Krauthammer, Theodor

This study was initiated to investigate the possible causes for excessive lamp failure rates on High Mast illumination towers in the State of Minnesota. This type of highway illumination system consists of high masts on which there are either three or four luminaires. The masts are 120 feet (36.6 meters) high and the luminaries are attached to a ring assembly that can be lowered for lamp replacement. The study consisted of two methods of analysis. The first step was to analyze numerically the complete system by employing a finite element code and to compute the motions of the complete system under typical wind conditions at the site (wind velocities between 5 to 60 mph). The second phase of the study consisted of an experimental effort during which one of the illumination towers was instrumented and motion data was collected for various wind conditions. The final phase of the study included the evaluation of the numerical as well as the experimental data that had been obtained from the preceding steps. This evaluation included the identification of modes of vibration in the frequency domain, filtering of data for acescent of modal effects, and comparisons between experimental and numerical results.

This study was conducted with the aim of improving the state of knowledge on the behavior of joints in concrete pavements, and to explore the feasibility of developing a non-destructive testing technique based on the frequency response of dynamically loaded joints. One of the objectives of the present study was to experimentally investigate the existence of a relationship between load transfer capacity of a joint in rigid pavements and its dynamic response. the experimental study involved the application of an impact testing approach for the evaluation of two test systems. One system represented an ideal condition of full load transfer across a joint, while the other system was used to simulate variable load transfer conditions. Acceleration-time histories captured from both sides of the joint, under short load pulses, were used for analysis both in the time and frequency domains. These results provided a comprehensive description of the joint response characteristics, and enabled the derivation of a clear relationship between the response frequencies and the joint's shear transfer capabilities. These results may be used as the starting point for the development of a precise non-destructive testing method for a wide range of cases in which shear transfer across discontinuities in concrete systems is a principal load resisting mechanism. Specific conclusions and recommendations on future developments have been provided.

This study was conducted with the aim of improving the state of knowledge on the behavior of joints in concrete pavements, and to explore the feasibility of developing a non-destructive testing technique based on frequency response of dynamically loaded joints. One of the objectives of this study was to numerically investigate the existence of a relationship between load transfer capacity of a joint in rigid pavements and its dynamic response. The approach adapted for the present study is based on a numerical model which accurately represents the mechanism of shear transfer in reinforced concrete members implemented it in a commercially available finite element code. That tool is then used for the analysis of two models which consisted of various joint conditions. One model represented an ideal condition of full load transfer across a joint, while the other model was used to simulate variable load transfer conditions. The results obtained are analyzed in the time and frequency domains. These results provided a comprehensive description of the joint response characteristics, and enabled the derivation of a clear relationship between the response frequencies and the joint's shear transfer capabilities. The results may be used as the starting point for the development of a precise/non-destructive testing method for a wide range of cases in which shear transfer across discontinuities in concrete systems is a principal load resisting mechanism. Specific conclusions and recommendations on future developments have been provided.