Existing classes of centrifugal clutch concepts were reviewed. The pseudo-rigid-body model (PRBM), rigid-body replacement synthesis, force-deflection analysis, compliance potential evaluation, and compliant concept evaluation were used to develop effective new centrifugal clutch concepts. These methods helped develop and model four novel compliant centrifugal clutch designs, model two existing designs, and identify a concept with excellent potential for low-cost centrifugal clutch applications. This concept, the floating opposing arm (FOA) clutch, doubles the torque capacity metric relative to existing compliant designs. Torque and engagement speed models for this clutch were developed and verified against four prototype clutches. Additional novel designs devel-oped through this work have lower torque capacities, but also show good potential because of other unique characteristics. All of the designs were prototyped and tested to measure their torque-speed relationships.

A series of lateral load tests were performed on a full-scale pile cap with three different backfill conditions, namely: with no backfill present, with densely compacted clean sand in place, and with loosely compacted clean sand in place. In addition to being displaced under a static loading, the pile cap was subjected to low frequency, small displacement loading cycles from load actuators and higher frequency, small displacement, dynamic loading cycles from an eccentric mass shaker. The passive earth pressure from the backfill was found to significantly increase the load capacity of the pile cap. At a displacement of about 46 mm, the loosely and densely compacted backfills increased the total resistance of the pile cap otherwise without backfill by 50% and 245%, respectively. The maximum passive earth pressure for the densely compacted backfill occurred at a displacement of approximately 50 mm, which corresponds to a displacement to pile cap height ratio of 0.03. Contrastingly passive earth pressure for the loosely compacted backfill occurred at a displacement of approximately 40 mm. Under low and high frequency cyclic loadings, the stiffness of the pile cap system increased with the presence of the backfill material. The loosely compacted backfill generally provided double the stiffness of the no backfill case. The densely compacted backfill generally provided double the stiffness of the loosely compacted sand, thus quadrupling the stiffness of the pile cap relative to the case with no backfill present. Under low frequency cyclic loadings, the damping ratio of the pile cap system decreased with cap displacement and with increasing stiffness of backfill material. After about 20 mm of pile cap displacement, the average damping ratio was about 18% with the looser backfill and about 24% for the denser backfill. Under higher frequency cyclic loadings, the damping ratio of the pile cap system was quite variable and appeared to vary with frequency. Damping ratios appear to peak in the vicinity of the natural frequency of the pile cap system for each backfill condition. On the whole, damping ratios tend to range between 10 and 30%, with an average of about 20% for the range of frequencies and displacement amplitudes occurring during the tests. The similar amount of damping for different ranges of frequency suggests that dynamic loadings do not appreciably increase the apparent resistance of the pile cap relative to slowly applied cyclic loadings.

Numerical Analysis of Passive Force on Skewed BridgeAbutments with Reinforced Concrete WingwallsScott Karl SnowDepartment of Civil and Environmental Engineering, BYU Master of Science Historically bridges with skewed abutments have proven more likely to fail during earthquake loadings (Toro et al, 2013) when compared to non-skewed bridges (Apirakvorapinit et al. 2012; Elnashai et al. 2010). Previous studies including small-scale laboratory tests by Jessee (2012), large-scale field tests by Smith (2014), and numerical modeling by Shamsabadi et al. (2006) have shown that 45° skewed bridge abutments experience a reduction in peak passive force by about 65%. With numerous skewed bridges in the United States, this study has great importance to the nation's infrastructure.The finite element models produced in this study model the large-scale field-testing performed by Smith (2014), which was performed to study the significant reduction in peak passive resistance for abutments with longitudinal reinforced concrete wingwalls. The finite element models largely confirm the findings of Smith (2014). Two models were created and designed to match the large-scale field tests and were used to calibrate the soil parameters for this study. Two additional models were then created by increasing the abutment widths from 11 feet to 38 feet to simulate a two-lane bridge. The 45° skewed 11-foot abutment experienced a 38% reduction in peak passive resistance compared to the non-skewed abutment. In contrast, the 45° skewed 38-foot abutment experienced a 65% reduction in peak passive resistance compared to the non-skewed abutment. When the wingwalls are extended 10 feet into the backfill the reduction decreased to 59% due to the change in effective skew angle.The finite element models generally confirmed the findings of Smith (2014). The results of the 11- and 38-foot abutment finite element models confirmed that the wingwall on the obtuse side of the 45° skewed abutments experienced approximately 4 to 5 times the amount of horizontal soil pressure and 5 times the amount of bending moment compared to the non-skewed abutment. Increases in the pressures and bending moments are likely caused by soil confined between the obtuse side of the abutment and the wingwall.A comparison of the 11- and 38-foot 45° skewed abutment models showed a decrease in the influence of the wingwalls as the abutment widened. The wingwall on the acute side of the 38-foot abutment developed approximately 50% of the horizontal soil pressure compared to the 11-foot abutment. The heave distribution of the 11-foot abutment showed approximately 1- to 2-inches of vertical displacement over a majority of the abutment backwall versus more than half of the 38-foot abutment producing ½ an inch or less.

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The Tom's Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load carrying members. The project is intended to serve two purposes. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution and deflections under service loading, the Tom's Creek Bridge will aid in modifying current AASHTO bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after being exposed to service conditions, the project will begin to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. This thesis details the In-Service analysis of the Tom's Creek Bridge. Five load tests, at six month intervals, were conducted on the bridge. Using mid-span strain and deflection data gathered from the FRP composite girders during these tests the above mentioned bridge design parameters have been determined. The Tom's Creek Bridge was determined to have a dynamic load allowance, IM, of 0.90, a transverse wheel load distribution factor, g, of 0.101 and a maximum deflection of L/488. Two bridge girders were removed from the Tom's Creek Bridge after fifteen months of service loading. These FRP composite girders were tested at the Structures and Materials Research Laboratory at Virginia Tech for stiffness and ultimate strength and compared to pre-service values for the same beams. This analysis indicates that after fifteen months of service, the FRP composite girders have not lost a significant amount of either stiffness or ultimate strength. / Master of Science

The Route 601 Bridge in Sugar Grove, Virginia spans 39 ft over Dickey Creek. The Bridge is the first to use the Strongwell 36 in. fiber reinforced polymer (FRP) double web beam (DWB) in its superstructure. Replacement of the old bridge began in June 2001, and construction of the new bridge was completed in October 2001. The bridge was field tested in October 2001 and June 2002. This thesis details the field evaluation of the Rt. 601 Bridge. Using mid span deflection and strain data from the October 2001 and June 2002 field tests, the primary goal of this research was to determine the following AASHTO bridge design parameters: wheel load distribution factor g, dynamic load allowance IM, and maximum deflection. The wheel load distribution factor was determined to be S/5, a dynamic load allowance was determined to be 0.30, and the maximum deflection of the bridge was L/1500. Deflection results were lower than the AASHTO L/800 limit. This discrepancy is attributed to partial composite action of the deck-to-girder connections, bearing restraint at the supports, and contribution of guardrail stiffness. Secondary goals of this research were to quantify the effect of diaphragm removal on girder distribution factor, determine torsion and axial effects of the FRP girders, compare responses to multiple lane symmetrical loading to superimposed single lane response, and compare the field test results to a finite element and a finite difference model. It was found that diaphragm removal had a small effect on the wheel load distribution factor. Torsional and axial effects were small. The bridge response to multilane loading coincided with superimposed single lane truck passes, and curb-stiffening effects in a finite difference model improved the accuracy of modeling the Rt. 601 Bridge behavior. / Master of Science