Journal of Bridge Engineering

Clamping force is crucial for resisting slip loads in friction-type high-strength bolted (FHSB) connections, and following corrosion, it diminishes due to sectional reduction of the nuts and/or bolt heads. Evaluating clamping force loss (CFL) in corroded FHSBs is essential for steel bridge inspection and maintenance. The cutting methods currently employed to simulate corrosion encounter challenges including limited shapes, low efficiency, and poor accuracy, leading to significant data dispersion in experiments and diminished reliability of evaluation models. Furthermore, existing evaluation models fail to fully consider the influence of factors such as corrosion shape, size, thread specifications, corrosion location, and initial clamping force (ICF) on clamping force. Hence, this research proposed a novel wire-cutting simulation corrosion method (WCSCM) and conducted experiments on 80 specimens. Based on experimental results, five clamping force evaluation models were systematically established for corrosion shapes including thickness uniform corrosion, height uniform corrosion, height and thickness corrosion, eccentric corrosion, and trapezoid corrosion, and their fitting accuracy was compared and analyzed. Furthermore, the impact of thread specifications, corrosion location, and ICF on clamping force was discussed. Finally, procedures for measuring field corrosion bolt dimensions and methods for approximating corrosion shapes were proposed, followed by validation of the evaluation model’s effectiveness through on-site bridge testing. The findings showed that the WCSCM accurately reproduced the corrosion shapes and sizes of the nuts and/or bolt heads, with regression equation coefficients exceeding 0.97, notably higher than those of existing models. The CFL resulting from various corrosion shapes and sizes exhibited variation, indicating the necessity for distinct models tailored to each corrosion damage pattern of the nuts and/or bolt heads. The impact of thickness uniform corrosion on clamping force primarily correlated with ICF, with less influence from thread specification or corrosion location. The proposed models were able to achieve an accuracy level within ±20%, providing a basis for replacing corroded bolts on steel bridges.

The provisions for avoidance of brittle fracture in various bridge design codes vary in complexity, from the simple tables in North American codes, which present impact energy requirements as a function of steel grade, climate zone, and member type, to the more involved methods presented in the Eurocodes, which allow factors such as plate thickness, demand-to-capacity ratio, and strain rate to be considered. While these provisions generally appear to be meeting the needs of the code users, two issues are noteworthy. The first is that the North American provisions offer less flexibility and guidance for handling unusual situations than the Eurocode methods. The second is that very few studies can be found in the literature attempting to assess the level of reliability against brittle fracture provided by any of the existing design provisions. The current paper presents a study that attempts to make a first step in addressing both issues, using the Canadian design provisions as an example. Specifically, this paper describes a time-dependent Monte Carlo simulation (MCS)-based probabilistic model and then uses it to assess the extent to which the Canadian provisions provide consistent and adequate levels of reliability against brittle fracture over a range of steel grades, plate thicknesses, and climates. Based on the analysis results, areas of potential improvement of these requirements are identified.

To explore the long-term deformation performance of a large-span prestressed concrete continuous box-girder bridge after overload, a three-span prestressed concrete continuous box-girder bridge model with a length of 24.88 m was designed. The long-term deformation performance experiment was conducted for 558 days, and the prestress loss, deflection behavior, strain development, crack increase, and support reaction transformation of the bridge model were analyzed, which could indicate that the deformation of the bridge model developed rapidly in the first 3 months, reaching 60%–70% of the total deformation, and then tended to be stable. The midspan section appeared to reverse arch at the beginning, and with the extension of time, the negative bending moment at the two middle supports decreased owing to the redistribution of the bending moment, resulting in the disappearance of the camber phenomenon. Besides, considering the influence of cracking on the redistribution of the internal force of the structure, the moment modulation coefficient was modified by introducing a damage coefficient. Based on the bending performance test results of the bridge model, the bending moment amplitude modulation method and long-term deflection theory were used for analysis, and the long-term deflection calculation formula of the bridge model was established according to the conjugate beam method. The results showed that the theoretical calculation value of long-term deflection of each midspan section of the test girder was in good agreement with the test results, and the maximum error was less than 15%, which can provide a reference for the safety evaluation of the prestressed concrete continuous box-girder bridges.

A self-centering isolated pier (SIP) with an elliptical rocking interface is proposed to enhance the seismic performance of bridge piers. Pseudostatic tests were conducted on two SIPs (one with and the other without tie bars) to study their damage patterns and hysteretic characteristics. Additionally, a finite-element model of a SIP was constructed to study the effect of SIP parameters on its hysteretic characteristics, such as the long radius of the ellipse, the ratio of the long to the short radii of the ellipse, the distance from the tie bar to the centerline of the pier, and the axial compression ratio. The results indicated that the pier bodies of the two SIPs are in the elastic stage. Increasing the long radius of the ellipse and axial compression ratio can enhance the hysteretic characteristics of the SIP. However, these larger values could lead to yield failure of the pier bottom. Furthermore, an increase in the ratio of the long to the short radii of the ellipse results in a progressively less plump hysteretic curve for the SIP, leading to a reduction in energy dissipation capacity. Nevertheless, an increase in this ratio can improve the self-centering ability of SIPs. The distance from the tie bar to the centerline of the pier has little effect on hysteretic characteristics of the SIP.

This paper uses numerical modeling to evaluate the ability of a geothermal bridge deck deicing system to mitigate concrete deterioration. A model of an experimental bridge deck with embedded heat exchanger tubing was created using COMSOL (version 5.6) Multiphysics software. The model accounts for heat transfer and structural behavior and was validated against temperature and strain data from physical experiments. Inlet fluid temperatures of 10°C and 50°C, reflecting average ground temperatures in Montana, were tested to evaluate the system's effect on deicing, frost action, and thermal stresses. A sensitivity analysis was also completed to investigate the influence of ambient temperature, inlet fluid temperature, and tube spacing in the efficiency of the geothermal deicing system. The results suggest that higher fluid temperatures and reduced pipe spacing improved the effectiveness for deicing and mitigating frost action and strain due to thermal movements, but also increased temperature gradients in the bridge deck. The deicing system shows promise in reducing some mechanisms of concrete deterioration, while staying within allowable limits for others. Numerical modeling provides insights into designing deicing systems to mitigate frost action and thermal stresses in bridge decks.

The traditional nonlinear aerostatic instability of long-span bridges is based on a two-layer iteration method that accurately predicts the structural equilibrium path before the critical buckling point. Due to strong nonlinearity after buckling, this traditional method cannot easily calculate the structural equilibrium and possible bifurcation using either Newton–Raphson or arc-length methods. In this study, a reduced order modeling (ROM) method for long-span bridge aerostatic deformation is proposed to approximate the bridge aerostatic equilibrium path after the critical point. The structural deformation mode shapes are extracted through singular value decomposition performed on the deformation matrix, and the nonlinear structural stiffness matrix is determined through the indirect displacement-based method on the finite-element method (FEM) platform. The ROM method is validated through comparison against the aerostatic deformation by the traditional two-layer iteration method based on FEM. By extending to higher wind speed, the ROM method can approximate the bridge deformation after initial buckling, and pitchfork bifurcation is observed after the structure undergoes rapid deformation growth. The stability of the equilibrium paths is examined through the Jacobian of restoring force vector, and the “snap-through” phenomenon exists for the equilibrium path before the bifurcation point.

Extensive vehicle fires threatening suspension bridges in the last decade have aroused an emerging demand to estimate the fire safety of hanger systems. One of the paramount tasks for evaluating the fire resistance of hangers is to calculate their temperatures. However, as plans always lag behind events, no competent temperature calculation methods are available now for engineers, whether vehicle fire models, thermal boundaries on hanger surfaces, or cross-sectional heat transfer formulations. This paper addresses these three issues and then proposes an integrated framework for assessing the thermal response of hanger systems subjected to vehicle fires. Vehicular fires were classified into five grades, adapted to cars, buses, light goods trucks, medium goods trucks, and tanker trucks, respectively. This hierarchy was validated using 16 full-scale vehicle fire tests in opening or tunnel conditions. An empirical formulation of thermal radiation developed for pool fires was adopted to envelope the heat flux applied by passenger vehicle fires on the hanger surface and was validated using five tests. Radiation from truck fires was constructed using a cuboid solid radiative flame. The spatial heat fluxes surrounding Grade-5 vehicle fires typified by tanker fires were computed using the computational fluid dynamics method validated by two large-scale outdoor trench fires. With these quantitative thermal boundaries on hanger exteriors, the transient temperature across the hanger section was derived using the lumped capacitance method, validated by finite-element models in various scenarios. As a multigrade temperature estimation methodology proposed for hangers subjected to vehicle fires, this method is easy to implement. It can serve in future structural fire design of critical suspension bridges with high exposure risks to vehicle fires.

In this study, the numerical investigation of the fatigue impact factor of critical structural details near the expansion joint for a modified composite steel box concrete girder bridge with corrugated steel webs (MCSBCGBCSW) was conducted using a vehicle–bridge coupled vibration system (VBCVS). Within the VBCVS framework, the MCSBCGBCSW served as the bridge model, and the three-axle vehicle model was employed as the fatigue vehicle loading model. Additionally, deterioration models for pavement roughness and expansion joints were established. The stress impact coefficient IM_S and stress amplitude impact coefficient IM_R of critical structural details near the expansion joint were investigated in detail, considering various vehicle speeds, pavement roughness conditions (PRCs), and expansion joint deterioration degrees (EJDDs). The results demonstrate that the most critical factor affecting IM_S and IM_R of the critical structural details near the expansion joint is the deterioration degree of the PRC rather than the vehicle speed or EJDD, with maximum values of 4.943 and 8.682, respectively, when the PRC is very poor. When the distance between the critical structural details and the expansion joint is within 6 m, a greater dynamic impact action is observed, with a maximum value of 4.067. The fluctuation range of IM_R between the critical structural details decreases and stabilizes as the distance between these details and the expansion joint exceeds 6 m. Based on the IM_R of the critical structural details near the expansion joint, a calculation formula for the design value of IM_R was developed for an MCSBCGBCSW, with a confidence level of 95% compared to the values stipulated by the American Association of State Highway and Transportation Officials specification. These results provide reference information for calculating the IM_R of the critical structural details near expansion joints for MCSBCGBCSWs.