scholarly journals Large-Scale Experimental and Numerical Study of Blast Acceleration Created by Close-In Buried Explosion on Underground Tunnel Lining

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Mohamad Reza Soheyli ◽  
A. H. Akhaveissy ◽  
S. M. Mirhosseini
Keyword(s):  
Field Data ◽  
Large Scale ◽  
Numerical Study ◽  
Free Field ◽  
Vertical Wall ◽  
Ground Surface ◽  
Vertical Acceleration ◽  
Element Analysis ◽  
Underground Tunnel ◽  
Water Transportation

Despite growing demands for structures in water transportation tunnels, underground installations, subsurface dams, and subterranean channels, there is limited field knowledge about the dynamic behavior of these structures in the face of near-fault earthquakes or impulse excitations. This study conducted a large-scale test on underground tunnel excited by two close-in subsurface explosions. The horizontal and vertical acceleration were recorded on the vertical wall of the tunnel and the free field data including the acceleration on the ground surface at 11-meter distance from the tunnel. The frequency domain analysis of recorded results determined the frequency 961 Hz and 968 Hz for 1.69 kg and 2.76 kg equivalent T.N.T., respectively. Then, finite element analysis results were compared with the test data. The comparisons demonstrated a good correlation and satisfied the field data. Finally, based on numerical modeling, a parametric study was applied to determine the effects of shear wave velocity distance of the crater with respect to the tunnel on impulse response of the tunnel.

scholarly journals Innovative Seismic Microzonation Maps of Urban Areas for the Management of Building Heritage: A Catania Case Study

Geosciences ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 480
Author(s):  
Glenda Abate ◽  
Simone Bramante ◽  
Maria Rossella Massimino
Keyword(s):  
Urban Areas ◽  
Large Scale ◽  
Free Field ◽  
Ground Surface ◽  
Seismic Microzonation ◽  
Field Conditions ◽  
Seismic Retrofitting ◽  
Geotechnical Characteristics ◽  
Fixed Base ◽  
Scale Estimate

Several urban areas in the Mediterranean have already been subjected to seismic microzonation studies aimed at determining the acceleration expected on the ground surface, therefore mitigating the associated seismic risks. These studies have been generally related to free-field conditions. The present paper shows innovative seismic microzonation maps based on a large-scale estimate of soil-structure interaction (SSI) effects on design accelerations for some areas characterized by a high seismic risk in Catania, Italy. The proposed procedure combined: (1) geotechnical characteristics; (2) building features; and (3) 1-D seismic response analyses in free-field conditions. The seismic hazard and site effects were evaluated using artificial inputs and inputs recorded recently in Catania. Structural fundamental periods and related spectral accelerations, considering both the fixed-base building configuration and flexible-base configuration, were mapped in the Google My Maps environment. These results showed that SSI often had a beneficial effect, but sometimes it had detrimental effects, especially for some masonry buildings. These maps provided important information for planning the seismic retrofitting of investigated buildings, which were based on more detailed analyses of SSI and the developed maps requiring them.

Numerical Study on the Residual Ultimate Strength of Hull Girder of a Bulk Carrier After Ship-Ship Collision

2014 ◽  
Author(s):  
Yasuhira Yamada
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Bending Moment ◽  
Second Step ◽  
Collapse Mechanism ◽  
Bulk Carrier ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Hull Girder ◽  
Ship Collision

The purpose of the present study is to investigate residual Ultimate Longitudinal Strength (ULS) of bulk carriers after ship-ship collision. A series of a large-scale explicit finite element analysis (FEA) as well as simplified analysis (SA) are carried out using a cape size bulk carrier. In order to accurately investigate collapse mechanism of “damaged ships” under vertical bending moment nonlinear FEA are carried out where two steps analysis is adopted. First step is ship-ship collision analysis; Second step is ULS analysis of the damaged ship. Ship-ship collision analysis is carried out assuming the right angle collision at the midship region of the struck ship, and damage extent of the struck ship is estimated with varying collision speed of 3kt, 6kt, 9kt and 12kt. In the second step of analysis, residual ULS analysis is carried out taking into account residual stress and deformation of the struck ship caused by ship-ship collision. Collapse mechanism of the bulk carrier in damaged condition due to sagging moment as well as combination of longitudinal and horizontal bending moment is investigated and discussed in detail. ULS of hull girder of the bulk carrier in intact condition is also estimated and compared with that in damaged condition. The effect of damaged condition on the reduction of ULS is discussed in detail. Finally some of numerical methodologies are summarized in assessing residual ULS of hull girder after collision.

scholarly journals Downwelling in Basins Subject to Buoyancy Loss

2012 ◽  
Vol 42 (11) ◽  
pp. 1817-1833 ◽  
Author(s):  
Claudia Cenedese
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Field Experiments ◽  
Numerical Study ◽  
Vertical Wall ◽  
Boundary Current ◽  
Boundary Currents ◽  
Rossby Radius Of Deformation ◽  
Buoyancy Loss

Abstract Recent observational, theoretical, and modeling studies all suggest that the upper part of the downwelling limb of the thermohaline circulation is concentrated in strong currents subject to buoyancy loss near lateral boundaries. This is fundamentally different from the traditional view that downwelling takes place in regions of deep convection. Even when resolving the buoyant boundary currents, coarse-resolution global circulation and climate models rely on parameterizations of poorly known turbulent mixing processes. In this study, the first direct measurements of downwelling occurring within a basin subject to buoyancy loss are obtained. Downwelling is observed near the basin’s vertical wall within the buoyant boundary current flowing cyclonically around the basin. Although the entire basin is cooled, large-scale mean downwelling is absent in the basin interior. Laboratory rotating experiments are conducted to explicitly resolve the turbulent mixing due to convective plumes and the baroclinic eddies generated by the boundary current, and to identify where downwelling takes place. Small vertical velocities can be measured more reliably in the laboratory than in many numerical calculations, whereas the measurement of these small vertical velocities is still a challenge for field experiments. Downwelling is observed near the vertical wall within a boundary layer with a thickness that scales with the baroclinic Rossby radius of deformation, consistent with the dynamical balance proposed by a previous numerical study. Hence, downwelling in the Labrador Sea and Lofoten Basin cyclonic boundary currents may be concentrated in a baroclinic Rossby radius of deformation thick boundary layer in regions with large eddy generation.

Seismic Response Analysis of Large-Scale Site with Circular Diaphragm Wall

2014 ◽  
Vol 607 ◽  
pp. 735-738
Author(s):  
Ru Lin Zhang ◽  
Wen Dong Yang ◽  
Feng Sun
Keyword(s):  
Seismic Response ◽  
Large Scale ◽  
Large Diameter ◽  
Free Field ◽  
Ground Surface ◽  
Diaphragm Wall ◽  
Response Analysis ◽  
Seismic Response Analysis ◽  
Soil Site ◽  
Circular Diaphragm

The seismic response analysis of project soil site is important to obtain the ground motion parameters for seismic design of upper structures. First, a simplified solving method is introduced, in which, the horizontal seismic loadings are expanded into Fourier series in the circumferential direction, using the orthogonality between the normal and tangential direction on the circumference, the three-dimensional problem is reduced to a series of two-dimensional problems. Then, the simplified method is used for seismic response analysis of a practical large-scale soil site with large diameter circular diaphragm wall. The influence of wall to the site is obtained through two field conditions, which are wall field and free field (without wall). Compare with the results of the site without wall, the peak acceleration of the pit bottom is increased owing to the confinement effect of wall, and the influence to ground surface far from the wall is very little.

scholarly journals Numerical Study on the Phase Sensitivity Variation in Low Frequency Primary Microphone Calibrations

2020 ◽  
Vol 10 (11) ◽  
pp. 3799
Author(s):  
Fan Zhang ◽  
Di Liu ◽  
Aibing Liu ◽  
Xianyue Gang ◽  
Lijun Li
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Low Frequency ◽  
Phase Variation ◽  
Time Domain Analysis ◽  
Phase Sensitivity ◽  
Element Analysis ◽  
Low Frequencies ◽  
The Time Domain ◽  
Frequency Phase

The low frequency phase characteristics of microphones in a monitoring system are crucial for characterizing large-scale natural and artificial activities—e.g., earthquakes, nuclear explosions, or rocket launchings. At present, microphones are simultaneously calibrated using in-situ or calibrator methods to get their phase consistency. However, the essential primary calibration, which traces their phase sensitivity to basic physical quantities, is grossly overlooked. Recently, we speculated that the microphone phase sensitivity is acoustically controlled by the pressure leakage and heat conduction effects in its back chamber, which will vary at low frequencies. Therefore, by means of the FEA (Finite Element Analysis) technique, simulations of laser pistonphone-based primary microphone calibrations are conducted both in the frequency and time domains. The frequency domain simulation quantifies the phase variation, while the time domain analysis helps us to understand the variation mechanism. It is found that the low frequency phase sensitivity is greatly influenced by its geometries and the venting state and should be pre-calibrated before serving.

Experimental and Numerical Study on the Collapse Strength of the Bulbous Bow Structure in Oblique Collision

2008 ◽  
Vol 45 (01) ◽  
pp. 42-53
Author(s):  
Yasuhira Yamada ◽  
Hisayoshi Endo
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Compressive Force ◽  
Bending Moment ◽  
Collapse Mechanism ◽  
Displacement Curve ◽  
Element Analysis ◽  
Oblique Collision ◽  
Collapse Strength ◽  
Bulbous Bow

The purpose of this paper is to investigate the collapse strength and the mechanism of the bulbous bow structure in case of an oblique collision. In this study, quasi-static experiments were conducted using two types of large-scale bulbous bow models using the scenario that a ship collides with another ship at oblique angle. One of the models is a prototype buffer bow adopting a transverse stiffening system, and the other model is a standard bow adopting a longitudinal stiffening system. Each model was collapsed by a thrusting rigid board while being subject to the combined action of compressive force and bending moment. Collapse mechanism, load-displacement curve, and energy absorption capability of the buffer bow structure were investigated as compared with those of standard bow structure. Nonlinear finite element analysis (FEA) corresponding to the experiments was also conducted, and fairly good agreement was achieved between FEA and the experiments. It is also found from these investigations that the buffer bow structure is expected to be efficient in reducing the risk of an oil spill, especially in case of oblique collision.

Finite element studies of reinforced concrete slab - edge column connections with openings

2007 ◽  
Vol 34 (8) ◽  
pp. 952-965 ◽  
Author(s):  
Hong Guan ◽  
Maria Anna Polak
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Large Scale ◽  
Numerical Study ◽  
Concrete Slab ◽  
Reinforced Concrete Slab ◽  
Element Analysis ◽  
Numerical Studies ◽  
Experimental Findings ◽  
Good Agreement

An extended nonlinear layered finite element method (LFEM) is used to investigate the influence of openings and shear stud reinforcement (SSR) on the behaviour of reinforced concrete slab – edge column connections. In all, ten large-scale slab – edge column connections tested previously are analyzed. The laboratory test variables were the size and location of the openings in the vicinity of an edge column and the existence of SSR. The numerical results of the load–deflection response, the ultimate strength, and the crack patterns are compared with the experimental findings and good agreement is achieved. A numerical study on two connections is also carried out to determine the influence of the locations of opening in slab – edge column connections with SSR. Discussion on code provisions for slabs with openings is provided. The comparative and numerical studies confirm the accuracy, reliability, and effectiveness of the LFEM in the analysis of slab – edge column connections with both openings and SSR.Key words:slab–column connection, punching shear, opening, shear stud reinforcement, finite element analysis.

scholarly journals BEACH PROFILE EVOLUTION IN FRONT OF STORM SEAWALLS: A PHYSICAL AND NUMERICAL STUDY

2018 ◽  
pp. 70 ◽  
Author(s):  
Alessandra Saponieri ◽  
Marcello Di Risio ◽  
Davide Pasquali ◽  
Nico Valentini ◽  
Francesco Aristodemo ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Study ◽  
Morphological Evolution ◽  
Vertical Wall ◽  
Experimental Results ◽  
Beach Profile ◽  
Physical Experiments ◽  
Preliminary Validation ◽  
Wave Conditions

Large-scale physical experiments (Froude scale, 1:4.3) were performed at the new Delta Flume in 2017, aimed at investigating wave impacts on a vertical wall placed on the top of a dike in a mild slope shallow foreshore. Experiments also allowed to investigate the morphological evolution of the sandy foreshore, the scour at the dike toe and its development under irregular and bi-chromatic wave conditions. Both experimental results and numerical study performed to design the experiments are reported. Moreover, preliminary validation of the model to investigate the scour within a wider range of wave conditions and foreshore slopes is illustrated.

scholarly journals Interaction of Very Large Scale Motion of Coherent Structures with Sediment Particle Exposure

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 248
Author(s):  
Sencer Yücesan ◽  
Daniel Wildt ◽  
Philipp Gmeiner ◽  
Johannes Schobesberger ◽  
Christoph Hauer ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Numerical Study ◽  
Local Maximum ◽  
Wave Number ◽  
Exposure Level ◽  
Sediment Particle ◽  
High Wave Number ◽  
Large Scale Motion ◽  
Scale Motion

A systematic variation of the exposure level of a spherical particle in an array of multiple spheres in a high Reynolds number turbulent open-channel flow regime was investigated while using the Large Eddy Simulation method. Our numerical study analysed hydrodynamic conditions of a sediment particle based on three different channel configurations, from full exposure to zero exposure level. Premultiplied spectrum analysis revealed that the effect of very-large-scale motion of coherent structures on the lift force on a fully exposed particle resulted in a bi-modal distribution with a weak low wave number and a local maximum of a high wave number. Lower exposure levels were found to exhibit a uni-modal distribution.

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