On the effectiveness of ventilation to mitigate the damage of spherical chambers subjected to confined trinitrotoluene detonations

2018 ◽  
Vol 22 (2) ◽  
pp. 486-501 ◽  
Author(s):  
Francisco Hernandez ◽  
Hong Hao ◽  
Xihong Zhang
Keyword(s):  
Shock Waves ◽  
Time History ◽  
Radial Breathing Mode ◽  
Gas Pressure ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Breathing Mode ◽  
Single Degree ◽  
Reflected Shock ◽  
Ductility Ratio

This article presents a comparative study on the effectiveness of ventilation to mitigate blasting effects on chambers subjected to confined detonations of high explosives. The pressure time-history that acts on the chamber walls is described by three components: (1) the first shock wave, (2) the train of re-reflected shock waves, and (3) the gas pressure. The radial response of spherical chambers is described by the radial breathing mode and modeled by an equivalent single degree of freedom system. The three pressure components are considered for the calculation of the maximum ductility ratio, which is obtained from the numerical solution of the single degree of freedom chamber response. It is assumed that openings reduce the gas pressure but they have an insignificant effect on shock waves. The dynamic response of fully and partially confined chambers are calculated and compared. Results show that intermediate/small openings (less than 10% of the surface of the chamber) are ineffective to mitigate the chamber response and damage. The vibratory response of the chamber is susceptible to elastic or plastic resonance but it is not considerably modified by the long-term gas pressure because of its high radial breathing mode frequency, allowing concluding that ventilation is ineffective to reduce the maximum response of spherical chambers subjected to internal high explosive explosion.

Design Tool for Base-Isolated Structures Modeled as Single-Degree-of-Freedom Oscillators

1997 ◽  
Vol 50 (11S) ◽  
pp. S125-S132
Author(s):  
Gustavo O. Maldonado
Keyword(s):  
Response Spectrum ◽  
Time History ◽  
Design Tool ◽  
Degree Of Freedom ◽  
Iteration Step ◽  
Complex Conjugate ◽  
Equivalent Linearization ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Isolated Structures

A stochastic equivalent linearization technique combined with a ground response spectrum approach is proposed to approximate the inelastic response of base-isolated structures. These structures are modeled by nonlinear oscillators with a single degree of freedom. The main advantage of the proposed methodology is the fast calculation of approximate results in comparison with the slow, but more accurate time history analyses. The Bouc-Wen constitutive model is used to represent the inelastic behavior of the isolators. The equations of motion are linearized by an iterative stochastic technique involving the a-priori unknown response statistics. At each iteration step, the modal contributions from one real and one pair of complex conjugate modes are combined by a response spectrum approach to obtain the maximum responses of interest. The process requires the use of conventional spectra (pseudo-acceleration and relative velocity) as well as the relative displacement spectrum of a massless oscillator. Floor response spectrum results above the isolators are calculated by the proposed approach and are compared against the results obtained by a simulation involving time history analyses.

scholarly journals Development of equivalent linear systems for single-degree-of-freedom structures with magneto-rheological dampers for seismic design application

2017 ◽  
Vol 28 (19) ◽  
pp. 2675-2687 ◽  
Author(s):  
Yunbyeong Chae ◽  
James M Ricles ◽  
Richard Sause
Keyword(s):  
Response Spectrum ◽  
Damping Ratio ◽  
Time History ◽  
Analysis Procedure ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Design Response Spectrum ◽  
Simplified Analysis ◽  
Magneto Rheological

Numerous studies have been conducted for magneto-rheological dampers, but the application of magneto-rheological dampers in seismic design is limited due to the lack of a systematical design procedure. In this article, a simplified analysis procedure is proposed to estimate the response of a single-degree-of-freedom structure with diagonal bracing and a magneto-rheological damper without performing the time history analysis. The proposed simplified analysis procedure is based on the equivalent linear system of a magneto-rheological damper. The equivalent damping ratio and the effective period of the single-degree-of-freedom system are determined from the loss factor and the effective stiffness of the magneto-rheological damper based on the quasi-static model. Design response spectrum is utilized to calculate the displacement of the single-degree-of-freedom system. The equivalent damping ratio and the effective stiffness of the single-degree-of-freedom system are dependent on the displacement of the system; thus, the proposed procedure is iterated until the displacement from the design response spectrum converges. The accuracy of the simplified analysis procedure is evaluated by comparing the estimated response from this procedure with the response from the time history analysis. The results show a good agreement between two methods, demonstrating the robustness of the proposed simplified analysis procedure.

Study on Evaluation Method of High-Rise Building Performance by Equivalent Single Degree of Freedom System

2008 ◽  
Vol 400-402 ◽  
pp. 599-605
Author(s):  
Xing Wen Liang ◽  
Li Xin ◽  
Yue Sheng Tong
Keyword(s):  
Evaluation Method ◽  
Demand Curve ◽  
Time History ◽  
Degree Of Freedom ◽  
Nonlinear Time History Analysis ◽  
Elastic Displacement ◽  
Natural Period ◽  
Single Degree Of Freedom ◽  
High Rise ◽  
Single Degree

A performance evaluation method of high-rise buildings is presented, by means of capacity spectra method which allows for higher mode effects. The multi-degree-of-freedom system (MDOF) of each mode is transformed into equivalent single-degree-of-freedom (ESDOF) system, and the ESDOF system is supposed to be elastic perfectly plastic. In elastic range, the equivalent displacement of ESDOF system for each mode is deduced by displacement response spectra based on the natural period, and the structural lateral elastic displacement of each mode could be determined by the corresponding equivalent displacement and mode shape. In inelastic range, according to capacity spectra method, the relationships among demand curve, capacity curve and ductility coefficient are built. The structural performance under moderate or major earthquake is determined by iteration method. The paper illustrates the application of the proposed procedure with an example and attempts to prove its feasibility by nonlinear time-history analysis.

Computer Analysis of the Dynamic Contact Behavior and Tracking Characteristics of a Single-Degree-of-Freedom Slider Model for a Contact Recording Head

1995 ◽  
Vol 117 (1) ◽  
pp. 124-129 ◽  
Author(s):  
Kyosuke Ono ◽  
Hiroshi Yamamura ◽  
Takaaki Mizokoshi
Keyword(s):  
Contact Stiffness ◽  
Time History ◽  
Dynamic Contact ◽  
Disk Surface ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Single Degree Of Freedom ◽  
Contact Behavior ◽  
Single Degree ◽  
Contact Slider

This paper presents a new theoretical approach to the dynamic contact behavior and tracking characteristics of a contact slider that is one of the candidates of head design for future high density magnetic recording disk storages. A slider and its suspension are modeled as a single-degree-of-freedom vibration system. The disk surface is assumed to have a harmonic wavy roughness with linear contact stiffness and damping. From the computer simulation of the time history of the slider motion after dropping from the initial height of 10 nm, it is found that the contact vibration of the slider can attenuate and finally track on the wavy disk surface in a low waviness frequency range. As the waviness frequency increases, however, the slider cannot stay on the disk surface and comes to exhibit a variety of contact vibrations, such as sub- and super-harmonic resonance responses and finally comes to exhibit non-periodic vibration. It is also found that, among design parameters, the slider load to mass ratio and contact damping can greatly increase the surface waviness frequency and amplitude for which the stable tracking of a contact slider is possible.

scholarly journals External Periodic Force Control of a Single-Degree-of-Freedom Vibroimpact System

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jingyue Wang ◽  
Haotian Wang ◽  
Tie Wang
Keyword(s):  
Periodic Orbits ◽  
Force Control ◽  
Time History ◽  
Degree Of Freedom ◽  
Bifurcation And Chaos ◽  
Periodic Force ◽  
Chaotic Motions ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Impact System

A single-degree-of-freedom mechanical model of vibro-impact system is established. Bifurcation and chaos in the system are revealed with the time history diagram, phase trajectory map, and Poincaré map. According to the bifurcation and chaos of the actual vibro-impact system, the paper puts forward external periodic force control strategy. The method of controlling chaos by external periodic force feedback controller is developed to guide chaotic motions towards regular motions. The stability of the control system is also analyzed especially by theory. By selecting appropriate feedback coefficients, the unstable periodic orbits of the original chaotic orbit can be stabilized to the stable periodic orbits. The effectiveness of this control method is verified by numerical simulation.

scholarly journals Advanced Modeling of Single Degree of Freedom System for Earthquake Ground Motion Using LabVIEW Software

2021 ◽  
Author(s):  
R.B. Malathy ◽  
Govardhan Bhat ◽  
U.K. Dewangan
Keyword(s):  
Ground Motion ◽  
Discrete Time ◽  
Virtual Instrument ◽  
Structural Engineering ◽  
Time History ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Time Histories

In this paper, the structural responses at discrete time steps are evaluated to understand the linear dynamics characteristics of a structural system using LabVIEW (Laboratory Virtual Instrument Engineering Workbench) tool. Time History Analysis (THA) which is an essential procedure to design a reliable structure when the structure is subjected to dynamic loading is taken into consideration for the study. Direct integration method was used to find out the dynamic response of the structure as it is applicable for both linear as well as nonlinear range. Block diagram that perform step-by-step integration to analyze the linear single degree of freedom (SDOF) system has been prepared in LabVIEW. The processing of data is carried out till the equilibrium is satisfied at all discrete time points within the interval of solution instead of any time t. Different ground motion time histories were considered for THA and responses of the SDOF system are evaluated. The results from LabVIEW were validated and the accuracy of the algorithms generated are discussed. It is observed that the accuracy and stability of the final solution depends on the variation of displacement, velocity and acceleration that is assumed in each step. Thus, LabVIEW workbench can therefore be recognized as an effective instrument in structural engineering owing to its fast sampling features.

scholarly journals P-delta actions in seismic resistant structures

1992 ◽  
Vol 25 (1) ◽  
pp. 56-69 ◽  
Author(s):  
R. C. Fenwick ◽  
B. J. Davidson ◽  
B. T. Chung
Keyword(s):  
Ground Motion ◽  
Time History ◽  
Degree Of Freedom ◽  
Delta Method ◽  
Background Information ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Factors Influencing ◽  
Seismic Resistant ◽  
Principal Factors

The results of several thousands of inelastic time history analyses, which have been made on single degree of freedom structures to assess P-delta effects induced in earthquakes, are reviewed. The principal factors influencing P-delta actions are shown to be the ductility, the duration of the severe ground motion, the level of damping and the period of the structure. A method of designing for P-delta effects for single degree of freedom structures is presented. A limited number of analyses of multi-storey frames and walls indicate that the approach may be used for multi-storey structures. This paper gives background information on the P-delta method of analysis given in an appendix to the commentary of the proposed loading code.

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