Journal of Bridge Engineering

Concrete-encased concrete-filled steel tube (CFST) box members have been recently used as piers and arches in bridges owing to their high stiffness and strength. However, the seismic behavior of these members has not been thoroughly investigated, which hinders the usage of such members in earthquake-prone zones. In this study, eight concrete-encased CFST box specimens and eight RC box counterparts were tested under constant axial load along the specimen and cyclic lateral load at the midspan. The experimental parameters were the axial-load level and cross-sectional type of the column. The effects of these parameters on the strength, ductility, stiffness degradation, and energy dissipation were studied. Compared with the corresponding RC box columns, the performances of concrete-encased CFST box columns, including the lateral resistance, stiffness degradation, ductility, and energy dissipation capacity, were significantly improved. A simplified calculation method was proposed to evaluate the flexural resistance of concrete-encased CFST box columns.

Segmental unbounded posttensioned concrete bridge piers can resist large lateral drifts and eliminate residual deformation during an earthquake. The seismic behavior of posttensioned bridge piers depends on several factors, including concrete strength, posttensioning (PT) force, aspect ratio, and axial-load ratio. This study investigated the effects of these factors and their interactions on the seismic behavior of such piers, which are not adequately addressed in the existing literature. Here, finite-element models of unbounded posttensioned concrete piers were generated to perform a parametric study. These models were first validated with experimental results and then used to predict the seismic behavior of unbounded posttensioned concrete piers. At the initial stage, full factorial analysis was performed by considering the following three factors: PT level, PT ratio, and concrete strength. The results indicate that none of them in combination resulted negatively on pier yielding capacity and postelastic stiffness, as long as the axial-load ratio was within 20%. After this preliminary study, a more comprehensive fractional factorial study, including seven factors, was performed. In the fractional factorial analysis, each of the factors was considered at two levels. The piers were analyzed under reverse cyclic loading. Based on the lateral load-displacement responses of the piers, regression analysis was performed to propose equations for calculating global yielding and stiffness of piers.

Heavy-duty riveted steel gratings often occur as open-grid deck systems used in movable bridge construction and in rehabilitation projects due to their light weight compared with conventional systems. Open-grid decks have been used in a number of bridges, with the majority fabricated as welded decks. Field and laboratory experience with heavy-duty riveted steel gratings indicates improved fatigue performance compared with welded decks, but no specific provisions currently exist. This study explored a fatigue life prediction methodology for riveted gratings using fracture mechanics. The models involve crack growth rate relations and approximate stress intensity factor solutions for a crack in a bearing bar of the grating. Two failure modes of the riveted gratings were considered based on results of fatigue testing of both full-size and smaller-size samples of a 37R5 lite panel under various stress ranges. Results from the fracture mechanics approach compared well with experimental results. The proposed methodology may be applied to different configurations of riveted grating that contains bearing bars with rivets as the critical detail. Using the proposed method, the predicted fatigue life of a 37R5 lite with riveted details is estimated.

In this study, a lightweight prestressed steel jacket (PSJ) was proposed and developed for rapid and cost-effective repair of a severely damaged circular reinforced concrete column. The PSJ is composed of several prestressed strands, and a thin steel sheet is restrained by these strands, which can be manually wrapped around and jointed to form a jacket on the column as part of a 12-h repair job by two workers. The prestressed strands restrain the thin sheet from buckling, while the steel sheet in turn prevents the strands from cutting into cracked concrete and thus preserves the prestressing forces. The PSJ was validated with cyclic (reversed) testing of two large-scale columns with lap-splice deficiency under incrementally increased displacements every three cycles. The ultimate strength and displacement ductility of the damaged column were restored to 115% and 140%, respectively, of those of the as-built column. The initial stiffness of the damaged column, however, was restored to only 84% of that of the as-built column because the PSJ was designed to restore the strength and ductility only. By connecting the damaged column to its footing through anchored dowel bars, the levels of restoration in ultimate strength, initial stiffness, and displacement ductility were all increased by at least 20%.

This paper presents a method and prototype implementation for tracking and assessing the structural condition of bridges. The method uses building information modeling (BIM) software to link and analyze data related to the inspection, evaluation, and management of bridges. In the proposed method, an inspector uses a custom software add-in, developed by the authors, to capture information on damage type, amount, severity, and location gathered during bridge inspection. Next, a custom tool in Microsoft Excel evaluates the structural performance and provides load ratings of the inspected bridge. The proposed method was validated through field testing on a case study bridge. Findings from this study suggest that BIM can effectively facilitate the inspection and evaluation of bridges, which may, in the future, enable transportation agencies to more efficiently manage bridge inventories and lead to a more automated practice.

This paper presents a new methodology for determining bridge inspection intervals and procedures. The methodology was developed using established risk-based methodologies with the goals of improving bridge safety and serviceability and optimizing the use of resources for bridge inspection. Current inspection intervals are calendar based and generally require routine inspections at a maximum interval of 24 months. This uniform, calendar-based approach results in the same inspection interval for new bridges and aging and deteriorated bridges. The uniform inspection interval does not consider the inspection needs for a given bridge based on age, condition, materials, environment, etc., and as a result, inspection resources may not be utilized most effectively. Using the methodology described in this paper, a bridge owner performs a simple risk-based assessment of bridges in his or her inventory to identify those for which shorter inspection intervals are needed and those for which longer intervals are more appropriate. This assessment identifies likely damage modes and associated consequences in terms of safety and serviceability of a bridge. A simple risk matrix is used to identify the appropriate inspection interval for bridges. The new, risk-based approach represents a new paradigm for bridge inspection that could transform traditional, uniform, and calendar-based inspection approaches and improve the allocation of resources for bridge inspection to improve the reliability and safety of bridges.

This paper presents two case studies that were conducted to evaluate the effectiveness of a new, risk-based inspection (RBI) method. The overall objectives of the case studies were to demonstrate the implementation of the methodology and to verify the effectiveness of RBI analysis for determining suitable inspection intervals for highway bridges. Expert elicitations were conducted to develop risk-based data models for RBI analysis for two families of bridges. These data models were used to assign inspection intervals for bridges ranging from 12 to 72 months. A new backcasting method was developed and used to analyze the effectiveness of these data models for identifying suitable inspection intervals. The results of the backcasting procedures verified that the RBI approach determined suitable inspection intervals for the sample bridges assessed through the research.

A new bridge bent system has been developed to reduce on-site construction time, minimize residual displacements even after a large earthquake, and reduce seismic damage in comparison with conventional cast-in-place construction. Accelerated construction is achieved through the use of precast columns and cap beams that can be assembled quickly. Postearthquake residual displacements are reduced by pretensioning the columns with partially unbonded tendons. Damage in the columns is nearly eliminated by concentrating flexural deformations to specially detailed regions at the top and bottom of the columns. In this study, the seismic performance of the new system was evaluated with a multi-shaking table test of a quarter scale, two-span bridge at the Network for Earthquake Engineering Simulation (NEES) Earthquake Engineering Laboratory at the University of Nevada, Reno. The maximum displacements of the bents were similar to those expected for a conventional bridge through the 100% design-level event [peak ground acceleration (PGA) = 0.75 g]. Residual drift ratios never exceeded 0.2% up to the 221% design-level motion (PGA = 1.66 g). Damage to the column concrete was negligible; the columns would not need any repair after being subjected to the 100% design-level motion. The only structural damage to the bridge was the eventual fracture of the column’s longitudinal reinforcement and bulging of the column’s confining tube, both of which occurred at drift ratios of approximately 6%. These damage states could be delayed by increasing the debonded length of the deformed bar reinforcement at the ends of the columns and by using a thicker steel tube for the confining detail.

Prefabrication of structural elements is the integral part of accelerated bridge construction (ABC). Providing constructible beam-column and column-foundation connections that can tolerate inelastic cyclic deformations is the primary challenge for ABC in seismic regions. This study developed pipe pins to simulate hinge supports at the column-footing connections and pocket details to make moment connections between the columns and pier caps. The pipe pins consisted of two steel pipes to transfer the shear and one threaded rod to transfer the uplift forces. The pocket connection was formed by extending the column into a prefabricated pocket in a precast cap beam and grouting the space between the column segment and the pocket. The primary objectives of this research were to investigate (1) the seismic performance of the proposed connections, (2) the cyclic behavior of a two-column bent utilizing column-footing pipe pins at the base and pocket connections at the top joints, and (3) the performance of engineered cementitious composites (ECCs) in the pocket details and plastic hinge zone of column. Comprehensive experimental studies of the connections and their components, including cyclic load studies of a large-scale two-column bent model, were conducted. Test results showed that the proposed pipe pin detail resisted the force and deformation demands under high drift ratios with minimal damage. Furthermore, the precast cap beam remained essentially elastic, and the pocket detail behaved similarly to a monolithic moment connection in hinging the column when conventional concrete was used in the embedded region. Study results also recommend that ECC not be used in the embedded portion of the column in the pocket.

An experimental verification of a parameter estimation algorithm for finite-element (FE) model updating for damage quantification of a concrete beam with extensive damage is presented using the measured frequency response function (FRF) data. The intact stage of the beam and four progressive damage stages are investigated to update the FE model to quantify the damage across the beam. The method uses a subset of measured FRF data for FE model updating via a quasi-linear sensitivity equation of structural response. A least-squares algorithm with an appropriate weighting technique is used for parameter estimation. Proper selection of excitation frequency ranges for model updating is addressed. Predicted equivalent stiffnesses demonstrate the success and robustness of the method in damage quantification, even when using only a subset of the measured FRF data.

Understanding of the performance of critical bridges, such as cable-supported bridges, during accidental fire is necessary for developing mitigation strategies against potential fire damage. In this research, the structure–fire interaction of long-span cable-supported bridges, in particular, anchored suspension bridges, self-anchored suspension bridges, and cable-stayed bridges, was investigated through nonlinear finite-element analysis. To investigate the stability of these bridges during fire, a typical steel orthotropic box girder was exposed to different fire scenarios representing fires during ship and truck accidents. The stability of the three bridges during two fire scenarios was investigated in terms of fire intensity and duration and axial compressive force in the deck. Simulation results indicate that the existing axial force in the deck negatively affected the structural performance by causing buckling failure under fire loads. Generally, anchored suspension bridges had the largest safety factor among the three bridges because of nearly zero axial force in the deck. On the other hand, self-anchored suspension bridges had a significantly higher amount of existing axial compressive force in the deck and were the most vulnerable during both the truck and the ship fire scenarios. The axial forces in cable-stayed bridge decks varied longitudinally. Hence, their vulnerability during fires depends on the location of fire, the magnitude of existing axial force, and the design capacity of the deck.

Bridge scour is a major cause of bridge failures and has emerged as a significant concern for bridge engineers. Most studies focus on the scour mechanism, modeling, detecting and monitoring, and countermeasures. To detect or monitor the scour, the scour effect on the response and feature change of the bridge structure should be studied first to choose an effective measurement. Currently, very few studies have been performed on the scour consequences. Therefore, the present study investigated the scour effect on the responses of the entire bridge, including the superstructure and substructure, and even the responses of vehicles traveling on the bridge, which in turn could be used to detect or monitor the scour of foundations. A field bridge with scour history was adopted, and the bridge–vehicle–wave interaction was considered. First, the soil model, scour model, and wave loads were created. The free vibrations and dynamic analyses under wave loads were then conducted on a single pile and pile groups with different scour depths. The results indicate that the scour effect on the substructure response is very significant. Finally, the vehicle–bridge–wave interaction was analyzed by incorporating the wave force as a time-variant force into the vehicle-bridge–coupled equations. The results indicate that the response changes of the bridge deck and vehicle are also significant and have the potential to be used for scour damage detection.

Panelized bridge systems (e.g., Bailey, Mabey Johnson, Acrow) are intended for girder-type bridges and have been implemented for military, civilian, and disaster relief applications. Design challenges, however, include material efficiency (span squared per number of panels), lateral bracing, and achieving longer spans. These challenges are addressed by investigating the promise of implementing panels in new configurations with longer spans and evaluating bracing strategies. Three new forms (Pratt truss, bowstring truss, and network tied arch) composed of standard length panels, with shapes determined based on geometric considerations and structural performance (resistance to buckling), are presented. A parametric study evaluates lateral bracing strategies for girder-like and column-like configurations. The promise of the new forms, also incorporating the developed bracing strategy, is demonstrated through finite element analyses. Following this investigation using a standard length panel, an optimization procedure for minimum self-weight and maximum structural performance is developed to determine an optimized panel length and form. This paper addresses the design challenges of efficiency, bracing, and span length for panelized bridge systems and indicates future areas for improvement through optimization.

Structural deformation caused by live loads is a major concern in the design of multispan suspension bridges. Deformation characteristics of double-cable multispan suspension bridges are the focus of this paper. The authors propose a simplified mechanical model of the double-cable multispan suspension bridge for static analysis. Analytical formulas for calculating maximum deflection of the girder in a loaded span were deduced on the basis of the mechanical model. Finite-element models were established to verify formulas, and a comparison of formulas with FEM analysis revealed excellent agreement. The effects of major design parameters on the deformation of double-cable multispan suspension bridges were also studied. Research shows that the distribution of dead loads to the top and bottom cables had little effect on deformation. The sag-to-span ratio of the main cable imposed a significant effect on deformation, and structural deformation decreased with a decrement in top-cable sag or an increment in bottom-cable sag. A comparison was made between double-cable multispan suspension bridges and traditional multispan suspension bridges regarding deformation. The results indicated that with the same tower stiffness, the deformation of a double-cable multispan suspension bridge was far less than that of a traditional multispan suspension bridge.

A reliable and robust shear connection is required in the cast in situ portion of a segmental composite bridge girder to carry the shear force between the steel and concrete. When the shear connectors are arranged with close spacing in order to satisfy design requirements, group effects will have a significant influence on the structural behavior of the shear connection. This paper presents an investigation of the static behavior of group-arranged stud–bolt hybrid shear connection in long-span segmental bridges, with the bolt shear connectors as the threaded outstands of the high-strength bolts used in the splice connections needed in segmental construction. Seven specimens with different arrangements of the studs and high-strength bolts were fabricated and tested. The failure modes, load-slip relationships, and shear strength were obtained and discussed. The results showed that the bolts could increase the shear strength of the connection and that the embedded length of the bolts had a marked effect on the structural response when the bolt diameter was large. In deference to stud connectors, the failure modes of the specimens with bolts were characterized by crushing the concrete at the ultimate-strength limit state.

Perfobond rib shear connectors are used widely in bridge engineering, and expressions for their shear capacity can be found in various codes and standards. Empirical expressions available for the strength of perfobond rib shear connectors have been obtained mostly by the numerical regression analysis of push-out test results. Because of discrepancies in both specimen dimensions and the test procedures, the various test results do not agree with each other, and the empirical strength predictions so derived are quite different. To resolve this discrepancy, the authors investigated the modes of failure of perfobond shear connections using a novel push-out test procedure. The mechanisms for the resistance to load of perfobond rib shear connectors were analyzed, and the effects of the concrete and transverse reinforcement on the shear resistance were investigated. An empirical expression for the shear strength of perfobond rib shear connectors with transverse reinforcement is proposed here. The calculated results agree well with test results reported elsewhere, which indicates that the new empirical expression has adequate accuracy and can be used in engineering design.