scholarly journals Pasternak Model-Based Tunnel Segment Uplift Model of Subway Shield Tunnel during Construction

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiang-Ling Tao ◽  
Yun-He Su ◽  
Qi-Yin Zhu ◽  
Wen-Long Wang
Keyword(s):  
Numerical Solution ◽  
Shear Stiffness ◽  
Longitudinal Direction ◽  
Calculation Model ◽  
Shield Tunnel ◽  
Beam Model ◽  
Model Based ◽  
Pasternak Model ◽  
Subgrade Modulus ◽  
Parametric Analyses

Segment uplift is a frequent problem during the construction of shield tunnels. The phenomenon of segment uplift in Xuzhou Metro Line 1 is investigated. The segment uplift magnitude in the shale layer is quite smaller than that in the clay layer. A tunnel segment uplift calculation model based on the Pasternak foundation beam model is proposed, which considers the hardening process of the grouted body with time. The finite difference method is adopted to calculate the magnitude of segment uplift during different tunnel construction stages, and a numerical solution of segment uplift on the longitudinal direction is obtained. The applicability of the numerical solution is studied by comparing with the field test results and parametric analyses are also performed to investigate the effects of different factors on segment uplifting. The results show that the coefficient of subgrade modulus, shear stiffness of the shear layer, and grout pressure all influence the segment uplifting of the tunnel. The influence of the coefficient of subgrade modulus and grout pressure on segment uplift is more significant.

scholarly journals A Numerical Solution for Modelling Mooring Dynamics, Including Bending and Shearing Effects, Using a Geometrically Exact Beam Model

2021 ◽  
Vol 9 (5) ◽  
pp. 486
Author(s):  
Tobias Martin ◽  
Hans Bihs
Keyword(s):  
Numerical Solution ◽  
Offshore Wind ◽  
Mooring Line ◽  
Beam Model ◽  
Tight Coupling ◽  
Energy Propagation ◽  
Two Phase ◽  
Geometrically Exact Beam ◽  
Mooring Dynamics ◽  
Rotational Deformation

During the operation of moored, floating devices in the renewable energy sector, the tight coupling between the mooring system and floater motion results in snap load conditions. Before snap events occur, the mooring line is typically slack. Here, the mechanism of energy propagation changes from axial to bending dominant, and the correct modelling of the rotational deformation of the lines becomes important. In this paper, a new numerical solution for modelling the mooring dynamics that includes bending and shearing effects is proposed for this purpose. The approach is based on a geometrically exact beam model and quaternion representations for the rotational deformations. Further, the model is coupled to a two-phase numerical wave tank to simulate the motion of a moored, floating offshore wind platform in waves. A good agreement between the proposed numerical model and reference solutions was found. The influence of the bending stiffness on the motion of the structure was studied subsequently. We found that increased stiffness increased the amplitudes of the heave and surge motion, whereas the motion frequencies were less altered.

A study of modeling experiments of the vibration behavior of elevated railway box girder

2018 ◽  
Vol 25 (5) ◽  
pp. 984-995 ◽  
Author(s):  
Kun Luo ◽  
Xiaoyan Lei
Keyword(s):  
High Speed ◽  
Similarity Theory ◽  
Longitudinal Direction ◽  
Calculation Model ◽  
Scale Model ◽  
Box Girder ◽  
Vibration Transmissibility ◽  
Girder Bridge ◽  
Structure Simplification ◽  
Model Similarity

Based on the model similarity theory, this article deduces the model similarity relationship of the elevated railway box girder at the elastic stage and designs a 1/10 box girder scale model by adopting a 32 m simply-supported box girder bridge from the Beijing–Shanghai Railway as the prototype. It then verifies the validity of the model design and the dynamic similarity between the 1/10 model and the prototype through constraint mode and free mode experiments on the 1/10 scale model, together with transient finite element calculation. The dynamic calculation model is utilized here for the analysis of the errors occurring in the production of the model, and the effect of the model structure simplification on the box girder mode frequency and vibration response. Finally, the article studies the vibration transmissibility characteristics between the plates and along the longitudinal direction by means of model testing. It also discusses the effect of different bridge support stiffness on the box girder vibration. The results presented in this paper can provide a method for forecasting and evaluating the existing or plan-to-build high speed railway environment vibration.

Modified Calculation Model for Segment Floating in Slurry Shield Tunnel

2021 ◽  
Vol 35 (5) ◽  
pp. 04021068
Author(s):  
Daxin Geng ◽  
Yuchen Hu ◽  
Yalong Jiang ◽  
Ning Wang ◽  
Wentao Hu
Keyword(s):  
Calculation Model ◽  
Shield Tunnel ◽  
Slurry Shield

scholarly journals Research on Tuning Fork Dimension Optimization and Density Calculation Model Based on Viscosity Compensation for Tuning Fork Density Sensor

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Hai Yang ◽  
Yue Rao ◽  
Li Li ◽  
Haibo Liang ◽  
Tao Luo ◽  
...  
Keyword(s):  
Real Time ◽  
Measurement Accuracy ◽  
Tuning Fork ◽  
High Viscosity ◽  
Calculation Model ◽  
Online Measurement ◽  
Liquid Viscosity ◽  
Density Calculation ◽  
Model Based ◽  
Measurement Resolution

At present, real-time online measurement of fluid density is of great significance to improve the automation level of petrochemical and food industries. The tuning fork density sensor is widely used because of its characteristics of real-time online measurement, high measurement accuracy, simple structure, and convenient use. The traditional tuning fork density sensor in the market has the disadvantage of low resolution and being susceptible to liquid viscosity, which makes the sensor’s measurement accuracy low and not suitable for the measurement of high-viscosity liquid density. The measurement resolution and antiviscosity interference capability of the tuning fork density sensor are two major indexes to measure the measurement performance of the sensor, among the antiviscosity interference capability refers to the degree to which the measurement results of the sensor are affected by viscosity properties. However, the structural design of the tuning fork density sensor results in the conflict between the measurement resolution and the antiviscosity interference capability of the sensor, and the improvement of one performance is bound to affect the performance of the other. Aiming at the problem of how to balance the measuring performance of the tuning fork sensor, a density calculation model based on viscosity compensation is proposed in this paper. By studying the working principle and structure design of the tuning fork, the vibration characteristics of tuning fork in liquid with different viscosities and densities are modelled and simulated. From the results of simulation analysis, the better set of dimensions with balanced measuring performance is selected. Not only does the structure of the tuning fork have the characteristics of high resonance frequency, but also the measured results are less affected by the viscosity of the liquid. To solve the problem that density measurement is still affected by high-viscosity liquid after tuning fork dimension optimization, in this paper, the partial least square model is used to fit the experimental data of the frequency-density characteristics; then, the density calculation model based on the viscosity compensation is obtained by combining the frequency-viscosity characteristic experiment. Finally, through the performance test experiment comparing with the traditional tuning fork density sensor, the measurement resolution of the improved tuning fork density sensor is as high as 0.0001 g/cm3; within the viscosity range of 180 MPa·s, the accuracy reached ±0.001 g/cm3, and within 480 MPa·s, the measurement accuracy reached ±0.002 g/cm3. When the liquid viscosity reaches more than 10 MPa·s, the improved tuning fork density sensor has better overall measurement performance than the traditional tuning fork density sensor, and both of its measurement resolution and antiviscosity interference capability have been greatly improved.

Mathematical Models for Model-Based Control in Offshore Pipelay Operations

2009 ◽  
Author(s):  
Gullik A. Jensen ◽  
Thor I. Fossen
Keyword(s):  
Mathematical Models ◽  
Dynamic Models ◽  
Controller Design ◽  
Computational Time ◽  
Beam Model ◽  
Time Dynamic ◽  
Model Based ◽  
On Line ◽  
Stability And Accuracy ◽  
Control Application

This paper considers mathematical models for model-based controller design in offshore pipelay operations. Three classes of models for control design are discussed, real-world models suitable for controller design verification, controller and observer models which are used on-line in the control system implementation. The control application place requirements on the model with respect to the computational time, dynamic behavior, stability and accuracy. Models such as the beam model, two catenary models, as well as general finite element (FE) models obtained from computer programs were not able to meet all of the requirements, and two recent dynamic models designed for control are presented, which bridge the gap between the simple analytical and more complex FE models. For completeness, modeling of the pipelay vessel, stinger and roller interaction, soil and seabed interaction and environmental loads are discussed.

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