Salient Features

1. Access for inspection and replacement of bearings should be provided at bearing locations.

2. Stub-walls or columns to function as backup systems should be provided to support the building in the event of isolator failure.

Figure 8.34c. Moat around base-isolated building.

3. A diaphragm capable of delivering lateral loads uniformly to each bearing is preferable. If the shear distribution is unequal, the bearings should be arranged such that larger bearings are under stiffer elements.

4. A moat to allow free movement for the maximum predicted horizontal displacement must be provided around the building (Figs. 8.34c and 8.34d).

5. The isolator must be free to deform horizontally in shear and must be capable of transferring maximum seismic forces between the superstructure and the foundation.

6. The isolators should be tested to ensure that they have lateral stiffness properties that are both predictable and repeatable. The tests should show that over a wide range of shear strains, the effective horizontal stiffness and area of the hysteresis loop are in agreement with values used in the design.

When earthquakes occur, the elastomeric hearings used for base isolation are subjected to large horizontal displacements, as much as 15 in. or greater in a 10-story steel-framed building. They must therefore be designed to carry the vertical loads safely at these displacements.

Permanent retailing wall

Figure 8.34d. Moat detail at ground level.

Permanent retailing wall

Figure 8.34d. Moat detail at ground level.

Isolation systems should be considered for achieving the immediate occupancy structural performance level and operational nonstructural performance level. Conversely, isolation will likely not be an appropriate design strategy for achieving the collapse prevention structural performance level. In general, isolation systems provide significant protection to the building structure, nonstructural components, and contents, but at a cost that precludes practical application when the budget and design objectives are modest.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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