Modelling and Seismic Response Analysis of Italian Code-Conforming Base-Isolated Buildings

ABSTRACT

This paper reports on results of nonlinear analyses performed within the RINTC project on an RC building isolated with different systems (High Damping Rubber Bearings, High Damping Rubber Bearings and Flat Sliding Bearings, Friction Pendulum System) and designed according to the Italian design code. The seismic response has been evaluated under different seismic input levels of two sites with different hazard and by considering two Limit States: Global Collapse and Usability-Preventing Damage. The influence of seismic stoppers and modelling uncertainties is also evaluated. Results permit to compute the implicit collapse risk and to identify critical aspects of current design procedures.     

‘Sharing the white man's burden’ Nazi colonial revisionism and Australia's New‐Guinea mandate

ABSTRACT

The September 2014 general elections in Fiji resulted in a decisive victory for Prime Minister Bainimarama and his FijiFirst Party. It indicated a desire for stability on the part of the electorate as well as the popularity of measures such as ‘free’ education and the removal of affirmative action programmes for Indigenous Fijians. The Social Democratic Liberal Party garnered a significant portion of the Indigenous vote through appeals to ethnic identity, but will need to broaden its base in future to have any chance of forming a government. The high voter enrolment and participation reflects a hope for more accountability as well as transparency, in contrast to the arbitrariness of the previous eight years. New oversight institutions and a more expansive bill of rights in the constitution offer some ground for cautious optimism in the face of cynicism about the gap between the government's rhetoric and its actions.     

Estimating Historical Total Fertility Rates for Australia and Its States

Abstract.

Australian Bureau of Statistics Total Fertility Rate (TFR) statistics are available from 1921 for Australia, and for census years between 1947 and 1966 for the states, and then on an annual basis from 1971. Using historical, statistical publications, annual TFRs for Australia and the states dating back to federation in 1901 were calculated directly in years where data are available and estimated indirectly via the standardized fertility ratio in other years. For some periods where direct TFR estimation was applied, age-specific births used in the numerators of fertility rates must be estimated from partial data. Combined with Australian Bureau of Statistics data, the authors’ estimated TFRs contribute an uninterrupted time series of national and state TFRs for Australia from 1901 to 2011.     

SEISMIC BEHAVIOUR OF A R/C WALL: NUMERICAL SIMULATION AND EXPERIMENTAL VALIDATION

This paper describes the numerical simulation of the seismic behaviour of a mock-up of a six-floor building, constituted by two parallel R/C walls and experimentally tested on a shaking table. Within the scope of an international benchmark the mock-up was submitted to three earthquakes with intensities up to 0.71 g, which induced nonlinear behaviour in the concrete and reinforcement. For the numerical simulations concrete is discretised with 2D finite elements, and its behaviour reproduced via a constitutive model with two scalar damage variables. Steel rebars are discretised with 2-noded truss elements, and their constitutive behaviour under cyclic conditions reproduced by the Menegottb-Pinto model. Specific attention is devoted to Rayleigh damping, focusing on two different strategies: (i) disregarding the damping contribution, or (ii) adopting a damping matrix that takes into account the stiffness changes during the nonlinear analyses. Main results and strategies for simulating the benchmark axe presented, with emphasis on the comparison between the numerical and the experimental results, which show good agreement when the damping contribution is neglected.     

MODELLING OF RC MEMBERS UNDER CYCLIC BIAXIAL FLEXURE AND AXIAL FORCE

A model is proposed for the incremental force-deformation behaviour of reinforced concrete sections and members, under generalised load or deformation histories in 3D, including cyclic loading, up to ultimate deformation. At the section level the model is of the Bounding Surface type and accounts for the coupling between the two directions of bending and between them and the axial direction. For the construction of the member tangent flexibility matrix on the basis of the section tangent flexibility matrix, a piecewise-linear variation along the member is assumed for the nine terms of the tangent section flexibility matrix. Model parameters are derived on the basis of available test results for: (a) the force-deformation response under cyclic biaxial bending with normal force; (b) the hysteretic energy dissipation; (c) the secant-to-yield member stiffness, and (d) the ultimate deformation of the member under cyclic biaxial load paths.     

SOIL DAMPING FORMULATION IN NONLINEAR TIME DOMAIN SITE RESPONSE ANALYSIS

Nonlinear time domain site response analysis is used to capture the soil hysteretic response and nonlinearity due to medium and large ground motions. Soil damping is captured primarily through the hysteretic energy dissipating response. Viscous damp-ing, using the Rayleigh damping formulation, is often added to represent damping at very small strains where many soil models are primarily linear. The Rayleigh damping formulation results in frequency dependent damping, in contrast to experiments that show that the damping of soil is mostly frequency independent. Artificially high damp-ing is introduced outside a limited frequency range that filters high frequency ground motion. The extended Rayleigh damping formulation is introduced to reduce the over-damping at high frequencies. The formulation reduces the filtering of high frequency motion content when examining the motion Fourier spectrum. With appropriate choice of frequency range, both formulations provide a similar response when represented by the 5% damped elastic response spectrum.

The proposed formulations used in non-linear site response analysis show that the equivalent linear frequency domain solution commonly used to approximate non-linear site response underestimates surface ground motion within a period range relevant to engineering applications. A new guideline is provided for the use of the proposed formulations in non-linear site response analysis.     

The Process of Policy Innovation: Prison Sitings in Rural North Carolina

We gauge the relative impact of economics, demographics, and politics on the decisions of 79 rural North Carolina counties whether to site a prison in the period 1970–2000. The results of this model demonstrate that, contrary to the expectation that counties site prisons in response to economic distress, the demographic characteristics of each county affect the relative likelihood of a prison siting more than its economics does. The influential demographic predictors are those inextricably bound up with development options—the education levels of its citizens—and those that limit its ability to pursue controversial projects—its not-in-my-backyard (NIMBY) constituencies—rather than those that measure its racial diversity. Therefore, prison siting is neither a simple story of economic determinism nor one of environmental racism. We use a proportional hazards regression to model this innovation adoption in response to the challenge to select methods that take the potential time dependence of adoptions into account. A duration model is also particularly suitable for cases such as this one for which the innovation adoption is better understood as a process than as an event.     

Der Natur‐Begriff des 17. Jahrhunderts und zwei seiner Inter‐pretamente: „res extensa”︁ und „intima rerum”︁

This article aims to show the general and broad use of the concept of nature in the philosophical discourse of the 17th century ‐ and in this context it is obvious that this discourse includes both philosophy and theology. I will discuss two opposite views concerning its fundamental understanding of nature, yet will not go into elaborating differences concerning such particular concepts as, for example, space, void or motion. These views and the theoretical positions from which they emerged will here be called res extensa and intima rerum ‐ this is done in order to clarify the basic opposition: there is no interior in pure extension and there is no extension at all in that what is called the interior. My aim is to show that these two views are, in fact, not quite as incompatible and contradictory as it easily may seem at first glance. Although I will for heuristic purposes introduce the two concepts res extensa and intima rerum as complete opposites and in a wholly contrary manner, ist should become clear that there exist both influences and interactions between these two notions. Theorists introduced here as advocates of the intima rerum‐position, can, for example, be seen as having been influenced by the mechanistic, or res extensa‐position, mainly through the formally and methodologically attractive geometric and mathematical argumentation. Likewise theorists advocating a mechanistic position can be said at some points to have been led by a substantial necessity concerning the contect of their argumentation to take recourse to the concept of intima rerum, at least partly or in a modified manner.     

STRENGTH REDUCTION FACTORS FOR DUCTILE STRUCTURES WITH PASSIVE ENERGY DISSIPATING DEVICES

In recent years, current seismic codes started contemplating the design of structures with passive energy dissipating devices. One important issue for the rational seismic design of these devices and the structure that contains them is the formulation of numerical methods to estimate their design seismic forces. From the study of the dynamic response of single-degree-of-freedom systems subjected to accelerograms recorded in Mexico during the last two decades, expressions to estimate the strength reduction factor that should be used to reduce the elastic design strength spectra for 5 percent damping, to establish the design seismic forces for structures having different combinations of plastic and viscous energy dissipating capacities, are formulated.     

COMPLEX MODE SUPERPOSITION ALGORITHM FOR SEISMIC RESPONSES OF NON-CLASSICALLY DAMPED LINEAR MDOF SYSTEM

This paper deals with a complex mode superposition method for the seismic responses of general multiple degrees of freedom (MDOF) discrete system with complex eigenvectors and eigenvalues. A delicate general solution, completely in real value form, for calculat-ing seismic time history response of the MDOF system which cannot be uncoupled by normal modes, is deduced based on the algorithms of the complex superposition method. This solution comprises of two parts which are in relation to the Duhamel integration to sine and cosine function respectively. The related term of the Duhamel integration to sine function is actually the displacement response of the oscillator with corresponding modal frequency and the damping ratio. The other can be transferred into a combina-tion of the displacement and velocity responses of the same oscillator. In order to meet the practical needs of seismic design based on code design spectra for various kinds of structures equipped by viscous dampers, the complex complete quadratic combination (CCQC) method is deduced following similar procedures such as the well-known CQC method, in which a new modal velocity correlation coefficient, together with a new modal displacement-velocity correlation coefficient are involved besides the modal displacement correlation coefficient in normal CQC formula. The new algorithm of CCQC is not only as concise as that of the normal CQC but also has explicit physical meaning. The results obtained from complex mode superposition approaches are discussed and verified in some examples through step by step integration computation under a prescribed earth-quake motion input. From these examplary analyses, it may be pointed that the CCQC algorithm normally yields conservative outcome and that the forced mode uncoupling approach has good approximation even the discussed examplary structures are strongly non-proportional.