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Questions and Answers
What characterizes a soft story in a building?
What characterizes a soft story in a building?
Where is a soft story most commonly located in a building?
Where is a soft story most commonly located in a building?
What is a significant consequence of a building having a soft story during an earthquake?
What is a significant consequence of a building having a soft story during an earthquake?
What leads to the weaknesses in buildings during an earthquake?
What leads to the weaknesses in buildings during an earthquake?
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Why is it crucial to avoid soft story configurations in modern buildings?
Why is it crucial to avoid soft story configurations in modern buildings?
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Which of the following best describes the impact of having a soft story on a building's structural integrity?
Which of the following best describes the impact of having a soft story on a building's structural integrity?
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What is the primary reason for the focus on evenly distributing flexibility, strength, and mass in a building?
What is the primary reason for the focus on evenly distributing flexibility, strength, and mass in a building?
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Which event highlighted the dangers of soft stories in buildings?
Which event highlighted the dangers of soft stories in buildings?
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What structural failure occurred in the upper floors of the parking garage during the Michoacan earthquake?
What structural failure occurred in the upper floors of the parking garage during the Michoacan earthquake?
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What type of structural systems can be used to resist inertia forces in buildings during earthquakes?
What type of structural systems can be used to resist inertia forces in buildings during earthquakes?
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What predominant forces do shear walls primarily resist?
What predominant forces do shear walls primarily resist?
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The Hyatt Terraces Hotel collapsed during an earthquake in which city?
The Hyatt Terraces Hotel collapsed during an earthquake in which city?
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Which earthquake caused significant damage to the West Anchorage High School shear wall?
Which earthquake caused significant damage to the West Anchorage High School shear wall?
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What is the primary function of shear walls in a building?
What is the primary function of shear walls in a building?
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Which floors of the parking garage were able to resist earthquake shaking?
Which floors of the parking garage were able to resist earthquake shaking?
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What phenomenon describes the collapse of multiple floors on top of each other during an earthquake?
What phenomenon describes the collapse of multiple floors on top of each other during an earthquake?
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What is a 'soft story' in the context of structural engineering?
What is a 'soft story' in the context of structural engineering?
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What does 'pancaking' refer to in building failure during an earthquake?
What does 'pancaking' refer to in building failure during an earthquake?
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What factor was primarily contributing to the widespread pancaking observed during the Izmit earthquake?
What factor was primarily contributing to the widespread pancaking observed during the Izmit earthquake?
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How many buildings were reported to be badly damaged or collapsed due to the Izmit earthquake?
How many buildings were reported to be badly damaged or collapsed due to the Izmit earthquake?
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What aspect of building design was highlighted as a failure contributing to pancaking?
What aspect of building design was highlighted as a failure contributing to pancaking?
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What is the expected action for buildings identified as highly vulnerable to seismic activity?
What is the expected action for buildings identified as highly vulnerable to seismic activity?
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What characteristic primarily describes the lower stories of buildings that contributed to pancaking during the Izmit earthquake?
What characteristic primarily describes the lower stories of buildings that contributed to pancaking during the Izmit earthquake?
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What can be inferred about the existing inventory of vulnerable buildings in Turkey following the earthquake?
What can be inferred about the existing inventory of vulnerable buildings in Turkey following the earthquake?
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What is a common cause of diagonal tension cracks in shear walls during an earthquake?
What is a common cause of diagonal tension cracks in shear walls during an earthquake?
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What can lead to the formation of a soft story in a building's structure?
What can lead to the formation of a soft story in a building's structure?
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Which type of shear wall failure has been observed during recent earthquakes?
Which type of shear wall failure has been observed during recent earthquakes?
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What is a misconception regarding shear walls in earthquake-resistant buildings?
What is a misconception regarding shear walls in earthquake-resistant buildings?
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What is NOT a typical form of damage to shear walls observed during earthquakes?
What is NOT a typical form of damage to shear walls observed during earthquakes?
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In the context of shear walls, which statement about window and door openings is accurate?
In the context of shear walls, which statement about window and door openings is accurate?
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What failure mechanism was highlighted as being a concern for shear walls during the earthquake in Christchurch?
What failure mechanism was highlighted as being a concern for shear walls during the earthquake in Christchurch?
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Which of the following is a typical characteristic of earthquake-induced damage in shear walls?
Which of the following is a typical characteristic of earthquake-induced damage in shear walls?
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What is a primary reason wood-frame structures fail during an earthquake?
What is a primary reason wood-frame structures fail during an earthquake?
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Which condition contributes to inadequate foundation performance in wood-frame structures?
Which condition contributes to inadequate foundation performance in wood-frame structures?
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What results from the interaction between two adjacent buildings during an earthquake?
What results from the interaction between two adjacent buildings during an earthquake?
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Pounding damage during an earthquake is most likely to occur when:
Pounding damage during an earthquake is most likely to occur when:
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What characteristic of buildings contributes to their potential for pounding damage?
What characteristic of buildings contributes to their potential for pounding damage?
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What type of roof material is commonly associated with wood-frame structures' failure in earthquakes?
What type of roof material is commonly associated with wood-frame structures' failure in earthquakes?
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What happens when the floors of two adjacent buildings collide at different elevations during an earthquake?
What happens when the floors of two adjacent buildings collide at different elevations during an earthquake?
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What is one reason the foundation of a wood-frame structure may be inadequate?
What is one reason the foundation of a wood-frame structure may be inadequate?
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What was the primary cause of the pounding damage observed in the Anchorage-Westward Hotel during the 1964 earthquake?
What was the primary cause of the pounding damage observed in the Anchorage-Westward Hotel during the 1964 earthquake?
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In the context of pounding damage, what can be inferred about the doorway mentioned in the discussion?
In the context of pounding damage, what can be inferred about the doorway mentioned in the discussion?
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What significant event occurred during the Izmit earthquake in relation to pounding damage?
What significant event occurred during the Izmit earthquake in relation to pounding damage?
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Why is it challenging to model the effects of pounding between two structures?
Why is it challenging to model the effects of pounding between two structures?
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Which of the following earthquake events did NOT feature pounding damage among the examples provided?
Which of the following earthquake events did NOT feature pounding damage among the examples provided?
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What type of buildings were primarily affected by the pounding damage described during the 1999 Athens earthquake?
What type of buildings were primarily affected by the pounding damage described during the 1999 Athens earthquake?
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What visual evidence was noted to illustrate pounding damage in the Anchorage-Westward Hotel?
What visual evidence was noted to illustrate pounding damage in the Anchorage-Westward Hotel?
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What was the observed impact of pounding damage during the M8.0 Wenchuan earthquake?
What was the observed impact of pounding damage during the M8.0 Wenchuan earthquake?
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Study Notes
Earthquake Structural Damage
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A soft story is a story in a building with less resistance to earthquake-induced stresses than the stories above or below it.
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Soft stories often occur on the ground floor due to open public areas.
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Earthquake-induced building movement stresses the soft story on the ground floor more than other stories.
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Earthquake ground motion in buildings searches for structural weaknesses.
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Weaknesses are caused by changes in stiffness, strength, or ductility.
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Poor reactive mass distribution compounds these effects.
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Severe structural damage in modern buildings highlights the need to avoid sudden changes in lateral stiffness and strength.
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Sof stories often cause serious problems during earthquakes.
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Avoiding soft stories requires even distribution of flexibility, strength, and mass.
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Historical examples of soft story damage are seen in buildings in Turkey, Nepal, etc.
Inspection of Earthquake Damage
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Earthquake damage inspection and analytical studies show that structural systems with soft stories can lead to significant problems during severe earthquake ground shaking.
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Examples highlight the need to use consistent distribution of these factors.
Soft Story
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In shaking a building, an earthquake ground motion will search for every structural weakness.
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These weaknesses are usually created by sharp changes in stiffness, strength and/or ductility, and the effects of these weaknesses are accentuated by poor distribution of reactive masses.
Severe Structural Damage
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Severe structural damage suffered by several modern buildings during recent earthquakes illustrates the importance of avoiding sudden changes in lateral stiffness and strength.
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A typical example of building damage due to a "soft story" is cited.
Inspection of Earthquake Damage
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Inspection of earthquake damage, as well as analytical studies, demonstrates that structural systems with a soft story can lead to significant problems during severe earthquake ground shaking.
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Examples emphasize the need to avoid soft stories by using an even distribution of flexibility, strength, and mass.
Pancaking
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Pancaking occurs when earthquake shaking causes a soft story to collapse, leading to the complete failure of the overlying floors.
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The resulting crushed floors form a stack-like structure from one floor to another, similar to a stack of pancakes.
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Pancaking of reinforced concrete multistory buildings was common throughout the earthquake-stricken region of Turkey due to the Izmit earthquake on August 17, 1999.
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Examples of this type of damage are documented in specific figures.
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The damage caused by pancaking is attributed to the presence of soft lower stories and insufficiently reinforced connections at column-beam joints.
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Most buildings with this type of damage had soft stories with open spaces and shallow foundations which offered limited lateral resistance to seismic activity.
Pounding Damage
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Pounding damage occurs when two closely constructed buildings collide during earthquake shaking.
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Even if the buildings have different constructions or heights, pounding can still occur if they are close enough.
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Pounding damage is often more impactful in cases where one floor of a building hits the supporting column of an adjacent building, at different elevations.
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An example of pounding damage is the Anchorage-Westward Hotel in Alaska, damaged during the Prince William Sound earthquake in 1964.
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Figure 4.17 illustrates a case in Mexico, where the restaurant building next to the parking garage prevented collapse of the lower floors.
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In a case featuring a taller and/or squat building, the buildings will vibrate at different frequencies and amplitudes causing collisions.
Impact Damage from Collapse of Adjacent Structures
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The collapse of one structure can lead to damage to nearby structures.
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An example from the Izmit earthquake of 1999 shows a building that lost a corner column due to neighbouring buildings collapsing.
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Note that the roof of the collapsed building now rests at the third-story corner of the adjacent standing structure.
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Geotechnical engineers and earthquake geologists need to analyze and evaluate potential collapse of adjacent buildings based on poor soils or geological hazards.
Asymmetry
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Asymmetric buildings (T-shaped or L-shaped) can experience greater damage during an earthquake.
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The different segments of asymmetric buildings are usually stiffer and more resistant along their longitudinal axes rather than across the segments.
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The damage often occurs at the junction of segments.
Shear Walls
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Shear walls are structural components that hold adjacent columns or vertical supports and transfer lateral forces to the foundation.
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Forces on shear walls are predominantly shear forces, but for slender walls bending is also an issue.
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Examples of shear wall failures are documented for the West Anchorage High School (during a 1964 earthquake)
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Several common problems associated with shear walls include inadequate strength and inadequate attachment to the foundation.
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Discontinuities between floors can create a soft story condition.
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Even properly designed shear walls may not prevent collapse if severe building settlement occurs due to seismic activity.
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Shear wall failure modes have been observed in recent earthquakes.
Wood Frame Structures
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While generally resistant to earthquakes, poorly constructed, aged wood-frame structures are especially vulnerable.
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The 1995 Kobe earthquake saw significant damage to wood frame structures.
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Age-related deterioration, open first-floor areas, weak foundation connections, inadequate foundations, poor soil conditions, heavy roofs have all been identified as factors leading to wood-frame collapse.
Additional Earthquake Damage
- Many different types of structural systems can be used to resist inertia forces in a structure, which are produced by earthquake ground motion, including braced frames, moment-resisting frames, and shear walls.
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