Floor response spectra in isolated structures, subjected to earthquakes weaker than the design earthquake-Part II: Isolation with magnetically controlled elastomeric bearings

2010 ◽  
Vol 18 (5) ◽  
pp. 540-553 ◽  
Author(s):  
Tatjana Isaković ◽  
Jaka Zevnik ◽  
Matej Fischinger
Keyword(s):  
Response Spectra ◽  
Elastomeric Bearings ◽  
Floor Response Spectra ◽  
Isolated Structures ◽  
Design Earthquake

scholarly journals Seismic Responses of NPP Structures Considering the Effects of Lead Rubber Bearing

2020 ◽  
Vol 10 (6) ◽  
pp. 6500-6503
Author(s):  
D. D. Nguyen ◽  
C. N. Nguyen
Keyword(s):  
Cross Sections ◽  
Nuclear Power ◽  
Low Frequency ◽  
Time History ◽  
Response Spectra ◽  
Floor Response Spectra ◽  
Lead Rubber Bearing ◽  
Isolated Structures ◽  
Rubber Bearings ◽  
Lumped Masses

Abstract-This study investigates the effects of Lead Rubber Bearings (LRBs) on Floor Response Spectra (FRS) of Nuclear Power Plant (NPP) structures. Three main structures in the Advanced Power Reactor 1400 (APR1400) NPP including the reactor containment building, an internal structure, and an auxiliary building were numerically developed in SAP2000. The structures were modeled using beam stick elements, and lumped masses were assigned to beam element nodes. All equivalent section properties of beam elements were calculated based on the designed cross-sections of the structures. A series of 40 ground motions with response spectra scaled to match the NRC 1.60 spectrum were utilized in numerical time-history analyses. Finally, a thorough comparison of FRS was conducted at different elevations of the structures, considering both with and without LRB. Numerical results showed that the FRS of base-isolated structures at higher elevations was significantly reduced compared to non-isolated structures. However, at lower elevations, the FRS was higher for the base-isolated structures compared to the non-isolated ones. Additionally, at a low-frequency range, roughly smaller than 3 Hz, the FRS of base-isolated structures was always greater than that of the non-isolated ones.

Toppling Fragility of Unrestrained Equipment

1998 ◽  
Vol 14 (4) ◽  
pp. 695-711 ◽  
Author(s):  
Z. Y. Zhu ◽  
T. T. Soong
Keyword(s):  
Fragility Curves ◽  
Response Spectra ◽  
Static Friction ◽  
Block Type ◽  
Base Excitation ◽  
Loss Of Function ◽  
Floor Response Spectra ◽  
Rocking Motion ◽  
Design Earthquake ◽  
Supporting Base

Block-type equipment without restraining devices and under earthquake loads can effectively be modeled as freestanding rigid blocks resting on supporting bases subjected to base excitations. Once the peak values of base excitation levels, the aspect ratio of the bock, and the static friction coefficient between the block and the supporting base are known, the motion type of the block that will be initiated under base excitation can be determined. One of the possible motion types is rocking. When rocking is initiated, the block may topple and suffer severe damage and permanent loss of function. The emphasis of this study is placed on quantifying the possibility of toppling of a rigid block during rocking motion given its geometry and design earthquake environment. Using floor response spectra to characterize excitation inputs, results are given in the form of toppling fragility curves, i.e., probability of toppling as a function of peak ground accelerations. Parametric sensitivity studies are also carried out to show the effects of several key parameters on the fragility results.

Inclusion of Aircraft Crash into NPP Design Bases and Probabilistic Justification of Loads on Civil Structures and Equipment

2020 ◽  
pp. 35-47
Author(s):  
Nikita Chernukha
Keyword(s):  
Nuclear Power ◽  
Response Spectra ◽  
Mechanical Action ◽  
Exceedance Probability ◽  
Civil Structures ◽  
Method Of Calculation ◽  
Floor Response Spectra ◽  
Aircraft Trajectory ◽  
Probabilistic Justification ◽  
Aircraft Crash

The article is about nuclear power plant (NPP) safety analysis in case of aircraft crash. Specifically, the article considers the following problems: inclusion of aircraft crash into NPP design bases regarding calculation of frequency of an aircraft crash into NPP; aspects of justification of loads on NPP structures, systems and components (SSCs) caused by mechanical action of a primary missile – aircraft fuselage impact. Probabilistic characteristics of such random parameters as frequency of aircraft crash and direction of aircraft trajectory are determined by the results of analysis of world statistics of aviation accidents. Method of calculation of aircraft crash frequency on structures, buildings and NPP as a whole is presented. It takes into account options of accidental and intentional aircraft crashes and various aircraft approach scenarios. Procedure of probabilistic justification of loads on civil structures under aircraft impact is described. The loads are specified so as not to exceed allowable value of failure probability of NPP as a whole. Calculation of failure frequency of civil structures of existing NPP is given as an example to show analysis in case of a crash of an aircraft heavier than considered in NPP design. Procedure of probabilistic justification of dynamic loads on NPP equipment in case of aircraft impact is described. Method of floor response spectra (FRS) calculation with the required non-exceedance probability is given. Probabilistically justified loads in case of intentional aircraft impact (act of terrorism) are also considered. Additionally it is presented how internal forces calculated with the use of FRS with the required non-exceedance probability can be summed to provide analysis of subsystems.

Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

2020 ◽  
Vol 36 (2_suppl) ◽  
pp. 213-237
Author(s):  
Miguel A Jaimes ◽  
Adrián D García-Soto
Keyword(s):  
Mexico City ◽  
Seismic Design ◽  
Soft Soil ◽  
Response Spectra ◽  
Elastic Model ◽  
Ground Acceleration ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Instrumented Buildings ◽  
Floor Acceleration

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

Inelastic Analysis of Reinforced Concrete Shear Wall Structures Under Seismic Excitation

1993 ◽  
Author(s):  
Ming L. Wang
Keyword(s):  
Reinforced Concrete ◽  
Response Spectra ◽  
Shear Wall ◽  
Stiffness Degradation ◽  
Structural Stiffness ◽  
Hysteresis Model ◽  
Safety Equipment ◽  
Floor Response Spectra ◽  
Wall Structures ◽  
Degradation Models

Abstract During strong ground motions, members of reinforced concrete structures undergo cyclic deformations and experience permanent damage. Members may lose their initial stiffness as well as strength. Recently, Los Alamos National Laboratory has performed experiments on scale models of shear wall structures subjected to recorded earthquake signals. In general, the results indicated that the measured structural stiffness decreased with increased levels of excitation in the linear response region. Furthermore, a significant reduction in strength as well as in stiffness was also observed in the inelastic range. Since the in-structure floor response spectra, which are used to design and qualify safety equipment, have been based on calculated structural stiffness and frequencies, it is possible that certain safety equipment could experience greater seismic loads than specified for qualification due to stiffness reduction. In this research, a hysteresis model based on the concept of accumulated damage has been developed to account for this stiffness degradation both in the linear and inelastic ranges. Single and three degrees of freedom seismic Category I structures were analyzed and compared with equivalent linear stiffness degradation models in terms of maximum displacement responses, permanent displacement, and floor response spectra. The results indicate significant differences in responses between the hysteresis model and equivalent linear stiffness degradation models. The hysteresis model is recommended in the analysis of reinforced concrete shear-wall structures to obtain the in-structure floor response spectra for equipment qualification. Results of both cumulative and one shot tests are compared.

Dynamics of Friction Damped Braced Frames With Secondary Structures

1999 ◽  
Author(s):  
C. Adam ◽  
F. Ziegler
Keyword(s):  
Iterative Process ◽  
Numerical Procedure ◽  
Response Spectra ◽  
Secondary Structures ◽  
Structural Behavior ◽  
Light Weight ◽  
Braced Frames ◽  
Acceleration Response ◽  
Floor Response Spectra ◽  
Iterative Synthesis

Abstract The influence of light-weight secondary structures on the dynamic response of earthquake excited hysteretically damped shear frames with various elastic and inelastic substructure properties is studied numerically. The numerical procedure used in this paper is based on an iterative synthesis, where interface conditions as well as inelastic deformations are treated as additional fictitious loads and their intensities are updated in an iterative process. Acceleration response spectra of shear frames as well as floor response spectra are generated for various modal primary to secondary mass ratios. Also spectra of the standard deviation of primary and secondary accelerations are computed. Results, efficiently derived by the proposed method, are set in contrast to those derived by decoupled analyses to estimate their capability with respect to hysteretic structural behavior.

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