21 research outputs found
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Behavior of Circular Fiber-Reinforced Polymer-Steel-Confined Concrete Columns Subjected to Reversed Cyclic Loads: Experimental Studies and Finite-Element Analysis
This paper studied experimentally the behavior of circular fiber-reinforced polymer (FRP)-steel-confined concrete columns subjected to reversed cyclic loads. The influence of main structural factors on the cyclic behavior of the columns is discussed. Test results showed the outstanding seismic performance of FRP-steel-confined RC and steel-reinforced concrete (SRC) columns. The lateral confinement effectiveness of glass fiber-reinforced polymer (GFRP) tubes and GFRP-steel tubes was verified and a simplified OpenSees-based finite-element method (FEM) model was developed to simulate the experimental results of the test columns. Based on the proposed FEM model, a parametric analysis was conducted to investigate the effects of main factors on the reversed cyclic behavior of GFRP-steel-confined RC columns. Based on the test and numerical analyses, the study discussed the influence of variables such as the lateral confinement on the plastic hinge region (PHR) height and peak drift ratio of the columns under reversed cyclic loads. Results indicate that lateral confinement significantly affects the PHR height of circular confined RC columns. Based on the analyses of the data from this study and literature, a simple model was suggested to predict the peak drift ratio of confined RC columns
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Monotonic axial compressive behaviour and confinement mechanism of square CFRP-steel tube confined concrete
Steel tube confined concrete (STCC) is widely used in the vertical members of high-rise buildings such as columns. The axial load is not directly resisted by the steel tube in STCC, but is resisted via the interfacial frictional stress between steel tube and concrete core, which is different with that of concrete filled steel tube (CFT) members and would effectively suppress the outward local buckling of steel tube at early stage. Recently, fibre-reinforced polymer (FRP) confined STCC presents a potential to enhance the ductility and durability of such vertical elements. This paper presents an experimental study on monotonic axial compressive behaviour of carbon FRP (CFRP) confined STCC (CFRP-STCC) stub column and an analytical study on the confinement mechanism of and the ultimate axial bearing capacity of the elements. A three-stage confinement mechanism involving the different contributions of the steel tube and the CFRP wrap in CFRP-STCC elements was proposed based on the test results. A prediction model of the ultimate axial bearing capacity of CFRP-STCC stub columns was developed subsequently. Results show that the presence of CFRP wrap enhances effectively the load-bearing capacity and the ductility of steel tube confined plain concrete and reinforced concrete elements, and significantly prevents the local buckling of the steel tubes in the elements. The proposed prediction model of ultimate axial bearing capacity assesses test results with a great agreement
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Damage control of the masonry infills in RC frames under cyclic loads: a full-scale test study and numerical analyses
This study investigates the effect of damage control methods on the seismic performance of masonry infilled walls in reinforced concrete (RC) frames, by experimentally investigating three full-scale infilled RC frames with different treatment details and finite element method (FEM) analysis. The control methods included full-length connecting steel rebars, styrene butadiene styrene (SBS) sliding layers, and two gaps between the wall and frame columns. The results indicated that the ductility, wall damage, and residual deformation of the frame with gaps or SBS layers were significantly improved. However, the initial stiffness, energy dissipation capacity, and lateral load-carrying capacity of the frames with SBS sliding layers all were reduced. The fully infilled frames exhibited a better lateral load-carrying capacity, stiffness, and energy dissipation capacity, but presented larger lateral residual deformation and lower ductility. The damage of the infilled walls in RC frames can be controlled by using longer connecting rebars. The gaps and sliding layers can both significantly reduce the in-plane damage of the walls. A simplified FEM model was proposed and applied to conduct a parametric analysis for an in-depth study of fully infilled RC frames with and without sliding layers. The results show that SBS is the optimal sliding layer material, and its optimal spacing in RC frames is recommended as 1000 mm
Urban air pollution and climate change: "The Decalogue: Allergy Safe Tree" for allergic and respiratory diseases care
Abstract
Background: According to the World Health Organization, air pollution is closely associated with climate change
and, in particular, with global warming. In addition to melting of ice and snow, rising sea level, and flooding of coastal
areas, global warming is leading to a tropicalization of temperate marine ecosystems. Moreover, the effects of air pollution
on airway and lung diseases are well documented as reported by the World Allergy Organization.
Methods: Scientific literature was searched for studies investigating the effect of the interaction between air pollution
and climate change on allergic and respiratory diseases.
Results: Since 1990s, a multitude of articles and reviews have been published on this topic, with many studies confirming
that the warming of our planet is caused by the âgreenhouse effectâ as a result of increased emission of âgreenhouseâ
gases. Air pollution is also closely linked to global warming: the emission of hydrocarbon combustion products
leads to increased concentrations of biological allergens such as pollens, generating a mixture of these particles called
particulate matter (PM). The concept is that global warming is linked to the emission of hydrocarbon combustion
products, since both carbon dioxide and heat increase pollen emission into the atmosphere, and all these particles
make up PM10. However, the understanding of the mechanisms by which PM affects human health is still limited.
Therefore, several studies are trying to determine the causes of global warming. There is also evidence that increased
concentrations of air pollutants and pollens can activate inflammatory mediators in the airways. Our Task Force has
prepared a Decalogue of rules addressing public administrators, which aims to limit the amount of allergenic pollen
in the air without sacrificing public green areas.
Conclusions: Several studies underscore the significant risks of global warming on human health due to increasing
levels of air pollution. The impact of climate change on respiratory diseases appears well documented. The last
decades have seen a rise in the concentrations of pollens and pollutants in the air. This rise parallels the increase in
the number of people presenting with allergic symptoms (e.g., allergic rhinitis, conjunctivitis, and asthma), who often
require emergency medical care. Our hope is that scientists from different disciplines will work together with institutions,
pharmaceutical companies and lay organizations to limit the adverse health effects of air pollution and global
warming.
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