On Categorization of Seismic Load As Primary or Secondary

2017 ◽  
Author(s):  
Pierre B. Labbé
Keyword(s):  
Natural Frequency ◽  
Response Spectrum ◽  
A Priori ◽  
Effective Stiffness ◽  
Seismic Load ◽  
Perfectly Plastic ◽  
Wide Range ◽  
Non Linear ◽  
Piping Systems ◽  
Non Linear Oscillator

The concept of primary/secondary categorization is first recalled and generalized for its application to an elastic-plastic oscillator subjected to a seismic load. Categorizing the seismic load requires calculating the input level associated to the oscillator ultimate capacity and compare it to the level associated to the plastic yield. In order to resolve this non-linear dynamic problem, it is assumed that the non-linear oscillator behaves like a linear equivalent oscillator, with an effective stiffness (or frequency) and an effective damping. However, as it is not a priori possible to predict the equivalent stiffness and damping, a wide range of possibilities is systematically considered. The input motion is represented by its conventional response spectrum. It turns out that key parameters for categorization are i) the “effective stiffness factor” (varying from 0 for perfect damage behaviour to 1 for elastic-perfectly plastic) and the slope of the response spectrum in the vicinity of the natural frequency of the oscillator. Effective damping and spectrum sensitivity to damping play a second order role. A formula is presented that enables to calculate the primary part of a seismically induced stress as a function of both the oscillator and input spectrum features. The formula is also presented in the form of an abacus. The actual “effective stiffness factor” of different piping systems is derived from outputs of experimental research programs carried out in the past in USA and Japan and still ongoing in India. It appears that even when experiencing large plastic strains under beyond design input motions, the observed effective frequency of piping systems is very close to their natural frequency, decreasing only by a few percents. These observations enable to calculate an effective stiffness factor value around 0.9 and lead to the conclusion that the seismic load, or the seismically induced inertial seismic strains, should basically be regarded as secondary in the sense of the definition adopted here.

On Categorization of Seismic Load As Primary or Secondary for Piping Systems With Hardening Capacity

2018 ◽  
Author(s):  
Pierre B. Labbé
Keyword(s):  
Natural Frequency ◽  
Response Spectrum ◽  
A Priori ◽  
Effective Stiffness ◽  
Linear Oscillator ◽  
Seismic Load ◽  
Wide Range ◽  
Non Linear ◽  
Piping Systems ◽  
Non Linear Oscillator

The concept of primary/secondary categorization is first reviewed and generalized for its application to a non-linear oscillator subjected to a seismic load. Categorizing the seismic load requires calculating the input level associated with the oscillator ultimate capacity and comparing it to the level associated with the plastic yield. To resolve this problem, it is assumed that the non-linear oscillator behaves like a linear equivalent oscillator, with an effective stiffness (or frequency) and an effective damping. However, as it is not a priori possible to predict the equivalent stiffness and damping, a wide range of possibilities is systematically considered. The input motion is represented by its conventional response spectrum. It turns out that key parameters for categorization are i) the “effective stiffness factor” (varying from 0 for perfect damage behaviour to 1 for elastic-perfectly plastic) and the slope of the response spectrum in the vicinity of the natural frequency of the oscillator. Effective damping and spectrum sensitivity to damping play a second order role. A formula is presented that enables the calculation of the primary part of a seismically induced stress as a function of both the oscillator and input spectrum features. The formula is also presented in the form of a diagram. This paper follows-up on a similar paper presented by the author at the PVP 2017 Conference [1]. The new development introduced here is that the oscillator exhibits hardening capacity, while no hardening was assumed in [1]. It appears that the conclusions are slightly modified but the trend is very similar to the non-hardening case. Regarding piping systems, it appears that even when experiencing large plastic strains under beyond design input motions, their observed effective frequency is very close to their natural frequency, decreasing only by a few percents (experimental data from USA, Japan and India are processed). These observations lead to the conclusion that the seismic load, or the seismically induced inertial seismic strains, should basically be regarded as secondary.

Fatigue-Ratcheting Behavior of 6 in Pressurized Carbon Steel Piping Systems Under Seismic Load: Experiments and Analysis

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
A. Ravi Kiran ◽  
G. R. Reddy ◽  
P. N. Dubey ◽  
M. K. Agrawal
Keyword(s):  
Carbon Steel ◽  
Response Spectrum ◽  
Thickness Variation ◽  
Seismic Load ◽  
Frequency Change ◽  
Shake Table Tests ◽  
Numerical Studies ◽  
Piping Systems ◽  
Earthquake Load ◽  
Steel Piping

This article presents the experimental and numerical studies of fatigue-ratcheting in carbon steel piping systems under internal pressure and earthquake load. Shake table tests are carried out on two identical 6 in pressurized piping systems made of carbon steel of grade SA333 Gr 6. Tests are carried out using similar incremental seismic load till failure. Wavelet analysis is carried to evaluate frequency change during testing. The tested piping systems are analyzed using iterative response spectrum (IRS) method, which is based on fatigue-ratcheting and compared with test results. Effect of thickness variation in elbow on strain accumulation is studied. Excitation level for fatigue-ratcheting failure is also evaluated and the details are given in this paper.

scholarly journals Modified Partial Capacity Design (M-PCD): achieving partial sidesway mechanism by using two steps design approach

2021 ◽  
Vol 907 (1) ◽  
pp. 012003
Author(s):  
L S Tanaya ◽  
H Herryanto ◽  
P Pudjisuryadi
Keyword(s):  
Response Spectrum ◽  
Pushover Analysis ◽  
Structural Models ◽  
Time History ◽  
Soil Classification ◽  
Seismic Load ◽  
Capacity Design ◽  
History Analysis ◽  
Design Response Spectrum ◽  
Non Linear

Abstract Partial Capacity Design (PCD) has been developed by using magnification factor to keep some columns undamaged during major earthquake. By doing so, the structures will experience the partial side sway mechanism which is also stable, instead of the beam sidesway mechanism. However, in some cases, structures designed by PCD method failed to show the partial side sway mechanism since unexpected damages were still occurred at some columns. In this research, modification of PCD method is proposed by using two structural models in the design process. The first model is used to design beams and columns which are allowed to experience plastic damages, while the second model is used to design columns which are intended to remain elastic when the structure is subjected to a target earthquake. Two nominal earthquakes corresponding to Elastic Design Response Spectrum (EDRS) level with seismic modification factors (R) of 8.0 and 1.6 are used in the first and second structural models, respectively. It should be noted that the second model is identical to the first model except that the stiffnesses are reduced for elements to simulate potential plastic damages. This proposed method is applied to symmetrical 6 and 10 storey buildings with seismic load according SNI 1726:2012 and with soil classification of SE in Surabaya city. A Non-linear Static Procedure (NSP) or pushover analysis and Non-linear Dynamic Procedure (NDP) or time history analysis are employed to evaluate the performance of the structure. The evaluation is conducted at three earthquake levels which are nominal earthquake that is used in second model, earthquake corresponding to EDRS level, and maximum considered earthquake (MCER) specified by the code (50% higher than EDRS level). The building performances satisfy the drift criteria in accordance with FEMA 273. However, the partial side sway mechanism was not achieved at NDP analysis at maximum seismic load, MCER.

scholarly journals COMPARISON OF METHODS USED FOR SEISMIC ANALYSIS OF STRUCTURES

2017 ◽  
Vol 13 ◽  
pp. 20 ◽  
Author(s):  
Petr Čada ◽  
Jiří Máca
Keyword(s):  
Seismic Analysis ◽  
Linear Time ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Time History ◽  
Time History Analysis ◽  
Seismic Load ◽  
Eurocode 8 ◽  
History Analysis ◽  
Non Linear

This paper investigates effects of the seismic load to a structure. The article describes main methods of the definition and practical application of the seismic load based on the Standard Eurocode 8. There was made a comparison of all methods using the same structure. A simple two-storeyed concrete 2D-frame with fixed joints was chosen. A one another model with rigid beams for some calculations was defined. The second model can be used for hand-calculations as a cantilever with two masses. The paper describes main dynamic properties of the chosen structure. Seismic load was defined by lateral force method, modal response spectrum, non-linear time-history analysis and pushover analysis. The time-history analysis is represented by accelerograms. There were made linear and non-linear calculations.

scholarly journals Earth-like planetary magnetotails as non-linear oscillators

2020 ◽  
Author(s):  
Robert J. Burston
Keyword(s):  
Chaotic Behavior ◽  
Noise Component ◽  
General Terms ◽  
Wide Range ◽  
Non Linear ◽  
Observational Noise ◽  
Short Term Forecasting ◽  
Non Linear Oscillator ◽  
Magnetotail Dynamics ◽  
First Time

Abstract. A non-linear oscillator model of a simple system analogous to Earth-like magnetotail plasmoid formation and release dynamics is presented. In this context, Earth-like refers to any magnetosphere with an upstream bow-shock and an elongated downstream tail that undergoes tail plasmoid formation and release. It includes, for the first time in such a model, separate drivers for the Dungey and Vasyliunas Cycles and the capacity to include stochastic and deterministic driving in varying relative and absolute terms. The effects of measurement noise on the model output can also be simulated. This makes the model suitable to investigate the magnetotail dynamics of Mercury, Earth, Jupiter, Saturn and hypothetical exoplanets with similar magnetospheric configurations. The capacity to predict, in general terms, the behavior of a wide range of stellar-wind – magnetosphere interactions has become even more important in the light of the discovery of thousands of exoplanets in recent years. This model represents the first step towards being able to make such predictions for a wide variety of cases without resorting to detailed modelling of individual cases. It is demonstrated that the model can exhibit limit cycle (periodic) and chaotic (long-term unpredictable) behavior. The effects of a sufficiently strong dynamical noise component (stochastic driving) are shown to be inherently different from the effects of an equivalent level of simulated observational noise (simulated Gaussian instrument error). The possibilities of chaotic behavior and of dynamical noise dominating the underlying determinism imply that often only short-term forecasting of magnetotail plasmoid formation is possible.

On Categorization of Seismic Load As Primary or Secondary for Multi-Modal Piping Systems

2020 ◽  
Author(s):  
Pierre Labbé
Keyword(s):  
Linear Time ◽  
Seismic Load ◽  
Piping System ◽  
Ductility Demand ◽  
Plastic Yield ◽  
Wide Range ◽  
Piping Systems ◽  
Practical Engineering ◽  
Input Motion ◽  
Input Level

Abstract Categorizing the seismic load requires calculating the input level associated with the ultimate capacity and comparing it to the level associated with the plastic yield. Therefore, an analysis of the seismically induced ductility demand in oscillators of variable frequencies was carried out by running non-linear time response analyses, the seismic input motion being simulated as samples of a stochastic process of central frequency fc. The response of oscillators with frequencies, f0, varying from 0.1 fc to 10 fc, was systematically analyzed. For every oscillator, 10000 time-responses were performed, corresponding to 1000 input samples multiplied by 10 input levels, covering a wide range of ductility demand up to 20. Output is that seismic loads should be regarded as secondary for flexible oscillators (f0 < fc) while it should be regarded as primary for very stiff oscillators (f0 > cut-off frequency of the input motion, fcut), with intermediate situations for fc < f0 < fcut. A practical engineering rule is presented to incorporate this result when calculating the primary part of seismically induced streeses in a multimodal piping system. This rule is currently tested in the framework of the OECD-NEA international benchmark MECOS.

Experimental and Numerical Studies of Ratcheting in a Pressurized Piping System Under Seismic Load

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
A. Ravikiran ◽  
P. N. Dubey ◽  
M. K. Agrawal ◽  
G. R. Reddy ◽  
R. K. Singh ◽  
...  
Keyword(s):  
Comprehensive Evaluation ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Seismic Loading ◽  
Seismic Load ◽  
Piping System ◽  
Inelastic Response ◽  
Design Procedures ◽  
Numerical Studies ◽  
Piping Systems

Rational seismic design procedures necessitate comprehensive evaluation of nuclear piping systems under large amplitude seismic loads. This comprehensive assessment requires accurate prediction of inelastic response of piping system till failure to ensure adequate margins for unexpected beyond design basis events. The present paper describes the details of experimental and numerical studies of inelastic response of pressurized piping system under seismic loading. Shake table test has been carried out on a three-dimensional stainless steel piping system under internal pressure and seismic load. The amplitude of base excitation has been increased till failure of the piping system. The tested piping system has been analyzed using iterative response spectrum (IRS) method for various levels of excitation. The comparison of numerical and experimental results is given in the paper.

scholarly journals Alternative approach in Partial Capacity Design (PCD) by using predicted post-elastic story shear distribution

2021 ◽  
Vol 907 (1) ◽  
pp. 012007
Author(s):  
H Herryanto ◽  
L S Tanaya ◽  
P Pudjisuryadi
Keyword(s):  
Design Method ◽  
Response Spectrum ◽  
Seismic Load ◽  
Capacity Design ◽  
Plastic Hinges ◽  
Design Response Spectrum ◽  
Non Linear ◽  
Earthquake Resistant Structures ◽  
The One ◽  
Design Earthquake

Abstract The Capacity Design Method is an approach widely used to design earthquake resistant structures. It allows the structures to dissipate earthquake energy by forming plastic hinges through beam side sway mechanism. In the design process, the columns need to be designed stronger than the beams connected to them. Several previous studies have been conducted to propose alternative method allowing partial side sway mechanism namely the Partial Capacity Design (PCD) Method. In this method, selected columns are designed to remain elastic and the plastic hinges are allowed to occur only at the columns base. These columns are designed to resist increased forces. Despite of some successful attempts, PCD method still needs to be developed because sometimes the intended mechanism was not observed. This study proposes a new approach to improve the Partial Capacity Design (PCD) method. Symmetrical 6 and 10 story buildings with 7 bays are analyzed using seismic load for city of Surabaya. Structure behavior under non-linear static analysis is well predicted by this approach. However, under non-linear dynamic analysis, a few unexpected plastic hinges of elastic columns were observed at upper stories. But it should be noted that the earthquake used for performance analysis (maximum considered earthquake) is 50% larger than the one used for design (earthquake level corresponding to elastic design response spectrum).

scholarly journals A Systematic Review and Qualitative Synthesis Resulting in a Typology of Elementary Classroom Movement Integration Interventions

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Spyridoula Vazou ◽  
Collin A. Webster ◽  
Gregory Stewart ◽  
Priscila Candal ◽  
Cate A. Egan ◽  
...  
Keyword(s):  
Physical Activity ◽  
Teacher Collaboration ◽  
A Priori ◽  
Real Life ◽  
Dose Intensity ◽  
Routine Practice ◽  
Qualitative Synthesis ◽  
Wide Range ◽  
Meta Analyses ◽  
Movement Integration

Abstract Background/Objective Movement integration (MI) involves infusing physical activity into normal classroom time. A wide range of MI interventions have succeeded in increasing children’s participation in physical activity. However, no previous research has attempted to unpack the various MI intervention approaches. Therefore, this study aimed to systematically review, qualitatively analyze, and develop a typology of MI interventions conducted in primary/elementary school settings. Subjects/Methods Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to identify published MI interventions. Irrelevant records were removed first by title, then by abstract, and finally by full texts of articles, resulting in 72 studies being retained for qualitative analysis. A deductive approach, using previous MI research as an a priori analytic framework, alongside inductive techniques were used to analyze the data. Results Four types of MI interventions were identified and labeled based on their design: student-driven, teacher-driven, researcher-teacher collaboration, and researcher-driven. Each type was further refined based on the MI strategies (movement breaks, active lessons, other: opening activity, transitions, reward, awareness), the level of intrapersonal and institutional support (training, resources), and the delivery (dose, intensity, type, fidelity). Nearly half of the interventions were researcher-driven, which may undermine the sustainability of MI as a routine practice by teachers in schools. An imbalance is evident on the MI strategies, with transitions, opening and awareness activities, and rewards being limitedly studied. Delivery should be further examined with a strong focus on reporting fidelity. Conclusions There are distinct approaches that are most often employed to promote the use of MI and these approaches may often lack a minimum standard for reporting MI intervention details. This typology may be useful to effectively translate the evidence into practice in real-life settings to better understand and study MI interventions.

scholarly journals Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

Symmetry ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 85
Author(s):  
Yasser Salah Hamed ◽  
Ali Kandil
Keyword(s):  
Time Delay ◽  
Natural Frequency ◽  
Multiple Scales ◽  
Control Process ◽  
Control Force ◽  
Specific Level ◽  
Loop Control ◽  
Positive Displacement ◽  
Non Linear ◽  
Linear Vibrations

Time delay is an obstacle in the way of actively controlling non-linear vibrations. In this paper, a rotating blade’s non-linear oscillations are reduced via a time-delayed non-linear saturation controller (NSC). This controller is excited by a positive displacement signal measured from the sensors on the blade, and its output is the suitable control force applied onto the actuators on the blade driving it to the desired minimum vibratory level. Based on the saturation phenomenon, the blade vibrations can be saturated at a specific level while the rest of the energy is transferred to the controller. This can be done by adjusting the controller natural frequency to be one half of the blade natural frequency. The whole behavior is governed by a system of first-order differential equations gained by the method of multiple scales. Different responses are included to show the influences of time delay on the closed-loop control process. Also, a good agreement can be noticed between the analytical curves and the numerically simulated ones.

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