Effect of depth on seismic response of circular tunnels

2011 ◽  
Vol 48 (1) ◽  
pp. 117-127 ◽  
Author(s):  
Ulas Cilingir ◽  
S. P. Gopal Madabhushi
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Dynamic Equilibrium ◽  
Digital Camera ◽  
Finite Element Simulations ◽  
Silica Sand ◽  
Seismic Behaviour ◽  
Dynamic Equilibrium State ◽  
Current Design ◽  
Tunnel Depth

Tunnels in seismically active areas are vulnerable to adverse effects of earthquake loading. Recent seismic events have shown that there is a need to validate current design methods to better understand the deformation mechanisms associated with the dynamic behaviour of tunnels. The research described in this paper consists of physical and numerical modelling of circular tunnels with dynamic centrifuge experiments and complementary finite element simulations. The aim is to develop an understanding of the effects of tunnel depth on the seismic behaviour of tunnels. Tunnels with different depth-to-diameter ratios were tested in dry, loose silica sand. Accelerations around the tunnel and earth pressures on the lining were measured. A high-speed digital camera was used to record soil and lining deformations. Particle image velocimetry analyses were carried out on the recorded images to measure the deformations. Complementary dynamic finite element simulations were also conducted with a code capable of managing contact simulations at the soil–lining interface. Measurement of centrifuge experiments and finite element analyses show that the tunnel shifts from a static equilibrium to a dynamic equilibrium state as soon as the earthquake starts. The nature of the dynamic equilibrium, however, is difficult to predict using conventional analysis methods.

Comparative Study of the Shock Resistance of Rubber Protective Coatings Subjected to Underwater Explosion

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Feng Xiao ◽  
Yong Chen ◽  
Hongxing Hua
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Protective Coatings ◽  
Dynamic Compression ◽  
Reaction Force ◽  
Compressive Load ◽  
Underwater Explosion ◽  
Finite Element Simulations ◽  
Compression Load ◽  
Shock Resistance

Finite element simulations of rubber protective coatings with different structures under two dynamic loading cases were performed. They were monolithic coating and honeycomb structures with three different cell topologies (hexachiral honeycomb, reentrant honeycomb, and circular honeycomb). The two loading cases were a dynamic compression load and water blast shock wave. The dynamic mechanical responses of those coatings under these two loading cases were compared. Finite element simulations have been undertaken using the ABAQUS/Explicit software package to provide insights into the coating's working mechanism and the relation between compression behavior and water blast shock resistance. The rubber materials were modeled as hyperelastic materials. The reaction force was selected as the major comparative criterion. It is concluded that when under dynamic compressive load, the cell topology played an important role at high speed, and when under underwater explosion, the honeycomb coatings can improve the shock resistance significantly at the initial stage. For honeycomb coatings with a given relative density, although structural absorbed energy has a significant contribution in the shock resistance, soft coating can significantly reduce the total incident impulse at the initial fluid-structure interaction stage. Further, a smaller fraction of incident impulse is imparted to the honeycomb coating with lower compressive strength.

Three-Dimensional Finite Element Simulations of Ground Vibration Generated by High-Speed Trains and Engineering Countermeasures

2005 ◽  
Vol 11 (12) ◽  
pp. 1437-1453 ◽  
Author(s):  
Judith C. Wang ◽  
Xiangwu Zeng ◽  
Robert L. Mullen
Keyword(s):  
Finite Element ◽  
Asphalt Concrete ◽  
High Speed ◽  
Three Dimensional ◽  
Ground Vibration ◽  
Finite Element Simulations ◽  
Modified Asphalt ◽  
Vibration Attenuation ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper we discuss the benefits of using rubber-modified asphalt concrete in high-speed railway foundations. We present the results from a series of three-dimensional finite element simulations modeling a high-speed train foundation utilizing various trackbed materials. Four trackbed materials were tested for their relative vibration attenuation capacities: ballast, concrete, conventional asphalt concrete, and rubber-modified asphalt concrete. Additionally, studies varying the speed and the weight of the passing train were performed. Parametric studies varying the dimensions of the trackbed underlayment were also examined. From these numerical simulations, it is shown that rubber-modified asphalt concrete outperforms other traditional paving materials in ground vibration attenuation. It is also shown that the speeds and weights of the passing trains and the dimensions of the trackbed have significant effects on the relative performance of the paving materials. Implications for design are discussed.

Electromagnetic Sheet Bulging: Analysis of Process Parameters by FE Simulations

2013 ◽  
Vol 554-557 ◽  
pp. 741-748 ◽  
Author(s):  
Joao Pedro M. Correia ◽  
Saïd Ahzi
Keyword(s):  
Finite Element ◽  
Process Parameters ◽  
High Speed ◽  
Finite Element Simulations ◽  
Electromagnetic Forming ◽  
Forming Process ◽  
High Speed Forming ◽  
Bulging Test ◽  
High Repeatability

Electromagnetic forming is a non-conventional forming process and is classified as a high-speed forming process. It provides certain advantages as compared to conventional forming processes: improved formability, high repeatability and productivity, reduction in tooling cost and reduction of springback and of wrinkling. However, various process parameters affect the performance of the electromagnetic forming system. Finite element simulations are very useful to optimize a process because they can reduce time and costs. With the aim of investigating the effects of the process parameters on the deformed blank geometry, finite element simulations of an electromagnetic sheet bulging test have been performed in this work. Furthermore the role of first impulse of discharged current is also investigated.

scholarly journals Response of Piping Tees to Propagating Detonations

2013 ◽  
Author(s):  
Thomas C. Ligon ◽  
David J. Gross ◽  
Joseph E. Shepherd
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Structural Response ◽  
Initial Pressure ◽  
Finite Element Simulations ◽  
Steel Plates ◽  
Digital Data ◽  
304 Stainless Steel ◽  
Piping System ◽  
Piping Systems

This paper reports the results of experiments and finite element simulations on the structural response of piping systems to internal detonation loading. Specifically, the work described in this paper focuses on the forces that are produced at tee-junctions that lead to axial and bending structural responses of the piping system. Detonation experiments were conducted in a 2-in. (50 mm) diameter schedule 40 piping system that was fabricated using 304 stainless steel and welded to ASME B31.3 standards. The 4.1 m (162-in.) long piping system included one tee and was supported using custom brackets and cantilever beams fastened to steel plates that were bolted to the laboratory walls. Nearly-ideal detonations were used in a 30/70 H2-N2O mixture at 1 atm initial pressure and 300 K. Pressure and hoop, axial, and support strains were measured using a high-speed (1 MHz) digital data acquisition system and calibrated signal conditioners. It was concluded that detonations propagate through the run of a 90° tee with relatively little disturbance in either direction. The detonation load increases by approximately a factor of 2 when the detonation enters through the branch. The deflections of the cantilever beam supports and the hoop and axial pipe strains could be adequately predicted by finite element simulations. The support loads are adequately predicted as long as the supports are constrained to the piping. This paper shows that with relatively simple models, quantitative predictions of tee forces can be made for the purposes of design or safety analysis of piping systems subject to internal detonations.

High-speed GPU-based finite element simulations for NDT

2015 ◽  
Author(s):  
P. Huthwaite ◽  
F. Shi ◽  
A. Van Pamel ◽  
M. J. S. Lowe
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Finite Element Simulations

Fatigue Analysis of Forward Fuselage under Dynamic Conditions

2015 ◽  
Vol 766-767 ◽  
pp. 1121-1126
Author(s):  
V. Abraham Boniface ◽  
A. Joseph Rijul Raj
Keyword(s):  
Aluminum Alloy ◽  
Equilibrium State ◽  
High Speed ◽  
High Weight ◽  
Dynamic Equilibrium ◽  
Fatigue Behavior ◽  
Dynamic Equilibrium State ◽  
Weight Structure ◽  
The Stability ◽  
Main Component

The fuselage is one of the main component in aircraft to carry payload and passenger. The fuselage enclosed with high weight structure. The fuselage is hollow tube which holds all parts of the airplane together. The shape of the fuselage based on the mission of the aircraft. A supersonic fighter plane will be having streamlined fuselage to reduce the drag force enclosed with high speed flight and similarly the shape vary depend on the velocity. The design of fuselage is very complicated for designers because it takes about 60% of total weight of the aircraft and the contribution of fuselage towards performance and the stability is very decent. This paper investigates the fatigue behavior of the fuselage under dynamic equilibrium state made of both aluminum alloy and Kevlar composite. Those results can be applied to optimize the fuselage structure thereby the better structure can be made.

scholarly journals On the Importance of Sleeve Flexibility in Passive Control of Critical Speeds of a Rotating Shaft Using Eccentric Sleeves

Machines ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 56
Author(s):  
Antony Kirk ◽  
Jonathan Griffiths
Keyword(s):  
Finite Element ◽  
Experimental Test ◽  
High Speed ◽  
Passive Control ◽  
Finite Element Simulations ◽  
Test Facility ◽  
Rotating Shaft ◽  
Critical Speeds ◽  
Dynamic Finite Element

In this paper, the critical speeds of a rotating shaft fitted with eccentric balance sleeves are identified from a scaled, high speed experimental test facility. The results are compared with the results of dynamic finite element simulations. It is shown that the stiffness of the sleeves must be accommodated when considering passive control characteristics critical speeds of a rotating shaft using eccentric sleeves.

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