Ground Motion Frequency Insensitivity of Bearing-Supported Pedestrian Bridge with Viscous Dampers

Mehrabi

2021

Metals

Normally, Laminated Rubber Bearing Pads (LRBPs) are directly placed between girders and piers and their role is to provide the bridge span with horizontal movement, and to transmit the gravity loads from the deck to the piers. Although not designed for seismic loads, they can act as a fuse, partially isolating the substructure from the superstructure and keeping the piers intact during earthquakes. However, recent investigations show that large relative displacement of superstructure against substructure caused by sliding at bearing (sliding between girders and LRBPs) can cause expansion joint failure or even bridge span collapse. Accordingly, proper restrainers should be selected to prevent large displacement. Among all types of restrainers, viscous dampers as passive energy dissipation devices have shown a great capacity in damping earthquake energy. This study investigates the effectiveness of a VD-LRBP system, a viscous damper in conjunction with LRBPs, in dissipating energy and reducing the displacement of the superstructure with reference to the substructure caused by sliding at bearing during a seismic event. A Finite Element (FE) model was first developed and validated using available experimental and numerical results. With the validated model, a 3D Nonlinear Time History Analysis (NTHA) was conducted on a reinforced concrete bridge model under various records of earthquakes using OpenSees, an open-source finite element software. The relative displacement histories were recorded for the bridge in two cases: 1- with only LRBPs and 2- with viscous dampers and LRBPs (VD-LRBP system). The results of this study show that applying viscous dampers can reduce the relative displacement of the superstructure with reference to the substructure for up to 60 percent. As importantly, it can also reduce the residual displacement after the earthquake to near zero.

Section: El Centro Ground Motion Recordmentioning

confidence: 97%

Section: Kobe Ground Motion Recordmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Application of Viscous Damper and Laminated Rubber Bearing Pads for Bridges in Seismic Regions

Mehrabi

2021

Metals

“…In the case of this bridge, dynamic response along the transverse direction is crucial since excessive shear displacement in the bearings will result in the unseating failure of the bridge deck [29]. To mitigate the seismic responses, a pair of BRBs combined with a gap in the symmetrical 'Chevron' configuration can be installed between the inner sides of limbs and the deck bottom.…”

Section: Modelling Of Isolation Systemsmentioning

confidence: 99%

Performance-Based Seismic Design of Hybrid Isolation Systems with Gap-Tunable BRBs for Bearing-Supported Bridges

et al. 2022

Self Cite

This study proposes a class of hybrid isolation systems constructed by combining Buckling Restrained Braces (BRBs) with Rubber Bearings (RBs) or Lead Rubber Bearings (LRBs) for mitigating the seismic responses in bearing-supported bridges under strong earthquakes. Firstly, two different hybrid isolation systems (RB–BRB and LRB–BRB) were preliminarily designed based on the energy-conservation concept in the case of a bridge with Y-shaped piers, which can meet all the energy demands at different seismic hazard levels. Further, seismic evaluations were conducted on the bridges with the LRB, RB–BRB, and LRB–BRB isolation systems based on the nonlinear time history analyses. The proposed hybrid isolation systems show a two-phase energy dissipation behavior, which facilitates the systems to reduce the seismic responses remarkably under different earthquake scenarios and achieve most of the performance objectives corresponding to the code-specified hazard levels. Finally, based on fragility analyses, the effects of the gap spacing and the stiffness ratio of the BRB to the pier were investigated with respect to the failure probability in the case of a bridge with LRB–BRB. It has been validated that the seismic performances of this study’s bridge can be improved considerably with the optimized gap spacing and BRB stiffness.

“…Using this method, some researchers have evaluated the seismic performances of bridges at the corresponding shaking intensities [24,25]. However, previous works were mainly focused on the seismic evaluation of the typical highway or railway piers where additional dampers were used for energy dissipation [26,27]. There are scarce reports on the seismic evaluation of pier systems by utilizing CFST members for extra energy dissipation.…”

Section: Introductionmentioning

confidence: 99%

Energy Dissipation Enhanced by Multiple Hinges in Bridge Piers with CFST Y-Shaped Fuses

Liu

Guo

et al. 2022

Symmetry

Self Cite

Concrete-filled steel tubular Y-shaped (CFST-Y) piers are good candidates for meeting the structural and aesthetic requirements of bridges. By using the theoretical and nonlinear static (pushover) analyses, the seismic performances of three types of CFST-Y piers were evaluated at different seismic hazard levels. The theoretical formulas were first proposed to estimate the lateral stiffnesses for piers with different pier–deck connections. Then, the structural ductility with the development of plastic hinges in piers was investigated based on the pushover analyses. The results demonstrate that the structural dimensions, deck mass, shear limit, and stiffness of bearings can remarkably affect the formation of hinges and thereby lead to different energy dissipation patterns to achieve the expected performance in piers. The findings suggest an economic design strategy of piers, using CFST-Y members as energy dissipation fuses with multiple hinges, to achieve low-level seismic performance cost-effectively.