Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item A new instrument for determining strength and temperature profiles in snowpack(Montana State University - Bozeman, College of Engineering, 1984) Dowd, Timothy FrancisThe purpose of this thesis project was the development of a new field instrument for determining strength and temperature profiles in snowpack. The standard tool now used for strength determination is the ram penetrometer, which is slow, cumbersome, inaccurate, and does not provide immediate results. Temperatures are generally taken with a dial stem thermometer in a snowpit wall, which is difficult to do accurately at specific intervals. The Digital Thermo-Resistograph was designed and built in an attempt to improve field snowpack data collection. The Digital Thermo-Resistograph is a portable microprocessor-based data acquisition system for quick and accurate field collection of snowpack compressive strength and temperature data. This was accomplished by building a probe with a load cell and thermistor, a small snow platform for probe position information, and a Z-80 microprocessor-based data acquisition system. The system provides information in digital form for every sampled point. A 64 x 240 dot matrix LCD graphic display unit is used to show complete strength and temperature profiles in the field. Provision is made to transfer these profiles to paper via an ordinary X-Y recorder for a permanent record of field data. Sufficient memory for the storage of 25 profiles is provided. The results of winter 1984 field tests are presented. The thermistor could not be made- to work accurately, and so was not integrated into the system. The Digital Thermo-Resistograph proved to be fast and reliable in collecting compressive snow strength information, which is measured from 0.0 to 2.55 kg/sq cm at five mm increments through the snowpack. Comparisons with the ram penetrometer are shown. Ideas for future developments are discussed.Item Preliminary analysis and hanger adjustment of tied arch bridges(Montana State University - Bozeman, College of Engineering, 1984) Beyer, William EdwardPreliminary design of a tied arch bridge is complex due to the many possible parameters of the problem. After obtaining a design the minimization of dead load moment is an important consideration. Similarly, obtaining proper tensions in the hangers of a tied arch bridge is very important, to prevent overstressing of the arch. By using matrix structural analysis, the effects of certain parameters upon tied arch behavior are investigated. The parameters include rise to span ratio, hanger spacing, ratio of areas of rib and tie, and ratio of moments of inertia of rib and tie. The geometry of an existing span was used for analysis. The results of the parametric study are portrayed graphically for a range of the parameters. Methods for analysis of dead load moment and hanger tension adjustment are developed. Finally a preliminary design example is considered.