The applicability of nonlinear static procedures for estimating seismic demands in a variety of building types was evaluated within the recently concluded ATC-76-6 project. Results are reported herein for several pushover methods applied to three RC moment frame buildings, relative to baseline data provided by nonlinear response history analysis. Response quantities include peak interstory drifts, floor accelerations, story shears, and floor overturning moments. The single-mode pushover methods that were evaluated include the N2 and ASCE 41 coefficient methods. Multi-modal pushover methods include the modal pushover with elastic higher modes, and the consecutive modal pushover. Target displacements were estimated using typical R-C1-T relationships. Results indicate that the good performance of the single-mode methods for low-rise buildings rapidly deteriorates as the number of stories increases. Multi-mode techniques generally can extend the range of applicability of static pushover methods, but at the cost of significant additional computation and with uncertainty about the reliability of the results.
No abstract is provided for this article.
The quantification of seismic performance, using metrics meaningful to both engineers and stakeholders, has been a focal point of research in performance-based earthquake engineering. The prevalent paradigm is currently offered by the FEMA P-58 guidelines in the form of a component-by-component approach that provides detailed assessment capabilities at the cost of requiring a complete inventory of the structural, nonstructural, and content components. In an attempt for simplification, a fully compatible story-by-story approach is offered instead, where story loss functions are employed to directly relate monetary losses to engineering demand parameters given the story area. These functions can be adjusted for application to different situations, assuming the ratio of cost and quantity of each component category inventory remains relatively constant. As an example, they are generated for a standard inventory makeup, characteristic of low/mid-rise steel office buildings. They are shown to offer a favorable compromise of simplicity and accuracy that lies between the component-by-component and building-level approaches that are currently prevalent in building-specific and regional loss assessment, respectively.
Childhood sexual abuse is associated with an increased incidence of age-concurrent and adult psychopathology. Little is known, however, about the biological manifestations and sequelae of childhood sexual abuse. In this study, we characterized the hypothalamic-pituitary-adrenal axis of a self-selected sample of sexually abused and control girls recruited from a prospective longitudinal study. Plasma ACTH and total and free cortisol responses to ovine CRH (oCRH) stimulation were measured in 13 sexually abused and 13 control girls, aged 7-15 yr. Psychiatric profiles and 24-h urinary free cortisol (UFC) measures were also obtained. Sexually abused girls had a greater incidence of suicidal ideation (chi 2 = 4.51; df = 1; P < 0.05), suicide attempts (chi 2 = 4.51; df = 1; P < 0.05), and dysthymia (chi 2 = 8.85; df = 1; P < 0.01) than control girls. Sexually abused girls showed significantly lower basal (t = 2.1; df = 24; P < 0.05), and net oCRH stimulated (t = 2.2; df = 24; P < 0.05) ACTH levels and significantly reduced total ACTH responses (t = 2.5; df = 24; P < 0.05) compared with control subjects. Their total and free basal and oCRH-stimulated plasma cortisol levels and 24-h UFC measures, however, were similar to those in controls. The attenuated plasma ACTH with corresponding robust plasma cortisol responses to oCRH stimulation and normal 24-h UFC measures in sexually abused girls suggest a dysregulatory disorder of the HPA axis in these individuals. This may reflect pituitary hyporesponsiveness to oCRH. The ability of sexually abused subjects to correct for the proposed pituitary hyporesponsiveness to CRH may be related to their young age and the presence of intact glucocorticoid feedback regulatory mechanisms.
This paper presents the results of an experimental study conducted to evaluate the influence of fly ash chemical composition on the physico-mechanical properties and the resistance of reinforced concrete against chloride penetration. The study examines cementitious composites prepared with two different types of fly ash, used at 5% w/w and 10% w/w as cement replacement, and compares them against reference specimens prepared without fly ash. Electrochemical (Half-cell potential, corrosion current) and mass loss of reinforcement steel measurements were performed, while the porosity, compressive/tensile strength and modulus of elasticity were measured to evaluate the quality of concrete; XRD patterns and SEM images coupled with EDX analysis were further recorded and used for mineral identification and microstructure observation respectively. The thermal properties of concrete samples were also estimated. Prior to testing, all specimens were partially immersed in 3.5% w/w NaCl solution. The experimental results indicate that the performance of hardened fly ash concrete depends not only on the CaO and SiO2 content of the additive, but also on its fineness, free lime and sulfate ions content. In particular, the durability properties of concrete containing fly ash with high SO3 and CaOf contents are improved, while concrete containing fly ash with significant amounts of clay minerals exhibits low chloride penetration resistance and strength; additionally, the composite concretes demonstrate low values of thermal diffusion comparing with the OPC concrete.
Patients with unexplained chronic pain and/or fatigue have been described for centuries in the medical literature, although the terms used to describe these symptom complexes have changed frequently. The currently preferred terms for these syndromes are fibromyalgia and chronic fatigue syndrome, names which describe the prominent clinical features of the illness without any attempt to identify the cause. This review delineates the definitions of these syndromes, and the overlapping clinical features. A hypothesis is presented to demonstrate how genetic and environmental factors may interact to cause the development of these syndromes, which we postulate are caused by central nervous system dysfunction. Various components of the central nervous system appear to be involved, including the hypothalamic pituitary axes, pain-processing pathways, and autonomic nervous system. These central nervous system changes lead to corresponding changes in immune function, which we postulate are epiphenomena rather than the cause of the illnesses.
