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Experimental Study of Ultra Shallow Floor Beams (USFB) with Perforated Steel Sections
ABSTRACT: In modern building construction design, floor spans are becoming longer. Hence, steel framed structures have become more competitive when compared with traditional reinforced concrete framed buildings. In order to minimise the structural section of the composite sections, and for economic reasons, steel perforated beams are designed to act compositely with the floor slab. When the concrete slab lies within the steel flanges, as in the Ultra Shallow Floor Beam (USFB), there is an additional benefit when considering fire resistance. The aim of this study is to investigate the contribution of the concrete in composite cellular beams in the case where the concrete slab lies between the beam flanges of a steel section, when resisting vertical shear forces. The concrete between the flanges enhances the load-carrying capacity by providing a load path to transfer the shear force. Four specimens of steel-concrete composite beams with web openings in the steel section were tested in this study. One bare steel section with web openings was also tested as a comparison. This is the first such investigation of the failure mode under shear resistance (Vierendeel action) of the Ultra Shallow Floor Beam. In the test specimens, the web opening diameter is 76% of the beam depth, which is the largest currently available. This represents the worst case in terms of Vierendeel bending forces generated in the vicinity of the web openings. The smaller the hole is, the easier it is for the trapped concrete between the flanges to transfer shear across the opening. The results from the composite beam tests show a significant increase in shear resistance. The percentage of the shear capacity improvement of the particular case is presented herein as well as the failure mode of the composite beams. The shear enhancement demonstrated in this study has been utilised software that is used in design practice
Nonperturbative Vertices in Supersymmetric Quantum Electrodynamics
We derive the complete set of supersymmetric Ward identities involving only
two- and three- point proper vertices in supersymmetric QED. We also present
the most general form of the proper vertices consistent with both the
supersymmetric and U(1) gauge Ward identities. These vertices are the
supersymmetric equivalent of the non supersymmetric Ball-Chiu vertices.Comment: seventeen pages late
Running coupling and fermion mass in strong coupling QED
Simple toy model is used in order to exhibit the technique of extracting the
non-perturbative information about Green's functions in Minkowski space. The
effective charge and the dynamical electron mass are calculated in strong
coupling 3+1 QED by solving the coupled Dyson-Schwinger equations for electron
and photon propagators. The minimal Ball-Chiu vertex was used for simplicity
and we impose the Landau gauge fixing on QED action. The solution obtained
separately in Euclidean and Minkowski space were compared, the latter one was
extracted with the help of spectral technique.Comment: 23 pages, 4 figures, v4: revised and extended version, one
introductory section adde
Evaluation of the Wellspring Model for Improving Nursing Home Quality
Examines how successfully the Wellspring model improved the quality of care for residents of eleven nonprofit nursing homes in Wisconsin. Looks at staff turnover, and evaluates the impact on facilities, employees, residents, and cost
Chiral symmetry breaking in dimensionally regularized nonperturbative quenched QED
In this paper we study dynamical chiral symmetry breaking in dimensionally
regularized quenched QED within the context of Dyson-Schwinger equations. In D
< 4 dimensions the theory has solutions which exhibit chiral symmetry breaking
for all values of the coupling. To begin with, we study this phenomenon both
numerically and, with some approximations, analytically within the rainbow
approximation in the Landau gauge. In particular, we discuss how to extract the
critical coupling alpha_c = pi/3 relevant in four dimensions from the D
dimensional theory. We further present analytic results for the chirally
symmetric solution obtained with the Curtis-Pennington vertex as well as
numerical results for solutions exhibiting chiral symmetry breaking. For these
we demonstrate that, using dimensional regularization, the extraction of the
critical coupling relevant for this vertex is feasible. Initial results for
this critical coupling are in agreement with cut-off based work within the
currently achievable numerical precision.Comment: 24 pages, including 5 figures; submitted to Phys. Rev.
Mean field exponents and small quark masses
We demonstrate that the restoration of chiral symmetry at finite-T in a class
of confining Dyson-Schwinger equation (DSE) models of QCD is a mean field
transition, and that an accurate determination of the critical exponents using
the chiral and thermal susceptibilities requires very small values of the
current-quark mass: log_{10}(m/m_u) < -5. Other classes of DSE models
characterised by qualitatively different interactions also exhibit a mean field
transition. Incipient in this observation is the suggestion that mean field
exponents are a result of the gap equation's fermion substructure and not of
the interaction.Comment: 13 pages, 3 figures, REVTEX, epsfi
On Renormalized Strong-Coupling Quenched QED in Four Dimensions
We study renormalized quenched strong-coupling QED in four dimensions in
arbitrary covariant gauge. Above the critical coupling leading to dynamical
chiral symmetry breaking, we show that there is no finite chiral limit. This
behaviour is found to be independent of the detailed choice of photon-fermion
proper vertex in the Dyson-Schwinger equation formalism, provided that the
vertex is consistent with the Ward-Takahashi identity and multiplicative
renormalizability. We show that the finite solutions previously reported lie in
an unphysical regime of the theory with multiple solutions and ultraviolet
oscillations in the mass functions. This study supports the assertion that in
four dimensions strong coupling QED does not have a continuum limit in the
conventional sense.Comment: REVTEX 3.0, 15 pages,including 4 eps files comprising 3 figures.
Submitted to Phys. Rev.
Pseudovector components of the pion, pi^0 -> gamma gamma, and F_pi(q^2)
As a consequence of dynamical chiral symmetry breaking the pion
Bethe-Salpeter amplitude necessarily contains terms proportional to gamma_5
gamma.P and gamma_5 gamma.k, where k is the relative and P the total momentum
of the constituents. These terms are essential for the preservation of low
energy theorems, such as the Gell-Mann--Oakes-Renner relation and those
describing anomalous decays of the pion, and to obtaining an electromagnetic
pion form factor that falls as 1/q^2 for large q^2, up to calculable
ln(q^2)-corrections. In a simple model, which correlates low- and high-energy
pion observables, we find q^2 F_pi(q^2) ~ 0.12 - 0.19 GeV^2 for q^2 >~10 GeV^2.Comment: 15 pages, 2 figures, REVTE
Multiplicative renormalizability and quark propagator
The renormalized Dyson-Schwinger equation for the quark propagator is
studied, in Landau gauge, in a novel truncation which preserves multiplicative
renormalizability. The renormalization constants are formally eliminated from
the integral equations, and the running coupling explicitly enters the kernels
of the new equations. To construct a truncation which preserves multiplicative
renormalizability, and reproduces the correct leading order perturbative
behavior, non-trivial cancellations involving the full quark-gluon vertex are
assumed in the quark self-energy loop. A model for the running coupling is
introduced, with infrared fixed point in agreement with previous
Dyson-Schwinger studies of the gauge sector, and with correct logarithmic tail.
Dynamical chiral symmetry breaking is investigated, and the generated quark
mass is of the order of the extension of the infrared plateau of the coupling,
and about three times larger than in the Abelian approximation, which violates
multiplicative renormalizability. The generated scale is of the right size for
hadronic phenomenology, without requiring an infrared enhancement of the
running coupling.Comment: 17 pages; minor corrections, comparison to lattice results added;
accepted for publication in Phys. Rev.
Facets of confinement and dynamical chiral symmetry breaking
The gap equation is a cornerstone in understanding dynamical chiral symmetry
breaking and may also provide clues to confinement. A symmetry-preserving
truncation of its kernel enables proofs of important results and the
development of an efficacious phenomenology. We describe a model of the kernel
that yields: a momentum-dependent dressed-quark propagator in fair agreement
with quenched lattice-QCD results; and chiral limit values: f_pi= 68 MeV and
= -(190 MeV)^3. It is compared with models inferred from studies of
the gauge sector.Comment: 5 pages, 3 figures; contribution to the proceedings of Quark Nuclear
Physics (QNP 2002), Juelich, Germany, 9-14 Jun 200
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