Hysteretic energy dissipation is often employed as a measure of performance for systems subjected to earthquake excitation. This mainly stems from quasi-static cyclic tests where fuller hysteresis loops (i.e., higher energy absorption) are taken to indicate better performance when comparing systems with similar strength under the same cyclic loading protocol. However, seismic loading offers a different proving ground, where energy absorption is strongly correlated with energy input, while the nonstationary loads imply that the beneficial hysteretic effects observed in a cyclic test may never be realized. Given the current state of art in models and methods of performance-based earthquake engineering, we ask whether earthquake records at a given seismic intensity will cause peak/residual displacements or accelerations that favor models having fuller hysteresis. Using incremental dynamic analysis on story-level oscillators with varying hysteretic characteristics, it is demonstrated that hysteretic energy dissipation does not consistently correlate with seismic performance.
The adrenocorticotrophic hormone (ACTH) receptor controls adrenal steroidogene-sis in response to circulating ACTH. The recent cloning of the receptor has opened a new understanding of the normal and pathologic functioning of the adrenal cortex. This chapter will focus on the clinical forms of hereditary ACTH resistance syndromes and their association with abnormalities of the ACTH receptor gene.
Background/Objectives: Resilience—a complex phenomenon embracing a number of factors on various levels—seems to be a most important skill to survive this vulnerable phase. One major factor is the perceived social support during adolescence. Recognizing gaps in perceived social support may lead to prevention of serious social and medical problems, including juvenile delinquency and stress-related diseases. Screening questionnaires to identify the gaps in perceived social support in Greek adolescents are lacking. The purpose of this study was to validate a Greek version of the Multidimensional Scale of Perceived Social Support (MSPSS), a self-report scale of perceived social support of the family, significant others, and friends. Methods: The MSPSS was translated into Greek and was administered to students of 15 to 18 years of age from several areas of Greece. Psychometric properties of the MSPSS tool were investigated by Exploratory Factor Analysis (EFA), using principal component analysis with the Varimax Rotation Method. For Confirmatory Factor Analysis (CFA), the Comparative Fit Index (CFI), Tucker–Lewis index (TLI), and the Root Mean Square Error of Approximation (RMSEA) were used. Results: A total of 999 students completed the MSPSS anonymously. The Greek version of the MSPSS scale exhibited large internal consistency (Cronbach’s α of 0.932, McDonald’s Omega of 0.926). Three of the factors explained 80.80% of total variance. Conclusions: The Greek adaptation of the MSPSS is a valid instrument, and professionals can apply it as a screening tool for perceived social support in adolescents.
A comparative study of alternative Intensity Measures (IMs) for structures of rocking response is presented, focusing on the salient characteristics that define the selection of an optimal IM for the problem at hand. An IM may play the role of an interfacing variable, linking hazard with fragility/vulnerability for the risk assessment of structures, or it may only be employed as a proxy for predicting structural response under a given ground motion. In the first case, low conditional variability (high efficiency) and low conditional dependence on seismological parameters (high sufficiency) are needed. For response proxy usage, one may place more importance on the predictive capability of the IM within a simple regression model, favoring high correlation and low fitting errors over an extended range of response. The results showcased that (i) the peak ground acceleration and peak ground velocity, tend to be highly efficient and sufficient in specific regions of rocking response, that is, onset of rocking and overturning, respectively, but not necessarily everywhere; (ii) the average spectral acceleration shows a more consistent performance at the cost of requiring the definition of a proper period range; (iii) magnitude sufficiency is generally more difficult to achieve, compared to the distance from the rupture, and (iv) IMs that may be unsuitable for risk and vulnerability assessment, can still be highly effective as response predictors in statistical models.
As proven by several past earthquakes, seismic losses associated with nonstructural damage in modern buildings are likely to significantly exceed those associated with structural damage. Hence, to satisfactorily assess the overall seismic performance of a building and consequently the associated losses, it is paramount to properly account for the nonstructural damage through the adequate estimation of acceleration demands that are imposed on its acceleration-sensitive nonstructural elements in any one-floor level during an earthquake. Component acceleration amplification factors, ap, which measure how much the acceleration of a component is amplified relative to the peak floor acceleration are evaluated by floor motions recorded during earthquakes on instrumented buildings in the United States. The study shows that component amplification factors currently used in codes significantly underestimate acceleration demands for components whose periods are tuned or nearly tuned to modal periods of the supporting structure. Simplified equations are proposed to estimate component acceleration amplifications. The study also evaluates inelastic floor acceleration spectral ordinates. As a result of the filtering and amplification of the ground motion by the structure, the results show that even small levels of nonlinearity in the nonstructural element or its attachment to the structure lead to significant reductions in acceleration demands.
