18 research outputs found
Mechanical safety of reinforced concrete structures at all stages of the life cycle
Ensuring the mechanical safety of operated buildings at all stages of the life cycle is an urgent task. This is especially important when planning major repairs and reconstruction in buildings, as well as determining the period of safe operation from the moment of the survey, i.e. clarification of the remaining service life.
The total service life at the design stage is set by the customer and the general designer in accordance with the recommendations of GOST 27751-2014 «Reliability for constructions and foundations. General principles». Mechanical safety and durability are ensured when calculating structures using the limit state method, assigning protection measures depending on the operating conditions, as well as complying with the requirements of SP 255.1325800.2016 «Buildings and structures. Operating rules. General Provisions».
A method for preliminary assessment of the mechanical safety of buildings and their structures is proposed for consideration, which eliminates some of the shortcomings of existing methods for calculating the residual life by physical wear (damage) of building structures based on the results of a visual inspection, the basis of which is the dependence of the allowable safe operation period on the percentage of reduced bearing capacity. It is proposed to use the results of a visual inspection performed in accordance with GOST 31937-2011 «Buildings and constructions. Rules of inspection and monitoring of the technical condition»
Mechanical safety of reinforced concrete structures at all stages of the life cycle
Ensuring the mechanical safety of operated buildings at all stages of the life cycle is an urgent task. This is especially important when planning major repairs and reconstruction in buildings, as well as determining the period of safe operation from the moment of the survey, i.e. clarification of the remaining service life.
The total service life at the design stage is set by the customer and the general designer in accordance with the recommendations of GOST 27751-2014 «Reliability for constructions and foundations. General principles». Mechanical safety and durability are ensured when calculating structures using the limit state method, assigning protection measures depending on the operating conditions, as well as complying with the requirements of SP 255.1325800.2016 «Buildings and structures. Operating rules. General Provisions».
A method for preliminary assessment of the mechanical safety of buildings and their structures is proposed for consideration, which eliminates some of the shortcomings of existing methods for calculating the residual life by physical wear (damage) of building structures based on the results of a visual inspection, the basis of which is the dependence of the allowable safe operation period on the percentage of reduced bearing capacity. It is proposed to use the results of a visual inspection performed in accordance with GOST 31937-2011 «Buildings and constructions. Rules of inspection and monitoring of the technical condition»
Facile directed assembly of hollow polymer nanocapsules within spontaneously formed catanionic surfactant vesicles
Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds. © 2013 American Chemical Society
Unraveling the Single-Nanometer Thickness of Shells of Vesicle-Templated Polymer Nanocapsules
Vesicle-templated
nanocapsules have emerged as a viable platform
for diverse applications. Shell thickness is a critical structural
parameter of nanocapsules, where the shell plays a crucial role providing
mechanical stability and control of permeability. Here we used small-angle
neutron scattering (SANS) to determine the thickness of freestanding
and surfactant-stabilized nanocapsules. Despite being at the edge
of detectability, we were able to show the polymer shell thickness
to be typically 1.0 ± 0.1 nm, which places vesicle-templated
nanocapsules among the thinnest materials ever created. The extreme
thinness of the shells has implications for several areas: mass-transport
through nanopores is relatively unimpeded; pore-forming molecules
are not limited to those spanning the entire bilayer; the internal
volume of the capsules is maximized; and insight has been gained on
how polymerization occurs in the confined geometry of a bilayer scaffold,
being predominantly located at the phase-separated layer of monomers
and cross-linkers between the surfactant leaflets
Facile Directed Assembly of Hollow Polymer Nanocapsules within Spontaneously Formed Catanionic Surfactant Vesicles
Surfactant vesicles containing monomers in the interior of the bilayer were used to templatehollow polymer nanocapsules. This study investigated the formation ofsurfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds
Encapsulation of Homogeneous Catalysts in Porous Polymer Nanocapsules Produces Fast-Acting Selective Nanoreactors
Nanoreactors
were created by entrapping homogeneous catalysts in
hollow nanocapsules with 200 nm diameter and semipermeable nanometer-thin
shells. The capsules were produced by the polymerization of hydrophobic
monomers in the hydrophobic interior of the bilayers of self-assembled
surfactant vesicles. Controlled nanopores in the shells of nanocapsules
ensured long-term retention of the catalysts coupled with the rapid
flow of substrates and products in and out of nanocapsules. The study
evaluated the effect of encapsulation on the catalytic activity and
stability of five different catalysts. Comparison of kinetics of five
diverse reactions performed in five different solvents revealed the
same reaction rates for free and encapsulated catalysts. Identical
reaction kinetics confirmed that placement of catalysts in the homogeneous
interior of polymer nanocapsules did not compromise catalytic efficiency.
Encapsulated organometallic catalysts showed no loss of metal ions
from nanocapsules suggesting stabilization of the complexes was provided
by nanocapsules. Controlled permeability of the shells of nanocapsules
enabled size-selective catalytic reactions