This study explored an optimal intensity measure for probabilistic seismic demand models of multiple components in cable-stayed bridges subjected to pulse-like ground motions. To achieve this goal, this study selected a cable-stayed bridge as a case study. Due to the limited number of recorded motions, artificial pulse-like motions were generated using an existing simulation method to obtain a reliable estimate of probability seismic demand models. For the subject bridge, seismic demand analyses were undertaken under a combined set of recorded (a total of 121 pairs) and artificial (a total of 121 pairs) ground motions. In total, seven structure-independent intensity measures and six types of engineering demand parameters representing maximum component responses were considered in this study. Peak ground acceleration (PGA) tended to be appropriate for the short-period components (i.e., pier and upper side of pylons), whereas peak ground velocity was found to be the optimal intensity measure for long-period components (i.e., lower side of pylons, cables, and displacement-related seismic demands). The lower side of pylons is more vulnerable than their upper side, and on the basis of efficiency, practicality, proficiency, sufficiency, and hazard computability, peak ground velocity appears to be the best intensity measure of the cable-stayed bridge subjected to pulse-like ground motions. However, PGA can be chosen as the ideal intensity measure for the piers.

This study presents a methodology to evaluate the optimal parameters of fluid viscous damper for cable-stayed bridges using the system-level fragility assessment approach. Instead of investigating the impact of different isolation devices on the component’s vulnerability separately, this study focuses on evaluating the optimal parameters of fluid viscous damper to achieve the best overall performance of cable-stayed bridge as a system. Numerical model of a cable-stayed bridge with the most common configuration in China is established using OpenSEES that can account for their nonlinear response and uncertainty treatment. A joint probabilistic seismic demand model and Monte Carlo simulation are employed to obtain the system fragility of cable-stayed bridges by accounting for the contribution of multicomponents to the global damage state. The system-level fragility curves and component fragility curves are compared before and after the application of fluid viscous damper with different parameters. The results indicate that a given parameter of the fluid viscous damper may have a negative impact on some components, yet lead to a better performance of the bridge as a system. Thus, in order to obtain comprehensive knowledge of bridge performance and derive the accurate optimal parameters of fluid viscous damper, it is necessary to consider the fragility based on bridge system.

In order to address the difficulty in determining the seismic damage probability of continuous girder bridges under construction, the seismic vulnerability analysis method of the construction state is proposed in this study. Firstly, taking a long-span prestressed concrete composite box girder bridge with corrugated steel webs (OSW) as an example, the finite element models (FEMs) of dynamic calculation in different phases of cantilever construction are simulated by OpenSEES. Secondly, by selecting reasonable seismic waves and seismic intensity measures, the non-linear time-history analysis is carried out, followed by the demand parameters and damage indexes suitable for the construction state proposed. Finally, the probabilistic seismic demand model (PSDA) of the continuous box girder bridge during the construction stage is constructed by using the “cloud method”, and the seismic vulnerability curves of the piers and temporary bearings are established to evaluate the seismic performance during the construction stage. The results indicate that the damage probability of piers and temporary bearings increases with the progress of construction. The initial formation of the cantilever structure and the sudden change in the size of the construction segmental girder correspond to a high probability of damage, and seismic protection measures should be strengthened during this construction state. Moreover, significantly higher damage probability of the components under construction compared to the completed bridge after it is built.

This study aims to investigate the seismic behavior of concrete-filled steel tubular (CFST)-laced piers; after verifying the model through engineering tests, the simplified finite element models (S-FEM) and refined ones (R-FEM) with CFST-laced piers are developed in this manuscript, respectively. Through comparison, it is found that the S-FEM can effectively improve analyzing efficiency while meeting the requirements of engineering analysis accuracy. In addition, the seismic response of assembled flange-connected CFST-laced piers bridge was studied based on the S-FEM, and different structural parameters, including pier height, axial compression ratios, steel ratios of CFST columns, steel lacing tube arrangement, and longitudinal slope, are considered to optimize the bridge design scheme. Results indicate that the parameters of 0.1 axial pressure ratios and 1:30 longitudinal slope show superior seismic performance. Meanwhile, the peak axial force and peak bending moment of CFST column limbs occur at the pier bottom, and the flanges, which are subject to larger bending moments, are generally located at the two connection positions above the pier bottom.

To accurately predict the shear-bearing capacity of UHPC beams, it is crucial to quantify the shear contribution of the fiber bridging effect and UHPC compression zone. Nevertheless, it should be noted that the shear contribution of UHPC in the compression zone is not fully considered in most existing calculation methods, and the probability distribution of fibers within the matrix is also not taken into full account, which reduces the calculation accuracy of the shear bearing capacity of UHPC beams. In this paper, a UHPC beam shear test database containing 247 samples was created, and the influencing factors on the shear capacity of UHPC beams, such as the shear span ratio, the web reinforcement ratio, and the volume fraction of steel fiber, were analyzed. It was found that the ratio of cracking load to ultimate load ranges from 0.2 to 0.6, and the failure in the compression zone of UHPC beams can be divided into diagonal tension failure and shear compression failure. Based on the failure mechanism of the compression zone, considering the contribution of fiber micro tensile strength, a formula for calculating the shear-bearing capacity of UHPC beams with and without web reinforcement was proposed. Verified by experimental data, the proposed formula accurately predicts the shear-bearing capacity of UHPC beams. In comparison with other shear capacity formulas in current design codes, the proposed formula in this paper provides a higher prediction accuracy.