Seismic control of benchmark cable-stayed bridge using passive hybrid systems

In this study, the seismic response of a benchmark highway bridge is investigated with passive hybrid systems consisting of high damping rubber bearing (HDRB) and linear and nonlinear viscous fluid damper (VFD). The Phase I problem of the benchmark highway bridge is considered for this study. The ground acceleration is applied at all supports of the bridge. A comparative study is performed among the passive control strategies for seismic response control of the highway bridge by calculating various evaluation criteria as mentioned in the benchmark highway bridge problem. A parametric study has been conducted to find different parameters of VFD and HDRB. The optimum damping coefficient and velocity exponent are found for VFD and optimum isolation time period and optimum damping ratio are found for HDRB. The passive hybrid control system consisting of HDRB and nonlinear VFD gives better performance for reduction of base shear, overturning moment, displacement at midspan, bearing deformation and displacement at abutment of the bridge. Hence, it can be deduced that the performance of passive hybrid control system consisting of HDRB and nonlinear VFD is better than individual VFD and HDRB control systems.

In this study, the seismic response of a benchmark highway bridge is investigated with passive hybrid systems consisting of high damping rubber bearing (HDRB) and linear and nonlinear viscous fluid damper (VFD). The Phase I problem of the benchmark highway bridge is considered for this study. The ground acceleration is applied at all supports of the bridge. A comparative study is performed among the passive control strategies for seismic response control of the highway bridge by calculating various evaluation criteria as mentioned in the benchmark highway bridge problem. A parametric study has been conducted to find different parameters of VFD and HDRB. The optimum damping coefficient and velocity exponent are found for VFD and optimum isolation time period and optimum damping ratio are found for HDRB. The passive hybrid control system consisting of HDRB and nonlinear VFD gives better performance for reduction of base shear, overturning moment, displacement at midspan, bearing deformation and displacement at abutment of the bridge. Hence, it can be deduced that the performance of passive hybrid control system consisting of HDRB and nonlinear VFD is better than individual VFD and HDRB control systems.

This paper presents a numerical study on the seismic damages and failure modes of a trial designed cable-stayed bridge (CSB) with a central span of 1,400 m under earthquake excitations. A passive hybrid control system is proposed to mitigate the seismic damage and improve the failure mode of the CSB; this is composed of a passive control system and several supplemental nonstructural links used as sacrificial energy dissipation devices. The passive control system, including conventional viscous fluid dampers (VFDs), is presented for comparison with the hybrid system. The results show that the top and bottom regions of the tower are simultaneously subjected to severe damage under extreme ground motion, indicating that the tower experiences an unexpected failure mode with double plastic hinges, whereas the piers experience a typical flexural failure mode, with only one plastic hinge concentrated at the bottom region of the pier in the transverse direction. The effects of the proposed passive hybrid control system on seismic damage control are superior to those of the passive control system with VFDs. As a result, the passive hybrid control strategy can successfully control seismic damage and effectively improve the failure mode of the CSB so that its seismic performance meets damage control targets based on seismic damage criteria.

The present paper deals with the optimum performance of the passive hybrid control system for the benchmark highway bridge under the six earthquakes ground motion. The investigation is carried out on a simplified finite element model of the 91/5 highway overcrossing located in Southern California. A viscous fluid damper (known as VFD) or non-linear fluid viscous spring damper has been used as a passive supplement device associated with polynomial friction pendulum isolator (known as PFPI) to form a passive hybrid control system. A parametric study is considered to find out the optimum parameters of the PFPI system for the optimal response of the bridge. The effect of the velocity exponent of the VFD and non-linear FV spring damper on the response of the bridge is carried out by considering different values of velocity exponent. Further, the influences of damping coefficient and vibration period of the dampers are also examined on the response of the bridge. To study the effectiveness of the passive hybrid system on the response of the isolated bridge, it is compared with the corresponding PFPI isolated bridges. The investigation showed that passive supplement damper such as VFD or non-linear FV spring damper associated with PFPI system is significantly reducing the seismic response of the benchmark highway bridge. Further, it is also observed that non-linear FV spring damper hybrid system is a more promising strategy in reducing the response of the bridge compared to the VFD associated hybrid system.

Abstract: This study focuses on the seismic response of a three-span deck slab RCC T-Girder bridge with and without LRB (Lead Rubber Bearing) and in combination with LRB and FVD (Fluid Viscous Damper). The bridge is subjected to AASHTO, IRC design standards, and IRC Class A vehicle load. Linear time history analysis using CsiBridge and SAPfire is conducted to assess the bridge's seismic behavior. Excessive deck displacement, which can lead to deck failure and bridge closure, is a key concern. The study utilizes finite element analysis with Csibridge and incorporates viscous dampers throughout the bridge. The findings show that the presence of supplemental dampers significantly reduces pier top displacements. Base shear, deck displacement, pier response, and structural time period are the primary response parameters examined. The effectiveness of different isolation system configurations is compared to the non-isolated bridge in terms of these response characteristics. The study offers suggestions for design improvements to enhance the structure's performance.

Passive hybrid systems for earthquake protection of cable-stayed bridge

Earthquake response of benchmark highway bridge, isolated with variable frequency pendulum isolator (VFPI) is investigated under six earthquakes, using a simplified lumped mass finite element model. The isolators are installed between deck-ends and abutments. Seismic response of the bridge with VFPI is compared with that of the bridge with the friction pendulum system (FPS). Parametric studies are carried to find the optimum values of coefficient of friction and isolation period of the FPS; and frequency variation factor, initial time period and coefficient of friction of VFPI. The response of the bridge with VFPI is compared with the uncontrolled case, with FPS, and that controlled by alternate sample control strategies. Significant reductions in base shear, base moment, deck displacements and bearing displacements are observed using FPS and VFPI. It is concluded that these isolators are quite effective in substantially reducing peak response quantities of the bridge, comparable to that of the sample controllers.

This paper presents hybrid control systems for seismic protection of a phase II benchmark cable‐stayed bridge. Because multiple control devices are operating, a hybrid control system could alleviate some of the restrictions and limitations that exist when each system is acting alone. In this study, two types of hybrid control system are considered to protect the cable‐stayed bridge under seismic events. Lead–rubber bearings are used as passive control devices to reduce the earthquake‐induced forces in the bridge and hydraulic actuators or magnetorheological fluid dampers are used as additional control devices to further reduce the bridge responses, especially deck displacements. Numerical simulation results show that the performances of the proposed hybrid control systems are superior to those of the passive control system, and slightly better than those of the active or semi‐active control system alone. Furthermore, it is verified that the hybrid control systems are robust to mass or stiffness parameter perturbation, and there is no sign of instability in the overall system due to the passive control part. Therefore, the proposed hybrid control systems could effectively be applied to seismically excited cable‐stayed bridges. Copyright © 2003 John Wiley & Sons, Ltd.

This paper presents a comparative seismic performance assessment of super-elastic-friction base isolator (S-FBI) systems in improving the response of bridges under near-field earthquakes. The S-FBI system consists of a steel-Teflon sliding bearing and a superelastic shape memory alloy (SMA) device. The other isolation systems considered here are lead rubber bearing (LRB), friction pendulum system (FPS), and resilient-friction base isolator (R-FBI). Each isolation system is designed to provide the same isolation period and characteristic strength. Nonlinear time-history analyses of an isolated bridge are performed to compare the performance of various isolation systems. The results indicate that the S-FBI system shows superior performance in reducing deck displacement response and effectively limits permanent bearing deformation, whereas residual deformations are present for the other isolation systems in some cases. It is also observed that the LRB system has the largest deck drifts while the FPS system and R-FBI system produce the smallest peak deck acceleration and base shear.

This paper presents an integrated passive-active (i.e. hybrid) system for seismic response control of a cable-stayed bridge. Since multiple control devices are operating, a hybrid control system could alleviate some of the restrictions and limitations that exist when each system is acting alone. Lead rubber bearings are used as passive control devices to reduce the earthquake-induced forces in the bridge and hydraulic actuators are used as active control devices to further reduce the bridge responses, especially deck displacements. In the proposed hybrid control system, a linear quadratic Gaussian control algorithm is adopted as a primary controller. In addition, a secondary bang-bang type (i.e. on-off type) controller according to the responses of lead rubber bearings is considered to increase the controller robustness. Numerical simulation results show that control performances of the integrated passive-active control system are superior to those of the passive control system and are slightly better than those of the fully active control system. Furthermore, it is verified that the hybrid control system with a bang-bang type controller is more robust for stiffness perturbation than the active controller with a μ-synthesis method, and there are no signs of instability in the over-all system whereas the active control system with linear quadratic Gaussian algorithm shows instabilities in the perturbed system. Therefore, the proposed hybrid protective system could effectively be used for seismically excited cable-stayed bridges.

This paper investigates the performance of a variable radius friction pendulum system (VRFPS) with supplementary damping using viscous fluid dampers (VFD) to control the seismic response of bridges.A VRFPS is similar to a frictional pendulum system (FPS), but the curvature of the sliding surface is varied, and it becomes the function of the sliding displacement.The bridge is seismically isolated with a VRFPS between the superstructure and the pier, and a VFD is added between the abutment and superstructure.Effectiveness of the proposed system is studied for a three-span continuous bridge isolated with a VRFPS and VFD hybrid system.The performance of a proposed system is compared to a corresponding performance of a hybrid system consisting of a conventional FPS with a VFD.The results of the numerical simulation showed that supplementary damping reduces the seismic response of the isolated bridge.Further, a hybrid system consisting of a VRFPS and a VFD is found to be more effective than a FPS and a VFD hybrid system for seismic control of bridges.

Highway bridges play a vital link role in surface transportation network, and their failures not only cause disruption of service but also danger people life. Seismic base isolation is an important technique that is used for reduce the seismic vulnerability by decreasing the seismic demand instead of increasing the seismic capacity. Present work deals with study of response of bridge using seismic control systems. For present study, a two-span prestressed concrete box girder highway bridge is considered and analyzed for seismic forces using SAP2000 software. The seismic response and behavior of Box Girder Bridge is studied by linear time history analysis using Newmark’s beta method. For the analysis four different ground motion data selected and scaled for target spectra as per zone IV. The highway bridge is isolated with Lead Rubber Bearing (LRB). The response of bridge system under earthquakes has been compared with the corresponding bridge with and without the isolation system. It is observed that LRB is highly effective for controlling not only the seismic response of the bridge but also include the structural response on the cost of slight increase in the displacement of the deck.

Recent earthquakes have illustrated the vulnerability of bridges to damage and collapse. One of the emerging tools for protecting bridges from the damaging effects of earthquakes is the use of isolation systems. However, to date, few adequate models exist to evaluate the comparative viability of the two main isolator types: sliding and elastomeric. This paper compares sliding versus elastomeric seismic isolation of a typical Multi-Span bridge to enhance the understanding of their unique impacts on bridge response. The Friction Pendulum System (FPS) and the Lead Rubber Bearing (LRB) are selected as representative examples of sliding and elastomeric isolators, respectively. Detailed isolator models that can account for the in-plane and vertical coupling of the response are developed in OpenSees. Particular emphasis is given to the distinct vertical load dependency modeling of the two isolators. A seismic evaluation of the bridge, isolated in one case with the LRB and in another case with the FPS, is performed for a hazard level of 7% in 75 years using a nonlinear three-dimensional (3-D) analytical model. Maximum isolator forces and displacements, and column drifts are selected as response quantities. The results show that despite attaining similar structural periods, there are notable differences among the two seismic isolation scenarios for the bridge. The FPS placed larger demands on the columns however acquired smaller deformations compared to the LRB. The LRB response is influenced less from the vertical components of ground motions compared to the FPS but susceptible from a stability point of view.

Seismic performance of isolated buildings with friction spring damper

ABSTRACTEarthquake response mitigation of base-isolated (BI) buildings with a tuned mass damper (TMD) is investigated. Two-dimensional reinforced concrete buildings having multiple degrees of freedom are numerically modelled. The placement of a TMD is varied on different floor levels and the building response under earthquake excitations is studied. The laminated rubber bearing (LRB), lead rubber bearing (N-Z), friction pendulum system and resilient-friction base isolator (R-FBI) are used as isolation systems for the buildings with 5, 10 and 15 floor levels. Newmark’s step-by-step method of integration is used for solving differential equations of motion of the coupled buildings. Installation of a TMD at different story of the BI buildings mitigates the acceleration at the top level and displacement at bearings. It is found that at increased time period of the isolators the effectiveness of the TMD is reduced. Further, for low-rise buildings, the placement of TMD has no significant role in reducing the response of the buildings. However, the efficiency of TMD placement is more noticeable for buildings with a larger number of stories.