GEOL 240Lg 1st Edition Lecture 21 Outline Current Lecture 1 How buildings respond to earthquakes 2 Different size and material of the foundation of the building 3 frequency 4 Energy 5 Magnitude and Amplitude Liquefaction Current Lecture I The way in which buildings respond to shaking during an earthquake is a function of many things including building a materials foundation materials and construction practices II The size of buildings and the competency of their geologic foundations have a dramatic impact on the amount of damage that occurs during shaking III Another factor that influences buildings is frequency and resonance IV Frequency is the number of cycles the wave goes through in a certain amount of time On the other hand Resonance is building and the response is a very large amplitude swaying of the building I An example of this is thinking of a wine glass and an opera singer When the frequency of the singer s voice matches the natural frequency of the glass vibrations increase and the glass is shaken to pieces II The same goes for the buildings Liquefaction is the condition of soil and unconsolidated sediments losing their resistance to shearing fluids cannot have a shear stress imparted on them Color Figure 3 Schematic diagram showing water filling in pore spaces in unconsolidated sand When materials like this are shaken water in the pore space is mobilized and the sand becomes liquefied Base Isolation A base isolated structure is supported by a series of bearing pads They are there to support the buildings strong during earthquakes different types of base isolation bearing pads have now been developed
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