Journal of Bridge Engineering

The use of fibers in reinforced concrete offers an opportunity to optimize the structural design while increasing durability. A sectional analysis that considers the stress-crack-width relation obtained for steel fiber–reinforced concrete (SFRC) and polyolefin fiber–reinforced concrete (PFRC) was used for the structural design of two fly-over bridge typologies. Moment-curvature diagrams were produced using an iterative process that took into account not only the strain conditions but also the crack appearance and evolution. The contribution of fibers to the shear resistance was calculated following the formulation proposed by Model Code 2010. The results obtained showed that the contribution of the fibers enabled a reduction in flexural reinforcement of up to 40% and 30% in the cases of SFRC and PFRC respectively. In relation to shear stirrups, notable reductions could be achieved for both SFRC and PFRC but could be greater in the case of PFRC. Lastly, the economic impact of the use of fibers in the construction costs was quantified.

This study aims to develop Load and Resistance Factor Design (LRFD) provisions for movable bridges’ mechanical components. It requires the formulation of the limit state functions, determination of the statistical parameters of loads and resistances, development of the reliability analysis method, selection of target reliability indices, and calibration of load and resistance factors. The service and overload limit states for electric and hydraulic motors were considered. Movable bridge owners and operators were surveyed to gather information about the bridge’s condition. The survey results helped to define the limit state functions and the acceptability limits. The target reliability index was established based on movable bridge performance determined by the bridge owner survey. It was concluded that the target reliability index is the same as is used in current practice. Finally, load and resistance factors were calculated and verified so that designed movable bridges’ mechanical components meet minimum safety requirements. The project results will be submitted for consideration as updates to the AASHTO LRFD Movable Highway Bridge Design Specification.

The dynamic performance of a new bridge system utilizing hybrid spread steel box girders, in which the steel box girders are spaced apart instead of conventional multicell box girders, was evaluated based on field tests and numerical analyses. In the live-load-testing program, the novel bridge superstructure was instrumented with a photogrammetric photoelectric transducer to measure the deflection responses of the spread steel box girders at midspan. The test was conducted using standard 38-t trucks under both quasi-static and dynamic conditions, in which the vehicle speed and transverse position were varied. Results obtained from the experimental tests, as well as from the developed three-dimensional finite-element models of the bridge superstructure, were examined to evaluate the dynamic impact factors. The maximum impact factor of the system under moving vehicles satisfies the Chinese and US bridge design codes, indicating that the novel system achieved the desired performance for in-service loading.

Finding the main cable shape is an essential step in the design and construction of suspension bridges. In this paper, shape-finding and force-assessment of suspension bridges based on loop adjustment are proposed and realized via the finite-element method. Here, loop adjustment refers to the process where the appropriate adjustment coefficient is chosen based on the results of the last modeling and deviations from the design goals to approach the target main cable shape gradually and to satisfy the design requirements. This method adopts a full-bridge model, which provides the comprehensive account of interactions between different components of the suspension bridge, including towers and stiffening girders, as well as the effect of tower compression and splay saddle rotation. Based on the full-bridge model in the completed bridge state, the inverted removal method is used for the calculation of key construction parameters in the free cable state, such as prebias of tower saddles, predeflected angle of splay saddles, and installation position of cable clamps. The proposed method’s feasibility and effectiveness are verified by its application to two particular suspension bridges, namely, the Great Belt Bridge (Denmark) with a main span of 1,624 m and the Jindong Bridge over the Jinsha River (China), with a main span of 730 m. Results of shape-finding and force-assessment both have good accuracy, which are generally consistent with those obtained by other methods.

The construction of bridges with suspenders, such as cable-stayed or tied-arch bridges, needs deep study of the prestressing forces to be applied to stays or hangers in all stages, depending on the construction technique adopted. In these cases, the main issue is the determination of the initial forces and optimization of the prestressing system in terms of stressing values and sequence. When the bridge is already built and suspenders have to be replaced for maintenance, a different problem has to be faced by the engineer, because the sequence of replacements and the values of the axial stresses depend very much on the service conditions of the bridge and on its historical evolution from construction to maintenance. Furthermore, the technique used for the original suspension system is fundamental in designing the replacement intervention. In this paper hanger replacement of tied-arch bridges with rigid bars is focused on, inspired by an actual case of a steel bridge of medium span in which replacement of the hangers for the entire suspension system was demanded by the high state of corrosion. This posed the problem of how to replace the hangers, which stressing sequence was the most suitable, together with evaluation of the choices made in the original design for the suspension system, which did not provide for the possibility of calibrating the state of tension through onsite adjustments of hanger prestress. Assessment of the stressing sequence for hanger replacement is presented and discussed and the results of the study performed in the actual case study are shown.

An innovative precast segmental bridge column (PSBC) was proposed to achieve a better durability performance in an aggressive coastal environment, which was reinforced with both longitudinal stainless steel (SS) bars and glass fiber reinforced polymer (GFRP) bars. Four 3/20-scale PSBCs with various ratios of GFRP to SS bars were tested quasi-statically. Test results showed that compared to SS-reinforced PSBCs (SR-PSBCs), the SS-GFRP-reinforced PSBCs (SFR-PSBCs) exhibited higher displacement ductility, less stiffness degradation, lower postyield stiffness ratios, and smaller residual drift ratios, although they presented lower lateral loading capacity and energy dissipation. Increasing the ratio of longitudinal GFRP bar to SS bar in SFR-PSBCs resulted in higher displacement ductility performance and more gentle stiffness degradation behavior. Furthermore, the increase of axial load affects the seismic behavior of SFR-PSBCs in an unfavorable way, which could result in severer damage, significant reduction in the displacement ductility, faster stiffness degradation beyond the peak lateral strength point, and increase in the residual displacement.

This paper presents a method of developing digital twins (DTs) of road bridges directly from field measurements taken under random traffic loading. In a physics-based approach, the full three-dimensional behavior of the bridge is represented using response functions and distribution factors. In contrast to conventional finite-element analysis, this approach focuses on the relationship between the applied loads and the measured responses, given the limitations on the information about the applied loads due to random passing traffic. At the same time, it takes advantage of some key features of bridge traffic loading that are consistent, regardless of the weights of the passing vehicles. The nature of traffic loading is that axles travel from one end of a bridge to the other and the response is a linear combination of axle weights and ordinates of the same influence line function, adjusted for relative axle locations. Small/medium span concrete slab–girder decks are the target structures of the study. The three-dimensional nature of such structures is a particular challenge, especially in the case of multiple vehicle presence. While these bridges are strongly orthotropic, there is a significant degree of load distribution between the girders immediately under the passing vehicle and girders under adjacent lanes. This is addressed using an iterative approach that uses transverse distribution factors. The proposed DT model is verified using both numerical simulation and field tests.

A possible scenario is proposed to put into evidence how the combined effect of fatigue at very high number of cycles and corrosion could have been responsible for the failure of one of the strands and the subsequent collapse of the so-called balanced system of the Polcevera Bridge designed by Morandi. The analysis accounts for an actual estimation of the heavy-lorry traffic and load spectrum, as well as for the European Standards prescription for the fatigue damage accumulation assessment. In addition, the effective construction phases of the viaduct are considered. The structural analysis is carried out by means of analytical models, in order to simplify the structure complexity without prejudice to the description of the most relevant aspects of the structural behavior. The main purpose is to warn the scientific community and the public administrations that the combined effects of low-amplitude fatigue and corrosion can be dangerously underestimated, and that the existing assets of 20th century bridges deserve special attention in this respect.

This paper presents a case study of using ultra-high-performance concrete (UHPC) to repair a large steel highway bridge severely damaged by corrosion at the plate girder ends and the steel rocker bearings. In addition to fixing the corrosion issues at the girder ends, the use of UHPC also enabled the jacking of the superstructure to allow rocker bearing repairs. Due to limitations posed by the bridge height and location, the surrounding facilities and constraints, and the high service demand, the conventional cut-and-replacement method to repair the corroded girders’ ends was found difficult to apply. The innovative method of encasing the corroded steel with UHPC and then jacking up the encasements was developed and proved to be an elegant solution to successfully address the aforementioned challenges. After briefly introducing the properties of UHPC, the paper describes the bridge geometry and location, the corrosion damage, and the temporary emergency repair measures. The challenges for the permanent repair using conventional repair methods are discussed, followed by a description of the concept development and the design considerations of the proposed UHPC repair. Design and analysis approaches are discussed and results are presented. Construction that lasted for approximately 6 months is briefly described. The bridge was successfully repaired without major incidents and with minimum disruption to traffic.

Long-term performance is one of the less-studied cases of the prestressed concrete bridge with corrugated steel webs. In this study, the time-dependent behavior of a bridge of this type was investigated. To consider the effects of creep and shrinkage of concrete and relaxation of tendons, a three-dimensional finite-element analytical model of the bridge with all its components was developed. Two static loading tests were performed at two separate times after bridge completion to evaluate the bridge’s characteristics, and the model was updated with the results. Different models, includes models ACI, Eurocode, fib, and upgraded B3, were used in the analysis compared with the local measurements to predict materials’ time history behavior. In addition, prestress loss prediction of internal and external cables in the bridge spans was evaluated. The results showed a significant difference in prestressing loss in the external cables compared to internal ones. Compared to the local reading, the long-term deflection results showed that the upgraded Model B3 gives a more realistic prediction than others.

This study proposes the design formulas of an inerter-based damper termed electromagnetic inertial mass damper (EIMD) for bridge stay cables. To maximize the modal damping ratio for a specific cable vibration mode, we derive the design formulas of the optimal inertance coefficient and damping coefficient of the EIMD, respectively. The accuracy of the design formulas has been validated via a numerical simulation and a full-scale experimental study of a 135-m-long stay cable, and the applicable scope of the design formulas is given accordingly. This study provides simple design formulas of the EIMD for easy use in the engineering practice of cable vibration mitigation.