Xu Wang

Compared with conventional normal-concrete (NC) piers, ultrahigh-performance concrete (UHPC) hollow piers may offer a lightweight, high-strength alternative. However, their seismic performance has not been systematically investigated. In this study, quasi-static tests were conducted on four hollow pier specimens, including one NC and three UHPC piers, with material type, stirrup ratio, and wall thickness as key parameters. Test results demonstrate that UHPC hollow piers exhibit superior yield and peak strength, ductility, energy dissipation capacity, and initial stiffness. Numerical models were developed in OpenSees to perform parametric analyses, indicating that reduced stirrup ratio mainly degrades ductility, whereas reduced wall thickness primarily decreases stiffness. Bridge-level fragility analyses further suggested that replacing conventional RC piers with UHPC hollow piers can reduce pier damage probability, while potentially increasing seismic demand on other bridge components. Overall, these findings support the seismic application of UHPC hollow piers.

Ultrahigh-performance concrete circular hollow columns (UHPC-CHCs) offer a lightweight and structurally efficient alternative to conventional solid bridge piers; however, their axial force–bending moment (P–M) interaction behavior remains insufficiently understood. This study develops an OpenSees-based fiber-element modeling framework to generate P–M interaction diagrams incorporating nonlinear compressive and tensile constitutive laws of UHPC. The approach is validated against experimental results from 0.5 m diameter UHPC hollow column tests and a full-scale 2.2 m reinforced concrete (RC) pier under eccentric loading. A case study evaluates the replacement of a solid RC pier with a UHPC hollow column designed for equivalent axial capacity. Results show that UHPC-CHCs achieve up to 40% higher flexural capacity at the balanced point while reducing concrete volume by approximately 70%. Parametric analyses indicate that the balanced axial load is consistently about 0.4 of the pure compression capacity. Flexural capacity is governed primarily by wall thickness ratio and UHPC compressive strength in the compression-controlled region, and by reinforcement ratio and UHPC tensile strength in the tension-controlled region. These findings highlight the structural efficiency of UHPC-CHCs and their potential as an alternative to conventional RC bridge piers.

This paper systematically investigated the mechanical behavior of welded-plate lifting lugs subjected to dynamic and eccentric loadings in steel structure hoisting applications. By integrating on-site stress monitoring throughout the hoisting process with finite element numerical simulations, the dynamic response characteristics of the lugs were comprehensively analyzed. The results indicated that the stress response followed a three-stage evolution comprising elastic growth stage, peak fluctuation stage, and gradual decay stage. Non-uniform loading significantly intensified stress concentrations at the edges of the lifting holes and in the lug–stiffener transition region, with local impact parameters ranging from 1.02 to 1.12 and exhibiting a distinctly non-uniform spatial distribution. A refined finite element model was established, and comparisons with experimental data confirmed that static and dynamic prediction errors were controlled within 5 MPa and 5%, respectively. The optimal lifting angle of 75° was identified, resulting in a significant reduction in dynamic amplification. Furthermore, a small-sample Bootstrap method was introduced to probabilistically correct the dynamic parameter, enhancing design reliability by approximately 10%. Overall, this research provided a more rigorous theoretical foundation and practical design tool for evaluating the safety of lifting lugs subjected to dynamic loading.

Precast piers have been widely adopted worldwide due to their advantages in rapid construction, high quality, and minimal disruption to traffic and the environment. Building upon this concept, precast thin-walled hollow piers offer additional benefits, including further reductions in self-weight and construction costs. Nevertheless, corrosion remains a critical factor affecting the service life of bridge piers. However, current research on precast piers (particularly hollow precast piers) remains limited, especially concerning their durability under corrosive conditions. To study the difference of seismic behaviors between cast-in-place (CIP) and precast thin-walled hollow piers (PTP) under varying corrosion ratios, a total of five piers were tested cyclically after the accelerated corrosion. Although high-strength mortar was poured to connect the precast pier shaft and footing, the detection suggested that the corrosion ratio of rebars within the interface region was nearly 1.9 times that of the rebars within the shaft. Furthermore, the stirrups were corroded much faster than the flexural counterparts, which resulted in rapid loss of strength and ductility of core concrete, and the occurrence of inelastic compressive buckling of flexural rebars. It was found that seismic-resistant capacity of PTP piers degraded faster than that of CIP counterparts when subject to moderate or high corrosion ratios. Based on experimental observations, modeling strategies were developed for corroded piers, incorporating bond-slip behavior, corrosion level assessments for flexural and shear reinforcement, and the mechanical properties of both cover and core concrete as well as corroded rebars. Inelastic compressive buckling of flexural rebars was found to play a critical role in the pinching behaviour of corroded piers. A hysteretic model within the OpenSees platform was adopted and calibrated accordingly. Finally, sensitivity analyses of key parameters were conducted to investigate their influence on the seismic performance of corroded piers.