scholarly journals Technical design and stability analysis procedure for horizontal stability construction of roads and railways

2021 ◽  
Author(s):  
Zvonimir Šepac
Keyword(s):  
Vertical Component ◽  
Vertical Direction ◽  
Retaining Walls ◽  
Stable Structure ◽  
Engineering Practice ◽  
Structural Peculiarity ◽  
Optimal Angle ◽  
Static Interaction ◽  
Horizontal Stability ◽  
Axial Resistance

Unstable sections of predominantly vertical roads and railways are usually stabilized by viaducts, while predominantly horizontal unstable sections of the same structures are regularly stabilized by special structures which have a common feature of spaciousness or massiveness, and which proportionally also require peculiarity in all aspects of the construction. The goal of the new solution is to avoid the highlighted structural peculiarity, that is, to apply a solution that will be more of a constructive element of roads and railways, like a viaduct in an approximate sense. There is such a solution, and that is the low-rise stable structure, which in a naturally appropriate way counteracts horizontal instabilities on low-rise objects. The horizontal effect on the object is converted to a vertical direction via this construction by means of pile coupling, while this effect is greatly reduced due to the effect of static interaction between the components of the coupling. If, instead of various vertical structures with horizontal anchors or mass structure retaining walls, we apply the slope-pile coupling at an optimal angle in the range of 15 to 20 degrees, then, by activating the external horizontal effect, i.e. instability, the primary axial resistance in the oblique pile is simultaneously activated through circumferential friction. The vertical component of this resistance decreases the active horizontal component, while the horizontal does the same, provided that the pile has a transverse static EI feature. This approach has not been used thus far in engineering practice and therefore represents a novelty. Therefore, it can be argued that by constructing a low-rise stable structure, we can achieve at least approximately the same structural impression that we enjoy regarding the viaduct construction for predominantly vertical instabilities.

SEISMIC ANALYSIS OF OFFSHORE TRIANGULAR TENSION LEG PLATFORMS

2006 ◽  
Vol 06 (01) ◽  
pp. 97-120 ◽  
Author(s):  
S. CHANDRASEKARAN ◽  
A. K. JAIN ◽  
N. R. CHANDAK
Keyword(s):  
Deep Water ◽  
Seismic Analysis ◽  
Vertical Component ◽  
Vertical Direction ◽  
Gas Production ◽  
Hydrodynamic Drag ◽  
Environmental Loads ◽  
Axial Forces ◽  
Seismic Force ◽  
Seismic Forces

Oil and gas production from deep-water offshore fields represent a major structural engineering challenge for the industry. The tension leg platform (TLP) is a well-established concept for deep-water oil exploration. It is necessary to design an offshore TLP such that it can respond to moderate environmental loads without damage, and is capable of resisting severe environmental loads without seriously endangering the occupants. Seismic analysis of triangular TLP under moderate regular waves is investigated. The analysis considers nonlinearities due to the change in tether tension and nonlinear hydrodynamic drag forces. The coupled response of TLP under moderate regular sea waves due to change in initial pretension in the tethers caused by seismic forces (vertical direction) is then investigated. Seismic forces are imposed at the bottom of each tether as axial forces. The tether tension becomes unbalanced when the hull is under offset position. The vertical component of seismic force is an important item to take into consideration, because it is directly superposed to pretension of tethers. The change in initial pretension due to the vertical component of the earthquake affects the response of the triangular TLP in degrees-of-freedom experiencing such forces. The tether tension varies nonlinearly when the platform is subjected to seismic forces caused by the El Centro earthquake and artificially generated earthquake using Kanai–Tajimi's power spectrum. The response due to earthquakes varies with the intensity of the input ground motion. The seismic response of the triangular TLP exhibits nonlinear behavior in the presence of waves and it is non-proportionately influenced by the wave period and the wave height.

The Research of the Governance of Instability Retaining Wall

2014 ◽  
Vol 1065-1069 ◽  
pp. 85-88
Author(s):  
Gang Qiu ◽  
Xin Sheng Ge
Keyword(s):  
Retaining Wall ◽  
Retaining Walls ◽  
Design Parameters ◽  
Engineering Practice ◽  
Construction Process ◽  
Reinforcement Scheme ◽  
Soil Nail ◽  
Joint Construction ◽  
Jet Grouting ◽  
Pavement Reinforcement

According to retaining walls of joint construction buildings and office building of the mine of three yuan weizi town, outdoor pavement reinforcement of engineering practice, introduced the design parameters and construction process of the high-pressure jet grouting pile, soil nail wall and drilling grouting, the results showed that reinforcement scheme is reasonable and feasible, there is reference to other similar projects.

Suppression of vertical diffusion in strongly stratified turbulence

2000 ◽  
Vol 402 ◽  
pp. 311-327 ◽  
Author(s):  
YUKIO KANEDA ◽  
TAKAKI ISHIDA
Keyword(s):  
Ad Hoc ◽  
Vertical Component ◽  
Vertical Direction ◽  
Passive Scalar ◽  
Time Correlation ◽  
Particle Dispersion ◽  
Stratified Turbulence ◽  
Vertical Diffusion ◽  
Velocity Autocorrelation ◽  
Highly Oscillatory

A spectral approximation for diffusion of passive scalar in stably and strongly stratified turbulence is presented. The approximation is based on a linearized approximation for the Eulerian two-time correlation and Corrsin's conjecture for the Lagrangian two-time correlation. For strongly stratified turbulence, the vertical component of the turbulent velocity field is well approximated by a collection of Fourier modes (waves) each of which oscillates with a frequency depending on the direction of the wavevector. The proposed approximation suggests that the phase mixing among the Fourier modes having different frequencies causes the decay of the Lagrangian two-time vertical velocity autocorrelation, and the highly oscillatory nature of these modes results in the suppression of single-particle dispersion in the vertical direction. The approximation is free from any ad hoc adjusting parameter and shows that the suppression depends on the spectra of the velocity and fluctuating density fields. It is in good agreement with direct numerical simulations for strongly stratified turbulence.

scholarly journals Study of ingots solidification kinetics based on physical modelling of casting and melt crystallization

2019 ◽  
Vol 75 (7) ◽  
pp. 818-827
Author(s):  
S. B. Gamanyuk ◽  
D. V. Rutskii ◽  
N. A. Zyuban ◽  
A. Ya. Puzikov ◽  
E. R. Koftunov
Keyword(s):  
Solid Phase ◽  
Vertical Component ◽  
Vertical Direction ◽  
Physical Modelling ◽  
Solidification Process ◽  
Melt Crystallization ◽  
Ingot Axis ◽  
Hard Particles ◽  
Solidification Kinetics ◽  
Heat Center

Study of the processes, taking place at the large ingots obtaining during steel casting, as well as during its solidification is a rather hard task. Therefore it is reasonable to use for the study of them methods of solidification modelling by application various hard particles (inoculators), being introduced into a melt. Evaluation of the inoculation effect on the solidification process, structure formation and defected zones extension in model ingots carried out. It was determined, that introduction of inoculators during melt casting results in decreasing of the diphasic zone thickness. It was determined also, that introduction of hard particles (inoculators) in the volume of from 6 till 12% results in reducing time of model ingots solidification. An increase the volume of inoculators leads to prevalence of solidification vertical component over the horizontal one. It was determined also, that introduction of inoculators allows increasing the solidification process orientation, that characterized by an increase of linear taper and as a result – the vertical solidification component increase. It was revealed, that introduction of inoculators at the liquid-solid casting leads to changing the heat center location. The introduction of inoculators results to “elongation” of heat center by the solidifying ingot axis, that relates with a quicker advance of the solid phase in vertical direction, as a result of the quick removal of solidifying ingot overheating.

Structural Response of a Multi-Hinged Articulated Offshore Tower Under Seismic Excitation

2009 ◽  
Author(s):  
Syed Danish Hasan ◽  
Nazrul Islam ◽  
Khalid Moin
Keyword(s):  
Water Depth ◽  
Vertical Component ◽  
Structural Response ◽  
Vertical Direction ◽  
Time History ◽  
Equation Of Motion ◽  
Offshore Structures ◽  
Rotational Degree ◽  
Energy Potential ◽  
Sea Bed

Articulated towers are the compliant offshore structures that are designed with high degree of compliancy in horizontal direction and to remain relatively stiff in vertical direction. The nonlinear effects due to large displacements, large rotations and high environmental forces are of prime importance in the analysis. This paper investigates the structural response of a 580 m high multi-hinged articulated tower under different seismic sea environment in a water depth of 545 m. The articulated tower is represented as an upright flexible pendulum supported on the sea-bed by a mass-less rotational spring of zero stiffness while the top of it rigidly supports a deck in the air; a concentrated mass above still water level (SWL). For computation of seismic loads, the tower is idealized as a “stick” model of finite elements with masses lumped at the nodes. The earthquake response is carried out by time history analysis using real sets of Californian earthquakes. Disturbed water particle kinematics due to seismic shaking of sea bed is taken into consideration. Nonlinear dynamic equation of motion is formulated using Lagrangian approach. The approach is based on energy principle that relates the kinetic energy, potential energy and work of the system in terms of rotational degree-of-freedom. The solution to the equation of motion is obtained by Newmark-β scheme in the time domain that counters the nonlinearities associated with the system in an iterative fashion. It is observed that with the increase in water depth, additional hinges are required to compensate the increased bending moment due to additional earthquake loads. Analysis results are compared and presented in the form of time-histories and PSDFs of various responses along with combined responses due to horizontal and vertical component of ground motion using direct sum and SRSS method.

scholarly journals Horizontally isotropic double porosity convection

2019 ◽  
Vol 475 (2221) ◽  
pp. 20180672 ◽  
Author(s):  
B. Straughan
Keyword(s):  
Porous Medium ◽  
Nonlinear Stability ◽  
Vertical Component ◽  
Vertical Direction ◽  
Transversely Isotropic ◽  
Double Porosity ◽  
Solid Skeleton ◽  
The Difference

We analyse instability and nonlinear stability in a layer of saturated double porosity medium. In a double porosity or bidisperse porous medium, there are normal pores which give rise to a macroporosity. But, there are also cracks or fissures in the solid skeleton and these give arise to another porosity known as micro porosity. In this paper, the macropermeability is horizontally isotropic, in the sense that the vertical component of permeability is different to the horizontal one which is the same in all horizontal directions. Thus, the permeability is transversely isotropic with the isotropy axis in the vertical direction of gravity. We also allow the micro permeability to be horizontally isotropic, but the permeability ratios of vertical to horizontal are different in the macro- and micro-phases. The effect of the difference of ratios is examined in detail.

Characteristics of Simian Adaptation Fields Produced by Behavioral Changes in Saccade Size and Direction

1999 ◽  
Vol 81 (6) ◽  
pp. 2798-2813 ◽  
Author(s):  
Christopher T. Noto ◽  
Shoji Watanabe ◽  
Albert F. Fuchs
Keyword(s):  
Vertical Component ◽  
Vertical Direction ◽  
Horizontal Component ◽  
Behavioral Changes ◽  
Spatial Extent ◽  
Horizontal Dimension ◽  
Saccade Size ◽  
Cross Axis ◽  
Adaptation Field ◽  
Gain Change

Characteristics of adaptation fields produced by behavioral changes in saccade size and direction. The gain of saccadic eye movements can be altered gradually by moving targets either forward or backward during targeting saccades. If the gain of saccades to targets of only one size is adapted, the gain change generalizes or transfers only to saccades with similar vectors. In this study, we examined the spatial extent of such saccadic size adaptation, i.e., the gain adaptation field. We also attempted to adapt saccade direction by moving the target orthogonally during the targeting saccade to document the extent of a direction or cross-axis adaptation field. After adaptive gain decreases of horizontal saccades to 15° target steps, >82% of the gain reduction transferred to saccades to 25° horizontal target steps but only ∼30% transferred to saccades to 5° steps. For the horizontal component of oblique saccades to target steps with 15° horizontal components and 10° upward or downward vertical components, the transfer was similar at 51 and 60%, respectively. Thus the gain decrease adaptation field was quite asymmetric in the horizontal dimension but symmetric in the vertical dimension. Although gain increase adaptation produced a smaller gain change (13% increase for a 30% forward adapting target step) than did gain decrease adaptation (20% decrease for a 30% backward adapting target step), the spatial extent of gain transfer was quite similar. In particular, the gain increase adaptation field displayed asymmetry in the horizontal dimension (58% transfer to 25° saccades but only 32% transfer to 5° saccades) and symmetry in the vertical direction (50% transfer to the horizontal component of 10° upward and 40% transfer to 10° downward oblique saccades). When a 5° vertical target movement was made to occur during a saccade to a horizontal 10° target step, a vertical component gradually appeared in saccades to horizontal targets. More than 88% of the cross-axis change in the vertical component produced in 10° saccades transferred to 20° saccades but only 12% transferred to 4° saccades. The transfer was similar to the vertical component of oblique saccades to target steps with either 10° upward (46%) or 10° downward (46%) vertical components. Therefore both gain and cross-axis adaptation fields have similar spatial profiles. These profiles resemble those of movement fields of neurons in the frontal eye fields and superior colliculus. How those structures might participate in the adaptation process is considered in the discussion.

Seismic Response Analysis of Long Span Cable-Stayed Bridge by Response Spectrum Method

2012 ◽  
Vol 204-208 ◽  
pp. 1992-1996 ◽  
Author(s):  
Min Chao Jin ◽  
Bao Fu Wang ◽  
Zhong Ren Feng ◽  
Xiong Jiang Wang
Keyword(s):  
Response Spectrum ◽  
Vertical Component ◽  
Vertical Direction ◽  
Longitudinal Direction ◽  
Response Analysis ◽  
Response Spectrum Method ◽  
Cable Stayed Bridge ◽  
Spectrum Method ◽  
Long Span ◽  
Significant Difference

Based on response spectrum method, the seismic behavior of a long span cable-stayed bridge is investigated through three dimensional finite element model established by ANSYS. By calculating the cumulative effective mass factors of the bridge, the minimum number of modes used for modal superposition analysis is obtained. Design acceleration response spectrums under two probabilities are used in the analysis. The response spectrums are input in the bridge longitudinal direction, vertical direction, transverse direction and combined horizontal and vertical directions. Displacements and internal forces results show that vertical component of the ground motion greatly influences the response of the bridge and there is significant difference between the results of the two probabilities.

scholarly journals Time synchronization requirement of global navigation satellite system augmentation system based on pseudolite

2019 ◽  
Vol 52 (3-4) ◽  
pp. 303-313 ◽  
Author(s):  
Chao Ma ◽  
Jun Yang ◽  
Jianyun Chen ◽  
Yinyin Tang
Keyword(s):  
Time Synchronization ◽  
Vertical Direction ◽  
Civil Aviation ◽  
Engineering Practice ◽  
Navigation Satellite ◽  
Positioning Accuracy ◽  
Dilution Of Precision ◽  
Global Navigation ◽  
Global Navigation Satellite ◽  
The Impact

Global navigation satellite systems are widely used across the world because of their continuous/all-weather, global coverage, and high precision positioning. But, three-dimensional positioning accuracy, especially in the vertical direction, remains insufficient because of the geometric distribution of satellites. This is especially true for air-borne objects such as unmanned aerial vehicles, civil aviation devices, and missiles. To solve this problem, we adopt a satellite-ground joint positioning system based on a pseudo-satellite (pseudolite). The introduction of ground pseudolites can significantly reduce the vertical dilution of precision and improve positioning accuracy. This method has been proposed in the 1980s. However, we have to ask a question, as long as we add a pseudolite, can the positioning accuracy be improved? The answer is no. Pseudolites can cause time synchronization problems with satellites, and the resulting timing errors of the pseudolite are converted into pseudorange errors, reducing accuracy. Here, we seek to evaluate the impact of the reduced vertical dilution of precision and the increased range errors associated with the introduction of a pseudolite on the ground. We derive a mathematical formula to explain this relationship. We conclude that when the satellite range error and the change in the position dilution of precision associated with a pseudolite are known, we can calculate an approximate limit for the pseudolite timing accuracy to ensure that the use of the pseudolite improves the positioning accuracy. This work should be of great value in guiding engineering practice.

Pseudo-static lateral earth pressures on broken-back retaining walls

2010 ◽  
Vol 47 (11) ◽  
pp. 1247-1258 ◽  
Author(s):  
Abouzar Sadrekarimi
Keyword(s):  
Earth Pressure ◽  
Retaining Walls ◽  
Shaking Table ◽  
Engineering Practice ◽  
Rear Face ◽  
Back Wall ◽  
Earth Pressures ◽  
Table Model ◽  
Concrete Blocks ◽  
Failure Wedge

Displacement of retaining walls during earthquakes causes damage to the structures founded on their backfill. The displacement of the wall can be reduced by decreasing the lateral earth pressure applied on its back. This can be achieved in a broken-back wall as the size of the failure wedge formed behind the wall is reduced; therefore, the calculation of lateral earth pressures is essential in assessing the safety of and designing broken-back retaining walls. In this study, a series of reduced-scale shaking table model experiments were performed on broken-back quay walls composed of concrete blocks with two different rear-face shapes. In comparison with a vertical-back wall, earth pressures increased at the upper forward (i.e., seaward) leaning rear-face segments of the wall, whereas they decreased at lower backward (i.e., landward) leaning elevations. Because of the wide application of the pseudo-static method of Mononobe–Okabe in engineering practice and design codes, lateral earth pressures have also been estimated using this approach. The comparison between the measured lateral earth pressures and those calculated using the Mononobe–Okabe method shows fairly good agreement in predicting the overall distribution of lateral active earth pressure during and after the shaking.

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