102,132 research outputs found
The tragic science: how economists cause harm (even as they aspire to do good) by George F. DeMartino
No full textBook review: DeMartino, G. F. (2022). The Tragic Science: How economists Cause Harm (Even as They Aspire to Do Good). University of Chicago Press (pp. 272)
This paper discusses the book The tragic science: how economists cause harm (even as they aspire to do good) by M. George F. DeMartino. The Author criticizes the moral geometry used by economists to evaluate harm, arguing for a more multifaceted understanding of harm that considers epistemic uncertainty. While the book under review lacks a systematic study of the moral dimension of harm, the Author’s versatility and scholarship are admirable, making it an inspiring read for both casual readers and professionals in economics and philosophy
Preliminary insights on the inelastic seismic response of structural systems under pulse-like ground motion
No full textNear-fault pulse-like seismic events exhibit a pulse in the velocity time history that mainly occurs in the strike-normal direction at locations towards which the earthquake rupture has propagated. The large damage potential associated with such seismic events is due to high displacement and velocity demands, together with the transmission of a large amount of energy in a relatively short time. In presence of specific geological conditions, they can also reveal unusual peaks of the spectral values in the long-period range. Additionally, it is well known that the intensity level of the vertical shaking close to the causative fault can be exceptionally high. Within this framework, the present study presents a preliminary sensitivity analysis of the inelastic response of structural systems under near-fault pulse-like ground motion accounting for the vertical component through the P-Delta effect for better understanding the damage potential of such seismic events and for supporting the development of proper design guidelines. First, some seismic records have been selected and processed. The dominant pulse embedded in the selected records and the corresponding pulse period value are derived
through a recent methodology based on the Variational Mode Decomposition technique. Several nonlinear dynamic analyses are then performed. Specifically, elastic and inelastic response spectra are first calculated taking into account the whole seismic signal and the dominant pulse only, without and with vertical seismic component and P-Delta effect. In doing so, acceleration, velocity, displacement and energy spectra are carried out and analyzed. The preliminary results here reported indicate that for large fundamental periods of the oscillator (e.g., larger than 3 s) the response can be significantly higher when the vertical component of the accelerogram and P-Delta effect are also taken into account.
Moreover, it is found that the nonlinear behavior of the oscillator can have a beneficial or detrimental effect. The outcomes of this preliminary analysis aim at providing useful insights toward a better characterization of the seismic demand in inelastic structural systems subjected to pulse-like seismic events
Cave-Surface electrical resistivity tomography in "castello di Lepre" Karst System (Marsico Nuovo, Southern Italy)
No full textSeveral geophysical methods, electrical resistivity tomography (ERT), gravimetric prospecting (G), Ground Penetrating Radar (GPR) and seismic methods (S), are commonly applied to characterize karst cave (Beres et al., 2001; Martínez-Moreno et al., 2015; Bermejo et al., 2016; and references therein). In detail, the geophysical approach provides information on cave geometry and subsurface geological structure. Several karst areas have a complex deep system, but the geophysical methods, such as geoelectrical ones, offer partial deep information due to a low-resolution. Therefore, this work would like to introduce a new 2D and 3D geoelectrical approach, that we call "cave-surface" ERT, which define an improvement of the deep resolution comparing to surface ERT. Finally, an application of this new methodology in the karst cave Castello di Lepre (Marsico Nuovo, Basilicata region, Italy) is described
Modeling of glubam roof truss, parameter identification and updating based on parallel genetic algorithm
No full textThis research introduces an innovative approach to the design and simulation of bio-based laminated structures, specifically focusing on glue-laminated bamboo (glubam) used in roof trusses. Our study fills a critical gap by investigating the mechanical behaviors of bolted connections in bamboo-based structures, which have not been comprehensively studied before. We employ a dual-phase methodology: initially, cyclic tests on bolted steel to glubam joints assess their hysteretic behavior, followed by tests on glubam planar roof trusses to evaluate structural responses under practical conditions. Our novel contribution is the development of a simplified mechanical-based hysteretic model, incorporating connector and spring elements in series or parallel within the ABAQUS software. This model significantly improves on existing models by allowing for initial calibration through a parallel genetic algorithm (PGA), enhancing both accuracy and efficiency. Subsequent incorporation of this model into the simulation of truss joints enabled the creation of an advanced hybrid roof truss model within ABAQUS. The final stage of our research demonstrates the application of a PGA-based model-updating framework, which substantially increases the model's predictive accuracy. This work not only advances the understanding of structural behavior in bio-based construction materials but also introduces a robust framework for model updating that can be applied to other engineering simulations, contributing to more sustainable and resource-efficient construction practices
Towards risk-targeted seismic hazard models for Europe
No full textAbstract Standards and Codes of Practice for designing new constructions and for assessing and strengthening existing ones are usually based on uniform hazard maps, where different Limit States (LSs) are associated with different hazard-exceedance probabilities. This approach yields non-homogeneous LS-exceedance probabilities across a territory, thus failing to achieve the goal of uniform risk throughout a territory. Such lack of uniformity stems from estimating the probability of failure using capacity and demand models. If the capacity of new constructions—or the capacity increase of strengthened existing constructions—are designed based on a prescribed hazard-exceedance probability, then the seismic risk depends on both the structure (depending on the design philosophy and corresponding design objectives), through the capacity model, and the location, through the hazard model. The aim of this study is threefold. First, it provides a seismic probability assessment formulation and a risk-targeted intensity measure based on a linear model in log–log coordinates of the hazard, under the assumption of log-normal capacity and demand. The proposed framework introduces a factor that multiplies the code hazard-based demand to account either for intentional (from design) over-capacity or for undesired (e.g., in existing constructions) under-capacity. Second, this paper shows an application to peak ground accelerations in Europe considering parameters taken from Standards and Codes of Practice. The developed framework is used to determine the risk-target levels of peak ground acceleration used for design in Europe, for both new and existing constructions. Third, the obtained target risk levels are used to determine a risk-based intensity modification factor and a risk-based mean return period modification factor, which can be readily implemented in current Standards to achieve risk-targeted design actions, with equal LS-exceedance probability across the territory. The framework is independent of the chosen hazard-based intensity measure, be it the commonly used peak ground acceleration or any other measure. The results highlight that in large areas of Europe the design peak ground acceleration should be increased to achieve the proposed seismic risk target and that this is particularly significant for existing constructions, given their larger uncertainties and typical low capacity with respect to the code hazard-based demand
Seismic loss-of-support conditions of frictional beam-to-column connections
No full textThe evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation
between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response
Experimental dynamic characterization of a new composite glubam-steel truss structure
No full textThe main characteristics of an original bamboo-steel composite truss structure are presented in this work. Specifically, the considered system is a spatial truss structure whose upper chord and diagonal bars are made by glubam elements whereas its lower chord is made by steel members with a hollow cross-section. This novel structural system has been conceived to build roofs and low/mid-span bridges (for example, footbridges), in such a way to ensure easy and rapid construction, efficient use of the constituent materials, low manufacturing costs and good environmental sustainability. A prototype spatial truss beam for laboratory tests is initially described by providing details about geometry, connections and materials properties. The results obtained from dynamic experimental tests are then discussed. In particular, the dynamic response under ambient vibrations and the free-decay response of this truss structure have been recorded and analyzed in order to estimate its modal properties. Design values of the viscous damping ratio for glubam truss structures with steel bolted connections are finally recommended. The numerical assessment of the human-induced vibration serviceability conditions for footbridges built by means of this structural system is finally performed
Dissipation in sheathing-to-framing connections of light-frame timber shear walls under seismic loads
No full textThe present study is concerned with the seismic analysis and design of light-frame timber shear walls, with focus on the energy dissipation ensured by sheathing-to-framing connections under in-plane lateral loads. In this perspective, a suitable parametric finite element model for light-frame timber shear walls is first developed using the software OpenSees. By means of such model, the equivalent viscous damping of the wall is assessed numerically, together with the damping factor adopted within the capacity spectrum method. Furthermore, the optimal layouts of slender (1.2 m x 2.4 m/3.94 ft x 7.88 ft) and squat (2.4 m x 2.4 m/7.88 ft x 7.88 ft) light-frame timber shear walls are found by solving a multi-objective optimization problem in which racking capacity and total material cost are optimized simultaneously (this task is accomplished via simple enumeration because of the low cardinality of the design variables set). So doing, it is shown that the total material cost of the optimal (non-dominated) wall configurations has a strong influence on the racking capacity whereas it does not affect the equivalent viscous damping ratio, which remains almost constant. A novel simplified analytical procedure for predicting the capacity curve of light-frame timber shear walls is finally proposed
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