Web Crippling Strength of Multi-web Steel Deck Sections Subjected to End One Flange Loading

Cold-formed steel deck profiles are extensively used in building construction due to their versatility and economical considerations. Web crippling is one of the failure modes for these multi-web profiles. The 1996-AISI Specification for the Design of Cold-Formed Steel Structural Members provisions for web crippling are believed to be conservative for multi-web deck sections. They are based on unfastened specimens and are limited to the use of decks with certain geometric parameters. The unified web crippling equation of the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI 2001) is also limited to certain geometric parameters. Although it has new web crippling coefficients for different load cases and different end conditions, in the End One Flange Loading case, coefficients for the unfastened configuration were used as a conservative solution for the fastened case because there was no directly applicable test data available in the literature. This paper presents the results of an experimental study on web crippling strength of multiple-web cold-formed steel deck sections subjected to End One Flange (EOF) loading. A total of 78 tests were conducted on deck sections at Virginia Tech. Test specimens lying inside and outside of certain geometric parameters of the specifications were tested with both unrestrained and restrained end conditions. Test specimens lying inside the specification parameters have revealed conservative results in the prediction of web crippling strength using both the AISI(1996) and the draft of the North American Specification (AISI 2001.

Effect of Non-Structural Components on the Dynamic Response of Steel-Framed Floors: Tests Before and After Component Installations

The effect of partition walls and non-structural elements on the dynamic response of floors is still not well understood, and there is a need for vibration testing of floors at various stages of construction. The best way to shed some light on the effect of non-structural components is to test additional floors (preferably the same floor) before and after the installation of non-structural elements and compare the dynamic properties. For that purpose, the authors conducted vibration testing on a building floor under construction at various stages of fit-out to quantify the effects of various non-structural elements on the vibration response. An elevated floor of a steel-framed building in the Southeastern United States was tested: the first test was performed for the bare slab conditions with minimal non-structural elements, while the second test was conducted after the installation of non-structural components and in the presence of various construction materials spread over the test floor. The modal tests were conducted by applying measured dynamic forces using an electrodynamic shaker while accelerations were measured at critical locations on the slab. The measurements were post-processed to determine the frequency response functions, which provided general information on the dynamic response. The selection of the test points and excitation functions were primarily to extract maximum data regarding the performance of non-structural elements rather than as part of a standard vibration serviceability assessment of the floor structure. The modal tests were repeated after the installation of non-structural components, electrical and mechanical ductwork, to determine their effect on the vibration characteristics of the floor. The resulting frequency response functions were compared for each condition, and finite element models were created to represent each test condition. As a result, the installation of non-structural components was observed to influence the dynamic response of the floor. Combined with the other test data in the literature, the results of the experimental testing presented in this paper might lead to more effective modeling techniques and provide guidance as to their inclusion into analytical models

Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers

Magnetoresistive effects are usually invariant upon inversion of the magnetization direction. In noncentrosymmetric conductors, however, nonlinear resistive terms can give rise to a current dependence that is quadratic in the applied voltage and linear in the magnetization. Here we demonstrate that such conditions are realized in simple bilayer metal films where the spin-orbit interaction and spin-dependent scattering couple the current-induced spin accumulation to the electrical conductivity. We show that the longitudinal resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of the current or the sign of the magnetization. This unidirectional magnetoresistance scales linearly with current density and has opposite sign in Ta and Pt, which we associate with the modification of the interface scattering potential induced by the spin Hall effect in these materials. Our results suggest a route to control the resistance and detect magnetization switching in spintronic devices using a two-terminal geometry, which applies also to heterostructures including topological insulators

Retrospective Evaluation of Optic Nerve Sheath Diameters of Patients Diagnosed with Brain Death

Purpose: Purpose of this study is to reveal the relationship between optic nerve sheath diameter (ONSD) and the etiology of brain death and to investigate whether there is a correlation between ONSD and blood gas parameters before and after the apnea test in patients diagnosed with brain death. Materıals and Methods: The data of 92 patients with brain death diagnoses were retrospectively analyzed for ONSD measurements for each eye, partial carbon dioxide pressure (pCO2), and blood gas parameters before and after the apnea test. Results: Subarachnoidal and intracerebral hemorrhages were the two most common brain death etiology. The mean ONSD for the right eye was 6.37±1.03 mm. The mean ONSD for the left eye was 6.43±1.02 mm. Only 8 patients had ONSD below 5.00 mm. There was no statistically significant correlation between the percent change of pCO2 and ONSD change (p>0.05). Conclusion: The present study shows that ONSD values are very high regardless of the partial pressure of carbon dioxide in patients with brain death diagnoses. We can suggest that ONSD can find a place for evaluating comatose patients for brain death diagnosis

Ultrafast magnetization switching by spin-orbit torques

Spin-orbit torques induced by spin Hall and interfacial effects in heavy metal/ferromagnetic bilayers allow for a switching geometry based on in-plane current injection. Using this geometry, we demonstrate deterministic magnetization reversal by current pulses ranging from 180~ps to ms in Pt/Co/AlOx dots with lateral dimensions of 90~nm. We characterize the switching probability and critical current $I_c$ as function of pulse length, amplitude, and external field. Our data evidence two distinct regimes: a short-time intrinsic regime, where $I_c$ scales linearly with the inverse of the pulse length, and a long-time thermally assisted regime where $I_c$ varies weakly. Both regimes are consistent with magnetization reversal proceeding by nucleation and fast propagation of domains. We find that $I_c$ is a factor 3-4 smaller compared to a single domain model and that the incubation time is negligibly small, which is a hallmark feature of spin-orbit torques