Journal of Bridge Engineering

This study investigated two overhanging 3-span composite girders to simulate the behavior of a suspension bridge. A new uplift-restricted and slip-permitted T-shape (URSP-T) connector is proposed to decrease the concrete slab tensile stress in composite girders. URSP-T connectors installed on one side of the specimen were compared with studs installed on the other side. Various elastic working conditions, ultimate sagging moment conditions, and ultimate hogging moment conditions were employed to investigate the behavior of composite girders with different connectors. The test results showed that the use of URSP-T connectors decreased the tensile stress of the concrete slab and prevented separation of the concrete slab from the steel beam. A hanger system was used to simulate hangers for suspension bridges, and it is demonstrated that girder displacement is predominantly due to cable deflection. The influence of URSP-T connectors on the mechanical properties of composite girders was investigated and design suggestions proposed. The results show that the use of URSP-T connectors increased the slippage of the interface and decreased the bending rigidity of the composite girder. Therefore, the thickness of the foamed plastics should meet the requirement of interface slippage and careful consideration of the buckling behavior of steel girders is required when URSP-T connectors are used.

Climate change poses a substantial threat to civil infrastructure systems. This paper proposes a systematic approach to evaluate the climate change impact on the risk of bridge scour. The proposed approach pivots on global climate models and their downscaled simulation data for future climate prediction. For scour hazard analysis, the climate simulation data are converted to flow discharge data using hydrologic modeling. Because future climates involve considerable uncertainties, different climate futures and global climate models are considered. In addition, long-term regional analyses are adopted to reduce these uncertainties. The proposed approach is applied to bridges over the Lehigh River in the Lehigh River watershed. With data from various public databases, the long-term regional risk of bridge scour is assessed using various global climate models under three climate change scenarios. The impact of climate change on bridge scour risk is quantified in monetary terms. The proposed approach and the obtained results provide an important basis for the planning of climate adaptation actions for river bridges.

Control of wind-induced flutter of a bridge deck section by using winglets is considered in this paper. The Scanlan-Tomko model was considered for self-excited wind forces acting on a deck and winglets. For this, the required flutter derivatives (FDs) of the deck were fitted using the Rogers rational function approximation. Vertical, lateral, and torsional degrees of freedom of the bluff body deck and their 18 corresponding experimental FDs were considered. Winglets were modeled as flat plates, for which FDs were obtained using Theodorsen's function. The time domain formulation involving aerodynamic states yields a divergence speed much lower than the correct divergence speed obtained by quasi-steady theory. Hence, a trial-and-error method involving sweeping through both speed and frequency was considered for the control study. Control inputs, that is, winglet rotations relative to the deck, were obtained using linear quadratic regulator (LQR) control with full state feedback. The state to be fed back was estimated by a full-order observer designed using pole placement. In order to prevent winglet stall, their absolute rotations were restricted within bounds. The flutter condition was verified using controlled responses and the results compared with those from closed-loop eigenvalue analysis. The control strategy appears to be quite effective in attenuating response and enhancing flutter speed.

Structural deformation under known loads is required for assessment and model calibration. In addition, deformations need to be measured under transient as well as intrinsic loads. These loads have significantly different application durations requiring significantly different sampling rates. Measurement of deformations and translations with traditional sensors is challenging because it requires sensor mounting to a fixed reference. In the case of monitoring structures during construction, limited access and schedule constraints necessitate placement of the monitoring equipment outside the active construction zone. This article presents an implementation as well as proof of concept of a noncontact technology for obtaining accurate measurements with minimum impact to the structure and construction activities. Indoor and outdoor calibration showed that the deviation of measurements made at an 81-m (266-ft) range was about ±7% of the linear displacement potentiometer sensors. The maximum deviation of deflection measurements made during load testing of a steel girder bridge was 8.3% of the linear displacement potentiometer sensors. The measurements included three-dimensional (3D) displacements at each location, a significant advancement over traditional technologies.

A cable-stayed bridge is a very competitive structural type owing to its aesthetic shape, structural efficiency, and spanning ability. Pile groups are an often-used foundation type in China, even for the piers and towers of long-span cable-stayed bridges. The seismic behavior of a bridge depends on its structural system type. The soil, pile foundation, and structure interaction is a significant influencing factor, especially for flexible structures such as super-long-span cable-stayed bridges. However, experimental studies on long-span cable-stayed bridges with pile foundations are scarce. In this study, a full-model shaking table test of a super-long-span cable-stayed bridge was conducted. The 1/70-scale model, which is of a preliminary-design cable-stayed bridge with a central span of 1,400 m, includes both superstructures and pile group foundations embedded in artificial soil contained in laminar shear boxes. The full model was subjected to a suite of ground motions in the longitudinal direction by using a shaking table array. The seismic performance of the bridge model with three types of structural systems—a floating structural system, elastically constrained structural system, and supporting pier structural system—was investigated experimentally. The experimental results show that the effects of the supporting pier structural system on reducing the longitudinal relative displacement at the tower top as well as between the tower and girder are superior to those of the elastically constrained structural system and floating structural system. However, the seismic demands of the supporting piers designed as sacrificial components increase noticeably. Moreover, the dynamic characteristics of the full model obtained from the numerical simulation are in good agreement with the experimental counterparts.

The performance of concrete shear keys as restraining devices for laminated rubber bearing–supported highway bridges was examined in past earthquakes such as the 1999 Chi-Chi and the 2008 Wenchuan earthquakes, where the widely observed shear key failure and bearing sliding significantly increased the risk of span unseating. To avoid such scenarios, economical yielding steel dampers are proposed to replace conventional shear keys as restraining devices on bridges. If designed properly, the steel dampers are expected to control bearing displacement within limit without imposing much additional demand on the substructure. The primary objective of this study was to develop a simplified procedure for designing the yielding steel dampers to control sliding displacement of the laminated rubber bearings to a specified value for the considered earthquake hazard. By treating the global bridge system as a serial-parallel combination of different components, the correlations of various parameters were investigated. On that basis, a simple formulation was developed, followed by a series of nonlinear time history analyses and a shake table test as verifications. The outcome of this study highlights the cost-effectiveness of using yielding steel dampers and laminated rubber bearings as an earthquake-resistant system for highway bridges compared with other popular isolation systems. The proposed design procedure was also verified to be quite efficient in properly designing the yielding steel dampers for a satisfactory bridge seismic performance.

The cable configuration of a suspension bridge is very sensitive to temperature changes. On the basis of multisegment catenary theory in combination with the conditions of geometric compatibility, mechanical equilibrium, and conservation of the unstrained cable length, an analytical method is proposed to model the temperature sensitivity of the cable configuration of suspension bridges. The main considerations were the elevation of the main cable and installation positions of cable clamps. The proposed method can adapt to different construction states (the completion state of the bridge, the free cable state, and the datum cable strand), boundary conditions (considering or not considering the saddle arc), and the stiffness of the towers (considering or not considering tower bending deformation). It is possible to switch between different cases by changing only a few parameters. An engineering example analysis was then performed for a suspension bridge with a main span of 730 m, which demonstrated the feasibility and effectiveness of the proposed method. The results showed that the deformation of the suspension bridge had a linear relationship with temperature. The construction state and bending deformation of the towers had a large impact on the temperature sensitivity coefficient of the main cable elevation. The bending deformation of the towers aggravated and lessened the temperature sensitivity coefficient of the main cable elevation for the main span and side span, respectively. The temperature sensitivity coefficient of midspan point elevation of the main cable correlated negatively to the span length. The maximum temperature sensitivity coefficient of the installation position of the cable clamp occurred near the interquartile point of the main span.

In this study, four 1/3-scale bridge column specimens were investigated both experimentally and numerically. The specimens consisted of two cast-in-place (CIP) reference columns and two precast columns for the study of socket and pocket connections, respectively. The precast columns were designed based on the actual application of precast urban viaducts in Shanghai, China. Therefore, this study investigated and verified the seismic performance of these connection approaches. Based on the test results of the hysteretic behavior and derived indexes, both columns with socket and pocket connections have shown equivalent seismic performances to their CIP references. The differences between precast and CIP columns were within 15% for all indexes, and the damage development and failure mechanism were also similar. Finite-element models were created with displacement analyser (DIANA) and calibrated with the test data. Bond-slip behavior with the built-in embedded reinforcement element, concrete cracking with tension softening, and material nonlinearity were considered. Under monotonic pushover analysis, the load-displacement curves were in good agreement with the backbone curves of the test results.

A quantitative framework was developed to assess life-cycle resilience of deteriorating reinforced concrete (RC) bridges under seismic ground motions (GMs). Deterioration of a three-span RC bridge due to chloride-induced corrosion was considered, and three-dimensional (3D) finite-element (FE) models of the bridge were generated at pristine and four degraded conditions. Nonlinear time history analyses of bridge models were performed to develop time-variant bridge fragility curves, which were utilized further to estimate postearthquake direct and indirect losses arising from bridge damage and associated downtime. Sigmoidal functions were used to numerically simulate realistic recovery paths depending on the extent of bridge damage after earthquakes. Finally, bridge resilience was estimated by integrating the bridge's seismic vulnerability, losses, and recovery functions. Obtained results revealed a degrading trend of resilience of the bridge as it aged, signifying the importance of considering a life cycle–oriented framework for estimating time-variant resilience of aging bridges. At a specific state of degradation, bridge resilience was observed to reduce linearly or nonlinearly with increasing GM intensity or peak ground acceleration (PGA). Finally, an uncertainty analysis with key uncertain input parameters showed resilience of the pristine bridge at any specific PGA to vary following a normal distribution.

Many prestressed concrete bridges exhibit increasing long-term deflections under heavy traffic loads. Cyclic creep from increasing heavy traffic has received gradually increasing attention in recent years, but the creep strain is usually treated as an empirical and nonrandom expression. In this paper, a multifactor coupled creep model for concrete is established, in which the material degradation and irrecoverable deformation under cyclic loads are redefined. Based on weigh-in-motion (WIM) and video data, a random vehicle model is presented and stress amplitudes from vehicle loads are obtained, through which fatigue damage and creep strain at every Gaussian integration point are calculated. Based on the concrete creep and random vehicle model, a three-dimensional (3D) probabilistic finite-element (FE) analysis is conducted on a prestressed continuous girder bridge subjected to heavy trucks and verified by 10-year measured data. Results show that the influence of concrete static creep and prestress loss is significant. Fatigue creep from heavy trucks plays a significant role, leading to continuous deflection and cracking of box girders. The range of deflection from random heavy trucks is about 18 mm after 10 years. The sources of different types of cracks are also distinguished. This study reveals the reasons for excessive deflection of bridges under heavy trucks via a new concrete creep model and accurate modeling of the random traffic loads.

This paper outlines a procedure to support the selection of repair strategies for damaged structures after an earthquake. Under strong shaking, modern code-compliant bridges can sustain significant damage to their ductile members and failure of sacrificial members. However, there are many choices of repair strategies and no clear guidance on their selection. This paper proposes a seismic performance assessment framework to determine repair costs for reinforced concrete bridges, considering costs associated with both the initial repair and future expected seismic repairs (which are based on the performance of the repaired bridge). For initial repair, the paper considers several common column repair techniques, which are separately evaluated in terms of direct costs. For future expected repairs, the paper proposes a method to evaluate the effect of each of the repair strategies on a repaired bridge's postrepair future seismic performance to quantify the expected repair costs associated with each strategy over the remaining service life of the bridge. The procedure is demonstrated for two conventional concrete bridges, but can be applied to any concrete bridge or other bridges with some modifications in the details. The results show the importance of considering postrepair performance in the choice of repair strategy. Although the initial seismic repair costs of competing repair strategies are similar, some repaired bridges will incur higher repair costs in subsequent events. As a result, in cases where the repairs need to be performed early in the life of the bridge, the service life expected costs of strategies can differ by a factor of two.

Concrete-filled steel tubes (CFSTs) have been applied widely as the main members in bridge structures; however, the temperature gradients have not been studied sufficiently. To fill this gap, a long-term experimental and analytic study was conducted on four CFST members with different inclinations and orientations. Then a systematic 2-step approach with curve fitting and extreme value analysis (EVA) was proposed to establish the most unfavorable vertical temperature gradient (VTG) and transverse temperature gradient (TTG) patterns with the extreme temperature differences (TDs) in a 100-year return period. The curve fittings show that both VTG and TTG profiles can be described by two piecewise functions with multiple parabolas. And EVA shows that TDs in positive VTG, negative VTG, and positive TTG all fit the Weibull distribution well, while the TDs in negative TTG all fit the Gumbel distribution better. Comparison analysis shows that the Chinese specification underestimates the temperature gradients of CFST bridges. The proposed temperature gradient patterns are more suitable for probabilistic limit-state design for thermal effect calculations of CFST bridges than the Chinese specification.