Reinforced concrete structures are normally exposed to various aggressive environmental conditions; thus it is essential to protect the steel reinforcement from corrosion and the concrete from degradation. This experimental study is aimed at optimising the physico-mechanical properties of reinforced concrete by using iron mill scale as a replacement for cement. Reinforced cement mortars and concrete specimens with and without the addition of iron mill scale were partially immersed in 3·5% w/w sodium chloride solution for 17 months and 130 d, respectively. The mill scale was added to the aforementioned cementitious composites in proportions of 5% and 10% by weight of cement. Its effect on chloride penetration resistance was evaluated using various standardised and non-standardised experimental techniques. The results showed that the additive increased the resistance of reinforced cementitious composites to chloride penetration, reduced the corrosion of steel reinforcement and improved the compressive strength of concrete. Furthermore, iron mill scale decreased the concentration of chloride ions in cement mortars which were partially immersed in sodium chloride solution.
This chapter articulates general principles relied upon in the design of earthquake-resistant structures. The linear elastic oscillator subjected to the ground motion has a complicated response over time that includes many cycles of response. Inelastic response is expected in most buildings located in higher seismic zones. The distribution of strength to the components of the structural system determines whether a single mechanism is dominant over a large suite of possible ground motions, or whether different mechanisms may develop under different excitations. The load path should be viewed from both force and deformation perspectives. Load paths that require complicated deformation patterns to mobilize the forces required for static equilibrium are associated with more complex dynamic response and may not work as envisaged. Capacity design principles are used to determine the strengths of the ductile, yielding portions of the structure as it deforms in a mechanism, typically associated with a quasi-first-mode deformation pattern.
Stress (i.e. the state of threatened homeostasis), is normally associated with adaptive physical and behavioural changes that promote individual survival. Successful maintenance of homeostasis leads to the state of eustasis, which represents health. The prolonged, excessive, or deficient response of the stress system to stress, however, may lead to a state of dyshomeostasis or cacostasis, which may lead to physical and mental health problems. Although research has focused on the detrimental effects of stress, only a few studies have been done on positive stress exposure adaptations. Increased resilience, post-traumatic psychological growth, and increased empathy may benefit chronically stressed individuals, enhancing their abilities to cope with distress. Therapeutic efforts in the treatment of short- or long-term stress aims at reducing its effect on neuroendocrine responses, behaviour changes, and so on. Community investments and interventions should focus on reducing threats and promoting positive adaptation during and after traumatic stress exposures.
No abstract is provided for this article.
A methodology based on incremental dynamic analysis (IDA) is presented for the evaluation of structures with vertical irregularities. Four types of storey-irregularities are considered: stiffness, strength, combined stiffness and strength, and mass irregularities. Using the well-known nine-storey LA9 steel frame as a base, the objective is to quantify the effect of irregularities, both for individual and for combinations of stories, on its response. In this context a rational methodology for comparing the seismic performance of different structural configurations is proposed by means of IDA. This entails performing non-linear time history analyses for a suite of ground motion records scaled to several intensity levels and suitably interpolating the results to calculate capacities for a number of limit-states, from elasticity to final global instability. By expressing all limit-state capacities with a common intensity measure, the reference and each modified structure can be naturally compared without needing to have the same period or yield base shear. Using the bootstrap method to construct appropriate confidence intervals, it becomes possible to isolate the effect of irregularities from the record-to-record variability. Thus, the proposed methodology enables a full-range performance evaluation using a highly accurate analysis method that pinpoints the effect of any source of irregularity for each limit-state. Copyright © 2006 John Wiley & Sons, Ltd.
Abstract Snoring is the most characteristic symptom of obstructive sleep‐disordered breathing (SDB) and recurrent wheezing is the most common clinical manifestation of asthma. The purpose of the present review is to outline the impact of SDB and recurrent wheezing/asthma on sleep quality and to summarize the epidemiologic and pathophysiologic evidence supporting an association between the two disorders. Enlarged tonsils and adenoid or obesity predispose to obstructive sleep apneas and hypopneas which are accompanied by arousals, restless sleep, and frequently daytime sleepiness, inattention, hyperactivity, and academic difficulties. Subjects with history of wheezing are also at risk for sleep disturbance and daytime cognitive dysfunction. Asthmatic children have more frequent snoring, apneas, and hypopneas during sleep than non‐asthmatic subjects and tonsillar hypertrophy mediates at least in part this epidemiologic association. In addition, preliminary evidence indicates that treatment of sleep apnea with adenotonsillectomy results in improved control of coexisting asthma. Elevated concentrations of leukotrienes and oxidative stress markers have been detected in the exhaled breath condensate of children with asthma and probably contribute to bronchoconstriction. Moreover, sleep apneic children have increased expression of leukotrienes and leukotriene receptors in adenotonsillar tissue. Viral respiratory infections may induce inflammation and oxidative stress in the asthmatic airway enhancing not only bronchospasm, but also biosynthesis of leukotrienes within pharyngeal lymphoid tissues, which promote adenotonsillar enlargement and sleep apnea. In conclusion, taking under consideration the epidemiologic association between obstructive SDB and asthma, when one of the two disorders is diagnosed, the possibility of the other disease being present should be entertained. Pediatr. Pulmonol. 2011; 46:1047–1054. © 2011 Wiley Periodicals, Inc.
