scholarly journals Exponentially Varying Load on Rayleigh Beam Resting on Pasternak Foundation.

2019 ◽  
Vol 16 ◽  
pp. 8449-8458
Author(s):  
Ahamed Jimoh ◽  
Emmanuel Omeiza Ajoge
Keyword(s):  
Dynamical System ◽  
Shear Modulus ◽  
Dynamic Behavior ◽  
Axial Force ◽  
Laplace Transformation ◽  
Convolution Theorem ◽  
Damping Coefficient ◽  
Pasternak Foundation ◽  
Rotatory Inertia ◽  
Rayleigh Beam

This paper investigates the dynamic behavior of uniform Rayleigh beam resting on Pasternak foundation and subjected to exponentially varying magnitude moving the load. The solution techniques are based on finite Fourier sine transformed Laplace transformation and convolution theorem. The results show that for a fixed value of axial force, damping coefficient and rotatory inertia, increases in shear modulus and foundation modulus reduces the response amplitude of the dynamical system. It was also found that increases in axial force, rotary inertia, and damping coefficient for fixed values of shear modulus and foundation modulus lead to decreases in the deflection profile of the Rayleigh beam resting on Pasternak foundation. Finally, it was found that the effect of shear modulus is more noticeable that of the foundation modulus.

Disk Position Nonlinearity Effects on the Chaotic Behavior of Rotating Flexible Shaft-Disk Systems

2012 ◽  
Vol 28 (3) ◽  
pp. 513-522 ◽  
Author(s):  
H. M. Khanlo ◽  
M. Ghayour ◽  
S. Ziaei-Rad
Keyword(s):  
Partial Differential Equations ◽  
Differential Equations ◽  
Dynamic Behavior ◽  
Chaotic Behavior ◽  
Equations Of Motion ◽  
Beam Theory ◽  
Disk System ◽  
Partial Differential ◽  
Rayleigh Beam ◽  
Flexible Shaft

AbstractThis study investigates the effects of disk position nonlinearities on the nonlinear dynamic behavior of a rotating flexible shaft-disk system. Displacement of the disk on the shaft causes certain nonlinear terms which appears in the equations of motion, which can in turn affect the dynamic behavior of the system. The system is modeled as a continuous shaft with a rigid disk in different locations. Also, the disk gyroscopic moment is considered. The partial differential equations of motion are extracted under the Rayleigh beam theory. The assumed modes method is used to discretize partial differential equations and the resulting equations are solved via numerical methods. The analytical methods used in this work are inclusive of time series, phase plane portrait, power spectrum, Poincaré map, bifurcation diagrams, and Lyapunov exponents. The effect of disk nonlinearities is studied for some disk positions. The results confirm that when the disk is located at mid-span of the shaft, only the regular motion (period one) is observed. However, periodic, sub-harmonic, quasi-periodic, and chaotic states can be observed for situations in which the disk is located at places other than the middle of the shaft. The results show nonlinear effects are negligible in some cases.

DEGRADATION EFFECT OF SEAWATER ON THE LONG-TERM DYNAMIC BEHAVIOR OF ARTIFICIALLY CEMENTED SAND

2013 ◽  
Vol 07 (04) ◽  
pp. 1350031 ◽  
Author(s):  
BO LI ◽  
YUANQIANG CAI ◽  
XIANGWU ZENG ◽  
LINYOU PAN
Keyword(s):  
Shear Modulus ◽  
Dynamic Behavior ◽  
Tap Water ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Resonant Column ◽  
Cyclic Triaxial Tests ◽  
Cemented Sand

The dynamic behavior of lightly cemented sand under long-term seawater attack was evaluated in this study. Resonant column and cyclic triaxial tests were employed to investigate the evolution of the shear modulus and damping ratio of cemented sand with respect to soaking period (SP), confining pressure, and cement content (CC). The results of this study show that the cementation of the sand is affected by soaking in seawater to a greater extent than by soaking in tap water. The shear modulus of the cemented sand soaked in seawater was smaller than that of the cemented sand soaked in tap water. The damping ratio increased significantly, as the SP increased and was greater for the cemented sand soaked in seawater than for the cemented sand soaked in tap water. The dynamic behavior of nonhomogenous specimens was examined. Crystallization of salts could be clearly observed and probably explains the evolution of the dynamic behavior of the cemented sand. Finally, the shear modulus was fitted using Rollins' Law [Rollins et al., 1998], which demonstrates that the parameters used in the equation can be reasonably fitted linearly over a range of SPs.

scholarly journals Dynamics of Biochar-Silty Clay Interaction Using In-House Fabricated Cyclic Loading Apparatus: A Case Study of Coastal Clay and Novel Peach Biochar from the Qingdao Region of China

2020 ◽  
Vol 12 (7) ◽  
pp. 2599 ◽  
Author(s):  
Junwei Liu ◽  
Suriya Prakash Ganesan ◽  
Xin Li ◽  
Ankit Garg ◽  
Aman Singhal ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Shear Modulus ◽  
Dynamic Behavior ◽  
Void Ratio ◽  
Water Pressure ◽  
Damping Ratio ◽  
Cyclic Strength ◽  
Silty Clay ◽  
Amended Soils ◽  
Amended Soil

Biochar has been recently investigated as an eco-friendly material in bio-engineered slopes/landfill covers. A majority of recent studies have focused on analyzing water retention behavior while very few have examined dynamic behavior (i.e., cyclic loading due to earthquake, wind, or wave) of biochar amended soil. As far as the authors are aware, there is no study on the dynamic behavior of biochar amended soils. Considering the above mentioned study as a major objective, field excavated soil was collected and mixed with in-house produced biochar from peach endocarps, at three amendment rates (5%, 10%, and 15%). The un-amended bare soil and biochar amended soil were imposed to a cyclic load in a self-designed apparatus and the corresponding stress-strain parameters were measured. Dynamic parameters such as shear modulus and damping ratio were computed and the results were compared between bare and biochar amended soil. Furthermore, the residual cyclic strength of each soil types were correlated with an estimated void ratio to understand the interrelation between dynamic loading responses and biochar amended soils. The major outcomes of this study show that the addition of biochar decreases the void ratio, thereby increasing the shear modulus and residual cyclic strength. However, the modulus and strength values attenuates after 15 cycles due to an increase in pore water pressure. In contrary, at higher amendment rates, Biochar Amended Soils (BAS) forms clay-carbon complex and decreases both shear modulus and residual cyclic strength.

Passive Dampers

2021 ◽  
pp. 158-169
Keyword(s):  
Energy Dissipation ◽  
Dynamic Behavior ◽  
Optimal Choice ◽  
Damping Coefficient ◽  
Severe Damage ◽  
Civil Structures ◽  
Fluid Viscous Dampers ◽  
Story Drift ◽  
Rc Building ◽  
Passive Dampers

Civil structures are subjected to various types of loading, which induce severe damage to the structures. Many techniques have been developed for structural rehabilitation; one of the emerging technologies is the use of energy dissipation systems such as fluid viscous dampers (referred to hereafter by FVD). In this chapter, the effect of these devices on the dynamic behavior of an RC building is investigated, with an optimal choice of the linear FVD parameter (i.e., damping coefficient), using a simplified and effective approach. It was found that the maximum inter-story drift of the analyzed retrofitted structures can be significantly reduced compared to the original ones.

Dynamics and stability analysis of a flexible liquid-filled rotor in a constant thermal environment

2021 ◽  
pp. 107754632110224
Author(s):  
Guangding Wang ◽  
Wenjun Yang ◽  
Huiqun Yuan
Keyword(s):  
Thermal Environment ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotatory Inertia ◽  
Rayleigh Beam ◽  
Comparison Results ◽  
The Stability ◽  
Spinning Speed ◽  
Thermoelastic Theory ◽  
Good Agreement

In this study, the dynamics and stability of a flexible rotor containing liquid in a constant thermal environment are investigated. According to thermoelastic theory, the thermal axial force exerted on the rotor is calculated by using the analytical method. A spinning Rayleigh beam is used as a simplified model of the rotor. Applying the Hamilton principle, the governing equation of motion for the flexible liquid-filled rotor system is derived. Using the obtained model, the stability prediction model and the critical spinning speed for the rotor system are formulated. To demonstrate the validity of the developed model, the present analysis is compared with the results reported in the previous study, and good agreement is observed from the comparison results. Finally, numerical results based on the obtained model are performed for a better understanding of the parameters including filling parameters, mode number, rotatory inertia and thermal effect on the stability, and critical spinning speed of the rotor system.

scholarly journals Effect of Sand Fouling on the Dynamic Properties and Volume Change of Gravel During Cyclic Loadings

2020 ◽  
Author(s):  
Meysam Bayat
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Dynamic Behavior ◽  
Volume Change ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Practical Applications ◽  
Large Shear Strain

Understanding the factors that influence the dynamic behavior of granular soils during cyclic loading is critical to infrastructure design. Previous research has lacked quantitative study of the effects of fouling index (FI), mean effective confining pressure, relative density, shear strain level and anisotropic consolidation, especially when the effective vertical stress is lower than the effective horizontal stress on the dynamic behavior of gravelly soils. The objective of the present study was to evaluate the dynamic behavior and volume change of both clean and fouled specimens for practical applications. To this end, cyclic triaxial tests with local strain measurements under both isotropic and anisotropic confining conditions were conducted. It is found that the fouled specimen with 50 % sand (i.e. the specimen which contains 50 % gravel and 50 % sand) has the highest shear modulus at low shear strain levels and the largest volume reduction and damping ratio at large shear strain levels. The results of tests indicate that the effect of fouling index on the shear modulus is reduced at large shear strain levels. Volumetric contraction due to the increase in mean effective confining pressure is more significant at large shear strain levels. The results also indicate that the stiffness of the specimens under anisotropic compression mode are larger than those in extension or isotropic mode.

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