Earthquake-Resistant Fiber Reinforced Concrete Coupling Beams Without Diagonal Bars

Results from large-scale tests on fibre-reinforced concrete coupling beams subjected to large displacement reversals are reported. The main goal of using fibre reinforcement was to eliminate the need for diagonal bars and reduce the amount of confinement reinforcement required for adequate seismic performance. Experimental results indicate that the use of 30 mm long, 0.38 mm diameter hooked steel fibres with a 2300 MPa minimum tensile strength and in a volume fraction of 1.5% allows elimination of diagonal bars in coupling beams with span-todepth ratios greater than or equal to 2.2. Further, no special confinement reinforcement is required except at the ends of the coupling beams. The fibre-reinforced concrete coupling beam design was implemented in a high-rise building in the city of Seattle, WA, USA. A brief description of the coupling beam design used for this building, and construction process followed in the field, is provided

Implementation of High-Performance Fiber Reinforced Concrete Coupling Beams in High-Rise Core-Wall Structures in the Seattle Area

Experimental and analytical studies that led to the incorporation of strain-hardening, high-performance fiber reinforced concrete (HPFRC) coupling beams in the design of a high-rise core-wall structure in Seattle, WA, are described. A total of eight HPFRC coupling beams with span-to-depth ratios ranging between 1.75 and 3.3 were tested under large displacement reversals. The tension and compression ductility of HPFRC materials allowed an approximately 70% reduction in diagonal reinforcement, relative to an ACI Building Code (318-08) compliant coupling beam design, in beams with a 1.75 span-to-depth aspect ratio and a total elimination of diagonal bars in beams with a 2.75 and 3.3 aspect ratio. Further, special column-type confinement reinforcement was not required except at the ends of the beams. When subjected to shear stress demands close to the upper limit in the 2008 ACI Building Code (0.83 f’c [MPa] (10 f’c [psi])), the coupling beams with aspect ratios of 1.75, 2.75 and 3.3 exhibited drift capacities of approximately 5%, 6% and 7%, respectively. The large drift and shear capacity exhibited by the HPFRC coupling beams, combined with the substantial reductions in reinforcement and associated improved constructability, led Cary Kopczynski & Co. to consider their use in a 134 m (440 ft) tall reinforced concrete tower. Results from inelastic dynamic analyses indicated adequate structural response with coupling beam drift demands below the observed drift capacities. Also, cost analyses indicated 20-30% savings in material costs, in addition to much easier constructability and reduced construction time

Correlation between depression and burden observed in informal caregivers of people suffering from dementia with time spent on caregiving and dementia severity

[Abstract] OBJECTIVE: The aim of the study is to compare data on the examined population of informal caregivers of people suffering from dementia with previous studies, as well as to assess the correlation between (i) depression determined on the basis of the Center for Epidemiologic Studies Depression Scale and (ii) caregiver burden measured by means of the Zarit Caregiver Burden Scale and some chosen parameters, such as total time devoted to caregiving, time of caregiving in hours per week and level of dementia severity measured by Global Deterioration Scale. PATIENTS AND METHODS: 41 informal caregivers of people suffering from dementia from different backgrounds were evaluated using the Zarit Caregiver Burden Scale and the Center for Epidemiologic Studies Depression Scale. Demographic data about the time devoted to caregiving and the number of hours spend on caregiving weekly were gathered. The type of dementia and its stage were registered using the Global Deterioration Scale (GDS). With the aid of the Statistica StatSoft program, mutual correlations between the parameters were measured. The study was conducted within the framework of AAL UnderstAID – a platform that supports and helps to understand and assist caregivers in the care of a relative with dementia. The international project is co-founded by the Joint Programme Ambient Assisted Living (Grant code: ESR-aal 2012 5 107). RESULTS: No significant correlations between the level of depression severity evaluated in caregivers and the total time of taking care of a demented person or time of caregiving in hours per week were observed. Similarly, no significant correlation between depression severity level and dementia severity level measured on the GDS scale were noted. There was also no significant correlation between Zarit Caregiver Burden Scale scores and the above-mentioned parameters. CONCLUSIONS: The level of depression among caregivers do not depend on socio-demographic factors

Dynamics of a faceted nematic-smectic B front in thin-sample directional solidification

We present an experimental study of the directional-solidification patterns of a nematic - smectic B front. The chosen system is C_4H_9-(C_6H_{10})_2CN (in short, CCH4) in 12 \mu m-thick samples, and in the planar configuration (director parallel to the plane of the sample). The nematic - smectic B interface presents a facet in one direction -- the direction parallel to the smectic layers -- and is otherwise rough, and devoid of forbidden directions. We measure the Mullins-Sekerka instability threshold and establish the morphology diagram of the system as a function of the solidification rate V and the angle theta_{0} between the facet and the isotherms. We focus on the phenomena occurring immediately above the instability threshold when theta_{0} is neither very small nor close to 90^{o}. Under these conditions we observe drifting shallow cells and a new type of solitary wave, called "faceton", which consists essentially of an isolated macroscopic facet traveling laterally at such a velocity that its growth rate with respect to the liquid is small. Facetons may propagate either in a stationary, or an oscillatory way. The detailed study of their dynamics casts light on the microscopic growth mechanisms of the facets in this system.Comment: 12 pages, 19 figures, submitted to Phys. Rev.

Classical big-bounce cosmology: dynamical analysis of a homogeneous and irrotational Weyssenhoff fluid

A dynamical analysis of an effective homogeneous and irrotational Weyssenhoff fluid in general relativity is performed using the 1+3 covariant approach that enables the dynamics of the fluid to be determined without assuming any particular form for the space-time metric. The spin contributions to the field equations produce a bounce that averts an initial singularity, provided that the spin density exceeds the rate of shear. At later times, when the spin contribution can be neglected, a Weyssenhoff fluid reduces to a standard cosmological fluid in general relativity. Numerical solutions for the time evolution of the generalised scale factor in spatially-curved models are presented, some of which exhibit eternal oscillatory behaviour without any singularities. In spatially-flat models, analytical solutions for particular values of the equation-of-state parameter are derived. Although the scale factor of a Weyssenhoff fluid generically has a positive temporal curvature near a bounce, it requires unreasonable fine tuning of the equation-of-state parameter to produce a sufficiently extended period of inflation to fit the current observational data.Comment: 34 pages, 18 figure

Torsion-induced spin precession

We investigate the motion of a spinning test particle in a spatially-flat FRW-type space-time in the framework of the Einstein-Cartan theory. The space-time has a torsion arising from a spinning fluid filling the space-time. We show that for spinning particles with nonzero transverse spin components, the torsion induces a precession of particle spin around the direction of the fluid spin. We also show that a charged spinning particle moving in a torsion-less spatially-flat FRW space-time in the presence of a uniform magnetic field undergoes a precession of a different character.Comment: latex, 4 eps figure

Symmetric Hyperbolic System in the Self-dual Teleparallel Gravity

In order to discuss the well-posed initial value formulation of the teleparallel gravity and apply it to numerical relativity a symmetric hyperbolic system in the self-dual teleparallel gravity which is equivalent to the Ashtekar formulation is posed. This system is different from the ones in other works by that the reality condition of the spatial metric is included in the symmetric hyperbolicity and then is no longer an independent condition. In addition the constraint equations of this system are rather simpler than the ones in other works.Comment: 8 pages, no figure