Thousands of coastal reinforced concrete structures using HRB400 bars have served for over three decades in China. Their reinforcement simultaneously endures chloride corrosion and seismic action, yet studies on performance degradation remain limited. This paper investigates the low-cycle fatigue (LCF) behavior of HRB400 bars under various strain amplitudes, systematically analyzing corrosion morphology, cyclic stress–strain response, fatigue life, and underlying mechanisms. Corrosion is induced by an adjusted accelerated method that replicates field conditions. Observations reveal that corrosion pits act as primary crack initiation sites. Crack paths and fracture surfaces progressively follow the local pit geometry as strain and corrosion grow. The detrimental effect of corrosion on LCF life is more pronounced for smaller bars. At a γ of around 8%, 20 mm bars lose 60.7% of the half cycles to failure at ε = ±1.5%, but only 37.5% at ε = ±5.0%. Predictive corrosion-inclusive strain amplitude (ε_a)–fatigue life models are proposed, yielding R² = 0.952 (16 mm) and 0.928 (20 mm). A unified LCF predictive model, calibrated on a database of 310 corroded/uncorroded bar tests, is established. The final model comprehensively considers the characteristics of rebars, seismic action, and corrosion damage, improving the conventional relationship between LCF life and seismic loading. This work contributes to the understanding of the fatigue behavior of HRB400 bars and provides support for time-dependent seismic reliability analysis of aging reinforced concrete structures in corrosive environments.

Modern landscape pedestrian bridges, characterized by distinctive landscape features, cause pedestrians to gather in certain places. This changes the loading distribution on the bridge, consequently impacting the vibration response of the structure. Due to the high sensitivity of pedestrians to vibration, it is essential to explore the effects of assembled crowd on vibration comfort of footbridges. The present study adopts the pedestrian load model of ISO 10137 to conduct the acceleration response analysis under both static and dynamic pedestrian loads. The presence of assembled crowd effect significantly influences the bridge vibration response by altering pedestrian pacing frequency. It increases peak acceleration within the pacing frequency range of 1.8 Hz to 2.0 Hz. However, at 2.1 Hz, pedestrian gathering significantly reduces the peak acceleration. Under different pacing frequencies, the effect of assembled crowd on the comfort of bridge traffic is completely opposite. Besides, the impact of pedestrian flow direction is also considered. The “double peaks” phenomenon in the acceleration response due to bidirectional pedestrian flow may cause the root mean square (RMS) acceleration to surpass the comfort thresholds. However, the peak acceleration is considerably lower compared to unidirectional flow, which is advantageous for traffic comfort. This paper may provide insights into understanding the dynamic performance of landscaped footbridges when assembled crowd occurs and support better designs.