Andrei M. Reinhorn

A Framework to Quantitatively Assess and Enhance the Seismic Resilience of Communities

This paper presents a conceptual framework to define seismic resilience of communities and quantitative measures of resilience that can be useful for a coordinated research effort focusing on enhancing this resilience. This framework relies on the complementary measures of resilience: “Reduced failure probabilities,” “Reduced consequences from failures,” and “Reduced time to recovery.” The framework also includes quantitative measures of the “ends” of robustness and rapidity, and the “means” of resourcefulness and redundancy, and integrates those measures into the four dimensions of community resilience—technical, organizational, social, and economic—all of which can be used to quantify measures of resilience for various types of physical and organizational systems. Systems diagrams then establish the tasks required to achieve these objectives. This framework can be useful in future research to determine the resiliency of different units of analysis and systems, and to develop resiliency targets and detailed analytical procedures to generate these values.

Seismic resilience of a hospital system

This paper presents a comprehensive model to quantify disaster resilience of systems that is defined as the capability to sustain functionality and recover from losses generated by extreme events. The model combines loss estimation and recovery models and can be applied to critical facilities (e.g. hospitals, military buildings, etc.), as well as utility lifelines (e.g. electric power systems, transportation networks, water systems etc.) that are crucial to the response of recovery processes, decisions and policies. Current research trend leads toward the definition of complex recovery models that are able to describe the process over time and the spatial definition of recovery (e.g. meta-models for the case of health care facilities). The model has been applied to a network of hospitals in Memphis, Tennessee. The resilience framework can be used as a decision support tool to increase the resilience index of systems, such as health care facilities, and reduce disaster vulnerability and consequences.

Exploring the concept of seismic resilience for acute care facilities

This paper explores the operational and physical resilience of acute care facilities, recognizing that the key dimension of acute care facilities is not a simple engineering unit. Quantification of resilience is first approached from the broader societal context, from which the engineering subproblem is formulated, recognizing that, to operate, hospitals depend intricately on the performance of their physical infrastructure (from the integrity of structural systems and nonstructural systems, lifelines, components, and equipment). Quantification relates the probability of exceeding floor accelerations and interstory drifts within a specified limit space, for the structural and nonstructural performance. Linear and nonlinear structural responses are considered, as well as the impact of retrofit or repair. Impact on time to recovery is considered in all cases. The proposed framework makes it possible to relate probability functions, fragilities, and resilience in a single integrated approach, and to further develop general tools to quantify resilience for sociopolitical-engineering decisions.

Study of wire rope systems for seismic protection of equipment in buildings

Abstract Wire rope isolators have found numerous applications in the shock and vibration isolation of military hardware and industrial machinery. In this study, the usefulness of these devices for the seismic protection of equipment in buildings is investigated. Installation methods of entirely supporting equipment on wire rope isolators and of combining them with locked casters are studied experimentally and analytically. It is found that the use of wire rope isolators in stiff configurations may substantially improve the seismic response of equipment in comparison to other installation methods. Mathematical models for describing the hysteretic behaviour of wire rope isolators are developed and experimentally calibrated and verified. Analytical predictions of seismic response are shown to agree well with experimental results.

Design of an active mass damper for a tall TV tower in Nanjing, China

The design of an active mass damper to reduce the effects of wind vibrations on a tall (340 m) communication tower in Nanjing, China is presented herein. The existing tower has excessive vibrations under the design wind loads, beyond the comfort level. The design of a mass damper needs to meet several constraints resulting from space, strength and power limitations. The selection of an active alternative for the mass damper is the result of economical and performance considerations within the specified constraints. The paper emphasizes the use of a single mode approach for the design evaluations vs the multi-modal approach. Nonlinear control strategies combined with the design constraints produce a feasible solution for the damper design. The paper emphasizes the system approach to the design in which the performance, the physical constraints and the implementation issues, such as power-force relations and frictional effects, are simultaneously considered. Neglecting any of the above issues may result in an inadequate solution.

Adaptive Negative Stiffness: New Structural Modification Approach for Seismic Protection

AbstractYielding can be emulated in a structural system by adding an adaptive negative stiffness device (NSD) and shifting the yielding away from the main structural system, leading to the new idea of apparent weakening that occurs, ensuring structural stability at all displacement amplitudes. This is achieved through an adaptive negative stiffness system (ANSS), a combination of NSD and a viscous damper. By engaging the NSD at an appropriate displacement (apparent yield displacement that is well below the actual yield displacement of the structural system) the composite structure-device assembly behaves like a yielding structure. The combined NSD-structure system presented in this study has a recentering mechanism that avoids permanent deformation in the composite structure-device assembly unless the main structure itself yields. Essentially, a yielding-structure is mimicked with no, or with minimal, permanent deformation or yielding in the main structure. As a result, the main structural system suffers ...

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.

Fragility Analysis and Seismic Record Selection

This paper explores the influence of spectrum-matched and amplitude-scaled ground motions on the development of fragility functions for structures. The quantification of the influence of these two types of ensembles on ground motions in predicting demands of structural and nonstructural systems is addressed. Moreover, the paper investigates the sensitivity of number of accelerograms in the ensembles, which produces consistent results in the nonlinear analyses. A multidegree-of-freedom (MDOF) inelastic shear-type building is used in the evaluations. The median and the dispersion of different types of damage measures are evaluated at each story and the effect of different levels of nonlinearity is investigated. Fragility functions are developed for structural and nonstructural components using the maxi- mum likelihood method from the response generated with the selected ground motions. The sufficient number of ground motions necessary in the estimation of the response parameters and on the evaluation of the fragility functions is presented herein. DOI: 10.1061/(ASCE)ST.1943- 541X.0000115.

Multidimensional Performance Limit State for Hazard Fragility Functions

This paper addresses an alternative methodology to calculate fragility functions that considers multiple limit states parameters, such as combinations of response variables of accelerations and interstory drifts. Limit states are defined using a generalized multidi- mensional limit states function that allows considering dependencies among limit thresholds modeled as random variables in the calcu- lation of fragility curves that are evaluated as function of the return period. A California hospital is used as example to illustrate the proposed approach for developing fragility curves. The study investigates the sensitivity of the proposed approach for evaluating fragility curves when uncertainties in limit states are considered. Influence of structural and response parameters, such as stiffness, damping, acceleration and displacement thresholds, ground motion input, and uncertainties in structural modeling, are also investigated. The proposed approach can be considered as an alternative approach for describing the vulnerable behavior of nonstructural components that are sensitive to multiple parameters such as displacements and accelerations e.g., partition walls, piping systems, etc..

Integrated Design of Controlled Linear Structural Systems

This paper addresses the integrated design of civil engineering structures with control systems. Simultaneous optimization of such controlled structures is considered, showing that new alternative solutions can be achieved through integrated design. A procedure for design of controlled structural systems is developed using a two-stage approach: (1) a design of an optimal control system using a linear quadratic regulator algorithm; and (2) a redesign using an optimization procedure to match the performance of the controlled system obtained in (1). A linear single degree of freedom steel portal frame and a linear nine degree of freedom shear-type structure are used as examples to illustrate the feasibility of the proposed approach that reduces the structural weight of buildings by incorporating active or passive control elements while preserving the performance objectives.