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Development of a Rotational Shear Vane for use in Avalanche Safety WorkHalsegger, Michael January 2007 (has links)
This Masters Thesis describes the continuation of the Snow Probe development. The focus of this project was to establish the rotational shear vane as a useful tool in avalanche safety work as well as develop a robust method for measuring the applied torque. A new and novel way of measuring the torque on a rotational shear vane has been developed to illustrate its effectiveness. The new system measures the power supplied to a cordless drill to get an indication of the applied torque. This was done because it was found that the earlier method of using a strain gauge/cantilever system repeatedly failed to work, largely due to complexity. The snow probe in its present embodiment has been shown to provide a good clear indication of the snow profile under easily repeated circumstances. Shear strength results are at this stage not sufficiently for reliable quantitative results. However the probe in its present form is able to give pictorial impressions of the snow pack that compare well to current hand hardness profiles derived from snow pit methods. Even in its current form the snow probe is able to collect useful snow profile data in a matter of minutes, much quicker than conventional snow pit methods. A loose relationship was found to exist between the approach angle of a shear vane blade and the clarity of the snow profile. These relationships are relatively inaccurate at present due to lack of rotational velocity data and therefore pproach angle data. It is believed that the addition of a rotation counter would greatly increase the accuracy of the probe results and enable a shear strength profile to be quantified. Further developments and testing are underway with a view to forming a company around the snow probe.
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Simple Models For Drift Estimates In Framed Structures During Near-field EarthquakesErdogan, Burcu 01 September 2007 (has links) (PDF)
Maximum interstory drift and the distribution of this drift along the height of the structure are the main causes of structural and nonstructural damage in frame type buildings subjected to earthquake ground motions. Estimation of maximum interstory drift ratio is a good measure of the local response of buildings. Recent earthquakes have revealed the susceptibility of the existing building stock to near-fault ground motions characterized by a large, long-duration velocity pulse. In order to find rational solutions for the destructive effects of near fault ground motions, it is necessary to determine drift demands of buildings. Practical, applicable and accurate methods that define the system behavior by means of some key parameters are needed to assess the building performances quickly instead of detailed modeling and calculations.
In this study, simple equations are proposed in order for the determination of the elastic interstory drift demand produced by near fault ground motions on regular and irregular steel frame structures. The proposed equations enable the prediction of maximum elastic ground story drift ratio of shear frames and the maximum elastic ground story drift ratio and maximum elastic interstory drift ratio of steel moment resisting frames. In addition, the effects of beam to column stiffness ratio, soft story factor, stiffness distribution coefficient, beam-to-column capacity ratio, seismic force reduction factor, ratio of pulse period to fundamental period, regular story height and number of stories on elastic and inelastic interstory drift demands are investigated in detail. An equation for the ratio of maximum inelastic interstory drift ratio to maximum elastic interstory drift ratio developed for a representative case is also presented.
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