Semi-analytical thermo-mechanical model for the shield tunnel segmental joint subjected to elevated temperatures

2021 ◽  
Vol 118 ◽  
pp. 104170
Author(s):  
Yi Shen ◽  
He-hua Zhu ◽  
Zhi-guo Yan ◽  
Long Zhou ◽  
Yong Lu
Keyword(s):  
Mechanical Model ◽  
Elevated Temperatures ◽  
Shield Tunnel

Mechanical modeling for predicting the axial restraint forces and rotations of steel top and seat angle connections at elevated temperatures

2017 ◽  
Vol 8 (3) ◽  
pp. 258-286 ◽  
Author(s):  
Sana El Kalash ◽  
Elie Hantouche
Keyword(s):  
Mechanical Model ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Experimental Results ◽  
Fe Model ◽  
Content Type ◽  
Analysis And Design ◽  
Axial Forces ◽  
Fe Simulations ◽  
Seat Angle

Purpose This paper aims at developing a mechanical-based model for predicting the thermally induced axial forces and rotation of steel top and seat angles connections with and without web angles subjected to elevated temperatures due to fire. Finite element (FE) simulations and experimental results are used to develop the mechanical model. Design/methodology/approach The model incorporates the overall connection and column-beam rotation of key component elements, and includes nonlinear behavior of bolts and base materials at elevated temperatures and some major geometric parameters that impact the behavior of such connections when exposed to fire. This includes load ratio, beam length, angle thickness, and gap distance. The mechanical model consists of multi-linear and nonlinear springs that predict each component stiffness, strength, and rotation. Findings The capability of the FE model to predict the strength of top and seat angles under fire loading was validated against full scale tests. Moreover, failure modes, temperature at failure, maximum compressive axial force, maximum rotation, and effect of web angles were all determined in the parametric study. Finally, the proposed mechanical model was validated against experimental results available in the literature and FE simulations developed as a part of this study. Originality/value The proposed model provides important insights into fire-induced axial forces and rotations and their implications on the design of steel bolted top and seat angle connections. The originality of the proposed mechanical model is that it requires low computational effort and can be used in more advanced modelling applications for fire analysis and design.

Influence of Segment Design of Shield Tunnel on the Magnitude of Joint Opening

2010 ◽  
Vol 160-162 ◽  
pp. 698-703
Author(s):  
Yin Liu ◽  
Hong Wei Huang ◽  
Dong Mei Zhang
Keyword(s):  
Analytical Solution ◽  
Mechanical Model ◽  
Tunnel Lining ◽  
Shield Tunnel ◽  
Flexural Stiffness ◽  
Water Leakage ◽  
Joint System ◽  
Joint Opening ◽  
Influence Mechanism

It is obviously a simplification to consider the tunnel lining as uniformly permeable.In reality it is more likely that there are specific leaks assocoated with segmental lining joints. In the case of in situ concrete linings, construction joints can provide leakage paths, accounting for most of the water leakage. In this paper, based on the mechanical model of segment joint, the analytical expression of magnitude of joint opening was developed, in light of which, the occurrence of water leakage through the joint system can be judged. Taking the metro line No.1 in Shanghai as an example, effects of such parameters as joint flexural stiffness, bolt location, bolt stiffness, bolt prestress, etc. on the magninitude of the joint opening were analyzed respectively through the analytical solution. The results not only help us realize the influence mechanism of segment design on the magnitude of joint opening of the segmental linings, but also provide the guidance for waterproof design of the shield tunnel.

Numerical Simulation of Residual Stresses Induced in Compact Tension Specimens Using Electron Beam Welding

2012 ◽  
Author(s):  
P. Kapadia ◽  
C. M. Davies ◽  
D. W. Dean ◽  
K. M. Nikbin
Keyword(s):  
Residual Stress ◽  
Electron Beam ◽  
Residual Stresses ◽  
Mechanical Model ◽  
Elevated Temperatures ◽  
Electron Beam Welding ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Compact Tension ◽  
Eb Welding

In welded components residual stresses on the order of yield magnitude can exist, allowing creep damage and cracking to occur under secondary stresses at elevated temperatures. A method of inducing residual stresses in compact tension, C(T), specimens is proposed using Electron Beam (EB) welding, which is simulated using a sequential thermal-mechanical model. The thermal model has been verified by comparison to thermocouple measurements obtained from instrumented EB welding experiments on blocks made of ex-service Type 316H stainless steel. Residual stress measurements, obtained by the neutron diffraction technique, have also been used to verify the mechanical model. It has been found that in the proposed EB welding method plasticity is localised and limited to just a few millimetres away from the notch whilst at the same time exhibiting a near yield level residual stress at the crack tip. Thus this technique may allow the effects of residual stresses on creep crack growth to be investigated by the EB welding technique without material property changes due to crack tip plasticity influencing the results.

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

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