Thermal Analysis and Experiment Design for Seismic Performance Evaluation of Ice and Water Contaminated Friction Pendulum Bearings
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Authors
Grijalva, Rolando
Issue Date
2021
Type
Thesis
Language
Keywords
Double pendulum , Friction Pendulum bearing , Ice contamination , Seismic Isolation , Single pendulum , Water contamination
Alternative Title
Abstract
Over the past few years, there have been several reports on water contaminated Friction Pendulum System (FPS) bearings across the country. Additionally, there is a concern in Alaska that water will freeze inside the bearing during the winter, potentially restraining the slider from moving along the bottom concave surface. The motivation for this project comes from the lack of experimental work to examine the effects of ice and water in FPS bearings.The objectives of the project are to assess the influence of water and ice contamination on the frictional properties and seismic response of FPS bearings, relative to uncontaminated bearings. This assessment may lead to modified analytical models to account for the effects of water and ice contamination, and recommendations to account for water and ice contamination in the design process and/or recommendations for mitigation. However, the scope of this thesis includes test setup and load frame design for shake table tests; and analysis and experiments to assess the feasibility, optimize the insulation arrangement, and estimate the time needed to freeze the water to a temperature of -30°F (239°K). A steel test frame was designed to transmit axial load to the bearing and to restrain the top plate of the bearing from displacement in all directions. The test frame consists of three pieces that form an “A”: 2 legs that are connected to rigid steel columns by a pin to allow for rotation, and 1 middle element that transmit axial load to the bearing. The frame was designed in accordance to AISC 360 to transmit an axial load of 100 kips to the bearing and to withstand a shear force of 23 kips, calculated using the maximum displacement capacity (11 in.) of Susitna Bridge bearing. A thermal finite volume model was developed to simulate the freezing process of a water-filled bearings placed inside an insulation box filled with dry ice. Two different approaches were used to model dry ice’s cooling capacity: Source Term and Temperature BC. In addition, two freezing tests were conducted to validate the results from the finite volume model. The freezing tests revealed that Source Term approach underestimates the dry ice cooling capacity while Temperature BC overestimates dry ice cooling capacity. Air gaps must be minimized in the final design of the insulation box, and insulation must be added above and below the bearing to achieve temperatures below -30°F or lower. The freezing tests also revealed that the insulation box needs to be refilled with dry ice after the water has changed phase from liquid to solid.