scholarly journals On estimating the reduction factor of bridge piers

2020 ◽  
Vol 157 ◽  
pp. 06012
Author(s):  
Andrei Benin ◽  
Olga Nesterova ◽  
Alexander Uzdin ◽  
Sergei Prokopovich ◽  
Yuri Rutman ◽  
...  
Keyword(s):  
Spectral Composition ◽  
Time History ◽  
Reduction Factor ◽  
Bridge Piers ◽  
Elastic Displacement ◽  
Mass Model ◽  
The Moment ◽  
Limit Position ◽  
Force Displacement ◽  
Displacement Diagram

Estimating the reduction factor for calculating massive reinforced concrete bridge piers was made. For this purpose a quasi-static “force-displacement” diagram was built up using the ANSYS software. This diagram has the form of a bilinear one, and the character of the bilinearity depends on the diameter of the reinforcing bars insignificantly. The percentage of reinforcement affects only the moment when all reinforcement bars begin to flow. The reinforcement flow takes place in the displacement interval from 3 to 5 cm. The collapse will occur when the reaction of the bearing part goes beyond the pier cross-section at pier displacements from 5 to 20 cm. Using “force-displacement” diagram, the behavior of the single-mass model with a bilinear deformation diagram and the limit displacement of 20 cm was analyzed. Then, it became possible to obtain for each accelerogram the limit elastic displacement and the limit position of the point corresponding to the maximum structure displacement during structure oscillations. It was done using real accelerograms of earthquakes with intensity 9 on the MSK scale without normalizing their amplitudes. In this case, long-period accelerograms had smaller peak accelerations, but resulted in greater plastic deformations. As a result, no evident dependence of plastic deformation on the input spectral composition was found and the value of reduction factor K1 turned out to be 0.25-0.27. However, it is shown that this reduction factor cannot be used to make transition from seismic loads obtained on the basis of time-history analysis by accelerograms to design loads.

CFD Modelling for Gas-Liquid and Liquid-Liquid Taylor Flows in the Entrance Region of Microchannels

2021 ◽  
Author(s):  
Amin Etminan ◽  
Yuri S. Muzychka ◽  
Kevin Pope
Keyword(s):  
Liquid Flow ◽  
Continuous Flow ◽  
Velocity Ratio ◽  
Time History ◽  
Simulation Method ◽  
Cfd Modelling ◽  
Cross Sectional ◽  
Systematic Analysis ◽  
Gas Liquid Flow ◽  
The Moment

Abstract This paper presents a CFD-based simulation method for air/water and water/dodecane Taylor flows through an axisymmetric microchannel with a circular cross-sectional area. A systematic analysis is conducted by exploring the effects of different superficial velocities and apparent viscosities on the hydrodynamics of a slug flow regime. A concentric junction is employed to make bubbles of air in a continuous flow of water and slugs of water in a continuous flow of dodecane oil. A time-history study is conducted to predict the air-bubble and water-slug evolution processes, in particular at the moment of slug breakup. The results show that the larger apparent viscosity ratio of phases involved in the liquid-liquid flow generates a more stable interface. However, the liquid slug length is less and film thickness is slightly larger in liquid-liquid compared to gas-liquid flow. Furthermore, variations in gas and liquid holdups are correlated by the superficial velocity ratio. The numerical analysis developed in this paper is in good agreement with the correlations and data in the literature.

Strength reduction factor of self-centering structures under near-fault pulse-like ground motions

2020 ◽  
Vol 24 (1) ◽  
pp. 119-133
Author(s):  
Huihui Dong ◽  
Qiang Han ◽  
Xiuli Du ◽  
Canxing Qiu
Keyword(s):  
Ground Motions ◽  
Time History ◽  
Reduction Factor ◽  
Strength Reduction ◽  
The Self ◽  
Hysteretic Behavior ◽  
Hysteretic Model ◽  
Strength Reduction Factor ◽  
Vibration Period ◽  
Near Fault

Many studies on the strength reduction factor mainly focused on structures with the conventional hysteretic models. However, for the self-centering structure with the typical flag-shaped hysteretic behavior, the corresponding study is limited. The main purpose of this study is to investigate the strength reduction factor of the self-centering structure with flag-shaped hysteretic behavior subjected to near-fault pulse-like ground motions by the time history analysis. For this purpose, the smooth flag-shaped model based on Bouc-Wen model which can show flag-shaped hysteretic behavior is first described. The strength reduction factor spectra of the flag-shaped model are then calculated under 85 near-fault pulse-like ground motions. The influences of the ductility level, vibration period, site condition, hysteretic parameter, and hysteretic model are investigated statistically. For comparison, the strength reduction factors under ordinary ground motions are also analyzed. The results show that the strength reduction factor from near-fault pulse-like ground motions is smaller. Finally, a predictive model is proposed to estimate the strength reduction factor for the self-centering structure with the flag-shaped model under near-fault pulse-like ground motions.

scholarly journals Study on determination method of hydrodynamic coefficient of Marine pile foundation

2020 ◽  
Vol 143 ◽  
pp. 01021
Author(s):  
Jiang Zongnan
Keyword(s):  
Fourier Analysis ◽  
Time History ◽  
Least Square Method ◽  
Wave Force ◽  
Least Square ◽  
Irregular Waves ◽  
Hydrodynamic Coefficient ◽  
Irregular Wave ◽  
Advantages And Disadvantages ◽  
The Moment

The irregular waves are simulated by using standard spectrum. Instantaneous value method, Fourier analysis method, least square method and "harbour hydrological code" are used to determine the moment force of coefficient CM and drag coefficient CD. Then CM and CD that linearized by Borgman L.E. equation are substituted into Morison equation. The time history curve of the wave force on the pile is calculated and compared with the measured wave force data under the action of irregular wave to analyze the advantages and disadvantages of several methods to determine CM and CD. The results show that the comparison between CM and CD determined by Fourier analysis and least square method is practical.

UAV Based Multi-Hazard Vulnerability Assessment System for Bridges Exposed to Scour

2020 ◽  
Author(s):  
Okan Özcan ◽  
Orkan Özcan
Keyword(s):  
Load Capacity ◽  
Time History ◽  
Element Model ◽  
Lateral Load ◽  
Assessment System ◽  
Bridge Piers ◽  
Scour Depth ◽  
River Bed ◽  
Principal Axes

<p>Evaluating the multi-hazard performance of river crossing bridges under probable earthquake, flood, and scouring scenarios is a cumbersome task in performance-based engineering. The loss of lateral load capacity at bridge foundations may induce bridges to become highly vulnerable to failure when the effects of scour and floods are combined. Besides, the assessment of local scouring mechanism around bridge piers provides information for decision‐making regarding the pile footing design and for predicting the safety of bridges under critical scoured conditions. Thereby, accurate high-resolution Digital Elevation Models (DEMs) are critical for many hydraulic applications such as erosion, hydraulic modelling, sediment transport, and morphodynamics. In the present study, an automated unmanned aerial vehicle (UAV) based multi-hazard performance assessment system was developed to respond to rapid performance evaluation and performance prediction needs for river crossing reinforced concrete (RC) bridges. The Bogacay Bridge constructed over Bogacay in Antalya, Turkey was selected as the case study. In the developed system, firstly the seasonally acquired UAV measurements were used to obtain the DEMs of the river bed from 2016 to 2019. The transverse cross sections of the river bed that were taken close to the inspected bridge were used to measure the depth of the scoured regions along the bridge piles under the present conditions. Separately, in conjunction with the flood simulation and validation with 2003 flood event (corresponds to Q<sub>50</sub>=1940 m<sup>3</sup>/s), the scour depth after maximum probable flood load according to the return period of 500 years (Q<sub>500</sub>=2560 m<sup>3</sup>/s) were predicted by HEC-RAS software. Afterwards, the 3D finite element model (FEM) of the bridge was constituted automatically with the developed code considering the scoured piles. The flood loads were exerted on the modeled bridge with regard to the HEC-RAS flood inundation map and relevant water depth estimations around the bridge piers. For the seismic evaluation, nonlinear time history analyses (THA) were conducted by using scaled eleven scaled earthquake acceleration records that were acting in both principal axes of the bridge simultaneously by considering maximum direction spectra (SaRotD100) as compatible with the region seismicity. In the analyses; as the scour depth increased, the fundamental periods, shear forces and the bending moments were observed to increase while the pile lateral load capacities diminished. Therefore, the applicability of the proposed system was verified using the case study bridge.</p>

scholarly journals Parametric Study of the Elementary Segment of an Antiprismatic Pop-Up Deployable Lattice Column

2014 ◽  
Vol 2 (2) ◽  
pp. 65-86
Author(s):  
Noémi Friedman ◽  
György Farkas ◽  
Adnan Ibrahimbegovic
Keyword(s):  
Parametric Study ◽  
Complex Structure ◽  
Basic Element ◽  
Element Formulation ◽  
Geometrically Nonlinear ◽  
Preliminary Design ◽  
Elementary Segment ◽  
Basic Segment ◽  
Force Displacement ◽  
Displacement Diagram

Abstract In this article the primary segment of an antiprismatic pop-up mast is analyzed, that can be applied for largely flexible architectural designs, like deployable bridges or transportable look-out towers. This deployable column, consisting of rigid plates, rigid and elastic bars, is characterized by its selfdeploying behavior due to the energy accumulated from lengthening the elastic bars during packing. The main goal of this paper is to prepare the analysis of the complex structure by a herein detailed investigation of the behavior of one, basic element of the deployable mast. After the analytical examination of the general behavior of the basic segment a geometrically nonlinear finite element formulation is used to trace the force-displacement diagram. Besides the parametric study, approximations of main mechanical parameters are herein given for facilitating preliminary design of such deployable structures.

scholarly journals Prediction of railway induced ground vibration through multibody and finite element modelling

2013 ◽  
Vol 4 (1) ◽  
pp. 167-183 ◽  
Author(s):  
G. Kouroussis ◽  
O. Verlinden
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Vertical Plane ◽  
Time History ◽  
Ground Vibration ◽  
Element Model ◽  
Contact Forces ◽  
Railway Transportation ◽  
Lumped Mass ◽  
Mass Model

Abstract. The multibody approach is now recognized as a reliable and mature computer aided engineering tool. Namely, it is commonly used in industry for the design of road or railway vehicles. The paper presents a framework developed for predicting the vibrations induced by railway transportation. Firstly, the vehicle/track subsystem is simulated, on the basis of the home-made C++ library EasyDyn, by mixing the multibody model of the vehicle and the finite element model of the track, coupled to each other through the wheel/rail contact forces. Only the motion in the vertical plane is considered, assuming a total symmetry between left and right rails. This first step produces the time history of the forces exerted by the ballast on the foundation, which are then applied to a full 3-D FEM model of the soil, defined under the commercial software ABAQUS. The paper points out the contribution of the pitch motion of the bogies and carbodies which were neglected in previous publications, as well as the interest of the so-called coupled-lumped mass model (CLM) to represent the influence of the foundation in the track model. The potentialities of the model are illustrated on the example of the Thalys high-speed train, riding at 300 km h−1 on the Belgian site of Mévergnies.

scholarly journals Angelic Dynamism: Humanity in Paul Klee’s Drawing Series of 1939–1940

2021 ◽  
Vol 11 (3) ◽  
pp. 512-531
Author(s):  
Sergey P. Purgin ◽  
Keyword(s):  
Walter Benjamin ◽  
Human Life ◽  
Time History ◽  
Main Theme ◽  
Human Beings ◽  
Temporal Dimension ◽  
Artistic Style ◽  
European Tradition ◽  
The Moment ◽  
The Universe

Since Walter Benjamin in “The Theses on the Philosophy of History” showcased Paul Klee’s angels, they remain mysterious figures that represent time, history or soul. The article focuses on the series of drawings that were created in the artist’s later period (1939−1940). The series can be regarded as the artist’s final will and testament as it expresses Klee’s condensed philosophy and mature views on man’s place in the universe. It also reflects the master’s cherished artistic methods and techniques, consistently honed in on during the course of his life. The author studies the relations within the series and the series relation to other artworks by Klee. It is demonstrated that it is humankind that is the main theme of the series. By contrasting human and angelic forms in his drawings Klee reinvigorates the European tradition of defining humanity through its relation to angelic orders and through its position on the hierarchy of creation. However, Klee strives to re-imagine the universe as a whole, for him it is not the ladder of perfections, which rises to angels and God. Therefore, the relations between human and angelic creatures are intimately familial rather than hierarchical. The author highlights that the artistic style and techniques emphasize visual dynamic and form creation (“formation”). In depicting angels, the artist brings forth his concern with temporal dimension of human nature and its significance in human life. Thus, in this dynamic interrelation, human beings become “angelic grotesque” with their own ontic temporality. This temporality specific to human creatures is defined as the “moment that transcends itself ” — since the latter is essentially “ecstatic” and “self-propelling”.

scholarly journals Inelastic Displacement Ratios for Evaluation of Degrading Peak – Oriented SDOF Systems

2017 ◽  
Vol 62 (1) ◽  
pp. 33-47 ◽  
Author(s):  
Muzaffer Borekci ◽  
Murat S. Kirçil ◽  
Ibrahim Ekiz
Keyword(s):  
Dynamic Instability ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Elastic Displacement ◽  
Hysteretic Model ◽  
Collapse Potential ◽  
Inelastic Displacement ◽  
The Mean ◽  
Displacement Demand ◽  
Inelastic Displacement Ratio

Estimation of the inelastic displacement demand (IDD) is an important part of the performance-based design. Coefficient method is one of the methods for the estimation of IDD and in this method, IDD is determined by multiplying elastic displacement demand with inelastic displacement ratio (CR ). Previous researches showed that structures deteriorate and also exhibit dynamic instability under severe earthquakes and these behaviors should be considered in the estimation of CR to estimate a reliable IDD. In this study, CR of the non-degrading bilinear hysteretic model and the degrading peak-oriented hysteretic model with collapse potential were determined and effects of degradation on IDD were investigated. Nonlinear time history analysis of SDOF systems were performed using considered hysteretic models. Furthermore a new equation is proposed for the mean CR of degrading SDOF systems. Also, effect of local site conditions and post-yield stiffness on the mean CR of degrading SDOF systems were investigated.

The Meckering earthquake of 14 October 1968: A possible downward propagating rupture

1987 ◽  
Vol 77 (5) ◽  
pp. 1558-1578
Author(s):  
Kristín S. Vogfjörd ◽  
Charles A. Langston
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Time History ◽  
Vertical Displacement ◽  
Body Waves ◽  
Finite Fault ◽  
Short Period ◽  
Double Couple ◽  
The Moment ◽  
Fault Length

Abstract Average source parameters of the 1968 Meckering, Australia earthquake are obtained by the inversion of body waves. The objectives of the inversion are the elements of the moment tensor and the source-time history. An optimum source depth of 3 km is determined, but because of source complexity the point source assumption fails and the moment tensor obtained at that depth has a large nondouble-couple term, compensated linear vector dipole = 34 per cent. The source parameters of the major double-couple are: strike = 341°; dip = 37°; rake = 61°; and seismic moment = 8.2 ×1025 dyne-cm. The source-time function is of approximately 4 sec duration, with a long rise time and a sharp fall-off. The fault length is constrained on the surface by the observed surface break, and results from vertical displacement modeling suggest a width of approximately 10 km in the middle, assuming a dip of 37°. That restricts the entire faulted area to lie above 6 km depth. Two finite fault models for the earthquake are presented, with rupture initiating at a point (1) near the top of the fault and (2) at the bottom of the fault. Both models produce similar long-period synthetics, but based on the short-period waveforms, model 1 is favored. It is argued that such a rupture process is the most reasonable in this cold shield region.

Numerical Simulation of Low Impact Velocity Behaviour of Polymeric Syntactic Foam

2020 ◽  
Vol 12 (8) ◽  
pp. 1044-1049
Author(s):  
Yash M. Chordiya ◽  
Manmohan Dass Goel
Keyword(s):  
Impact Velocity ◽  
Reaction Force ◽  
Syntactic Foam ◽  
Time History ◽  
Material Model ◽  
Fe Model ◽  
Foam Material ◽  
Weight Impact ◽  
Force Time ◽  
Force Displacement

In this study a FE model is prepared for drop weight impact hammer testing of polymeric syntactic foam. The foam is modelled using crushable foam material and hammer is modelled using bilinear material model of LS-DYNA®. A series of simulation is performed by varying density of foam and impact velocity of hammer. Based on the prepared FE model and the force-displacement relation, energy absorption of the foam is computed and compared for three densities and three velocities. A comparative study is presented based on the displacement, reaction force-time history, and forcedisplacement behaviour.

Sign in / Sign up

Export Citation Format

Share Document