Hierarchical tapered bar elements undergoing axial deformation

A method is described to model the dynamics of tapered axial bars of various cross sections based on the well-known Craig/Bampton component mode synthesis technique. This element is formed in terms of the static constraint modes and interface restrained normal modes. This is in contrast with the finite elements as implemented in NASTRAN where the interface restrained normal modes are neglected. These normal modes are in terms of Bessel functions. Restoration of a few of these modes leads to higher accuracy with fewer generalized coordinates. The proposed models are hierarchical so that all lower order element matrices are embedded in higher order element matrices. The advantages of this formulation compared to standard NASTRAN truss element formulation are demonstrated through simple numerical examples

Rapid chloride penetration on high performance fly ash incorporated silica fume concrete

Mechanical and durability properties of fly ash incorporated high performance silica fume concretes are discussed with respective to the obtained experimental results. Concrete specimens are prepared at the water-to-binder ratio of 0.28.  The effect of inclusion of various percentages of silica fume (4%, 8%, 10% and 12%) on the workability, the Compressive strength and the Rapid chloride penetration, according to ASTM C 1202  are determined and compared with the reference mix in which 12% of fly ash is kept constant as cement replacement material. The consumption of alternative  fine aggregate is an accepted step towards solving part of the depletion of natural aggregate and hence sand was substituted with M-sand of 50 %. Total binder content was kept constant as  600 kg/m3 for all the concrete mixtures. Result show that the combination of 8 to 10 % silica fume and 12% fly ash increase the  strength  of concrete, but beyond 10% of silica fume with 12% of fly ash combination the compressive strength get decreased. The incorporation of  silica fume and fly ash in the concrete mixtures, increased the resistance to chloride ions while an increasing percentage of silica fume in ternary mix and shaped the concretes with very low permeability - high performance

CHLORIDE PENETRATION ON GROUND NUT SHELL ASH CONCRETE UNDER ACIDIC ENVIRONMENT

Groundnut shell ash is one of the important pozzolanic materials containing that can be mixed with ordinary Portland cement for the manufactured of long durable and good valuable product. The present experimental evaluation is rapid chloride permeability test (RCPT). The effect of hydrochloric acid (HCL) on properties of replaced ground nut shell ash concrete is taken as research area. However at 20% replacement level of ground nutshell ash more resistance to 3% Hydrochloric acid attack

Transient loads analysis for space flight applications

A significant part of the flight readiness verification process involves transient analysis of the coupled Shuttle-payload system to determine the low frequency transient loads. This paper describes a methodology for transient loads analysis and its implementation for the Spacelab Life Sciences Mission. The analysis is carried out using two major software tools - NASTRAN and an external FORTRAN code called EZTRAN. This approach is adopted to overcome some of the limitations of NASTRAN's standard transient analysis capabilities. The method uses Data Recovery Matrices (DRM) to improve computational efficiency. The mode acceleration method is fully implemented in the DRM formulation to recover accurate displacements, stresses, and forces. The advantages of the method are demonstrated through a numerical example

Tensor Minkowski Functionals for random fields on the sphere

We generalize the translation invariant tensor-valued Minkowski Functionals which are defined on two-dimensional flat space to the unit sphere. We apply them to level sets of random fields. The contours enclosing boundaries of level sets of random fields give a spatial distribution of random smooth closed curves. We obtain analytic expressions for the ensemble expectation values for the matrix elements of the tensor-valued Minkowski Functionals for isotropic Gaussian and Rayleigh fields. We elucidate the way in which the elements of the tensor Minkowski Functionals encode information about the nature and statistical isotropy (or departure from isotropy) of the field. We then implement our method to compute the tensor-valued Minkowski Functionals numerically and demonstrate how they encode statistical anisotropy and departure from Gaussianity by applying the method to maps of the Galactic foreground emissions from the PLANCK data.Comment: 1+23 pages, 5 figures, Significantly expanded from version 1. To appear in JCA