Physical Modelling of Hydrodynamic Loads on Piggyback Pipelines in Combined Wave and Current Conditions

2010 ◽  
Author(s):  
Masˇa Brankovic´ ◽  
Hammam Zeitoun ◽  
James Sutherland ◽  
Andrew Pearce ◽  
Vagner Jacobsen ◽  
...  
Keyword(s):  
Time History ◽  
Physical Modelling ◽  
Model Tests ◽  
Test Method ◽  
Hydrodynamic Loads ◽  
Time Histories ◽  
Flow Mechanisms ◽  
Force Time ◽  
The Stability ◽  
Pipeline Design

One of the aspects of pipeline design is ensuring pipeline stability on the seabed under the action of environmental loads. During the 1980s, significant efforts were made to improve the understanding of hydrodynamic loads on single pipeline configurations on the seabed (Reference 1). The stability of piggyback (bundled) pipeline configurations is less well understood, with little quantitative data readily available to the design engineer for practical application in engineering problems (References 2–6). This paper describes an extensive set of physical model tests performed for piggyback on-seabed and piggyback-raised-from seabed (spanning or lifting pipeline) configurations to determine hydrodynamic forces in combined wave and current conditions. The piggyback is nominally in the 12 o’clock position. The well-established carriage technique was used, in order to obtain data for use in full-scale stability modelling. The model tests are benchmarked against existing test data, to confirm the validity of the test method. Key findings are presented in terms of non-dimensional coefficients, and force time histories for the vertical and horizontal forces. A brief interpretation of the hydrodynamic load behaviour of the Piggyback System is provided by considering the physical flow mechanisms causing the force time history variation; furthermore the influence of the seabed separation on the piggyback loads is also discussed.

Damage Detection in Rods Using Wave Propagation and Regression Analysis

1999 ◽  
Author(s):  
K. T. Feroz ◽  
S. O. Oyadiji
Keyword(s):  
Wave Propagation ◽  
Regression Analysis ◽  
Damage Detection ◽  
Numerical Study ◽  
Time History ◽  
Ball Impact ◽  
Spherical Ball ◽  
Time Histories ◽  
Measured Strain ◽  
Force Time

Abstract The phenomena of wave propagation in rods was studied both numerically and experimentally. The finite element (FE) code ABAQUS was used for the numerical study while PZT (lead zirconium titanate) sensors and a 50 MHz transient recorder were used experimentally to monitor and to capture the propagation of stress pulses. For the study of damage detection in the rods the analyses and the experiments were repeated by introducing slots in a fixed axial location of the rod. A longitudinal wave was induced in the rod via collinear impact which was modelled in the FE analyses using the force-time history computed from the classical Hertz contact theory. In the experimental measurements this was achieved by a spherical ball impact at one plane end of the rods. It is shown that the predicted and measured strain-time histories for the defect-free rod and for the rods with defect correlate quite well. These results also show that defects can be located using the wave propagation phenomena. A regression analysis technique of the predicted and measured strain histories of the defect free rod and of the rod with defect was also performed. The results show that this technique is more efficient for smaller defects. In particular, it is shown that the area enclosed by the regression curve increases as the defect size increases.

Displacement Time Histories by Direct Numerical Integration of Acceleration Data

1991 ◽  
Author(s):  
M. L. Wang ◽  
S. R. Subia
Keyword(s):  
Time History ◽  
Shear Walls ◽  
Model Tests ◽  
Seismic Events ◽  
Scaled Model ◽  
Acceleration Data ◽  
Time Histories ◽  
Seismic Loadings ◽  
The Time Domain ◽  
Direct Numerical Integration

Abstract Acceleration measurements often provide the engineer with a means by which to determine the forces within dynamic structural systems. However for certain problems, information about the structural motion, the displacement-time history, may also be of interest. One such application deals with the evaluation of stiffness in reinforced concrete structures during seismic events. Scaled model tests of these events suggest that the stiffness of these structures often degrades drastically. The displacement response of these seismic events are required both for the development and evaluation of postulated structural stiffness models. This paper discusses the processing of acceleration data from scaled model tests to obtain displacement-time histories for low aspect shear walls subject to simulated seismic loadings. Displacement histories obtained in the time domain are compared with those produced using a frequency domain system identification analysis.

EFFECT OF THE FLUID ON THE IMPACT FORCE OF THE WET MISSILE

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Duc-Kien Thai ◽  
Seung-Eock Kim
Keyword(s):  
Impact Force ◽  
Force Plate ◽  
Time History ◽  
Research Centre ◽  
Element Analysis ◽  
Time Histories ◽  
Target Wall ◽  
Force Time ◽  
Missile Test ◽  
The Impact

In this paper, the force-time histories of soft missiles, with and without filled water, impacting the target wall were investigated using finite element analysis. The force plate tests, with a dry missile (test FP8) and a wet missile (test FP16) carried out by Technical Research Centre of Finland (VTT), were used. The numerical analysis results were verified by comparing with those of experiments. A parametric analysis with different missile velocities was also performed to investigate the force-time history and impulse of the missile impact on target plate. Based on a comparison with the Riera approach, the coefficients were proposed to modify the Riera function. The analysis results show that, the Riera function accurately predicted the impact force time history in the case of the dry missile. However, in the case of the wet missile, the coefficients α from 1.24 to 1.45 are recommended to be added to the second term of the Riera function in the case in which the impact velocity is in the range of 70 m/s to 200 m/s.

scholarly journals An Evidence Basis for Future Equestrian Helmet Lateral Crush Certification Tests

2020 ◽  
Vol 10 (7) ◽  
pp. 2623 ◽  
Author(s):  
Thomas A. Connor ◽  
J. Michio Clark ◽  
Pieter Brama ◽  
Matt Stewart ◽  
Aisling Ní Annaidh ◽  
...  
Keyword(s):  
Time History ◽  
Test Method ◽  
Published Data ◽  
Mean Values ◽  
Safety Outcome ◽  
Certification Tests ◽  
Impact Location ◽  
Peak Loads ◽  
Equestrian Sports ◽  
Force Time

The aim of this study is to determine what loads are likely to be applied to the head in the event of a horse falling onto it and to determine by how much a typical equestrian helmet reduces these loads. An instrumented headform was designed and built to measure applied dynamic loads from a falling horse. Two differently weighted equine cadavers were then dropped repeatedly from a height of 1 m (theoretical impact velocity of 4.43 m/s) onto both the un-helmeted and helmeted instrumented headforms to collect primary force–time history data. The highest mean peak loads applied to the headform by the lighter horse were measured at the bony sacral impact location (15.57 kN ± 1.11 SD). The lowest mean peak loads were measured at the relatively fleshier right hind quarter (7.91 kN ± 1.84 SD). For the heavier horse, highest mean peak loads applied to the headform were measured at the same bony sacral impact location (16.02 kN ± 0.83 SD), whilst lowest mean peak loads were measured at the more compliant left hind quarter (10.47 kN ± 1.08 SD). When compared with the un-helmeted mean values, a reduction of 29.7% was recorded for the sacral impact location and a reduction of 43.3% for the lumbosacral junction location for helmeted tests. Notably, all measured loads were within or exceeded the range of published data for the fracture of the adult lateral skull bone. Current helmet certification tests are not biofidelic and inadequately represent the loading conditions of real-world “lateral crush” accidents sustained in equestrian sports. This work presents the first ever evidence basis upon which any future changes to a certification standards test method might be established, thereby ensuring that such a test would be both useful, biofidelic, and could ensure the desired safety outcome.

scholarly journals Dynamic effects induced by the impact of debris flows on protection barriers

2018 ◽  
Vol 10 (1) ◽  
pp. 116-131 ◽  
Author(s):  
Maddalena Marchelli ◽  
Valerio De Biagi
Keyword(s):  
Impact Force ◽  
Time History ◽  
Element Model ◽  
Interaction Force ◽  
Accurate Analysis ◽  
Vibration Period ◽  
Time Histories ◽  
Mode Vibration ◽  
Force Time ◽  
The Impact

Debris flow is a transient phenomenon that causes large disasters. Retaining systems, whose design is still nowadays a crucial issue, can mitigate this risk. Multiple surges can arise during this phenomenon; thus, an accurate analysis might consider the impact force time histories rather than only its maxima. The aim of this work is to analyze the effects of the interaction between the debris and the barrier during one surging phenomenon. A discrete element model models the granular motion and the interaction between the debris and a rigid open barrier set at the end of the channel. The estimated interaction force time history is then used as input impact force for the dynamic structural analyses of the piles. A total of 12 different structural sections are adopted and the internal forces at the base are critically compared. It results that the first mode vibration period is the parameter that largely affects the behavior of the piles.

Impact factor method for design of bridge foundations under ship collisions

2016 ◽  
Vol 20 (4) ◽  
pp. 534-548 ◽  
Author(s):  
Junjie Wang ◽  
Yanchen Song ◽  
Zhiran Yu
Keyword(s):  
Impact Factor ◽  
Impact Force ◽  
Time History ◽  
Rigid Wall ◽  
Static Method ◽  
Factor Method ◽  
Empirical Function ◽  
Time Histories ◽  
Dynamic Amplification ◽  
Force Time

Due to the complexity involved and limited study on the topic, the equivalent static method, adopted in the current codes for structural design of bridges under ship collisions, does not take into account the dynamic amplification effect correctly. In this article, impact factor method is proposed to estimate the response of bridge’s piers and foundations, as a better alternative of the equivalent static method. Through refined numerical simulations of ship-rigid wall collisions for nine typical ships under various impact velocities, 81 impact force time-histories are obtained. The period-dependent impact factor is defined, and empirical function of it is proposed and parameters in the empirical function are determined by the 81 sample impact force time-histories. Finally, both impact factor method and dynamic time-history method are used to estimate the responses of piers and foundations of two example bridges, and the precision of impact factor method is discussed.

Brain Tissue Material and Damage Properties for Blast Trauma

2018 ◽  
Author(s):  
Soroush Assari ◽  
Kurosh Darvish
Keyword(s):  
Tissue Damage ◽  
Tissue Injury ◽  
Time History ◽  
Bovine Brain ◽  
Test Method ◽  
Material Behavior ◽  
Strain Rates ◽  
Path Dependent ◽  
Force Time ◽  
Blast Induced Neurotrauma

The aim of this study was to develop a test method to characterize the material behavior of bovine brain samples in large shear deformations and high strain rates relevant to blast-induced neurotrauma (BINT) and evaluate tissue damage. A novel shear test setup was designed and built capable of applying strain rates ranging from 300 to 1000 s−1. Based on the shear force time history and propagation of shear waves, it was found that the instantaneous shear modulus (about 6 kPa) was more than 3 times higher than the values previously reported in the literature. The shear wave velocity was found to be strain path dependent which is an indication of tissue damage at strains greater than 10%. The results of this study can help in improving finite element models of the brain for simulating tissue injury during BINT.

scholarly journals Phase manipulation and the harmonic components of ringing forces on a surface-piercing column

2014 ◽  
Vol 470 (2168) ◽  
pp. 20130847 ◽  
Author(s):  
C. J. Fitzgerald ◽  
P. H. Taylor ◽  
R. Eatock Taylor ◽  
J. Grice ◽  
J. Zang
Keyword(s):  
Water Waves ◽  
Fourier Transforms ◽  
Time History ◽  
Wave Force ◽  
Separation Method ◽  
Coastal Protection ◽  
Time Histories ◽  
Local Wave ◽  
Harmonic Components ◽  
Force Time

A general phase-based harmonic separation method for the hydrodynamic loading on a fixed structure in water waves of moderate steepness is proposed. An existing method demonstrated in the experimental study described by Zang et al. (Zang et al. 2010 In Proc. Third Int. Conf. on Appl. of Phys. Modelling to Port and Coastal Protection. pp. 1–7.) achieves the separation of a total diffraction force into odd and even harmonics by controlling the phase of incident focused waves. Underlying this method is the assumption that the hydrodynamic force in focused waves possesses a Stokes-like structure. Under the same assumption, it is shown here how the harmonic separation method can be generalized, so that the first four sum harmonics can be separated by phase control and linear combinations of the resultant time-histories. The effectiveness of the method is demonstrated by comparisons of the Fourier transforms of the combined time-histories containing the harmonics of interest. The local wave elevations around the focus time are also visualized for the first three harmonics in order to reveal the local dynamics driving components within the wave force time-history.

Soft Computing Based Force Recovery Technique for Hypersonic Shock Tunnel Tests

2018 ◽  
Vol 18 (05) ◽  
pp. 1871004 ◽  
Author(s):  
Ramesh Babu Pallekonda ◽  
Soumya Ranjan Nanda ◽  
Santosha K. Dwivedy ◽  
Vinayak Kulkarni ◽  
Viren Menezes
Keyword(s):  
Fuzzy Inference ◽  
Time History ◽  
Shock Tunnel ◽  
Force Balance ◽  
Inference System ◽  
Time Histories ◽  
Recovery Technique ◽  
Hypersonic Shock ◽  
Force Recovery ◽  
Force Time

A hemispherical model equipped with a three component accelerometer force balance has been tested in a shock tunnel at Mach 8.0 freestream conditions. A novel technique has been devised using the Artificial Neuro-Fuzzy Inference System (ANFIS) for recovering the forces experienced by the model during the experiments. Implementation of this methodology in calibration of the force balance showed encouraging agreement with the impulse forces recovered from the calibration tests. The same recovery procedure is then adopted to obtain the time history of the forces for 0[Formula: see text] and 15[Formula: see text] angle of attack experiments. The drag recovered in steady state is found to agree well with the conventional methods with minor discrimination for the lift and pitching moment. In light of the limitation of the accelerometer force balance theory due to the unaccountability of model dynamics, the force recovery technique proposed herein is found simple to implement and can be opted as a tool for prediction of the aerodynamic coefficients and force time histories.

An Energy-Based Method for Testing Cushioning Durability of Running Shoes

1993 ◽  
Vol 9 (1) ◽  
pp. 27-46 ◽  
Author(s):  
John F. Swigart ◽  
Arthur G. Erdman ◽  
Patrick J. Cain
Keyword(s):  
Maximum Energy ◽  
Test Method ◽  
New Method ◽  
Testing System ◽  
Materials Testing ◽  
Wear Factor ◽  
Time Profiles ◽  
Running Shoes ◽  
Computer Controlled ◽  
Force Time

A new method for quantifying shoe cushioning durability was developed. This method used a computer-controlled, closed-loop materials testing system to subject the shoes to force-time profiles that were indicative of running. The change in the magnitude of the maximum energy absorbed by a shoe and the change in the magnitude of the energy balance of the shoe were quantified after the shoe had been worn running for a given distance. A shoe that changed very little in these quantities had a small energy wear factor and was deemed to have durable cushioning. The test method was roughly validated through comparison of three shoes of different midsole constructions with known relative durabilities. The shoes were tested at four simulated running speeds for energy properties when they were new and after they were run in for 161 km. The relative durabilities of the tested shoes were consistent with expectations based on the shoes' materials and constructions, showing that the new method has promise in predicting shoe cushioning durability, and thus more complete studies of the method may prove useful.

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