Volume 2 Issue 4
Authors: Jaya V; Annie Joy
Abstract: Soil nailing is one of the extensively used techniques for stabilizing cut slopes in railway and highway construction. In this method, the native soil is strengthened by placing steel rods into drilled holes in the walls and grouted. The dynamic behaviour of soil nail walls is affected by the relative density of backfill, the length and diameter of nails, axial force, shear force and bending moment developed along the nails. Laboratory plate load tests were performed on a soil nail wall model of 1 m height having vertical facing with relative densities of 25% and 50% and two nail lengths of 0.5 m and 0.6 m to study the effect of relative density of soil and length of nails on stability of soil nail wall. A detailed finite element analysis was carried out on soil nail wall model having 1 m height and vertical facing in order to determine the axial force, shear force and bending moment developed along nails. The settlement of the soil nail wall was decreased with the increase in relative density of sand. The increase in length of nail from 0.5 m to 0.6 m resulted in decrease of settlement for the soil nail wall having 1 m heght. The axial force along nails increased with the embedment depth. Both the bending moment and shear force were found to be concentrated near the face of the wall. A parametric study was also carried out and design tables were prepared for various earthquake coefficients.
Keywords: Soil Nail Walls; Factor of Safety; Relative Density; Settlement
Authors: Lyes Amara; Ali Berreksi; Bachir Achour
Abstract: An adapted second-order accurate MacCormack finite-differences scheme is introduced and tested for the integration of the water hammer equations for a friction pipe. A fractional method is used to solve the governing equations in two steps with the Runge-Kutta splitting technique. The details of the proposed improvement technique, boundary condition inclusion and the shock capturing capability are presented in this paper. The numerical oscillations resulting from the dispersive errors of the MacCormack original scheme are treated using the artificial viscosity procedure. The results computed using the adapted MacCormack scheme for a friction pipeline with the original scheme with numerical viscosity are compared and analyzed. It is shown that for an abrupt varied flow, the proposed technique leads to better results.
Keywords: Water Hammer; MacCormack; Numerical Oscillations; Artificial Viscosity; Splitting Technique; Runge-Kutta
Authors: S.M.R. Hosseini; M. Jesmani
Abstract: In most of geotechnical projects linear Mohr-Coulomb envelope is used. In fact, aforementioned envelope is curved for coarse-grained soils and is affected by some factors such as confining pressure and normal stress. The curved strength envelope could be used to study the behavior of deep foundations, earth dams, soil slopes, and the other earth structures in which failure occurs under considerable normal stresses. A deep failure surface may be more critical than a shallow surface when the phenomenon of curved strength envelope is considered, because in fact the internal friction angle decreases with increasing the depth of soil layers and confining pressure. The main purpose of this research is to express the internal friction angle of sands as a function of normal stress and relative compaction. In this study, direct shear tests are performed on air dried and saturated sand samples at different normal stresses to evaluate the variation of internal friction angle with these factors.
Keywords: Dilatancy; Internal Friction Angle; Normal Stress; Relative Compaction; Stress Level
Authors: C.Y. Shao
Abstract: Hangzhou Jiubao Bridge crosses the Qiantang River with full length of 1855 m, which is the first large river crossing project completely using composite structure in China. The main navigation span, of span arrangement of 3x210 m, uses the continuous hybrid arch-girder structure, with multi-point simultaneously incremental launching construction method. The design scheme comes out an integrated consideration of both structure and construction technology. For the purpose of safe, reliable, efficient and economical construction, tracked incremental launching equipment is especially developed with only one temporary pier considered for the 210 m main arch span during the launching construction. Design scheme of this bridge presents new design philosophy, technology and creativity.
Keywords: Hybrid Arch-Girder Bridge; Design Scheme; Tracked Incremental Launching Equipment; Incremental Launching Construction
Authors: Rasoul Daneshfaraz
Abstract: This paper describes numerical investigation of velocity profile and pressure distribution of 3-D bends with different diversion angles via CFD model. Reynolds number, diversion angle and section angle, are introduced as important variable parameters of current study. Reynolds number's range was 100 to 1900 and the diversion angles of bends were 90, 135 and 180 degree with regard to inlet flow. The mail goal of current study is to investigate the effect of Reynolds number and the diversion angle on velocity profiles and pressure distribution. It is worth mentioning that the experimental results of former study in a 90-degree bend are used for validating the numerical model. Studies of velocity profiles show that by increasing the section angle, the velocity profile inclines to outer wall, and maximum deviation from inlet velocity profile happens at 45 section angle. Also the maximum velocity occurs at 0.7 to 0.9 of the pipe diameter from inner wall. By increasing the section angle, the pressure profile inclines to outer wall and in this inclination, pressure loss is observed. For low Reynolds numbers, the variation of pressure loss is linear but by increasing the Reynolds number maximum pressure loss happens at limited section angle.
Keywords: Confined Flow; Bends; Reynolds Number; Velocity Profiles; Pressure Distribution
Authors: Giuseppe Campione
Abstract: Equations for a hand computation of moment-axial forced domain of R.C. members externally strengthened with steel angles and strips are developed here. The analytical derivation was made assuming equivalent stress-block parameters for internal force considering the confinement effect induced in concrete core by external cages. Simple analytical equations are proposed on the basis of constitutive laws of confined concrete and steel angles recently developed by the author. The proposed model gives results in a good agreement with available experimental data and it allows one a hand control of the influence of main parameters governing the problems (angles and strips geometry and mechanical properties of constituent material) on the behaviour of R.C. columns externally strengthened with steel cages.
Keywords: Concrete Columns; Strengthening; Steel Angles; Strips; Confinement; Moment-axial Force Domain