Journal of Bridge Engineering

Highway bridges are vital infrastructure engineering whose safety severely influences the safety and stability of society. Damage identification, as the core part of structural health monitoring, plays an essential role in highway-bridge maintenance to help detect potential damage. There have been many studies conducted, with various damage identification methods proposed. However, there are still several problems with the durability of sensors and the reliability of methods, such as the issue of false alarm. Under this background, this paper proposed a multi-cross-reference method for highway-bridge damage identification method utilizing long-gauge fiber Bragg-grating (FBG) sensors. Through several numerical simulations and on-site testing, its feasibility under various conditions was verified. The results demonstrated that through this method the location of damage can be accurately identified with error of less than 5% in identified damage extent.

Four variable-depth pier cap beams were constructed and tested. These specimens were designed to have reinforcement details that had similar features to two different types of pier cap beams used in the Champlain Bridge in Montréal, Canada. The objectives were to examine the behavior of variable-depth cap beams at service loading and at failure to analyze the effectiveness of crack control reinforcement and inclined reinforcement, as well as to investigate the influence of added external horizontal post-tensioning. The observed cap beam responses were compared with two prediction models: sectional analyses and nonlinear finite-element analyses. The amount of crack control reinforcement was important in controlling crack widths at the service load level. The inclined shear reinforcement was found to be effective in resisting shear. Horizontal post-tensioning was effective in reducing crack widths and increasing the overall stiffness of the cap beams but did not lead to significant increases in shear strength. Failure shears predicted by the sectional analyses were conservative. Nonlinear finite element analyses gave good predictions of the complete behavior and strength of the cap beams.

The stochastic response of cross-sea bridges is susceptible to the significant effects of wind and waves. In this study, an efficient probabilistic assessment framework for cross-sea bridges was developed by combining a wind–wave bridge (WWB) model with machine learning methods. The WWB model was first proposed based on finite element analysis (FEA) where the wind and wave parameters were obtained by structural health monitoring (SHM) and then correlated using copula models. The coupling effects in the wind–bridge and the wave–bridge were solved using the Newmark-β method. Taking a cable-stayed bridge as an example to illustrate the accuracy and efficiency of the proposed method, the WWB model was established and then performed to compute the dynamic response at different positions on the bridge. To deal with the time-consuming issues, a learning machine including support vector regression (SVR) and Latin hypercube sampling (LHS) was implemented to substitute further finite element calculations. The WWB model was simplified parametrically as response surfaces for stochastic wind and wave variables, and probabilistic simulations with a large number of samples were performed. The results show that the wind load controlled the displacement response of the girder, while the wave load dominated the base shear response of the foundation. The bridge response, considering when wind and waves were correlated, was 6%–25% lower than that when wind and waves were independent. Further response contour analysis demonstrated a direct relationship between the environmental parameters and the structural response to quickly estimate the bridge's maximum response in different return periods.

This paper presents a novel approach to measuring shear stresses within embedded studs and investigates the effects of stud clustering and steel flange surface friction on resulting stud demands during fatigue loading. In this study, thin flexible transverse pressure gauges are attached to the studs of composite beam specimens to measure the peak contact pressure and allow calculation of stud shear demands from existing elasticity theory. A total of three large-scale composite girders are fatigue tested, representing both uniform and clustered stud configurations and two levels of flange surface friction. One noncomposite beam test is also performed to better understand friction contributions to composite action. Results from the fatigue testing and instrumentation suggest that stud demands estimated by the AASHTO provisions are conservative. All composite specimens survived over 4,500,000 fatigue cycles at an applied stress range of 67.6 MPa (9.8 Ksi) while maintaining full composite action and experiencing negligible increases in slab slip. Stud shear stress measurements for specimens having a Class A flange friction surface (cleaned mill-scale surface) experienced stud demands that were nearly 66% lower than those estimated by the AASHTO provisions which neglect friction effects. When PTFE sheeting was added to reduce friction at the steel–concrete interface, AASHTO stud demand estimations were within 10% of measurements. Modifications to the current AASHTO stud fatigue demand provisions are proposed.

This study evaluated the influence of crack opening size on the corrosion initiation and propagation of reinforcing steel bars in precracked concrete as a result of chloride ingress. Uncracked (reference) and transversely cracked reinforced concrete beam specimens were prepared for laboratory experiments. Specimens were fabricated with crack mouth opening widths of 0.1, 0.3, and 0.7 mm (0.004, 0.012, and 0.028 in.). A ponding well was installed on top of the specimens above the cracks; specimens were subjected to two-week wet and two-week dry cycles with 3% by weight NaCl solution in the pond. Electrochemical tests and visual inspections were conducted to evaluate the condition of the reinforcing bars. The results after approximately 550 days of the experiment showed that steel in specimens with a 0.7 mm (0.028 in.) crack opening exhibited more severe corrosion than steel in specimens with a 0.3 mm (0.012 in.) crack opening. Corrosion behavior of steel bars in specimens with 0.1 mm (0.004 in.) crack opening was distinct. Bars in these specimens had high corrosion rates initially, but as time progressed, the corrosion rate decreased significantly.

The structural behavior of the anchorage zone is a key issue in prestressed ultra-high performance concrete (UHPC) box-girder bridges. This study investigates the mechanical behavior of a diaphragm–blister integrated anchorage system (DBIAS) used in UHPC box-girder bridges through the full-scale model test. Parametric analyses were also conducted using test-validated finite-element models. Experimental results show that no visible cracks have emerged when the applied load reaches 4,700 kN, which is 1.36 times the design value. Although the strain in some local areas has entered into the tensile strain-hardening domain of UHPC under the prestressing force, the whole structure still works well. The contribution of strain-hardening behavior of UHPC to the loading capacity of anchorage blister is 8.7%, based on nonlinear finite-element analysis. Therefore, the tensile strain capacity of UHPC may be taken into consideration in the design so as to fully make use of the material strength. Compared with the conventional independent blister anchorage system, the local effects on the anchorage zone are significantly reduced by setting anchorage diaphragms and transverse ribs in a DBIAS. The increase in the width and longitudinal spacing of adjacent diaphragms shows effectiveness in relieving the stress concentration in the anchorage zone. However, local effects will not be continuously reduced when the width of the diaphragm is more than six times that of the anchorage blister or the spacing between the diaphragm and the transverse rib exceeds a certain distance (2 m in the present study case).