Many in-service bridges with steel–concrete composite beams are currently aging and experiencing performance deterioration. Under long-term cyclic loads from traffic on bridges, headed shear studs in steel–concrete composite beams are vulnerable to fatigue damage. The comprehensive understanding of fatigue behaviors and the feasible detection of fatigue damage of headed shear studs is, thus, crucial for the accurate numerical simulation of the fatigue crack propagation process. The paper, thus, experimentally investigates the fatigue behaviors of headed shear studs through push-out tests of three specimens. The fatigue failure modes and cyclic strain evolution of specimens are analyzed. The fatigue lives of headed shear studs are compared with the S–N curves of the AASHTO, Eurocode 4 and BS5400 codes. The fatigue crack details of shear studs in push-out tests are then detected using the ultrasonic non-destructive testing. The results show that the root fracture is the main fatigue failure mode of shear studs under fatigue loading. The fatigue life estimations based on the three current codes (i.e., AASHTO, Eurocode 4 and BS5400) can be safely guaranteed only with different safety redundancies. The strain at the shear stud with fatigue damage shows a consistent increasing trend followed by decreasing behavior after reaching the peak value with the loading cycles. Moreover, the feasibility of the ultrasonic non-destructive testing with the combination of a strain measurement for fatigue crack details detection of headed shear studs in composite beams is proved.

High-rise reinforced concrete chimneys, used to expel waste gases, are commonly used structures in facilities such as chemical and power plants. Chimney structures located in marine areas are prone to corrosion. Regardless of the causing factors, corrosion causes the degradation of the strength of steel bars, creating a detriment to the safety of the chimney structure. A more severe situation is a corroded chimney structure that is subjected to other natural hazards such as strong winds and earthquakes. Very few documented research studies have evaluated the seismic performance of chimney structures under the combined hazards of corrosion and seismic loading. In this study, seismic fragility was used to compute the probability of damage to two corroded chimney structures of differing heights under near-fault ground motions. In the fragility analysis, the uncertainties of materials and ground motions were considered. Based on the numerical simulation results, fragility curves were generated. The results indicated that corrosion had a significant effect on the seismic performance of chimney structures. With an increased corrosion level, the probability of moderate damage, major damage, and collapse increased significantly if the intensity of the ground motion was greater than a threshold value. The threshold value was determined by the corrosion severity. Therefore, it is suggested to inspect the severity of corrosion and adopt measures for reinforcement to minimize the impact of that corrosion on the stability of the chimney, especially in areas susceptible to earthquakes.

Seismic fragility analysis is often conducted to quantify the vulnerability of civil structures under earthquake excitation. In recent years, besides mainshocks, strong aftershocks have been often witnessed to induce structural damage to engineered structures, including bridges. How to accurately and straightforwardly quantify the vulnerability of bridges due to sequential mainshocks and aftershocks is essential for an efficient assessment of bridge performance. While recognizing the limitation of existing methods, this paper proposes a mainshock integrated aftershock fragility function model, which empirically encodes the effects of mainshocks and retains the simple form of traditional fragility curves. A pile foundation-supported bridge system is modeled considering seismic soil-structure interaction to demonstrate the proposed fragility model. Numerical examples show that the resulting fragility curves incorporate the initial value for the probability of collapse of the bridge system due to a mainshock and the effects of the variable aftershocks conditional on the mainshock. Statistical analysis confirms that the proposed model fits the simulated vulnerability data (e.g., seismic intensities of aftershocks and the response demands conditional a select mainshock ground motion) both accurately and robustly.

Engineered Cementitious Composite (ECC) has emerged as a promising solution with which to address the longstanding challenge of cracking in the tensile zone of reinforced concrete beams. This study conducts an experimental and analytical exploration of the flexural performance of ECC-concrete composite beams reinforced with hot-rolled ribbed steel bars. Sixteen beams, featuring diverse reinforcement ratios and ECC layer thicknesses, underwent rigorous testing through a four-point bending setup. The experimental findings underscore a substantial improvement in crack resistance and flexural bearing capacity of ECC-concrete composite beams reinforced with steel bars. Building on these results, a theoretical model was formulated to predict the moment-deflection responses of ECC-concrete composite beams incorporating steel bars. Furthermore, practical and simplified methods were introduced to predict flexural bearing capacity and effective moment of inertia, as well as anticipate failure modes, offering a user-friendly approach for engineering applications. Validation of the proposed approaches was achieved through simulation results, demonstrating a high degree of accuracy when compared with the experimental outcomes. Moreover, the average crack width at serviceability limit states of composite beams was sensitive to specimen size and the yield strength of steel bars, and a size effect was also observed for ductility expressed as deflection.

Previous earthquake events have shown that chimneys are one of the most fragile structures. Studies have focused on the seismic behavior of reinforced concrete (RC) chimney structures subjected to earthquake load only along the horizontal direction. However, the vertical component of strong ground motion has been proven to damage or completely destroy civil structures. Therefore, it is essential to determine the failure probability of RC chimneys under both horizontal and vertical directions. In this study, the seismic behavior of an RC chimney was studied through seismic fragility analysis, wherein a fragility model based on the intensity ratio between the vertical and horizontal components was proposed. In the fragility analysis, different intensity ratios of near‐fault ground motions (NFGMs) between the vertical and horizontal components were considered. The findings indicate that the NFGMs along the vertical and horizontal directions significantly affect the failure probability if the intensity of the horizontal component is above a certain threshold. Moreover, the failure probability increases with the intensity of the vertical and horizontal ground motions. Therefore, the influence of the combination of the vertical and horizontal components of the NFGMs should be considered in the safety evaluation of RC chimney structures.