1. Seismic risk is typically defined as a function of three elements: (1) the seismic hazard or likelihood of occurrence of an earthquake and the associated severity of shaking, (2) the seismic vulnerability or expected damage to buildings and other structures given the occurrence of an earthquake, and (3) the expected consequences or losses resulting from the predicted damage. True False 2. Seismic risk management is simply the act of managing activities and decision making relating to building design, construction, and operations so as to reduce the impact of earthquakes. True False 3. Local soil profiles can be highly variable, especially near water, on sloped surfaces, or close to faults. In an extreme case, siting on poor soils can lead to liquefaction, landsliding, or lateral spreading. Often, as was the case in the 1989 Loma Prieta earthquake near San Francisco, similar structures located less than a mile apart each performed in dramatically different ways because of differing soil conditions. Even when soil-related hazards are not present, the amplitude, duration, and frequency content of earthquake motions that have to travel through softer soils can be significantly different than those traveling through firm soils or rock. True False 4. If relocating to a region of lower seismicity or to an area with a better natural soil profile is not a cost effective option, the soil at the designated site can often be re-engineered to reduce the hazard. On a liquefiable site, for instance, the soil can be grouted or otherwise treated to reduce the likelihood of liquefaction occurring. Soft soils can be excavated and replaced, or combined with foreign materials to make them stiffer. The building foundation itself can be modified to account for the potential effects of the soil, reducing the building’s susceptibility to damage even if liquefaction or limited land sliding does occur. True False 5. An earthquake generates inertial forces in a building that are a function of the structure’s mass, stiffness, and damping, and of the acceleration and frequency of the earthquake motion. The parameters associated with the earthquake can only be altered by reducing hazards, as described above. While the actual mass of the building (the weight of the structure, contents, and people) typically cannot be significantly altered, the effective mass can be changed by providing special devices, such as passive or active mass dampers, that can effectively reduce the overall mass that is accelerated by the earthquake.
Stiffness can be altered by modifying the structural system (e.g., concrete shear wall, steel moment frame) or by using braces and seismic dampers. The building’s fundamental period, which is an important parameter in determining building response, can be significantly increased (and resulting forces reduced) by providing seismic isolating devices at the building foundation.
True False 6. The most traditional method for decreasing vulnerability of buildings is to make them "stronger." By increasing the forces that a building can resist, such as by providing larger structural elements or increasing the amount of bracing for nonstructural systems, less damage would be expected. This strategy can be costly and, in some cases, may not be the most efficient means of increasing performance. Another option is to increase the ductility of the structural or nonstructural systems, improving their ability to absorb the energy of the earthquake without permanent damage. True False 7. Figure 3-1 shows the Six-story concrete-moment-frame medical building that was severely damaged by the magnitude-6.8 Northridge, California, earthquake of January 17, 1994. The building was subsequently demolished without removing contents. (photo courtesy of the Earthquake Engineering Research Center, University of California at Berkeley) True False 8. Figure 3-2 shows Eight-story reinforced-concrete-frame office building in Kobe, Japan that partially collapsed during the magnitude-7.8 earthquake of January 17, 1995. Note that the sixth floor is missing, due to collapsed columns . Seismic codes in Japan are essentially equivalent to those in the United States. at that level was built according to the seismic code was not built according to the seismic code. 9. Figure 3-4 shows a building that was damaged during an earthquake. The building : True False 10. Most current seismic design codes are not intended to prevent damage due to surface fault rupture; liquefaction, landslides, ground subsidence, or inundation. True False 11. Surface fault rupture is the abrupt shearing displacement that occurs along a fault that extends to the ground surface when the fault ruptures to cause an earthquake (Figure 3-8). Generally, a fault rupture extends to the ground surface only during earthquakes of magnitude 6 or higher. True False 12. Soil liquefaction is a phenomenon in which a loose granular soil deposit below the ground water table may lose a substantial amount of strength due to earthquake ground shaking. There are many potential adverse consequences of liquefaction, including small building settlements, larger settlements associated with reduction of foundation bearing strength, and large lateral ground displacements that would tend to shear a building apart. An often cited soil liquefaction failure is shown in Figure 3-9. True False 13. Hillside and sloped sites may be susceptible to seismically induced landslides. Landslides during earthquakes occur due to horizontal seismic inertia forces induced in the slopes by the ground shaking. Buildings located on slopes, or above or below slopes but close to either the top or the toe of the slope, could be affected by landslides. Landslides having large displacements have devastating effects on a building. An example of a building damaged by a landslide is shown in Figure 3-10. True False 14. Seismic Codes do not provide the designer with the difference in performance between different structural systems. True False 15. Figure 4-3 illustrates buildings in, Operational, Immediate Occupancy, Life-Safety, and Collapse Prevention level. True False 16. The buildings in "Life Safety Level" may not be safe for continued occupancy until repairs are done. Repair of the structure is feasible, but it may not be economically attractive to do so. True False