Search results for "Structural engineering"
showing 10 items of 1998 documents
Stochastic seismic analysis of structures with nonlinear viscous dampers
2007
Fluid damper devices inserted in buildings or bridges are commonly used as energy sinks for seismic protection. In the response analysis of structures with filled damper devices the main problem exists in the strong nonlinear behavior of such equipment, as a consequence the differential equation of motion remains nonlinear and the response spectrum analysis still cannot be applied. In this note, by using the concept of power spectral density function coherent with the elastic response spectrum and by using the statistical linearization technique, expressions for finding the equivalent linear damping have been found. Comparisons with results obtained by Monte Carlo simulations confirm that f…
LES of the flow around two cylinders in tandem
2008
The flow around an arrangement of two-in-tandem cylinders exhibits a remarkably\ud complex behaviour that is of interest for many engineering problems, such as environmental\ud flows or structural design. In the present paper, a Large Eddy Simulation using a staggered\ud Cartesian grid has been performed for the flow around two-in-tandem cylinders of diameter\ud D=20mm and height H=50mm submerged in an open channel with height h=60 mm. The two\ud axes have a streamwise spacing of 2D. The Reynolds number is 1500, based on the cylinder\ud diameter and the free-stream velocity u�. The results obtained show that no vortex shedding\ud occurs in the gap between the two cylinders where the separat…
On the Path and Area J<sub>x1</sub>-Integral Components and their Relationship to the Out-of-Plane Constraint in Elastic Cracked Plates
2009
In this paper, the path and area components of the Jx1-integral, JP and JA, in three dimensional elastic cracked plates under mode-I loading are investigated aiming at relating them to the out-of-plane constraint conditions resulting from different specimen thicknesses. It is concluded that the JP and JA components of the Jx1-integral vary in the region where the out-of-plane constraint extends. Sufficiently far from the crack front, these integrals tend to stabilize, indicating that the thickness constraint vanishes and that a 2D-like stress and strain fields have been reached. A pure plane strain condition is only attained when the specimen thickness is very large when compared to the in-…
An Influence of Permanent Magnet Shape on the Torque Ripple of Disc-Type Brushless DC Motors
2006
An analysis of the torque developed by two types of the disc-type permanent magnet (PM), brushless DC motors: slotted torus motor and motor with stator salient poles is presented. The calculations were performed using three-dimensional finite element method (FEM). Two shapes of PMs are analyzed: trapezoidal and rectangular. The results show that application of rectangular shaped PMs provides significant reduction of the torque ripple in both considered motors.
A lumped model for a seismic source
1993
A lumped mechanical model is proposed and solved. This model is dynamically equivalent, in the mean field approximation, to a faulted lithosphere. The transition from the continuous system (modelled according to W. H. Prescott and A. Nur) to the lumped one, has been made by preserving all the relevant features exhibited by the continuous system. In particular the coupling between different components of the stress and strain tensors is suitably taken into account. The dynamics of the lumped system depends on six control parameters fixed by the physical properties of the continuous system. Three of the control parameters are dimensionless and describe: the seismic wave quality factor of the…
BEF Analogy for Concrete Box Girder Analysis of Bridges
2010
<p>Box girder, due to its high torsional stiffness, is very appropriate for railway and highway long- medium span bridges. This type of cross section, subjected to transversely non-uniform loads, present warping and distortion phenomena. Accurate but time-consuming numerical procedures are available for determination of further strains and stresses caused by cross-section deformation. In this paper warping and distortion of box girders is evaluated through BEF analogy, by writing a 4th order differential equation. The problem is solved for practical cases of box girders by considering internal diaphragms stiffness. Graphs are supplied to designers and main design parameters affecting …
Shakedown of Structures Subjected to Dynamic External Actions and Related Bounding Techniques
2002
The shakedown theory for dynamic external actions is expounded considering elastic-plastic internal-variable material models endowed with hardening saturation surface and assuming small displacements and strains as long with negligible effects of temperature variations on material data. Two sorts of dynamic shakedown theories are presented, i.e.: i) Unrestricted dynamic shakedown, in which the structure is subjected to (unknown) sequences of short-duration excitations belonging to a known excitation domain, with no-load no-motion time periods in between and for which a unified framework with quasi-static shakedown is presented; and ii) Restricted dynamic shakedown, in which the structure is…
Shear strength degradation due to flexural ductility demand in circular RC columns
2014
An analytical model was developed to estimate the shear-strength degradation and the residual capacity of circular reinforced concrete (RC) columns subjected to seismic action. The proposed model is an upgrade of a previously proposed model for axial force $$N$$ , bending moment $$M$$ and shear force $$V$$ ( $$N$$ – $$M$$ – $$V$$ ) interaction domain evaluation for rectangular and circular cross-section RC elements subjected to static loading. The model was extended to the case of circular cross-sections subjected to seismic actions with limitation of the range of variability of the deviation angle between the directions of the stress fields and the crack inclinations, as a function of the …
Risk of failure for the salso river railroad steel bridge
2020
Abstract The degradation state of railroad steel bridges is one of the most important and difficult aspects to be interpreted. The use of steel bridges started from 1900, and they are still in service today as railroad bridges. The case study examined was that of a bridge railroad steel bridge having a total length of 112 m and constituted by three isostatic, reticular beams having a Pratt type composition. The substructures (two shoulders and two intermediate piles) are in masonry with a reinforced concrete beam in the upper portion. The structure (steel bridge and piers) is in a degraded state. To determine the degradation level, non-destructive and partially destructive tests were carrie…
Experimental investigations of the soil–concrete interface: physical mechanisms, cyclic mobilization, and behaviour at different temperatures
2016
Behaviour of the pile–soil interface is important to correctly predict the response of floating piles in terms of displacement and lateral friction. Regarding energy piles, which couple the structural roles of deep foundations with the principle of shallow geothermal energy, the response of pile–soil interfaces is influenced by seasonal and daily cyclic thermal variations. Accordingly, the goal of this paper is to experimentally investigate the response of the pile–soil interface at different temperatures. This experimental campaign aims to analyse (i) the cyclic mobilization of the shear strength of the soil–pile interface that is induced by thermal deformation of the pile and (ii) the di…