This paper investigated the corrosion fatigue crack propagation mechanism of high-strength steel bar HRB400 in various corrosive environments. Fatigue crack growth (FCG) tests were conducted under different fatigue loading types, environments, and stress ratios. The fatigue loading type included the constant and stepwise decreasing load amplitude. The environments were air, distilled water, 3.5% NaCl solution, and an artificially accelerated corrosive environment. The stress ratio ranged from 0.1 to 0.7. The threshold stress-intensity factor range and FCG rate under various test conditions were obtained. The FCG path and fracture morphology were examined by optical microscopy and scanning electron microscopy, respectively. The threshold stress-intensity factor ranges, FCG rates, FCG paths, and fracture features under different conditions were compared. The corrosion fatigue mechanism of the steel bar under the test environments were quantitatively analyzed. The results showed that hydrogen embrittlement played a predominant role in the corrosion fatigue process of the HRB400 steel bar. The contribution of anodic dissolution to the FCG rate increased as the aggressiveness level increased. The contribution of hydrogen embrittlement to the FCG rate increased with the increase of stress ratio and stress-intensity factor range.

The Tianjin West Railway Station, located along the Beijing-Shanghai high-speed railway, is an elevated structure and has been constructed as a novel, integrated bridge-station system. In this study, dynamic responses of this integrated train-track-railway station are computed using finite-element analysis (FEA) in conjunction with the adaptation of (analytical) system coupling techniques. In particular, a multi–rigid-body dynamics treatment of the train-track-railway system is given, based on coupling of displacements between the track and contact points of train wheels. Further, the corresponding dynamic equations of motion include considerations for nonlinear contact. Finite-element (FE) modeling of the Tianjin West Railway Station is carried out to compute modal and transient responses over a range of train passage scenarios. The analytical framework results support that (1) vibrations induced by train passages are predominately vertical; (2) vibrations are highly attenuated regardless of train passage speed; (3) such attenuation, in turn, diminishes the propensity for dynamic response of the integrated, elevated level, and roof components; and (4) the integrated structure satisfies applicable railway design-code requirements.

Short ultrahigh-modulus (UHM) carbon fiber–reinforced polymer (CFRP) strip panels connected through a finger joint configuration offer a convenient modular method for strengthening steel girders. Three-dimensional nonlinear finite-element (FE) analysis was conducted to characterize the interfacial and flexural behavior of strip panels. The calibrated FE model provides an efficient and economical method of evaluating different parameters related to the material properties and strengthening configuration of the UHM CFRP strip panels, for which experimental data are not available. Analysis implemented robust features, including debonding of CFRP using a mixed-mode bond–slip model, CFRP rupture, steel yielding, and concrete slab crushing. Predictions were calibrated and validated against experimental results from double lap shear tests and flexural tests of steel beams and steel–concrete composite beams. The FE model was used to investigate the effects of finger joint location, joint length, and laminate thickness. Strip panels with 300-mm-long finger joints and thicknesses of up to 2 mm equaled the strength of a continuous laminate with the same CFRP area. Both failed by CFRP rupture. At greater thicknesses, debonding occurred at lower ultimate loads than for a continuous laminate. The finger joint splice was also compared to the traditional splice plate method. The splice plate length required to achieve the same level of load transfer was longer than the finger joint length when the connection was in the maximum moment region. For a given CFRP thickness and splice plate length (or finger joint length), strip panels with finger joints provide greater load-carrying capacity.

CFRP Rod Panels (CRPs) have been recently developed to externally strengthening concrete structures in flexure, especially over multi-lane highways. Both exterior beams of a reinforced concrete (RC) bridge traversing southbound Interstate 71 (I-71) in Kentucky were damaged by an over-height truck impact. Rebars within the bottom mat of each exterior beam were severely bent due to the impact. CRP 195, with CFRP rods 3.96-mm (0.156 in) in diameter, and having a capacity of 870 kN (195.6 kips) per 300 mm (12 in) width of panel, were selected for flexural strengthening. CRPs were chosen due to their modular construction capability permitting a smaller work crew to carry out the retrofit construction while requiring closure of only a single lane of traffic on I-71. As current codes do not address CRPs, the retrofit design was based on American Association of State Highway and Transportation Officials (AASHTO) guidelines for externally bonded FRP. A load rating of the impacted girders was carried out for the as-built, damaged, and retrofitted stages. This paper details the retrofit construction of the bridge girders, highlighting the advantages of the CRPs.

Structural health monitoring has been utilized in numerous ways to investigate the performance and integrity of highway bridges. This paper highlights the use of six structural health monitoring systems, which were deployed to monitor distinct behaviors on six bridges in Kentucky. The structural health monitoring systems are as follows: (1) Over-height truck impact detection and monitoring on the I-64 over US 60 bridge, (2) Barge impact detection and monitoring on northbound US 41 over the Ohio River, (3) effectiveness of carbon fiber-reinforced polymer retrofit evaluation based on prestressed concrete I-girder crack movement on the I-65 elevated expressway in Louisville, (4) effect of thermal loads on bridge substructure evaluation on KY 100 over Trammel Creek, (5) thermal movement of expansion joints evaluation on eastbound I-24 over the Tennessee River, and (6) crack growth monitoring on steel floor beam on I-275 over the Ohio River. The deployment of the different structural health monitoring systems on Kentucky bridges has provided valuable insights on their planning, implementation, and maintenance, which can be applied on future structural health monitoring projects. While several of the projects have proved immensely successful, with some still being continuously monitored, others, due to numerous complications, have met with only limited success. The best return on investment was realized from structural health monitoring instrumentation that was focused and limited in scope. The successful structural health monitoring systems had continuous communication between all stakeholders during planning, implementation, and monitoring phases of the projects. Following implementation, the availability of contingency funds through the funding source, to replace/upgrade sensors and networking equipment and costs for reprogramming and reinstallation outside of regular maintenance costs, was also important for the structural health monitoring to be successful.

Culverts are typically used as short span bridge substitutes for spans less 50 ft (15 m). The corrugated metal arch culvert (CMAC) is one of the most popular types, which is frequently installed under highways, airport pavements and railroad tracks. For the purpose of validating the service conditions of CMAC, a load rating method is developed in this study based on AASHTO Manual for Bridge Evaluation. The rating factors (RFs) for culverts are derived to verify the capacity of the culverts to carry current standard truck loads. In order to carry out the load rating, a finite element model of the CMAC is developed for analysing the axial thrust of the culvert wall when subjected to static and dynamic moving truck loads. A method to calculate the CMAC wall thrust capacity is derived by summarizing existing capacity calculation approaches for arch culvert and corrugated metal plates.