The objective of this study is to identify differences in fully softened shear strength testing based on sample preparation technique and water source. Two sample preparation techniques were used, the blenderizing technique outlined in EM 1110-2-1906 and the hand disaggregation technique outlined in ASTM D 4318-10. The samples used for this study were clay shale samples from the Dallas, Texas area. The two water sources are groundwater and deionized water. Shear strength testing was conducted using a direct shear box. The clay shale Atterberg limits, shear strength, mineralogy, and water chemistry were analyzed to determine the effect on variations in the results.

Chicken breast samples, (n=90; n=30 normal, n=30 moderate woody breast (WB), n=30 severe WB) were collected from a commercial processing plant on 5 separate occasions. After 5 days of storage at 2-4 ºC, 84% of severe WB fillets dissipated to moderate WB, which was greater (P<0.05) than all other storage times. In comparison, 40-52% of the moderate WB fillets dissipated to slight WB or normal breasts after 3 to 5 days of storage. Shear force was greater (P<0.05) for normal breast meat than moderate and severe WB meat on day 0. After 2, 3, 4, and 5 days of storage the upper position (cranial part) of severe WB had greater shear force than normal fillets (P<0.05). Therefore, the dissipation that occurred in woody breast meat over refrigerated storage was apparent through palpation but did not result in improved texture in the cranial portion of the breast, based on shear force results.

The full-width, full-depth precast panel system is very convenient for rehabilitation of deteriorated decks as well as for new bridge construction. The horizontal shear strength at the interface between the two interconnected elements is of primary importance in order to provide composite action. The strength of the bond between the two precast members should be high enough to prevent any progressive slip from taking place. Flexural strength, shear strength and deflection characteristics all depend on the satisfactory performance of the interface to provide composite action. However, the case when both of the interconnected elements are precast members bonded by means of grout, is not currently addressed by ACI or AASHTO. This is the main impetus for this project. A total of 36 push-off tests were performed to develop a method for quantifying horizontal shear strength and to recommend the best practice for the system. Test parameters included different haunch heights, different grout types, different amount and different type of shear connectors. Two equations, for uncracked and cracked concrete interfaces, are proposed to be used in horizontal shear design when the precast panels are used. Predictive equations are compared with available methods for the horizontal shear strength of the precast panel system. Conclusions and recommendations for the optimum system are made. / Master of Science

A new approach to soft tissue elastography is presented. The work was motivated by the need to understand and mitigate the effects of anthropogenic sound on marine mammals. These efforts have been hampered by a lack of knowledge of in vivo tissue viscoelastic moduli. To address this problem, a measurement system concept was developed to non-invasively determine shear viscoelastic properties at tissue depths of over 12 cm – well beyond the capabilities of existing systems. The central design feature of the measurement system is a focused, sectored, annular ultrasonic source that generates a ring-like pressure field. This in turn produces a ring-like radiation force distribution in soft tissue, the response of which is primarily observable as a shear wave field that converges to the center of the force pattern. A second confocal transducer nested inside the shear wave generation source is used to measure the component of the shear wave motion along the beam axis. Propagation speed is estimated from displacement phase changes resulting from drive frequency induced dilation of the forcing radius. Forcing beams are modulated in order to establish shear speed frequency dependence, allowing quantification of shear speed dispersion. This concept for convergent field elastography (CFE) is intended to significantly improve the overall ability to estimate soft tissue shear speeds in thick, complex tissues while keeping within FDA-mandated ultrasound exposure limits. A prototype system was developed and tested in tissue mimicking materials for which properties were independently determined. Experiments were first carried out in a homogeneous material, and subsequently in a material containing elastic contrast inclusions. Transmission experiments with re-hydrated samples of bottlenose dolphin skull and mandibular bone samples were conducted to quantify ultrasonic beam attenuation and distortion effects, and their cumulative impact on CFE shear estimation performance. In addition to supporting marine mammal studies, the techniques developed in this thesis may enable or extend a wide range of human medical diagnostics.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The use of externally bounded Carbon Fiber Reinforced Polymer (CFRP) for strengthening existing RC structures has shown promising results. Although CFRP materials have high tensile strength, the ability to utilize that strength is limited by debonding of the CFRP laminates from the concrete surface. In order to prevent or delay debonding, CFRP anchors were used to provide an alternative means of transferring forces from CFRP strips to the concrete. Previous tests on prestressed I-girders strengthened with uni-directional and bi-directional CFRP strips showed that bi-directional CFRP application resulted in significant shear strength gain in comparison to a uni-directional application. The objective of this thesis is to evaluate the behavior of reinforced concrete beams strengthened in shear with bi-directional CFRP strips and CFRP anchors so that the findings from the previous work can be understood and implemented. Four 24 in. deep T-beams were fabricated at the Phil M. Ferguson Structural Engineering Laboratory at The University of Texas at Austin. Eight tests were conducted on these specimens to examine the effect of the bi-directional layout of CFRP on the shear strength. Specimens with 14-in. web width were selected as a part of the experimental program to allow for direct comparison with test results from the previous project. Additional beams with a web width of 8 in. were included to evaluate thinner webs similar to those in the I-girders. Test results indicate a significant increase in shear strength due to the bi-directional application of CFRP strips with CFRP anchors installed on beams with a shear span-to-depth ratio (a/d) of 3. Substantial shear strength gain up to 62% was achieved in beams with 14-in. webs. and up to 43% for beams with 8-in. webs. However, negligible shear strength gain was observed in beams with a/d of 1.5 (deep beams). Experimental test results demonstrate an interaction between the contribution of concrete, transverse steel and CFRP to the shear resistance of a reinforced concrete beam. The findings of this research contribute to a better understanding of the shear behavior of reinforced concrete members strengthened with externally bonded CFRP applied bi-directionally. Experimental results from this research project provide data needed in the field of CFRP shear strengthening since limited data are available on large-scale tests. / text

Shear wave attenuation measurements were made using ceramic bimorph transducers to excite transverse vibrations in a cylindrical column of unconsolidated sediment. Three different water-saturated sediments were used in an attempt to determine the effects of grain shape and sorting on the frequency dependence of attenuation. The mean grain size of the sediments was held constant while the grain shape and size distributions were varied. The sediment assemblages used in the attenuation measurements included a moderately-sorted angular quartz sand, a well-sorted angular quartz sand, and well-sorted spherical glass beads. The moderately-sorted sand showed the greatest attenuation over the measurement frequency range of 1 to 20 kHz. The well-sorted sand and the glass beads showed generally lower attenuation with the beads being the least lossy propagation medium. All three sediments showed evidence of viscous attenuation due to fluid-to-grain relative motion. This mechanism leads to a non-linear relationship between attenuation and frequency. Sediment physical properties were measured for use as inputs to a theoretical attenuation model based on the Biot theory of propagation of waves in porous media. The model allowed attenuation versus frequency predictions to be made for each of the three sediment assemblages. The resultant comparisons between the measured and predicted attenuations demonstrated the importance of using measured model inputs obtained under controlled laboratory conditions when theoretical model capabilities are being evaluated. The model comparison shed significant light on the ability of this particular model to predict shear wave attenuation in non-ideal sediments. / Graduation date: 1984

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