved segments or on piers with fixed bearings.