Xiaoyun Shao

Real-Time Hybrid Simulation Using Shake Tables and Dynamic Actuators

The development and implementation of the real-time hybrid simulation (RTHS), a seismic response simulation method with a combination of numerical computation and physical specimens excited by shake tables and auxiliary actuators, are presented. The structure to be simulated is divided into one or more experimental and computational substructures. The loadings generated by the seismic excitations at the interfaces between the experimental and computational substructures, in terms of accelerations and forces, are imposed by shake tables and actuators in a step-by-step manner at a real-time rate. The measured displacement and velocity responses of the experimental substructure are fed back to determine the loading commands of the next time step. The unique aspect of the aforementioned hybrid simulation method is the versatile implementation of inertia forces and a force-based substructuring. The general formulation of RTHS enables this hybrid simulation method being executed as real-time pseudodynamic (PSD) testing, dynamic testing, and a combination of both, depending on the availability of the laboratory testing equipment and their capacity. The derivation of the general formulation and the corresponding testing system are presented in this paper. Numerical simulation and physical experiment were conducted on the RTHS of a three-story structural model. Simulation and experimental results verify the concept of the proposed general formulation of RTHS and the feasibility of the developed corresponding controller platform.

Development of a Versatile Hybrid Testing System for Seismic Experimentation

The hybrid testing method for earthquake engineering was developed to evaluate the seismic performance of civil structural systems. During hybrid testing, part of the structure, called physical substructure, is physically tested using hydraulic loading equipment while the rest of the structure, named numerical substructure, is numerically simulated with a computer model. Thus, hybrid testing allows a complex physical substructure being tested experimentally, while the relatively simple part of the structure is numerically simulated to economically obtain the full structural response. Recently, a versatile hybrid testing system was built at Western Michigan University consisting of a shake table, an actuator/reaction system, and an advanced hybrid testing controller. Such a testing system is capable of conducting various seismic experiments such as displacement-based pseudodynamic substructure testing as well as force-based real time dynamic hybrid testing. Because of its versatility and easy operation at the benchmark scale, the developed testing system is particularly suitable for the development of advanced hybrid testing techniques and, earthquake engineering education/outreach activities. The development of the testing system is described in this article focusing on the hardware and software integrations. A three story shake table hybrid test is presented as an example to demonstrate the system’s capability and feasibility.

Development of a Controller Platform for Force-Based Real-Time Hybrid Simulation

Force-based real-time hybrid simulation is a seismic experimental method that combines physical testing using shake tables and dynamic actuators with numerical analysis. The unique aspect of this force-based formulation is that various hybrid simulation techniques, such as dynamic, pseudo-dynamic, and quasi-dynamic testing, can be similarly executed. To implement such a method, the hardware components and the corresponding software were designed and integrated into a modular controller platform. This article focuses on the implementation issues of such formulation. A pilot scale setup was assembled to conduct proof of concept experiments of the controller platform and is presented herein.

Real-time hybrid simulation with Online model updating: Methodology and implementation

AbstractHybrid simulations have shown great potential for economic and reliable assessment of structural seismic performance by combining physical experimentation on part of the structural system and numerical simulation of the remaining structural components. Current hybrid simulation practices often use a fixed numerical model without considering the possible availability of a more-accurate model obtained during hybrid simulation through an online model updating technique. To address this limitation and improve the reliability of numerical models in hybrid simulations, this paper presents a method and an implementation procedure of conducting real-time hybrid simulation (RTHS) with online model updating. The Unscented Kalman Filter (UKF) was adopted as the parameter identification algorithm applied to the Bouc-Wen model that defines the hysteresis of the experimental substructure. The identified parameters are then used to update the models of the numerical substructures during RTHS. A parametric study ...

Real time dynamic hybrid testing using shake tables and force-based substructuring

This paper presents the development and implementation of a novel structural testing method involving the combined use of shake tables, actuators and computational engines for the seismic simulation of structures. The structure to be simulated is divided into one or more experimental and computational substructures. The interface forces between the experimental and computational substructures are imposed by actuators and resulting displacements and velocities are fed back to the computational engine. The earthquake ground motion is applied to the experimental substructures by shake tables. The unique aspect of the above hybrid system is force-based substructuring. Since the shake tables induce inertia forces in the experimental substructures, the actuators have to be operated in dynamic force control as well, since either the force or the displacement, but not both can be controlled at a given point and at a given instant of time. The substructuring strategy and the numerical integration algorithms associated with the computational substructures are presented along with the implementation of the computational engine. A new dynamic force control strategy developed for this purpose using series elasticity and displacement compensation is briefly reviewed. Issues related to time-delay compensation are also discussed. Finally, an example of a real-time hybrid test implementation, and results from this experiment are presented. INTRODUCTION Simulation of structures under seismic loads is usually performed either experimentally or computationally. Experimental results are used to develop and calibrate computational models of structural components and assemblies. These computational models are used to predict the response of structures. Further experiments are then performed to validate and refine the computational models. Structural simulation is thus an iterative process involving alternate stages of experimentation and computation. This paper describes a new method of Real-time Dynamic Hybrid Testing (RTDHT) of structures which involves combined use of experimentation and computation and some of the above iteration can potentially be performed online. The new development was facilitated by 17 ANALYSIS AND COMPUTATION SPECIALTY CONFERENCE th Copyright ASCE 2006 17th Analysis and Computation Conference the new George E. Brown Network for Earthquake Engineering Simulation (NEES) deployment at University at Buffalo which provides unique opportunities for integrated experimentation and computing. Real time dynamic hybrid testing is a novel structural testing method involving the combined use of shake tables, actuators, and computational engines for the seismic simulation of structures. The structure to be simulated is divided into a physical substructure and one or more computational substructures. The interface forces between the physical and computational substructures are imposed by actuators and resulting displacements and velocities are fed back to the computational engine. The earthquake ground motion, or motion of other computational substructures, is applied to the experimental substructure by shake tables. A schematic of the RTDHT system is shown in Figure 1. The right side in Figure 1 shows the physical computational infrastructure including parallel operating computers required for the implementation of the forces and motions at the interface of the physical and computational substructures. The theoretical basis and the implementation of real time dynamic hybrid testing (RTDHT) is presented in the next sections. UNIFORM SUBSTRUCTURE STRATEGY IN HYBRID TESTING Substructuring using RTDHT required first modeling the entire structure and idealizing the interface conditions between the computational and the physical substructure. In this paper, a unified substrucutre technique for hybrid testing is derived for multistory models.

Full-scale experimental verification of soft-story-only retrofits of wood-frame buildings using hybrid testing

The FEMA P-807 Guidelines were developed for retrofitting soft-story wood-frame buildings based on existing data, and the method had not been verified through full-scale experimental testing. This article presents two different retrofit designs based directly on the FEMA P-807 Guidelines that were examined at several different seismic intensity levels. The effects of the retrofits on damage to the upper stories were investigated. The results from the hybrid testing verify that designs following the FEMA P-807 Guidelines meet specified performance levels and appear to successfully prevent collapse at significantly higher seismic intensity levels well beyond for which they were designed. Based on the test results presented in this article, it is recommended that the soft-story-only retrofit procedure can be followed when financial or other constraints limit the retrofit from bringing the soft-story building up to current code or applying performance-based procedures.

A conceptual evolutionary aseismic decision support framework for hospitals

In this paper, aconceptual evolutionary framework for aseismic decision support for hospitalsthat attempts to integrate a range of engineering and sociotechnical models is presented. Genetic algorithms are applied to find the optimal decision sets. A case study is completed to demonstrate how the frameworkmay applytoa specific hospital.The simulations show that the proposed evolutionary decision support framework is able to discover robust policy sets in either uncertain or fixed environments. The framework also qualitatively identifies some of the characteristicbehavior of the critical care organization. Thus, by utilizing the proposedframework, the decision makers are able to make more informed decisions, especially toenhance the seismic safety of the hospitals.

Hybrid testing in NEESR projects

Hybrid testing, as an advanced seismic response simulation method, combines experimental physical models with analytical numerical models; its versatility and capability of testing large-scale specimens make it particularly applicable to the study of seismic performance. Hybrid testing has been applied in approximately twenty George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) research projects. This paper provides a review of hybrid testing techniques used in these projects based on the information available at the NEEShub project warehouse. An overview of hybrid testing is firstly presented. Then a list of NEESR projects involving hybrid testing methods are discussed in details, including experimental specimen, substructuring, integration algorithms, rate of loading and testing results validation. The paper concludes that hybrid testing is an effective experimental method in earthquake engineering simulation but needs further development in the areas of providing more realistic structural responses and validated general hybrid testing procedure for broader application.

Unified Formulation for Real Time Dynamic Hybrid Testing

This paper proposes a unified formulation for Real time dynamic hybrid testing (RTDHT), which is a structural seismic response simulation method com- bining the numerical simulation of the computational substructure and the physi- cal testing of the experimental substructure. By introducing a set of splitting coef- ficient matrices to the general equation of motion of the structural model subjected to investigation, various seismic testing methods can be formulated, including real time pseudo-dynamic substructure testing, effective force testing and shake table testing. This paper first reviews the seismic testing methods currently used in earthquake engineering with a brief introduction about the RTDHT. Then the uni- fied formulation is presented with a detailed discussion of the splitting coefficient matrices. Hardware components necessary to implement the unified formulation RTDHT are integrated into a unified test platform. While a number of tests were performed in medium scale, a small-scale pilot setup was used in the verification tests. Test results which validated the concept of the proposed unified formulation and the feasibility of the corresponding platform for RTDHS are discussed at last.

A Versatile Hybrid Testing System and Its Application in Developing Hybrid Simulation Methods for NEESR Projects

Hybrid simulation method in earthquake engineering, which combines physical testing and numerical simulation, was developed to evaluate seismic performance of civil structural systems. Thus, instead of constructing a full sized structural specimen, hybrid simulation allows researchers to build a complex experimental substructure tested experimentally while the relatively simple part of the structure is numerically simulated to economically obtain the full structural responses. Recently a versatile hybrid testing system was built at the Laboratory of Earthquake and Structural Simulation (LESS) at Western Michigan University. The major equipment consists of a seismic simulator (often called shake table), an actuator/reaction system and an advanced hybrid testing controller. Such testing system is capable of conducting various hybrid simulation experiments such as displacement-based pseudodynamic substructure testing as well as force-based real time dynamic hybrid testing. The benchmark scale testing system at LESS is particularly suitable for development of hybrid simulation techniques and earthquake engineering education and outreach activities. The development of this testing system including both hardware and software integration is presented. Example hybrid simulation methods that can be conducted using the developed testing system as well as its applications in the hybrid simulation method development of two NEESR projects are discussed.