RESEARCH ON ROBUSTNESS OF BRIDGE SYSTEMS USING SEISMIC ISOLATION BEARINGS AND SEISMIC DAMPERS

不確定性が高い地震外力に対してロバスト性の高い構造システムの重要性が示されており，そのような構造システムが求められている．免震構造と制震構造を組み合わせることにより，ロバスト性の高い橋梁構造を実現するための取り組みがなされている．本研究では，免震支承と制震ダンパーを併用した橋梁システムを対象とし，そのロバスト性に及ぼす免震・制震デバイスの特性の影響について検討を行った．地震応答特性の変動が小さいことをロバスト性が優れていることであると考え，免震支承と制震ダンパーを併用した橋梁システムを2質点2自由度系にモデル化し，地震応答解析結果に基づき橋脚の最大応答変位の変動係数等を評価した．検討の結果，免震支承と制震ダンパーの特性は，橋脚の最大応答変位の変動係数等に顕著な影響を与えることがわかった．The importance of a structural system with high robustness against seismic forces with high uncertainty has been shown, and such a structural system is required. Efforts are being made to realize a highly robust bridge structure by combining seismic isolation bearings and seismic dampers. In this study, we investigated the influence of characteristics of seismic isolation bearings and seismic dampers on the robustness of bridge systems using seismic isolation bearings and seismic dampers. It was found that characteristics of seismic isolation bearings and seismic dampers have a great influence on the coefficient of variation of the maximum response displacement of a pier and maximum plasticity rate

RTHS of a BMD System

The building mass damper (BMD) system, which incorporates the concept of a tuned mass damper into a mid-story isolation system, has been demonstrated as an effective system for suppressing structural vibration due to earthquakes. The BMD system separates a building into a substructure, a control layer and a superstructure. By applying well-design parameters, the seismic responses of the superstructure and substructure of a building can be mitigated simultaneously. However, merely limited design parameters have been verified by shaking table testing because it is difficult to construct several sets of specimens with limited research funding. Therefore, real-time hybrid simulation (RTHS) may become an alternative to conduct parametric studies of the BMD system efficiently and economically. In this study, the BMD system is separated into a numerical substructure and an experimental substructure. The experimental substructure includes the control layer and the superstructure of the BMD system installed on a seismic shake table while the substructure is numerically simulated. Then, substructuring method of the BMD system is derived and the stability analysis considering the dynamics of the shake table is performed to realize the potential feasibility of RTHS for BMD systems. The stability margin is represented as an allowable mass ratio of the experimental substructure to the entire BMD system. Finally, RTHS of a simplified BMD system has been conducted to verify the stability margin in the laboratory. Phase-lead compensation and force correction are applied to RTHS in order to improve the accuracy of RTHS for the simplified BMD system

Hybrid simulation of a structure to tsunami loading

A new hybrid simulation technique has been developed to assess the behavior of a structure under hydrodynamic loading. It integrates the computational fluid dynamics and structural hybrid simulation and couples the fluid loading and structure response at each simulation step. The conventional displacement-based and recently developed force-based hybrid simulation approaches are adopted in the structural analysis. The concept, procedure, and required components of the proposed hybrid simulation are introduced in this paper. The proposed hybrid simulation has been numerically and physically tested in case of a coastal building impacted by a tsunami wave. It is demonstrated that the force error in the displacement-based approach is significantly larger than that in the force-based approach. The force-based approach allows for a more realistic and reliable structural assessment under tsunami loading

Multi-Dimensional Mixed-Mode Hybrid Simulation, Control and Applications

338 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.The fourth and final task is to validate the hybrid simulation framework through the study of the three-dimensional behavior of a skew RC bridge. First, extensive analyses of skew bridges are conducted to prepare for the hybrid simulation. Subsequently, a small-scale RC pier is experimentally tested as a physical substructure, while the rest of the piers and the bridge deck are analyzed using a finite element model. The mixed-mode control capability is employed to impose on the RC pier simultaneous gravity loads in the axial direction and earthquake-induced displacements in the other directions. The experimental results show that the multi-dimensional hybrid simulation with versatile six degrees-of-freedom loading capability is a promising approach that provides a reliable means for evaluation of the seismic performance of large and complex structural systems.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Multi-dimensional Mixed-mode Hybrid Simulation Control and Applications

Hybrid simulation is an effective method for the assessment of the seismic response of structures, combining laboratory testing, computational simulation, and numerical time-step integration of the equations of motion. While this approach has been used for evaluation of the seismic performance of a variety of structures, applications to date have been limited to planar loading and to relatively simple structural systems. In contrast, actions during strong earthquakes are three-dimensional and continuously varying and modern structures can be extremely complex. Further development is required to evaluate the seismic performance of structures, in particular complex structural systems, under realistic loading. The objectives of this study are to develop a multi-dimensional hybrid simulation framework using a six-actuator, self-reaction, loading system, referred to as the Load and Boundary Condition Box (LBCB), for evaluation of the seismic performance of large and complex structural systems and to demonstrate the framework through three-dimensional hybrid simulation of a skew reinforced concrete (RC) bridge. This report contains results for four major tasks that are intended to provide enhanced seismic performance evaluation using advance experimental techniques. The first task is the calibration of the LBCB in global Cartesian coordinates. Due to imperfections in system geometry (e.g., the actuator configuration), errors in the Cartesian measurements are generated from errors in the transformation from actuator to Cartesian space. A sensitivity-based external calibration method is developed to improve the precision by which the LBCB can be controlled in Cartesian space. The second task is to develop, implement, and experimentally verify a mixed load and displacement (mixed-mode) control strategy. A mixed-mode control capability is required, for example, to simulate gravity loads in the axial direction and displacements in the other directions on structural members such as RC piers in hybrid simulation. However, because of the nonlinear nature of the coordinate transformation, mixed-mode control for a multi-axial loading system is still a major theoretical and practical challenge. The mixed-mode control strategy developed in this study accounts for the spatial interaction of actuators both in displacement and load, and the stiffness variation of the structure specimen. The third task is to integrate the control system and its capabilities into a hybrid simulation framework. The framework needs to also incorporate robust network communication for hybrid simulation. The fourth and final task is to validate the hybrid simulation framework through the study of the three-dimensional behavior of a skew RC bridge. First, extensive analyses of skew bridges are conducted to prepare for the hybrid simulation. Subsequently, a smallscale RC pier is experimentally tested as a physical substructure, while the rest of the piers and the bridge deck are analyzed using a finite element model. The mixed-mode control capability is employed to impose on the RC pier simultaneous gravity loads in the axial direction and earthquake-induced displacements in the other directions. The experimental results show that the multi-dimensional hybrid simulation with versatile six degrees-of-freedom loading capability is a promising approach that provides a reliable means for evaluation of the seismic performance of large and complex structural systems.published or submitted for publicatio