scholarly journals Experimental Research on the Transverse Effective Bending Rigidity of Shield Tunnels

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Gang Zheng ◽  
Yawei Lei ◽  
Tao Cui ◽  
Xuesong Cheng ◽  
Yu Diao ◽  
...  
Keyword(s):  
Sandy Soil ◽  
Bending Rigidity ◽  
Concentrated Force ◽  
Concentrated Load ◽  
Ring Model ◽  
Loading Patterns ◽  
Steel Tank ◽  
Practical Engineering ◽  
Tunnel Diameter ◽  
Load Tests

The uniform rigidity ring model is commonly used to design the segmented structures of shield tunnels. However, model tests have been primarily used to study the transverse effective rigidity ratio η with a concentrated force, which is notably different from realistic loading patterns. To obtain more reasonable η values, in this study, tests were performed with a concentrated load on an experimental bench and with a realistic loading pattern in sandy soil in a rigid steel tank. Three types of segmental ring models were designed and tested: straight-jointed, stagger-jointed, and uniform rings. The test results indicated that the η values of the stagger-jointed assembly mode were clearly larger than those of the straight-jointed assembly mode under both loading patterns. η increased as the load increased under the realistic loading conditions, whereas η decreased as the load increased under the concentrated load. More importantly, the η values derived from the realistic load tests were considerably larger than those derived from the concentrated load tests for both assembly modes (i.e., 0.423–0.672 and 0.587–0.761 for the straight-jointed and stagger-jointed assembly modes, respectively), and the former should be recommended for practical engineering applications. Furthermore, formulas relating η to the ratio of the cover depth to the tunnel diameter were proposed for sandy soil.

scholarly journals Experimental Study on the Transverse Effective Bending Rigidity of Segmental Lining Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Yong-feng Tang ◽  
Han-cheng Chen ◽  
Zhen-wei Ye ◽  
Ting-jin Liu ◽  
Yu-bing Yang
Keyword(s):  
Regression Equation ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Test Results ◽  
Bending Rigidity ◽  
Segmental Lining ◽  
Ring Model ◽  
Scale Models ◽  
Elastic Stage

The transverse effective rigidity ratio is a key parameter when the uniform rigidity ring model is adopted to design or numerically analyse segmental lining structures commonly used on a shield-driven tunnel. Traditionally, the transverse effective rigidity ratio η is treated as a constant, which can be evaluated through theoretical analysis and model tests. In this study, scale models were designed and tested to investigate the variation of the transverse effective rigidity ratio in the segmental linings’ flattening deformation process. The test results suggested that in the elastic stage, the transverse effective rigidity ratio fluctuated between 0.667 and 0.734 for the stagger-jointed rings and fluctuated between 0.503 and 0.642 for the straight-jointed rings. When segmental linings were squashed and started to crack at the circumferential joints, the transverse effective rigidity ratio decreases sharply. Then, a regression equation was obtained to fit the variation trend of η with the increase of horizontal convergence to the outer-diameter ratio (ΔD/Dout). Finally, in a case study, the regression equation was adapted to determine the value of η of an operated shield tunnel which was once surcharged accidentally and deformed severely so as to numerically predict the prospective deformation induced by the upcoming adjacent excavation. Numerical results indicated that as the value of η decreases, the horizontal convergences of shield tunnel induced by adjacent excavation increase significantly and even more than doubled in the case study. Comparatively, through taking account of the operating tunnels’ exiting transverse deformation, the predicted deformation tends to be unfavourable.

Study on Flexural Behavior of Pre-Stressed Concrete Hollow Slabs Strengthen with CFRP

2013 ◽  
Vol 446-447 ◽  
pp. 1413-1416
Author(s):  
Bo Wang ◽  
Juan Han
Keyword(s):  
Experimental Method ◽  
Engineering Application ◽  
Flexural Behavior ◽  
Experimental Basis ◽  
Concentrated Force ◽  
Disaster Area ◽  
Practical Engineering ◽  
Symmetrical Load

The purpose of this paper is to focus on studying its flexural behavior after different damages pre-stressed concrete hollow slab is strengthened with CFRP. By the experimental method, twelve residential pre-stressed concrete hollow slabs are tested under concentrated force at the two points of the symmetrical load in order to analyze both flexural behavior and effects factored by different bonding modes. The conclusion can be drawn that the flexural behavior of pre-stressed concrete hollow slabs strengthened with CFRP is well-tried. It provides design suggestions and reference for pre-stressed concrete hollow slabs strengthened with CFRP, and also provides an experimental basis for the repairing and reinforcing practical engineering application in Wenchuan disaster area.

Effect of Strand Indentation Types on the Development Length and Flexural Capacity of Concrete Railroad Ties Made With Different Prestressing Strands

2019 ◽  
Author(s):  
Amir Farid Momeni ◽  
Robert J. Peterman ◽  
B. Terry Beck ◽  
Chih-Hang John Wu
Keyword(s):  
The Other ◽  
Development Length ◽  
Concrete Compressive Strength ◽  
Concentrated Load ◽  
Bonding Performance ◽  
Pretensioned Concrete ◽  
Load Tests ◽  
Prestressing Strands ◽  
Wire Strand ◽  
Prestressing Strand

Pretensioned concrete prisms made with five different prestressing strand types (four 7-wire strands and one 3-wire strand) were load tested to failure to understand the effect of strand indentation types on the development length and bonding performance of these different reinforcements. The prestressing strands were denoted SA, SB, SD, SE and SF. SA was a smooth strand while the other four were indented strands. All strands utilized in manufacturing ofprisms had diameter of 3/8″ (9.52 mm). Among all types of strands, SF was the only 3-wire strand and the remaining strands were all 7-wire strands. For all types of strands, four straight strands were embedded into each concrete prism, which had a 5.5″ (139.7 mm) × 5.5″ (139.7 mm) square cross section. The strands were tensioned to 75 percent of ultimate tensile strength of strands and gradually de-tensioned when the concrete compressive strength reached 4500 psi (31.03 Mpa). A consistent concrete mixture with type III cement, water-cement ratio of 0.32 and a 6-in. slump was used for all prisms. Prisms were load tested in 3-point-bending at different embedment lengths to obtain estimations of the development length of each type of strand. Two out of three identical 69-in.-long (175.26 cm) prisms were load tested at one end and one was tested at both ends for each reinforcement type evaluated. First prisms were tested at 28-in. (71.12 cm) from the end, while second prisms were tested at 20-in. (33.02 cm) from the end. Third prisms were loaded at 16.5-in. (41.9 cm) from one end and 13-in. (33.02 cm) from the other end. Thus, a total of 20 load tests (5 strand types × 4 tests each) were conducted in this study. During each test, a concentrated load with the rate of 900 lb/min (4003 N/min) was applied at mid-span until failure occurred. Values of load, mid-span deflection, and strand endslip were continuously monitored and recorded during each test. Plots of load-vs-deflection were then compared for prisms with each strand type and span, and the maximum sustained moment was also calculated for each test. The load tests revealed that there is a large difference in the development length of the strands based on their indentation type.

DMT for Load-Settlement Curve Prediction in a Tropical Sandy Soil Compared to Plate Load Tests

2019 ◽  
Vol 43 (1) ◽  
pp. 20180079
Author(s):  
Roberto A. Dos Santos ◽  
Breno P. Rocha ◽  
Heraldo L. Giacheti
Keyword(s):  
Sandy Soil ◽  
Load Tests

Analysis on Bearing Capacity of CFG Pile Composite Foundation in Baotou

2013 ◽  
Vol 353-356 ◽  
pp. 337-340
Author(s):  
Ying Hao Wang ◽  
Yu Qin Feng ◽  
Shuo Li
Keyword(s):  
Bearing Capacity ◽  
Sandy Soil ◽  
Inner Mongolia ◽  
Composite Foundation ◽  
Engineering Project ◽  
Silty Soil ◽  
Practical Engineering ◽  
Soil Foundation ◽  
Cfg Pile Composite Foundation ◽  
Cfg Pile

By uniting composite foundation with CFG pile composite foundation for a practical engineering project in Baotou, the bearing capacity of CFG pile in sandy soil and silty soil foundation were analyzed. The conclusion can be applied to the similar projects in the region of Inner Mongolia.

Surface Vibration of a Multilayered Elastic Medium due to Harmonic Concentrated Force

2011 ◽  
Author(s):  
Akindeji Ojetola ◽  
Hamid Hamidzadeh
Keyword(s):  
Fourier Transform ◽  
Elastic Medium ◽  
Three Dimensional ◽  
Concentrated Force ◽  
Double Complex ◽  
Concentrated Load ◽  
Propagator Matrix ◽  
Displacement Vectors ◽  
Bottom Interface ◽  
Similar Information

Dynamic response of a multi-layer elastic medium subjected to harmonic surface concentrated load is considered. In development of the analytical solution, the three-dimensional theory of elasto-dynamic is utilized for derivation of the governing partial differential equations for each layer. These equations are solved in the Fourier domain by employing the Double Complex Fourier Transform technique. In the analysis, each layer of the medium is assumed to be extended infinitely in the horizontal x and z directions and has uniform depth in the y direction and is considered to be linearly elastic, homogeneous, and isotropic. Utilizing the Integral Fourier Transform, displacements and stresses at any point in each layer can be determined in terms of boundary stresses for each layer. Also, the presented solution provides the relation between stress and displacement vectors for the top and bottom of each layer in matrix notation. By satisfying the compatibility of displacements and stresses for each interface, a propagator matrix relating displacements and stresses at the top of the medium to the bottom interface will be obtained. This relates the displacement and stress vector on the top surface to the bottom interface by eliminating similar information for the other interfaces. In this study, the displacements on the surface of the layered medium are computed for the two cases where the surface of the medium is subjected to a concentrated harmonic vertical or horizontal harmonic force.

The Elastic Sphere Under Concentrated Loads

1952 ◽  
Vol 19 (4) ◽  
pp. 413-421 ◽  
Author(s):  
E. Sternberg ◽  
F. Rosenthal
Keyword(s):  
Three Dimensional ◽  
Plane Boundary ◽  
Elastic Sphere ◽  
Concentrated Loads ◽  
Concentrated Force ◽  
Concentrated Load ◽  
Load Axis ◽  
Present Solution ◽  
Photoelastic Investigation ◽  
Axisymmetric Problems

Abstract This paper contains an exact solution for the stress distribution in an elastic sphere under two equal and opposite concentrated loads, applied at the end points of a diameter. The solution is based on the Boussinesq stress-function approach to axisymmetric problems and is represented as a sum of two solutions: A singular solution in closed form, and a series solution corresponding to surface tractions which are finite and continuous throughout the surface of the sphere. It is shown that the singularity at the points of application of the loads is not identical with that arising at a concentrated load acting normal to a plane boundary. The existence of pseudosolutions to the problem under consideration, as well as to concentrated-force problems in general, is illustrated, and the validity of the present solution is confirmed through a limit process applied to the case of tractions uniformly distributed over a portion of the boundary. The numerical results for the normal stress on the plane of symmetry perpendicular to the load axis, are compared with the corresponding stress values obtained in a recent three-dimensional photoelastic investigation of the same problem by Frocht and Guernsey (1).

Experimental Study on Flexural Behavior of Different Damages Prestressed Concrete Hollow Slabs Strengthened with CFRP

2013 ◽  
Vol 351-352 ◽  
pp. 592-595
Author(s):  
Juan Han ◽  
Yin Liang
Keyword(s):  
Experimental Study ◽  
Experimental Method ◽  
Prestressed Concrete ◽  
Engineering Application ◽  
Flexural Behavior ◽  
Experimental Basis ◽  
Concentrated Force ◽  
Disaster Area ◽  
Practical Engineering ◽  
Symmetrical Load

The purpose of this paper is to focus on studying its flexural behavior after different damages prestressed concrete hollow slab is strengthened with CFRP.By the experimental method, twelve residential prestressed concrete hollow slabs are tested under concentrated force at the two points of the symmetrical load in order to analyze both flexural behavior and effects factored by different bonding modes.The conclusion can be drawn that the flexural behavior of prestressed concrete hollow slabs strengthened with CFRP is well-tried.It provides design suggestions and reference for prestressed concrete hollow slabs strengthened with CFRP, and also provides an experimental basis for the repairing and reinforcing practical engineering application in Wenchuan disaster area.

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