scholarly journals Numerical Study on the Fracture Properties of Concrete Shield Tunnel Lining Segments

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Longgang Tian ◽  
Xiao Wang ◽  
Ziling Cheng
Keyword(s):  
Crack Propagation ◽  
Bearing Capacity ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Complex Loading ◽  
Tunnel Lining ◽  
Shield Tunnel ◽  
Loading Eccentricity ◽  
Element Method

Shield tunnel lining structure is usually under very complex loading conditions in the underground space. As a kind of the common concrete structures, any defect in the tunnel lining segment may deteriorate its bearing capacity and even cause severe disasters. Three-dimensional numerical models of shield tunnel lining segments with initial cracks are built using the Symmetric Galerkin Boundary Element Method- (SGBEM-) Finite Element Method (FEM) Alternating Method. The cracking load and ultimate load of the tunnel segments are obtained, and crack propagation under fatigue load is also simulated by employing the Paris Fatigue Law. Results show that loading eccentricity has a very large influence on the bearing capacity of the cracked lining segment; the larger the loading eccentricity, the smaller the bearing capacity. Deformation and damage of the lining segment show obvious phases, which consist of the initial crack, cracking stage, steady crack propagation, unsteady crack propagation, and eventual failure.

Boundary element method in numerical study of three-dimensional Stokes flows in channels of arbitrary shape

2012 ◽  
Vol 9 (1) ◽  
pp. 94-97
Author(s):  
Yu.A. Itkulova
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Cross Section ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Periodic Flows ◽  
Element Method

In the present work creeping three-dimensional flows of a viscous liquid in a cylindrical tube and a channel of variable cross-section are studied. A qualitative triangulation of the surface of a cylindrical tube, a smoothed and experimental channel of a variable cross section is constructed. The problem is solved numerically using boundary element method in several modifications for a periodic and non-periodic flows. The obtained numerical results are compared with the analytical solution for the Poiseuille flow.

scholarly journals Numerical and Experimental Study on Deficient Short Steel Tubes Strengthened with CFRP Under Compression

2019 ◽  
Author(s):  
Mohammad Reza Ghaemdoust ◽  
Omid Yousefi ◽  
Kambiz Narmashiri ◽  
Masoumeh Karimian
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Three Dimensional ◽  
Local Buckling ◽  
Steel Tubes ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Steel Columns ◽  
Repair Costs ◽  
The Impact

In view of development and repair costs, support of structures is imperative. Several factors, for example, design and calculation errors, absence of appropriate installation, change of structures application, exhaustion, seismic tremor, fire and natural conditions diminish their strength. In such cases, structures have need of rehabilitation and restoration to achieve their original performance. One of the most up to date materials for retrofitting is carbon fiber reinforced polymer (CFRP) that can provide an amount of restriction to postpone buckling of thin steel walls. This paper provides a numerical and experimental investigation on CFRP strengthened short steel tubes with initial horizontal and vertical deficiency under compression. Ten square and circular specimens were tested to study effects of the following parameters: (1) position of deficiency, horizontal or vertical; (2) tube shape, square or circular; (3) CFRP strengthening. In the experiments, axial static loading was gradually applied and for the numerical study three-dimensional (3D) static nonlinear analysis method using ABAQUS software was performed. The results show that deficiency reduces load-bearing capacity of steel columns and the impact of horizontal deficiency is higher than the impact of vertical deficiency, in both square and circular tubes. Use of CFRP materials for strengthening of short steel columns with initial deficiency indicates that fibers play a considerable role on increasing load bearing capacity, reducing stress at the damage location, preventing deformation caused by deficiency and delaying local buckling. Both numerical and experimental outcomes are in good agreement, which underlines the accuracy of the models adopted.

scholarly journals Consideration of Moving Tooth Load in Gear Crack Propagation Predictions

2000 ◽  
Author(s):  
David G. Lewicki ◽  
Lisa E. Spievak ◽  
Paul A. Wawrzynek ◽  
Anthony R. Ingraffea ◽  
Robert F. Handschuh
Keyword(s):  
Crack Propagation ◽  
Dimensional Analysis ◽  
Gear Tooth ◽  
Contact Region ◽  
Three Dimensional ◽  
Spur Gear ◽  
Calculated Stress ◽  
Prediction Techniques ◽  
Gear Crack ◽  
Element Method

Abstract Robust gear designs consider not only crack initiation, but crack propagation trajectories for a fail-safe design. In actual gear operation, the magnitude as well as the position of the force changes as the gear rotates through the mesh. A study to determine the effect of moving gear tooth load on crack propagation predictions was performed. Two-dimensional analysis of an involute spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studied and compared to experiments. A modified theory for predicting gear crack propagation paths based on the criteria of Erdogan and Sih was investigated. Crack simulation based on calculated stress intensity factors and mixed mode crack angle prediction techniques using a simple static analysis in which the tooth load was located at the highest point of single tooth contact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.

Numerical study of flow pattern around lateral intake in a curved channel

2019 ◽  
Vol 30 (11) ◽  
pp. 1950083 ◽  
Author(s):  
Hossien Montaseri ◽  
Hossein Asiaei ◽  
Abdolhossein Baghlani ◽  
Pourya Omidvar
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Flow Pattern ◽  
Numerical Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Curved Channel ◽  
Channel Bend ◽  
Outer Bank ◽  
Center Region

This paper deals with numerical study of flow field in a channel bend in presence of a lateral intake using three-dimensional numerical model SSIIM2. The effects of bend on the structure of the flow around the intake are investigated and compared with the experimental data. The tests are carried out in a U-shaped channel bend with a lateral intake. The intake is located at the outer bank of an 180∘ bend at position 115∘ with 45∘ diversion angle and the experimental data can be used to calibrate and validate numerical models. The results show that both the center-region and outer-bank cross-stream circulations are observed in the experiments while only the former is captured by the numerical model due to the limitations of the turbulence model. In the curved channel after the intake, both experimental and numerical results show another type of bi-cellular circulations in which clockwise center-region circulations and counterclockwise circulations near the inner bank and the free surface (inner-bank circulations) are captured. The study shows that the numerical model very satisfactorily predicts streamlines, velocity field and flow pattern in the channel and in vicinity of the intake. Investigation of flow pattern around lateral intake in channel bends shows that contrary to the case of flow diversion in straight channels, the width of the dividing stream surface near water surface level is greater than that of near bed level. Finally, the effects of position and diversion angle of the lateral intake, discharge ratio and upstream Froude number on the flow pattern are investigated.

Axial compressive capacity of helical piles from field tests and numerical study

2013 ◽  
Vol 50 (12) ◽  
pp. 1191-1203 ◽  
Author(s):  
Zeyad H. Elsherbiny ◽  
M. Hesham El Naggar
Keyword(s):  
Bearing Capacity ◽  
Load Transfer ◽  
Numerical Study ◽  
Numerical Models ◽  
Field Tests ◽  
Reduction Factor ◽  
Full Scale ◽  
Cohesionless Soil ◽  
Soil Parameters ◽  
Helical Piles

The compressive capacity of helical piles in sand and clay is investigated by means of field testing and numerical modeling. The numerical models are conducted using the computer program ABAQUS and are calibrated and verified using full-scale load testing data. The calibration was accomplished by using reasonable assumptions regarding soil–pile interaction and soil parameters reported from the literature. The model was verified by comparing its predictions with observed load–displacement curves obtained from full-scale pile load tests. The verified numerical model was used to perform a parametric study considering different pile configurations and soil parameters to evaluate the compressive capacity and load-transfer mechanism of helical piles. The compressive capacity obtained from the numerical models is compared with that obtained from existing theoretical methods for calculating the capacity. It is found that the predictions of theoretical equations for piles in cohesionless soil vary largely depending on the choice of bearing capacity factors and proper failure criteria. The interaction of closely spaced helices on the capacity of a helical pile is also evaluated. A bearing capacity reduction factor, R, and helix efficiency factor, EH, are proposed to evaluate the compressive capacity of helical piles in cohesionless soil considering an industry-acceptable ultimate load criterion corresponding to settlement equal to 5% of helix diameter, D.

Sign in / Sign up

Export Citation Format

Share Document