279 research outputs found
Globally Anisotropic High Porosity Silica Aerogels
We discuss two methods by which high porosity silica aerogels can be
engineered to exhibit global anisotropy. First, anisotropy can be introduced
with axial strain. In addition, intrinsic anisotropy can result during growth
and drying stages and, suitably controlled, it can be correlated with
preferential radial shrinkage in cylindrical samples. We have performed small
angle X-ray scattering (SAXS) to characterize these two types of anisotropy. We
show that global anisotropy originating from either strain or shrinkage leads
to optical birefringence and that optical cross-polarization studies are a
useful characterization of the uniformity of the imposed global anisotropy.Comment: 18 pages, 14 figures, submitted to Journal of Non-Crystalline Solid
Bridge distress caused by approach embankment settlement
Surtees Bridge, which carries the A66(T) over the River
Tees near Thornaby-on-Tees in the UK, has been
showing signs of distress that predate its opening in
1981. Subsequent investigations have shown that the
bridge distress is related to unexpectedly large
settlement of the eastern approach embankment.
Recent ground investigations prompted by a proposed
widening of the river crossing have produced many new
data on the alluvial deposits underlying the site, and
explain why embankment settlement was so much larger
than originally anticipated. Comparison of the
geotechnical parameters obtained from the original and
more recent ground investigations suggests that the
original investigation significantly underestimated the
thickness of an alluvial clay layer underlying the site, and
that its coefficient of consolidation was overestimated.
Settlement analyses using geotechnical data from the
original ground investigations predict moderate
embankment settlements occurring principally during
construction. Settlement analyses based on all the
available data predict far larger embankment
settlements occurring over extended time periods. The
latter analyses predict an embankment settlement
similar to that observed and of sufficient magnitude to
cause the observed lateral displacement of the bridge
due to lateral loading of its piled foundation
Shear Behaviour of Ligthweight Sandwich Reinforced Concrete Slabs
A new lightweight sandwich reinforced concrete (LSRC) section has been developed using prefabricated autoclaved aerated concrete (AAC) blocks as infill in the section where concrete is considered ineffective under bending. This paper presents an investigation into the strength and behaviour of LSRC slabs subjected to shear. Eight tests were conducted on four slabs, one solid and three different types of LSRC slabs. Based on the test results, all LSRC slabs exhibited similar behaviour to the equivalent solid slab and had varying shear capacities depending on the profile of AAC blocks infill. The obtained shear capacities were compared with the design values based on several major design codes and found to be within the safety predictions of the codes. ANSYS was employed to develop nonlinear finite element models of LSRC slabs. The numerical results agree well with the experimental one
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