Adolfo Santini

Dynamic response of a flexural non-classically damped continuous beam under moving loadings

Abstract In this paper an extension of the complex mode superposition method is presented for the dynamic analysis of a uniform simply supported beam with two rotational viscous dampers attached at its ends subjected to a constant moving loading. The mass of the loading has been assumed small with respect to the beam mass and, therefore, has been neglected. A parametric analysis has been performed, which has shown that the effectiveness of the dampers in reducing the response amplitude strongly depends on the loading speed. A comparative study between the exact response functions, obtained by means of the complex modal analysis, and the approximate ones, provided by the classical modal analysis, has been performed showing significant differences. In those cases where the exact response is larger than the approximate one the reliability of approximate methods may be seriously affected.

A simplified model for the dynamic soil-structure interaction of planar frame-wall systems

Abstract This paper presents two simplified methods for the dynamical analysis of the response of frame-wall plane systems interacting with the foundation soil. These methods are based on approximations widely used in the literature and form an extension of those already presented by the authors for structures on rigid soil. Interaction effects on the dynamical structural response are shown by using the numerical results obtained by these methods.

The dynamic response of coupled frame—wall systems to earthquake excitations

Abstract This paper presents a method for the analysis of the response of periodic frame—wall systems to earthquake excitations modelled as stationary random or evolutionary random processes. The transfer matrix required by the analysis, together with its powers is provided directly, thus avoiding calculation of the left and right-hand eigenvectors of the transfer matrix and eliminating computations for the evaluation of all its powers. It is shown how the method can be applied to structures that are only piecewise periodic and how results can be obtained for the static case. Finally, it is shown how the method may be used for both deterministic and probabilistic analyses.

Time domain response of a one-dimensional soil-structure interacting model via complex analysis

This paper considers a simple continuous model which embodies some aspects of the dynamic soil-structure interaction problem. For this model the equations of motion are first written, then complex frequencies and eigenmodes are evaluated. A physical interpretation of complex modes and frequencies is also provided. Subsequently a set of orthogonality conditions is established and is used in decoupling the equations of motion in principal coordinates. The complex mode superposition method is then used to provide the dynamic response of the model in the time domain. Some numerical applications are provided in order to show the performance of the method.

A simplified model for linear dynamic analyses of planar frame - wall systems

Abstract This paper presents two simplified methods for dynamic analyses of frame-wall structures. The methods are based on some simplifying assumptions widely used in the literature. One method has been derived for frequency-domain analyses and may be most useful when dynamic loads are specified as random processes. One particular feature of the method is that all modal components of the physical model are included in the analyses. A second aspect of interest is that hysteretic as well as viscous damping may be easily included. The second model is better suited for time-domain analyses. Novel aspects of the two methods are the inclusion of shear deformation effects in the structural elements, rotational inertia in the girders and a rotational component for the base motion. Some results obtained by the present methods are also compared with those available in the literature. Finally some parametric studies are conducted in order to assess the behaviour of uniform frame-wall systems.

Fatigue Analysis of Offshore Wind Turbines on Fixed Support Structures

A stochastic time domain fatigue analysis is pursued on steel tripod and jacket support structures for offshore wind turbines, following the basic concepts of recently validated simplified linear analyses. A set of environmental lumped load cases with corresponding probabilities of occurrence is considered. Results are compared in terms of a lifetime damage equivalent load.

Mitigation of Railway Traffic Induced Vibrations: The Influence of Barriers in Elastic Half-Space

In this paper, the problem of vibrations induced by trains and their propagation through the soil is studied. Particular attention is focused on the vibration induced by trains in motion and on the effects of such vibrations on the foundations of buildings in proximity of the tracks. The interaction between propagating waves induced by trains in motion and buildings foundations is a problem which does not admit a straightforward analytical solution; thus a solution is given by the use of a model based on the finite elements method. Firstly, we analyze the theoretical aspects of the problem by considering constant or harmonic loads moving along a straight railway track; then, we define a transfer function soil-railway and the response function of the entire system. The study aims to address the wave propagation in an elastic semi-space and the presence in the ground of a discontinuity element, such as a barrier of a given depth is considered. The efficiency variation of barriers is analyzed in function of the different materials used, and different numerical simulations are analyzed in order to study how the wave propagation and the track-soil interaction are influenced by the membrane, seen as damping barrier.

Two-Step Pushover Analysis of an Ancient Masonry Oil-Mill in the Southern Italy

Historical masonry buildings located in the Southern Italy are usually built with irregular stones joined with mortar with poor mechanical properties. Therefore, piers and spandrels ultimate resistance is not always well predicted by simplified formulas suggested by codes of practice, which typically are tailored to regular patterns. In this framework, we present a two-step numerical model –within the equivalent frame approach assumption– for the pushover analysis of in-plane loaded historical masonry walls constituted by an irregular assemblage of stones. In Step I, ultimate bending moment-shear force strength domains of piers and spandrels are derived by means of a heterogeneous upper bound FE limit analysis and the results are stored in a database. Assessing the capacity of both piers and spandrels is crucial for correctly predicting the ultimate resistance of masonry walls acted upon by in-plane loads. Heterogeneous limit analysis is particularly suitable for computing failure loads, since it permits a distinct modeling of stones and mortar joints. Appropriate static and kinematic boundary conditions are set to account for the complex interaction of internal forces and deformed shapes of single elements. At Step II, a frame model of the masonry wall is assembled, where piers and spandrels are modeled as elastic Timoshenko beams. At each analysis step it is checked that the internal forces in each structural element are smaller than the failure loads stored in the database created at Step I. If the capacity is exceeded, suitable flexural hinges are introduced at the end of the structural elements. The resistance of the element is then set to zero when a limit chord rotation is exceeded. With the numerical tool developed, a real scale old masonry oil-mill located in the Southern Italy is analyzed in the inelastic range under increasing static loads.

A Comparison Among Plastic Deformation Capacities of RC Members According to International Codes

The aim is to compare plastic deformation capacities of flexure‐controlled reinforced concrete members, as predicted by the Italian Seismic Code, Eurocode 8 and FEMA356. For completeness, recent studies in the literature are also referred to. The comparison is pursued in context with a nonlinear static analysis run on 2D frame structures. This allows to assess whether and to which extent plastic deformation capacities may be affected by variations in those quantities, such as shear span and/or axial load, depending on which plastic deformation capacities are generally given.