Response Of Secondary Systems Research Articles

Accuracy of analytical models to predict primary and secondary system response in seismically isolated buildings

Seismic isolation is generally considered an effective earthquake protection strategy. As application of seismic isolation increases, decisions on the use of one particular isolator versus another isolator increasingly depend on computed responses with complex analytical models. Accordingly, validation of analytical models to predict primary (structural) and secondary system (non-structural component) response in seismically isolated buildings becomes very important. This paper presents comparisons of experimental and analytical results on the primary and secondary system response of a building model in order to provide information on the accuracy of the predicted response. The tested model was configured as a 6-story building at quarter length scale in a moment-frame configuration, and with the following seismic isolation systems: a) Low damping elastomeric bearings with and without linear or nonlinear viscous dampers, b) Single Friction Pendulum (FP) bearings with and without linear or nonlinear viscous dampers, and c) Lead-rubber bearings. Response quantities compared include story drifts and isolator shear forces and displacements for the primary system, and peak floor total velocities and floor response spectra that relate to secondary system response. This paper presents samples results out of a total of 288 comparisons of experimental and analytical results presented in an MCEER report. It is shown that the primary and secondary system response is computed with sufficient accuracy by the analytical models but some response quantities may be underestimated or overestimated by significant amounts.

On Seismic Torsional Response of Secondary Systems

On Seismic Torsional Response of Secondary Systems

Cyclic Load Protocol for Anchored Nonstructural Components and Systems

This work is motivated by the need to investigate the cyclic load response of restrained (via anchorage or other) nonstructural components and systems (NCSs). For this purpose, a load protocol is developed for capturing the behavior of the restraining element when subjected to seismic loading. The protocol incorporates numerical analyses of buildings designed to respond nonlinearly under design earthquake events, analysis of secondary systems located in these buildings and rainflow counting of time history results extracted from these analyses. Secondary system response results are used to develop tension and shear load protocols. Protocol statistics are presented and envisioned to be useful in anchor or other restraint system qualification tests.

Definition of Seismic Input for Out-of-Plane Response of Masonry Walls: I. Parametric Study

Response of masonry walls to out-of-plane excitation is a complex, yet inadequately addressed theme in seismic analysis. The seismic input expected on an out-of-plane wall (or a generic “secondary system”) in a masonry building is the ground excitation filtered by the in-plane response of the walls and the floor diaphragm response. More generally, the dynamic response of the primary structure, which can be nonlinear, contributes to the filtering phenomenon. The current article delves into the details and results of several nonlinear dynamic time-history analyses executed within a parametric framework. The study addresses masonry structures with rigid diaphragm response to lateral loads. The scope of the parametric study is to demonstrate the influence of inelastic structural response on the seismic response of secondary systems and eventually develop an expression to estimate the seismic input on secondary systems that explicitly accounts for the level of inelasticity in the primary structure in terms of the displacement ductility demand. The proposed formulation is discussed in the companion article.

Definition of Seismic Input for Out-of-Plane Response of Masonry Walls: II. Formulation

The seismic input expected on an out-of-plane wall (or a generic secondary element) in a URM building is the ground excitation filtered by the in-plane response of the walls and the response of the floor diaphragms. More generally, the dynamic response of the primary structure, which can be nonlinear, contributes to the filtering phenomenon. Inelastic response of the primary structure can alter the secondary system response considerably in comparison to that under elastic structural response. The current article proposes a semi-analytical formulation to estimate the acceleration demand on an out-of-plane URM wall that explicitly takes into account the level of inelasticity in the primary structure in terms of the displacement ductility demand. A simplified approach to determine the acceleration profile over the height of a structure is also introduced. The formulation is based on statistical evaluation of the results of several inelastic time-history analyses treated within a parametric framework, which are presented in the companion article.

G1000-2-5 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 振幅および周波数非定常性を考慮した付加構造物系の応答(機械力学・計測制御部門一般講演(2):振動,社会変革を技術で廻す機械工学)

G1000-2-5 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 振幅および周波数非定常性を考慮した付加構造物系の応答(機械力学・計測制御部門一般講演(2):振動,社会変革を技術で廻す機械工学)

Seismic Response of Secondary Systems Supported by Torsionally Yielding Structures

Substantial damage sustained during several recent earthquakes was non structural in nature. The economic consequence in terms of non structural component damage far exceeded the structural damage. Currently, there are several analytical studies that address the interaction between non structural components or Secondary systems (S-systems) and the main supporting structure or Primary system (P-system). Only a few of these analytical approaches have been proposed to evaluate and characterize the response of the S-systems attached to torsionally coupled P-systems. In addition, the experimental verification for the analytical approaches is scarce. In the current study, the results and observations of an experimental research program conducted to characterize the behavior of both stiffness eccentric and mass eccentric torsionally coupled Primary-Secondary systems (PS-systems) are presented. From this experimental investigation it was found that the torsional yielding of the primary system has significant implications on the deamplification of near tuned secondary system response. The location of the S-system mounted on the P-system affects the peak response amplification, and interaction with the coupled P-system.

402 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 付加構造物系の応答に対する計算法

402 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 付加構造物系の応答に対する計算法

2721 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 付加構造物系の応答について(OS27.一般セッション(1),ポスターセッションP-4)

2721 非定常不規則振動応答の自乗平均値の積分値の簡易計算法 : 付加構造物系の応答について(OS27.一般セッション(1),ポスターセッションP-4)

Response of Nonstructural Components in Structures with Damping Systems

An analytical study of buildings without and with seismic damping systems was conducted to investigate the dynamic response of secondary systems. The buildings were represented by steel frames designed by the procedures described in the 2000 NEHRP Recommended Provisions. Nonlinear response analyses were performed for the undamped frames and the damped frames equipped with different energy dissipation systems and for far-field, near-field, and soft-soil earthquake histories. The study shows that significant benefits may be provided by viscous damping systems in terms of reduced floor spectral accelerations and floor absolute velocities.

Variability in seismic response of secondary systems due to uncertain soil properties

A mode acceleration formulation is presented to investigate the variability in the response of a secondary system which is supported on a flexible-base primary system at multiple attachment points. The response functions are considered to be uncertain due to uncertainties in the values of shear wave velocity and Poisson’s ratio of the foundation soil. Both soil parameters are assumed to be statistically independent variables with Gaussian distributions. A numerical study with the help of an example primary-secondary (P–S) system shows that dynamic response should be ignored only for very stiff secondary modes, say > 7 times as stiff as the dominant mode of the primary system, for the proposed formulation to work well. It is also seen that uncertainty in shear wave velocity can be ignored in case of limited soil-structure interaction, while uncertainty in Poisson’s ratio should be considered only when soil damping is sensitive to the Poisson’s ratio and there is significant soil-structure interaction.

An Experimental Study on the Seismic Response of Base-Isolated Secondary Systems

The paper provides an experimental study on the feasibility of base isolation for seismic protection of nonstructural secondary system such as sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission systems housed in nonisolated primary structures. Damages to these secondary systems may result in significant social chaos and costly economic loss. A one-sixth-scaled three-story building model with a single-degree-of-freedom secondary system placed on its third floor is employed in this study. The secondary system is base-isolated by a laminated rubber bearing (LRB) base isolation system from the supporting floor. The ground motion input is simulated by a shaking table which generates three different types of signal including sweeping harmonic sinusoidal, the S00E component of the 1940 E1 Centro earthquake, and the simulated white noise. The experimental results demonstrate significant reduction in both displacement and acceleration responses of the secondary system by using the base isolation. Effects of parameters of the base isolation such as damping ratio and mass on its performance are also investigated. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Hou et al., 2001). Secondary systems in a structure can be divided into two categories: structural and nonstructural. A thorough review of these types of systems and their response behavior under seismic loading has been presented by (Chen and Soong, 1988). In this paper, only nonstructural secondary systems are the subject of the study. These systems include sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission system that reside within a primary structure system. The huge investment made, the mission, and the critical role played by secondary systems in modern day warrant an effective protection strategy against earthquake-induced vibrations. Studies on employing base isolation techniques to protect primary structures have shown the ability of such techniques to limit dynamic response of structures in seismic disturbance (Kelley, 1986; and Ahmadi, 1988); this paper proposes the adoption of a base isolation mechanism for seismic protection of secondary systems and presents the experimental results achieved with this strategy in a scaled-down system designed without primary structural isolation. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Ghantous, 1991; and Samaha, 1992).

Stochastic seismic response of multiply-supported secondary systems in flexible-base structures

A formulation has been proposed for the transfer function of a secondary system response while the primary system is supported on a compliant soil and the excitation comprises of translational ground motion at its base. For this purpose, the earlier formulation of the authors for the fixed-base case, which exactly considers the interaction between the two sub-systems and is based on the use of their individual modal properties, has been extended. Also, the concept of modifying the input excitation for the interaction accelerations (associated with the soil–structure interaction) has been used. An example P–S system and three example earthquake excitations have been considered to illustrate the proposed formulation and to estimate the expected response peak amplitudes in the secondary system. This study shows that ‘detuning’ of the tuned systems may occur in case of significant soil–structure interaction. Further, for the reasons of both safety and economy, ignoring the interaction effects in designing the secondary systems may not always be justified. Copyright © 1999 John Wiley & Sons, Ltd.

Rabies ribonucleocapsid as an oral immunogen and immunological enhancer.

The administration of rabies ribonucleocapsid (RNP) by oral as well as parenteral routes was found to prime specific T cells and elicit N-protein-specific antibodies. per os and intramuscular immunization led to the production of antibodies of the IgA and IgG isotypes, respectively. Mice primed orally with RNP produced significantly enhanced amounts of virus-neutralizing antibody, compared with non-immune controls, upon subsequent parenteral booster immunization with inactivated rabies virus. Thus oral immunization with rabies RNP primed cells capable of mediating a secondary systemic response to rabies virus. The results of experiments in which peptide and protein antigens were administered either physically coupled to or mixed with RNP indicate that RNP has an inherent capacity to enhance immune responses.

Stochastic sensitivity analysis of nonlinear primary-secondary structural systems

A response and sensitivity analysis of the mean-square response of secondary systems attached to yielding primary structures is presented. The main objective is to examine the effect of nonlinearity in the primary structural behaviour on the response characteristics and its sensitivity to secondary systems in a stochastic environment. The procedure follows equivalent linearization with partitioning in order to alleviate the dimensionality problem. Under white noise excitation, results show that yielding of the primary structure generally favours the secondary system response and its sensitivity, except in the tuning region in which amplification can take place due to the frequency shift of the yielding primary structure. With regard to the placement problem of secondary systems, while position sensitivity varies significantly in the linear case, yielding of the primary structure tends to produce a smoothing effect, leading to a more uniform sensitivity behaviour.

Nonlinear Stochastic Response and Reliability of Secondary Systems

The response and reliability of a linear secondary system attached to a multi‐degree‐of‐freedom yielding primary structure under white‐noise or filtered white‐noise excitations are studied by using equivalent linearization and digital simulation. It is shown that the effect of the primary‐structure yielding on response and reliability of the secondary system mainly depends on the ratio of the secondary‐system natural frequency to the natural frequencies of the primary structure and on the excitation spectral density shape in the range of natural frequencies of the primary structure. Under white‐noise excitation, amplification of the secondary system response results due both to tuning of the secondary system with one of the modes of the postyield primary structure and to an increase in excitation spectral density values at natural frequencies of the postyield primary structure. High‐frequency amplification is possible in this case. It is also shown that amplification of the secondary system response can b...

Experimental Study of Secondary Systems in Base‐Isolated Structure

This work investigates the response of secondary systems attached to a base-isolated, six-story model structure that is subjected to base motions. The secondary systems are modeled by cantilevered, inverted pendulums. They have natural frequencies and mass ratios that span a wide range of values. The scaled model structure is base-isolated through the use of sliding Teflon disc bearings coupled with restoring helical springs. The structural system is placed on a seismic simulator and is subjected to several prerecorded earthquake accelerograms. Time histories and frequency spectra for the secondary systems and their supporting floors are presented. Subsequently, a numerical model is developed to reproduce the results obtained from the experiments. The level of agreement between numerical and experimental results indicates that the numerical model can be used for the construction of floor response spectra (FRS) for the secondary systems. The experimental results and the numerical studies show that under most circumstances, this novel structural base isolation system reduces the effects of vibrations in the secondary systems.

Stochastic earthquake response of secondary systems in base‐isolated structures

AbstractThis paper studies the stochastic responses of secondary systems in base‐isolated shear beam structures. A number of base isolation systems such as the laminated rubber bearing (LRB), the resilient‐friction base isolator (R‐FBI) with or without sliding upper plate, and the EDF system are considered. The stochastic models for the El Centro 1940 and the Mexico City 1985 earthquakes which preserve the non‐stationary evolutions of amplitude and frequency content of ground accelerations are used as earthquake excitations. The technique of equivalent linearization is utilized and the mean‐square response statistics of secondary systems and primary structure are evaluated. The accuracy of the linearization scheme is verified by comparison with the Monte Carlo simulation results. Statistically estimated peak responses of the secondary system are evaluated and the results are compared with the response spectra for actual earthquake accelerograms. It is shown that the use of base isolation systems, generally, provides considerable protection for structural contents. In particular, the LRB system is remarkably effective in reducing responses of secondary systems. Results for the Mexico City earthquake show that the base‐isolated structures are sensitive to long period ground excitations.

Stochastic response of secondary systems in base-isolated structures

In this work, the stochastic response of secondary systems attached to a base-isolated structure undergoing random ground motions is examined. It is assumed that the properties of this combined structural system are deterministic, while the ground motions are described by a filtered white noise model. The only nonlinear component of this structural system is its base isolation mechanism, which is linearized by using equivalent linearization. Also, a substructuring algorithm is developed which requires the dynamic properties of the individual, fixed-base components of the structural system. Both stationary as well as nonstationary cases are considered and comparisons are made with the results of Monte-Carlo simulations to ascertain the validity of this methodology. The example studied herein is a six-storey steel building frame with a base isolation system consisting of sliding bearings and restoring force springs. For this example, spectra are constructed that account for primary-secondary system interaction and depict the effect of variations in the base isolator's structural parameters and in the mass and location of the secondary system on the latter's root-mean-square (RMS) accelerations.

Seismic Design Considerations for Secondary Structural Systems

In practice, light secondary systems attached to the massive primary system are treated independently in the seismic design. Evaluation of the secondary systems and their design forces are performed as equivalent static lateral forces applied to the approximate centers of gravity of the systems being analyzed. These design forces, since they are statics based, do not lend themselves to providing realistic design guidelines of secondary systems. In this paper, possible dynamic design considerations for primary‐secondary (P‐S) systems are studied. A simple yet efficient design procedure is developed. It is shown that, while an increase in damping ratio of the secondary system can always decrease the relative displacement between the primary system and the secondary system, there is an optimum damping ratio for minimizing the maximum acceleration of the secondary system. Compromises thus need to be made when there is a conflict in achieving the best global secondary‐system performance. For illustration purposes, a series of design surfaces for different system configurations under the case of white‐noise input are presented for obtaining the lowest maximum response of secondary systems.