مقاله انگلیسی رایگان در مورد بهینه سازی مبتنی بر سیستم میراگر ویسکوز در پل کابلی – Sage 2018

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.

Introduction

In recent decades, cable-stayed bridges have been widely constructed around the world because of their aesthetics, efficient use of construction materials, and fast construction period. Many studies focused on the dynamic characteristics of cable-stayed bridges subjected to earthquake (Bruneau, 1992; Ren and Obata, 1999; Wilson and Gravelle, 1991). These studies showed that the seismic demand of towers would experience a significant increase in terms of bending moment and shear forces when restraining the bridge deck completely at tower locations. When there are no additional restraints in the longitudinal direction, larger deck displacement would occur during earthquake, resulting in pounding and unseating (Aiken and Kelly, 1992), which is not desirable for performancebased earthquake engineering. Therefore, there is an agreement among many researchers that mitigation devices should be equipped to allow some sort of deck movement, which would lead to the balance of the force and displacement demand of the cable-stayed bridges (Sharabash and Andrawes, 2009). Many researchers have conducted work on the isolation devices to reduce the overall seismic response of cablestayed bridges (Ali and Abdel-Ghaffar, 1994; Sharabash and Andrawes, 2009; Zhang et al., 2009; Zhu and Qiu, 2014); however, these studies are determined methods, which could not account for the earthquake uncertainties, because of the unpredictable nature of seismic events (Zhang and Huo, 2009). In order to consider the uncertainties of earthquake and structure information, it is a widely used approach to develop probabilistic model in the form of fragility curves (Basoz et al., 1999; Choi et al., 2004; Hwang et al., 2001; Nielson, 2005; Padgett and DesRoches, 2008; Pan et al., 2007; Ramanathan, 2012; Shinozuka et al., 2000a, 2000b). Fragility function is quite useful for comparing and selecting mitigation strategies. Casciati et al. (2008) evaluated the seismic vulnerability of components (bending moment, shearing force, deck displacement, cable strain, etc.) of a cable-stayed bridge with passive hysteretic devices in terms of damage exceedance probability. Barnawi and Dyke (2014) developed component (deck displacement, overturning moment, deck shear, etc.) fragility curves of a benchmark cable-stayed bridge equipped with response modification systems. These studies evaluated the effectiveness of the mitigation devices using component fragility separately, rather than the system fragility of the overall bridge performance. For example, some kind of isolation devices might decrease the fragility of bending moment, but would increase the fragility of deck displacement. Hence, a comprehensive evaluation of seismic isolation on bridges should be based on system-level fragility instead of on the component level. It is still worth noting that the above-mentioned studies did not emphasize on selecting optimum mitigation devices to achieve the best performance of cable-stayed bridges.